Would it be geographically feasible to store water on land to counteract sea level rise? Based on a misunderstanding of another post, I prepared an estimate of how much water would be required to lower sea level by one meter. the main question would be: could this be stored on land?

Using the eTopo1 data Eakins and Sharman has calculated a hypsographic curve for the earth. In the elevation span between + 6 to -6 m they found that land area will change by 396 000 km2 per meter sea level change. In the range -7 to -51 m below current sea level the land area will change by 251 000 km2 per meter sea level. Thus to get an area the size of Zimbabwe (391 000 km2) or Norway (385 000 km2) (data from the World bank) sea level will currently have to be lowered by 1 m. Since the ocean surface is about 360 000 000 km2 (e.g. The Physics factbook) this would mean a total of about 360 000 km3 of water which in turn is comparable to the Caspian Sea (371 000 km3 according to a Wikipedia compilation)

So where does that lead? Clearly adding a Caspian Sea somewhere on land is not an easy task so the question is how much land need to be gained and where? Remember that all coasts are not the same, topographically.

As a side point, the Greenland ice sheet contains enough water to raise sea level by about 7 m. Hence the ongoing warming is a far more problematic issue when it comes to sea level change and counteracting this volume would be 7 times more challenging than the calculation made above. That is a sobering perspective.

Reference

Eakins, B.W. and G.F. Sharman. Hypsographic Curve of Earth's Surface from ETOPO1, NOAA National Geophysical Data Center, Boulder, CO, 2012


What atmospheric phenomenon am I seeing in this photo? On a trip to Brighton, England on April 12th, 2015, I noticed this strange plume in the sky over the English Channel at about 13:00 hours. It looks like;

Something that fell out of the sky - the news and other chatter over the following days revealed nothing which would support that.
A tornado/wind vortex drawing water up from the surface?

Please note, I took this photo with my phone, with the window down and it is completely unedited. Is this a meteorological phenomenon, and if so, what is it?

You are seeing an older jet contrail and its shadow. You can also see some newer contrails, and maybe even some older ones.

Contrails are not necessarily continuous. For example, the contrail that appears to be horizontal in the image below appears to magically appear near the left end of the image.

That's what you are seeing in your image, but in this case the contrail in question appears to be vertical. The contrail stops about 1/3 the way up the picture. Given that the contrail gets thicker with increasing height up the picture, and becomes very diffuse near the top, I suspect that where the contrail stops is the youngest part of the contrail. That would mean the plane was flying away from your position (i.e., toward the horizon visible in the picture). The contrail stops at that point because the plane entered a region of dry, stable air. Contrails persist for seconds to several hours, depending on the local atmospheric conditions.

What about the dark band below the contrail? That's the contrail's volumetric shadow. You were in just the right place to see it. Notice that while the contrail is twisted and not quite straight, that dark band is straight. If you look closely, you can see that it doesn't end at the horizon. It appears to extend into the water. It's a shadow, a volumetric shadow to be precise.

The next two links are to images that show exactly this effect. These images appear to be copyrighted, so I'm going to leave them as links rather than embed them.

Link to image portraying a jet chasing it's volumetric shadow

Link to another image of a contrail and its volumetric shadow

Finally, this is a very striking example of the volumetric shadow from a contrail, in this case the launch of STS-98. This image is from Wikipedia, so it's fair use. In other images (you can search for them) taken from other angles, the shadow isn't nearly as striking, sometimes even non-existent.


Have we looked for human-like signals in the geological record? This is somewhat of a follow up to some interesting discussion here about using synthetic radioisotopes to define the start of the anthropocene. It is also sort of related to a question asked here, but with some additional thought put into it that I hope merits its own response. My question is simply:
Has there been any serious thought put into the search for ancient industrialised civilisations that would generate a signal comparable to human civilisation in the sediment record?
As a complete layman, it seems at least possible that paleontological (archaeological?) record may be incomplete enough that we have completely missed or misinterpreted evidence of an ancient civilisation. I would imagine that not a lot of human structures/artifacts would survive weathering over millions of years. It would stand to reason that there would not be a whole lot left from this hypothetical ancient civilisation.
Given the discussion in the question I linked above, what would last a long time would be evidence of our atmospheric nuclear explosions/accidents. One could imagine that isotopes that are not normally naturally present, such as long lived fission products like I-129, unused nuclear fuel like U-235, or their decay products such as U-236 from the alpha decay of Pu-240 could be present in a thin layer in the sediment record. In addition, one could also look for a spike of naturally present isotopes that would result from the incorporation of radioisotopes by living organisms (for example spikes in Zr-90 from the incorporation of Sr-90 replacing calcium in foraminifera). Given the types of isotopes present, one might even be able to guess at their origin (e.g. nuclear detonation, reactor accident, or breach of waste storage)
Moving away from the radioisotopes, this hypothetical civilisation might also have used fossil fuels, resulting in global warming similar to what we see today. Intriguingly, from my reading it seems that there are events that produced abrupt warming (e.g. Paleocene–Eocene Thermal Maximum) whose cause and/or trigger is poorly understood, though I won't speculate too much about this as it's not my area.
I think there are probably other signals that one could look for, for example evidence of industrial pollution or agriculture. However, I think these might be trickier to see than the radioisotope signal, as they are chemical and therefore might be difficult to distinguish from a sudden natural process. Nevertheless, it seems like the combination several of these types of signals with an abrupt onset and end in the sediment records would be pretty convincing evidence for an ancient civilisation. Perhaps more exciting, it seems like these could be tested with existing methods or even existing samples.
I don't want to come off as a total crackpot, but I hope that this has shown why this seem like an interesting and accessible line of inquiry to a non-geologist, even if I don't think the hypothesis of an ancient civilisation is particularly likely. What I will jokingly call SATI (Search for Ancient Terrestial Intelligence) seems to me equally significant to the much more well known SETI, and is much more likely to give some kind of result, whether positive or negative. Genuinely curious if this sort of thing has been seriously thought about and researched, or if there is something that I'm not understanding that would make this not as clear-cut as I'm making it out to be.

Any nuclear activity would be visible in the changes of the isotope ratios far longer than the existence of our Universe. Nothing was found until now, except one in Gabon. It was natural phenomenon: at the time, 2billion years ago, there was far more ${}^{235} \rm U$ and the ground water could moderate uranium ore, if it was enough rich.
Except that, nothing was found until now.
Offtopic, but the case is same for radio signals. If any Earth-like civilization would exist in 100 light years away, we would see their radio signals. There is radio silence.


How do I convert Relative Humidity into specific humidity I am using NCEP_DOE reanalysis 2 data set. It include only relative humidity while I need specific humidity. How do I convert the relative humidity into specific humidity?

The Engineering Toolbox gives the following equation for converting relative humidity to specific humidity.

  If we know the relative humidity of the moist air and the water vapor density and density of the air, the specific humidity can be expressed as:

x = 0.622 φ ρws / (ρ - ρws) 100%         (1)

where

x = specific humidity of air vapor mixture (kg/kg)

φ = relative humidity (%)

ρws = density of water vapor (kg/m3)

ρ = density of the moist or humid air (kg/m3)


CO₂ level is high enough that it reduces cognitive ability. Isn't that a reason to worry? I think the level of carbon dioxide in the air is high enough to reduce the intelligence of humans. This has nothing to do with climate change.

Except that both mean we should reduce CO₂.

I never heard of that, surprisingly, but deducted that from simple known facts. I hope I'm missing something.

Maybe my idea is just wrong? It's simple enough to explain here:

Elevated CO₂ levels in office air reduce the cognitive ability of office workers, that is well established.
That is measurable by experiment. Complaints about drowsiness start at about 1000 ppm CO₂ in air.
Reduction in cognitive ability does happen with drowsiness, almost by definition.

The level of CO₂ is currently a significant fraction of 1000 ppm, about 409 ppm as of November 2019.

The CO₂ level in a typical western indoor working environment raises by multiple 100 ppm over the day, exhaled by people breathing in the working environment.

With an increasing base level, an increasing level in workplace air reaches a fixed threshold sooner, because CO₂ levels are additive.

The base level does increase. Therefore a level of CO₂ that reduce the cognitive ability of humans is reached earlier in a working day.

If the base level is higher, base level plus the additional CO₂ in office air  reach a level that reduces cognitive ability sooner during a work day.

This happens globally in many workplaces.

That is true for any values of base concentration, threshold concentration and maximum of increase during a day that are of the same order of magnitude. This estimation is optimistic, because it assumes that the effect has a sudden onset at a level that causes obvious symptoms.

To summarize the central points: Some CO₂ concentration exists that has negative effects. An offset in base air concentration results in an offset in the workplace concentration. That means the detrimental concentration is reached more often. For this to be true, the exact numbers are not even relevant.

Ok, what's wrong with that deduction?
I really hope there is something wrong.

If this is a reason to care about the level of carbon dioxide in common air, it is completely independent of climate change, an alternative motivation to do exactly the same thing. That seems very relevant to me.

There looks like legitimate cause for further study, preferably by scientists breathing air under 950 ppm $\small\mathsf{CO_2}$ (this study showing a 15% decline in cognitive ability at this level).

Because it is not known what mechanisms are involved in this decline in cognitive ability it is not clear if there are threshold levels, with step changes in impacts or if the effect is linear, but changes at below 950 ppm is indicated and subtle impacts at much lower level seem likely, with one leading expert (Vivian Loftness) on Health, Productivity, and the Quality of the Built Environment suggesting atmospheric levels above 600 ppm would be cause for concern about cognitive effects. For people with poor cognitive abilities potential impacts of $\small\mathsf{CO_2}$ levels is not known, but could be significant - this, along with impacts more generally at levels that are within the range of possible $\small\mathsf{CO_2}$ concentrations people now living can expect outdoors needs more study.

The principle response in the near term is improving air quality in buildings, with raised atmospheric $\small\mathsf{CO_2}$ levels most significant with respect to rates of $\small\mathsf{CO_2}$ buildup and the required air replacement by ventilation systems. There are ample reasons to commit to actions that reduce emissions and $\small\mathsf{CO_2}$ rise in the atmosphere, but better understanding of all the potential consequences is worthwhile.


Simple way to understand these narrow frequency peaks in recently published "ice shelf singing"? The Earther.Gizmodo.com article Scientists Discover a Weird Noise Coming From Antarctic Ice Shelf links to the American Geophysical Union video (an more importantly audio) (AGU) This is what an Antarctic Ice Shelf sounds like.

It also links to the recently published Geophysical Research Letter (Chaput et al. 2018) Near‐Surface Environmentally Forced Changes in the Ross Ice Shelf Observed With Ambient Seismic Noise (open access) from where the image below is taken.

EDIT: In the same issue there is a commentary: Seismology Gets Under the Skin of the Antarctic Ice Sheet which was written by Douglas MacAyeal, a glaciologist at the University of Chicago who was not connected to the new study which I also do not understand!

Dimensional analysis alone suggests that a length scale of the phenomenon resulting in these slightly sub-sonic oscillations can be obtained from speed divided by frequency (e.g. m/s divided by 1/s) but using the speed of sound in ice or water (roughly 4,000 and 1,500 m/s respectively) and circa 10 Hz suggests a length scale of a few hundred meters.

The paper itself is quite technical and in depth. Somewhere in there, is there a physical distance in water, or in ice that corresponds to this frequency, or are the oscillation frequencies due to a dynamic process like sticking and slipping, rather than to the propagation speed of sound?

Caption of Figure 3:

  (a) Marginal PPD for Vp and Vs for the premelt resonances at station DR09, obtained by MCMC inversion of power spectra (See Suppl. S4: 1‐D MCMC inversion, Capelli et al., 2016). The red curves indicate the marginal posterior mean for P and S velocities. (b) Top panel, representative subset of power spectral models (red curves) from the PPD in (a) for station DR09, compared with the observed premelt spectrum (blue curve). Bottom panel, averaged observed premelt and postmelt spectral resonances (blue and green curves, respectively) at DR09. (1) and (2) indicate the position of a higher frequency peak of interest before and after the melt event. (c) Contour plot depicting a grid search of penetration depth versus velocity perturbation applied to the premelt model (peak pattern (1), in b), and fit to the postmelt resonance peak pattern, as denoted by peak pattern (2) in (b), lower panel. The minimum with respect to a least squares fit is represented by the red star, denoting a 35–40% perturbation with a depth penetration of 3–4 m. The premelt model used here is the mean posterior model shown in (a). (d) Example frequency peak response to a 40% velocity drop with varying degrees of depth penetration for the DR09 premelt velocity model in (a). Note that lower frequency spectral peaks can be nearly unaffected if the perturbation depth is shallow. (1) and (2) denote observed premelt and postmelt peaks plotted in (b). PPD = Posterior Probability Distributions; MCMC = Markov chain Monte Carlo.

The wavelengths that travel through the ice have a faster speed of travel, and the physical size of the pressure variations that cause the sound are not 100 meters. It's more like 1 meter, so it's similar to having an oversized speaker cone blasting air waves into the ice, which the ice then transmits to the microphone most clearly at a depth of 1-2 meters.

The best illustration I can find of pressure differentials and resonance modes from wind, of about 5-15 hz are from this 1960's YouTube video:

https://youtu.be/TqTSyFz6DJc?t=176

The frequencies of the speaker cones are guided by air turbulence buffeting from the angles of the snow dunes and the wind, which generate 1/2/3 frequencies, perhaps from 1/2/3 different snow dunes types in the same area, depending on the local dune shapes, and when a storm changes the dune shapes, the frequencies change correspondingly.

The compressed snow has an elastic property which absorbs higher frequencies at depth and adds higher waves together to form lower waves, so the frequency sounds lower in the ice.

It's not probable that the frequencies are generated by 100 meter wide diaphragms and pressure differentials because that would correspond to very high dunes and long valleys. the high dunes are not likely, and the wind pressure events in the valleys would not generate major pressure differentials.

If I was a bob moog, and I wanted to copy the physical resonance process of the dunes, It would be a relatively easy synthesizer to design. They have place bass audio cones at different zones of the dune at different times, and measure a 3D map of frequencies and timings from a zone near the artificial sound generator.

The unclear statements of the article say that:

They measured Perturbation Velocity, a coefficient of flow dynamics for seizmology and of aerodynamics turbulance equations for physics? which kind of perturbation velocity is implied? Where are the equations for perturbation velocity and what a the name of the equations?

Sound propagates through the firn layer, a study which may have already been measured and demonstrated by other snow and ice physicists? Sounds travel through snow, ice and water for different distances. To what distance and efficiency does firn transmit sound? there are graphs for snow acoustics and some of the research is hilarious:

one of the most complex pages of research i have ever seen

from this page: https://www.google.fr/search?q=sound+propagation+in+ice&num=100&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjYptm3s5feAhVLOBoKHa2sBpEQ_AUIDigB&biw=1572&bih=808&dpr=1.5#imgrc=1z-RRNglm0UEGM:


Carbonate reef not horizontal in seismic section? Carbonate reefs usually appear as homogeneous bodies surrounded by sediment layers in seismic reflection data, but in the figure below the high amplitude reflection from the top of sediment (layer 2  at 0.3-0.34 seconds) is not horizontal yet the geological interface is horizontal.

Can anyone explain why? I appreciate any input, thanks.

This phenomenom is called velocity pull-up. The seismic waves that reflected off the top of Layer 2 beneath the carbonate layer have also travelled through the carbonate. Because carbonate (at least in this case) has a faster P-velocity than the surrounding shale, waves that have travelled through the carbonate will return to the surface receivers in a shorter amount of time, relative to waves that only travelled through the shale. Thus the carbonate/Layer 2 interface appears at an earlier two-way-time relative to the Layer 3/Layer 2 shale interface.


Carbon dioxide and ocean acidification based on temperature For our assignment, we are required to analyse and compare the $\ce{CO2}$ level (in both ocean and air) of two different sites. Theoretically, shouldn't the $\ce{CO2}$ level of a colder region (e.g., Alaska) be higher due to $\ce{CO2}$ being more soluble in colder temperatures?

I've looked at the data (I'm comparing Alaska and the Equator) and the carbon dioxide concentration is higher for the equator. What could explain this? The data can be found at NOAA's PMEL Carbon Data Observation Data page.*

* The US National Oceanic and Atmospheric Administration / Pacific Marine Environmental Laboratory

From Sabine, et al., 2004:

  The capacity for ocean waters to take up anthropogenic CO2 from the
  atmosphere is inversely proportional to the value of the Revelle
  Factor, hence the lower the Revelle Factor, the higher the oceanic
  equilibrium  concentration of anthropogenic CO2 for a given
  atmospheric CO2 perturbation.

The Revelle Factor is, "the ratio of instantaneous change in carbon dioxide to the change in total dissolved inorganic carbon (DIC)"

Therefore, the controlling factor for CO$_2$ absorption in seawater is presence of DIC and buffering. If you add CO$_2$ and a relatively small portion of it becomes other DIC species such as HCO$_3^{-}$ or CO$_3^{2-}$, then you have a low Revelle factor and high uptake of atmospheric CO$_2$. Alkaline waters (lower pH) can absorb more CO$_2$ because they have less of the acidic CO$_3^{2-}$ and neutral buffering HCO$_3^{-}$.


Why would a suite of related rocks have one anomalous sample? I have a suite of rocks that have nearly identical major element chemistry, but a single sample has quite different trace element concentrations. All the rocks are trachydacites. I know the analysis was done corrected. What process could cause this?

Under the assumption that we don't know anything about sampling, preparation and analysis we have to proceed with caution. Any of these steps can introduce effects that can produce stronger signals than the natural geochemistry of a rock sample.

Just to give you an idea of the errors:

Sampling a heterogeneous rock can produce very different whole rock chemistry. If you take your sample from a mica-rich layer you will get different results than from a feldspar-rich layer.
During sample preparation you can inadvertently through grinding, sieving and pouring produce aliquots which don't have the same mineral composition. Micas pour different from one vessel into another than quartz-grains. A certain mineral you want to analyze might have a smaller grain size and sit at the bottom of your vessel or in a different sieve your not analyzing. Each step in the lab can result in chemical fractioning!
Analytics is a whole science on its own. Without knowing how the mineral sample was dissolved (did everything dissolve?) and values for detection limit and standard deviation you will have uncertainties in your data that might be make these values meaningless.

Now assuming that the data is somewhat trustworthy:

The left plot shows you the chondrite normalized rare earth element pattern. The light rare earths are 100 to 1000 times enriched relative to the chondrite (should actually be cited which one). Heavy earth elements are also enriched but less. The sample CCS01 has lower enrichment and a positive Eu-anomaly. This could indicate that the sample has a different mineral composition than the other samples. Maybe a rare-earth-element-enriched mineral has a lower concentration in the CCS01-sample.
The right plot the CCS01-sample sticks out again. It has lower P-concentrations. Think again of how your sample might have fewer phosphates. The relative depletion in Ce and La might correlate with P. The sample might just have less monazite (But other minerals could cause this too). Lower Nb and Ta might indicate that the sample has fewer columbite and tantalite (but the Elements occur in other minerals too).

Conclusion:

Instead of guessing you should find out everything you can about the samples history (sampling, preparation, analysis). If possible suggest more analytics. A day at the microprobe could show you which minerals are contained in your sample (rock slide or strewn grain concentrate). If not available a polarizing microscope could also help you figure out the differences in the sample (excluding very small grains).


Where does all the earth from surface mining go? Surface mining digs up a lot of earth and rock. After the desired ore is separated, where do the earth and rock mined go?

In opencast mining it is dumped on a huge spoil heap, and if the company is environmentally conscientious or wants to avoid penalties, it is used to fill in the hole left when the mining is finished. With underground mining it is also dumped on spoil heaps, and as it is not practical to infill the mine workings, in best practice the spoil heaps are later landscaped, or at least restored to nature so they are no longer unsightly and could become a nature reserve. Some mining companies are reckless with their waste and dump it into lakes and rivers, potentially causing pollution incidents, though not all mining waste is hazardous.


Wildfire acreage, two dimenional or three? When wildfire acreage is reported, does anyone know if local terrain is taken into consideration, or is the reported acreage the area as viewed on a map? I ask because the two figures are different. A square unit of area on a 30° slope would appear to be .866 square units on a map, whereas a square unit of area on a map would actually be 1.155 units of area on the slope (assuming I've done the math correctly, which I think I have). I'm guessing it's just the area as viewed on a map, because figuring out the average terrain would be pretty difficult, though not impossible.

The same issue arises when land is bought and sold. The area used is the flat area from a plan. Slope is not considered because it would require at lot of data because the rate of change of topography and slopes is never uniform. Also the calculations to determine the true area can be convoluted if the change in topography is complex.


Is there any open source, stochastic rain forecast data available for the UK? I'm sometimes frustrated by publicly available precipitation forecasts, such as those offered by the Met Office or Google. If I understand these forecasts correctly, they tell me:

The expected volume of rain (e.g. 5ml of rain)
The overall likelihood of there being any rain (e.g. 50% chance of rain)

This is generally a sufficient level of data, but sometimes it would be useful to see a more statistically nuanced prediction, which could let me know things like:

The 95% confidence interval of the expected volume of rain
A probability-density of rainfall volume
Maximum/minimum possible volume within a given interval of confidence

Is there any rainfall data of that sort available for the UK?

Well there is ensemble data that you can use. For the UK, you can probably use the ECMWF ensemble prediction system data or GEFS from the US NWS. Both are global models, so they can be extended beyond their respective centers.
These ensembles can be used as samples of the probability density function. Normally (pun unintended), with these types of ensembles, the pdf can be assumed to take the form of a Gaussian distribution per ensemble filters. Obviously, this is problematic, as it implies a probability that there is negative precipitation, which is unrealistic. However, if you want to be clever, you can probably fit a kernel to the data. Or you could choose your own distribution. The distribution that is most widely used is the Gamma distribution, though the Pearson distribution has been shown to perform well too. Perhaps using the Kolmogorov-Smirnov test could help you determine which distribution is best.


What is this geological formation in the Santa Cruz mountains that looks like a cave interior? Stevens Canyon Road in the Santa Cruz Mountains (near Cupertino, California) passes right next to a large rock formation that, to my untrained eye, reminds me of the inside of a limestone cave. Here's some photos I snapped from when I was there:

This is right off the road; you can see other pictures here on Google Maps.
The rock surface usually has water dripping over it, even in the summer when nearby creeks are otherwise dry, and it's covered in rippled ridges that remind me of the inside of the few limestone caves I've visited. This spot is right at a bend in the road and has no markings indicating what it is.
My current guess - based on absolutely no expert knowledge at all - is that there's a spring at the top of the rock that's slowly dripping over the surface and slowly depositing calcium carbonate when it lands. The mountains here have a bunch of old limestone kilns (and an active cement plant, and at least one active quarry), so it seems at least somewhat plausible that rainwater is dissolving the minerals and depositing them here.
Any guesses as to what, geologically, is going on here? Is there a name for this sort of formation?
Update: Based on the comments that this looks like travertine, I climbed up to the top of the formation. I found a small cave carved into a rock just above it that had a steady drip of water coming down. The water was cold and clearly had a bunch of red minerals dissolved in it. (Sorry about the quality - it was getting dark)

There was a clear path the water from there was taking that produced the drip over the surface:

And finally, I noticed some largish rocks pushed off to the side of the road. They look like this:

I noticed that the rocks near the water path up top look a lot like these, and these look a lot like random pictures of travertine that I've been Googling for.
So based on this, I'm going to make the educated guess that I'm looking at travertine that's deposited on the surface of the rock. I don't think there are any nearby hot springs, but maybe this is simply water flowing through the limestone in the rock above, dissolving the minerals, and slowly depositing them on the surface?
I see that questions of the form "identify this rock" are off-topic here, and I'm not sure if this counts. If so, let me know where else I should ask this.

Well given that travertine springs trail is right next door, in castle rocks state park I am going to guess travertine. Which is a calcium carbonate mineral deposited from geothermal springs, hot ground water brings up the dissolved travertine which is deposited as the hot water evaporates, but can also slowly be dissolved and redeposited by rain. Thy can form very quickly, on the span of years or decades. There are many travertine geothermal springs in the area. If you want more information try this link for a start.
https://en.wikipedia.org/wiki/Travertine_Hot_Springs


Does the gravitational pull of the moon affect the composition of Earth's atmosphere? In particular, does the pull of the moon affect the amount of water vapour in the Earth's atmosphere? In other words, if the moon were larger, or orbiting more closely to the earth, would the increased gravity cause the composition of the atmosphere to change?

The atmosphere is continuously mixed by turbulence, so no sorting of its  ordinary components can occur easily and rapidly. Twice a day change, anyway, is far too fast for anything but some tidal effect on pressure and thus on temperature. Ok, these might indirectly slightly modify some thresholds and balance e.g. between states change (water) and some atmospheric chemistry, by a fraction of what day/night change does. I wouldn't call that "change of composition", though.


What are the hottest temperatures ocean life can survive at What are the hottest average annual temperature for life in the ocean to withstand? Particularly algae
This could include life from all points in earth history.

The previous record-holder, P. fumarii, could live at temperatures as high as 113 °C (235 °F), well above the boiling point of water. But the new microbe, for now called “Strain 121,” thrives at 121 °C and can even survive for two hours at 130 °C.


Is there a way to tell whether land is cleared from forest, or naturally bare? In Scotland, the Caledonian Forest has been cut down by humans.  According to an unsourced Wikipedia article the tree line in Scotland is at 500 metre (it does not indicate the tree line elevation difference between southeast and northwest Scotland, which should be considerable).  That means considerable areas are naturally bare, and therefore arguably less unnatural than the areas where forests have been cleared.  When I pass through Scotland, is there a way to tell whether the spot I stand on had a forest before that was cleared, or that it is a naturally bare area?

Just by looking at a treeless region it would be difficult to know whether it was naturally treeless or whether the lack of trees was due to human actions. The history of the region would need to be known.

In Scotland, due to the extent of glaciation during the last ice age some of the ground was scoured, leaving bare rock when the ice finally melted.

With soil removed there is little opportunity for trees to develop deep roots and establish forests.

Loss of soil can result from natural causes and human actions. The area around Queenstown, Tasmania, in Australia is now denuded of trees due to a combination of logging and sulfuric acid rain from smelter fumes that killed the then existing trees followed by heavy rainfall washing away the soil from the steep terrain.

One of the best ways to tell if an area is naturally bare is to leave it allow for at least several decades so that no humans can do anything to it. If trees naturally return to the area, that area once was capable of having a forest. If trees do not grow, the area either never had a  forest  or it has been so badly degraded that  trees can no longer grow there.

Despite the environment carnage experienced by Queenstown, Tasmania during the 19th and 20th centuries and the subsequent lack  of soil, if left alone, trees will try to grow in the area.


How to get cell indices from latitude and longitude in WRF model grids? I am using Weather Research and Forecasting model WRF and the WRF Preprocessing System WPS and could not get a satisfying answer from wrfhelp. Can anyone guide me in transforming latitude and longitude to grid points especially for nested grids?
Specifically http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Basics/GEOGRID/geogrid_namelist.htm and http://www2.mmm.ucar.edu/wrf/users/docs/user_guide_V3/users_guide_chap3.htm#_Description_of_the_1

How does one transform latitude and longitude to i_parent_start and j_parent_start? How is this related to dx and dy and ref_lat and ref_lon? A simple example and an explanation would be very helpful.

I've been a WRF user for almost 5 years now, and contributed code to a recent public release. I am not aware that WPS (WRF Preprocessing System) has such a tool that takes in the grid and point coordinates and returns the appropriate index. However, it is very straightforward to do so yourself. Some suggest using an external library, I think that may be an overkill for such a simple task. Here is what you need to do:

1) Run geogrid.exe to generate the parent grid. Since you don't know the exact location of the nest yet, set max_dom = 1 in namelist.wps. This will generate a file called geo_em.d01.nc.

2) Look at the geo_em.d01.nc file to find the right indices for your child domain. i_parent_start and j_parent_start refer to the x and y indices on the parent grid at which the southwest corner of the child grid will be positioned. XLONG_M and XLAT_M are the longitude and latitude grids of the mass (pressure) points. Using a programming language of choice, find the grid cell that is closest to your desired location for the child nest corner. This is typically done by looking for the minimum value of distance between desired location and all the points on the grid. For example, in Fortran, you can do something like:

integer :: i_parent_start,j_parent_start
integer,dimension(2) :: coords

coords = minloc((lon0-xlong_m)**2+(lat0-xlat_m)**2)
i_parent_start = coords(1)
j_parent_start = coords(2)

where xlong_m and xlat_m are 2-dimensional arrays that you read from the grid, and lat0 and lon0 are the desired coordinates of the child nest southwest corner. Similarly, if you use Python, you could do:

import numpy as np

j_parent_start,i_parent_start = np.unravel_index(\
    np.argmin((lon0-xlong_m)**2+(lat0-xlat_m)**2),xlon_m.shape)

# Add one because WRF indices start from 1
i_parent_start += 1
j_parent_start += 1

3) Now edit namelist.wps again, set the i_parent_start and j_parent_start to the values that you calculated in step 3, set max_dom = 2, and re-run geogrid.exe. The child domain file geo_em.d02.nc should be created.

4) Look at the geo_em.d02.nc file. Repeat the procedure until happy with the domain location.

About the parent_grid_ratio parameter. This is an integer factor of child grid refinement relative to the parent grid. For example, if set to 3, and parent grid resolution is 12 km, the child grid resolution will be 4 km. Odd values for parent_grid_ratio (3, 5, etc.) are recommended because for even values, interpolation errors arise due to the nature of Arakawa C-grid staggering. parent_grid_ratio = 3 is the most commonly used value, and recommended by myself.


Identifying a desert landform I saw this landform on Google Earth on the border of Algeria/Tunisia/Libya and wondered what it is called (so that I can read up on it and find out how it forms - I am not a geologist):

Here is a 3D view: (Press Ctrl + drag left mouse button to rotate)

Does anyone know what kind of landform this is?

Star dunes, caused by the prevailing winds coming from multiple directions.

Take a look at these different dune types.


Reason for rotting smell after first rain of the season? Last day we had first rain after 3-4 months of hot&dry weather, and within 3-4 minutes a rotting smell came from nowhere. Due this smell I had running nose for a day. What might be the reason for this bad smell? Did anyone heard of this kind of problem? (or is this just some local issue related to sewage, or some animal dead body which was dry came in contact with water)

I am not referring to Petrichor, which is fresh earthly smell.
And I am in India.

I hope this is on-topic here

When rain displaces pore gasses in the soil, bubbles of soil gas are released into the atmosphere. It's impossible to be precise about the composition because it is so variable from place to place. It varies according to soil type, organic content, degree of rotting, temperature, and the microbiological cross section (itself hugely variable). Most soil gas is odourless, such as nitrogen, carbon dioxide, methane, etc. Others, like geosmin, are very smelly. In addition  to 'petrichor' there are terpenes, aldehydes, alcohols and esters, to name but a few of the natural volatile organic compounds.
Of course, one cannot rule out the foul smell or rotting animals in some places.


What's the difference between snow cover and fractional snow cover? What's the difference between snow cover and fractional snow cover? Are they kind of synonyms? What would be a definition of fractional snow cover?

thanks a lot!

Fractional Snow Cover (FSC) is a property of snow cover.  The fractional snow cover property is used in a variety of contexts, most common of which is meteorological models.  Snow cover algorithms applied to visible imagery remote sensing data are used to derive fractional snow cover for each pixel.  This information is typically re-gridded and time-averaged for use by external users.

This GOES site explains:

  Most satellite-based snow cover products provide a "binary" map, whereby each pixel is classified as either "snow" or "not snow". In contrast, the FSC algorithm is an optimized spectral mixture analysis that uses the broad spectrum from ABI to determine the fractional cover of snow, vegetation, and soils.

More information about snow cover products from GOES and MODIS can be seen here:

http://www.goes-r.gov/products/baseline-snow-cover.html

https://modis.gsfc.nasa.gov/data/dataprod/mod10.php


What would be the predicted/calculated ages using several samples of soil with the help of carbon 14 test? Assume there are several soil/rock (take it) samples as follows taken from different depth of the earth

sample from surface of the earth = Sample A
sample from 1km deep of the earth = Sample B
sample from 10km deep of the earth = Sample C
sample from 20km deep of the earth = Sample D
Cooled lava (in solid state) sample = Sample E  (Assume lava was taken just after they cooled)

If these samples are tested using carbon 14 test what will be there ages according to test results?

  NOTE: I'm not expecting any exact values.
  Please order them in ascending order

As I think it should be in the order of A
Because with the time new layer of soil/rock creates on top of the current existing layer and it's obvious(as I think) layer 1(first existed layer as the top layer) that first layer is older than new layer.
Above is my explanation.

Radiocarbon dating cannot be used to date rocks or lava, only organisms that absorbed carbon from the atmosphere in the last 50'000 years or so.

The older the samples, the more difficult it is to get an accurate age because the amount of 14C remaining becomes close to zero and thus the more likely it is that a few atoms of 14C from sample handling or atmospheric exposure may significantly change the number. That is why, for instance, coal contains trace amounts of 14C.

More generally, sample age does not always correlate with sample depth and it is strongly dependent on the geological setting. In a sedimentary basin, deeper rocks are older than shallower rocks but tectonic activity such as thrust faults and folds can upset this relationship.

In granitic and metamorphic terranes, there is no general correlation of age with depth, because granites intrude into older rocks


How Can Adjacent Parts of an Oceanic Plate be Subducted in Different Directions? It is claimed by some that the reason for gaps in chains of volcanoes generated by plate subduction is that some parts of the plate dive deep into the mantle and generate magma plumes, while other parts of the plate continue in an almost horizontal direction and therefore don't create magma plumes, hence the lack of volcanoes. Where one part of a plate continues almost horizontally while an adjacent section is driven down into the mantle, wouldn't that cause a violent fracture of the plate, and if not, why not?

Push a sheet of cardboard along a table top so that the leading edge of the cardboard overlaps the edge of the table, then grab a bit of cardboard and force it to descend. It will either carry the rest of the cardboard down with it, or it will break. I know that plates are not made of cardboard, but that's the best analogy I could think of to illustrate the principle. A similar fracture in an oceanic plate would surely be quite violent.

Where one part of a plate continues almost horizontally while an adjacent section is driven down into the mantle, wouldn't that cause a violent fracture of the plate, and if not, why not?

In case of the Nazca plate probably not because that is still warm and partly ductile (see the linked work in the other thread). Also, these cracks and deformations happen as the plate subducts, they don't displace a huge pile of material in one single event, like does a movement along a transform crack (e.g. San Andreas), or a "megathrust" earthquake along a subduction zone. A whole plate breaking along the bend line otoh can trigger catastrophic earthquakes.

I could not find a specific work that deals with the interface between a steep and a shallow subduction, but a work discussing the dynamics of the Nazca plate subduction. They state that the ridges (being warm and buoyant) are subducted because of the movement of the adjacent slabs (dragged along so to say), and becaue of global plate motion, meaning the earth can't change volume so some parts just must give way for emerging parts elsewhere (Atlantic opening is mentioned). There is a map of epicenters of (generally low mag) earthquakes (and links to other work) along the Nazca subduction as well as above the flat segments, suggesting that the cause there is the greater friction. The oceanic crust, being quite topographic, is flattened while being pushed or drawn under the continent.

Earthquakes because of segmenting as asked in the OP aren't mentioned specifically.

I find it interesting, maybe someone else knows more.


Are there any high-resolution urban CO2 concentration data sets? I gather that higher-than-ambient CO2 "domes" can form above urban areas, enhancing other local air pollution. Are there papers or datasets of average CO2 concentrations down at ground level (say 0-20 metres upwards from the ground), in the spaces between buildings - streets, parks and so on?

From what I've read, CO2 concentrations at higher levels are more temporally stable, but understate concentrations across the city; whereas monitoring stations down at street level give representative concentrations for that specific place, but are temporally highly variable, and comparisons between sites suggest that they are spatially highly variable too.

Are there papers or datasets of average CO2 concentrations down at
  ground level (say 0-20 metres upwards from the ground), in the spaces
  between buildings - streets, parks and so on?

Yes, THE URBAN CO2 DOME OF PHOENIX, ARIZONA has measurements at a height of 2 meters above ground level, 1.6 km horizontal resolution. CO2 concentrations are 555 ppm near the center of the city.

An intensive two-week study of an urban CO2 dome in Phoenix, Arizona, USA has higher resolution data along selected transects.


Farthest point from the center of the Earth At first glance, this seems like such a simple question of "What's the highest point on Earth".  However, I also know that the Earth isn't perfectly round.  So that "highest point" may be in a relative valley.

Also, because it's non-spherical, the "center" may not be easily obvious either.  So, I'm curious if there are different answers based on different definitions of "center" (such as geographic center versus center of mass).

So, what is the point on the Earth's surface farthest from the center of the Earth?  Is this different based on different definitions of "center"?

It's Chimborazo, Ecuador, but only just, beating Huascarán, Peru, by less than 50 metres. Both are over 2 km 'higher' than Everest.

I made a plot of some mountains — height above centre of the earth vs absolute latitude. You can download the IPython Notebook source code here. Warning: v. hacky.

I can't find anything on the position of the centre of the earth. The formula I used for the latitude-dependent radius requires major (equatorial) and minor (polar) radii, but I don't have citations for them either. Argus in his article Defining the translational velocity of the reference frame of Earth gave some numbers for its temporal variance, but I have no idea how this might affect these mountain heights.

Last thing: Apparently, the floor of the Arctic Ocean is the closest point on the surface to the Earth's center (about 6353 km, 30 km 'below' Chimborazo), if you call the bottom of the sea the 'surface'.


Why do some planets have lots of $\mathrm{N_2}$ and others none? Earth, Titan and Venus all have large amounts of $\mathrm{N_2}$ in their atmospheres. (In the case of Venus it's a small proportion, but Venus' atmosphere is very thick, and the total mass of $\mathrm{N_2}$ is greater than Earth's.) However, other planets and moons, and Mars in particular, have hardly any. Why is this?

$\mathrm{N_2}$ is a relatively light molecule, so I suppose it could be lost to space from smaller bodies. Did Mars start with a thick nitrogen atmosphere and then lose it? Or alternatively, is there some process that produced lots of $\mathrm{N_2}$ on Earth, Titan and Venus, which didn't occur on Mars or the other outer Solar system moons? If so, what is this process likely to be?

For Earth, Titan and Venus, I think there are continuing processes that are providing $\ce{N2}$ to the atmosphere of these planets.

Concerning the Earth, there is the well documented Nitrogen cycle based on flora.  There are also other significant sources for nitrogen from inorganic processes.

Deep crust/mantle core sources for nitrogen: Nitrogen solubility in mantle minerals
Volcanic eruptions : Volcanic gas
Metamorphic processes : Anomalous nitrogen isotopes in ultra high-pressure metamorphic rocks from the Sulu orogenic belt: Effect of abiotic nitrogen reduction during fluid–rock interaction

Assuming the rock processes on Earth are also occurring on Titan and Venus, similar inorganic processes may be occurring on other worlds. I think it is a good educated guess even though we really have very very little hard evidence of rock processes other planets.

As for Mars, its thin atmosphere may indicate that is cannot hold onto $\ce{N2}$ and there may be very little $\ce{N2}$ currently being created on Mars.


Are beaches found all along the coast? If not, what is required for them to be formed? Why are beaches not found all along the coast?
If not beaches,  what else can be found along the coast.

Not all coastlines have beaches. Some have cliffs, such the Great Australian Bight, which forms a significant part of the southern coast of Australia. The limestone cliff portion of the Bight is over 1000 km in length and between 60 and 120 metres in height.

Similarly, in the Otway region of the Australian state of Victoria forested hills form the coast in regions. As can be seen when travelling along the Great Ocean Road.

In Western Australia, the Zuytdorp Cliffs form 150 km of the coast. Like the Great Australian Bight, these cliffs are formed formed of ancient limestone. Some of the cliffs rise to 170 m in height.

Additionally, many of the fjords of Norway and Fiordland in New Zealand also have coastlines without beaches, where hills & ranges meet the sea.

Beaches are only formed when land gently slopes into the sea. They

  typically occur in areas along the coast where wave or current action deposits and reworks sediments.

The sediments can be sand, pebbles, or biological materials such as shells and coralline algae.

In addition to forming on ocean coastlines, some beach for on lake shores.


Lights associated with earthquakes? According to the New Madrid, Missouri web site, during the 1811-1812 earthquakes there were reports of lights coming from the ground due to quartz crystals being squeezed.  They call this phenomena “seismoluminescence.”  There are also videos online taken during the 2017 Chiapas, Mexico earthquake showing strange lights in the sky.  Lights have been reported associated with numerous other earthquakes throughout history.

Is there any research that has been done to either prove or disprove that these reported lights are actually being caused by the earthquake, and if so how are the lights created?

I am not too much into the subject, but it is a curious phenomenon indeed.
There is a recent publication in Scientific Reports (Enomoto et al., 2017) where a group of scientists performed some lab experiments and reported:

  CO2 gases passing through the newly created fracture surface of the rock were electrified to generate pressure-impressed current/electric dipoles, which could induce a magnetic field following Biot-Savart’s law, decrease the atmospheric electric field and generate dielectric-barrier discharge lightning affected by the coupling effect between the seismic and meteorological activities

If you want to read the full paper you can search it with this reference:

Enomoto, Y., Yamabe, T., & Okumura, N. (2017). Causal mechanisms of seismo-EM phenomena during the 1965–1967 Matsushiro earthquake swarm. Scientific Reports, 7. doi: 10.1038/srep44774.

It is open access.


How can we accurately quantify the degree of scientific certainty that global heating is caused by humans? How can we accurately quantify the degree of scientific certainty that global heating is caused by humans?

It seem virtually certain that the huge 100 ppm spike in $\small\mathsf{CO_2}$ since 1950 can only be caused by humans. Can we be as sure that this huge spike in $\small\mathsf{CO_2}$ caused the 1 $\small\mathsf{^o}$C increase in global temperatures as we are that tobacco causes cancer?

Do validated alternative explanations exist?

What kinds of objective measures are typically used to determine the specific degree of scientific certainty?

There is a trend showing an increasing slope in the following graph data
1910 to 1960---0.41---50 years / 0.41 = 122 years per degree
1960 to 2018---1.03---58 years / 0.87 =  67 years per degree

https://data.giss.nasa.gov/gistemp/graphs/graph_data/Global_Mean_Estimates_based_on_Land_and_Ocean_Data/graph.txt

I am trying to point out exactly how implausible global heating NOT CAUSED BY BY HUMANS really is to skeptical minds that are not very good with science.

There are a few ways

Basically the best way is to see how many experts in the field are convinced, as great as it would be to assess the evidence individually, one person can't be an expert in everything and unless you and your audience are a climate scientists most papers are going to be beyond a lay assessment. So the best thing you can do for the lay public is look to the experts, people who have spent decades researching the subject and have the best ability to assess the data, and see what their assessment is.

NASA has a wonderful site dedicated to collecting assessments. They fall into three rough categories.

Meta analysis

A meta analysis of published works shows the number of scientific papers rejecting anthropomorphic climate change is vanishingly small (0.7%) and shrinking. those uncertain was even smaller (0.3%)

Professional survey

the same analysis also surveyed 29,000 published climatologists and showed a 97% support for anthropomorphic climate change and the rest being largely no-position. this is even skewed by expertise, when accounting for the number of published papers (a rough way of measuring expertise) it shows even stronger support among more published authors with most of the opposition being from authors that only publish a small number of papers.

Public statements by relevant scientific societies.

The American Meteorological Society and Geological Society of America as well as many others have made public statements in favor of anthropomorphic climate change. And of course you have the statements by the Intergovernmental Panel on Climate Change.


Acoustic impedance in geophysical context What is the intuition behind acoustic impedance? Yes, I know that it is the opposition to a seismic wave travelling in the medium. But why it is defined as density × velocity?

The velocity of a seismic wave depends on density, so why not use only the velocity contrast or density contrast between layers instead of the impedance contrast?

This concept actually comes from the electrical. They define the impedance as $Z=\frac{V}{I}$.
Where V is potential difference/ voltage and I is current.

In acoustics, a similar expression can be obtained using the plane wave equation.
Since,
                $$\partial_t V = -\rho^{-1}\partial_xP$$
where $P$ is pressure and $V$ is velocity.
Now take fourier transform of both sides and defined impedance as $$Z(\omega)= \frac{P(\omega)}{V(\omega)} = \rho c$$
Where, obviously, $P$ is analougous to potential difference and $V$ is analougous to current.

You may refer to any wave theory book for details.


Non-invasive techniques to find rock composition If we had access to a totally new kind of rock (maybe a new meteorite), is it possible to tell what the rock is composed of without touching it / drilling into it?

I'm thinking of something like firing sound waves or some kind of electromagnetic radiation at it and seeing what emerges from the other side.

Are there any techniques like this in geology?

You are looking for a portable XRF.

It does (almost) exactly what you said. It sends electromagnetic radiation to the rock (X-rays), which excites electrons in the atoms and when they bounce back they return X-ray of different energies which are detected by the instrument. It looks like this, for example:

Using the different peaks you can figure out what the rock is made of.

This is not as good as lab-based XRF, but it's so easy to use it's now standard practice for exploration and mining geologists to use it.

Note that this will only give you surface information. It analyses what it can see. If you want to know what is inside the rock, you have to drill or break it.

If you want to know what is inside the rock without breaking it, you can use a CT scanner, but it only gives information on density. Inferring what the material is based on its density can be a challenging task and it is made easier if you have pre-existing information on what it could be. There are no portable CT scanners however (at least not hand-held). They can me mounted on trucks though.

There are other methods, such as infrared, Raman, LIBS, etc etc.

The Mars Curiosity Rover has quite a lot of those instruments on board. It is essentially a semi-automated geologist exploring another planet.


What would happen if we could revert $\mathrm{CO}_2$ production but took it too far? So recently, scientists managed to produce fuel basically out of thin air (water, air and sunlight).

And in a discussion I had with a friend, the question came up, what would happen if you took that idea too far?

Say you could build an air-to-fuel plant large and efficient enough to take CO2 out of the atmosphere faster than all the things we currently do to increase CO2 levels add it in.

What would happen? First of all, how far could you realistically even take this: Would it be possible with the used process to go all the way down to 0 atmospheric CO2 (or at least approach this arbitrarily closely)? And what effects would this have on the environment?

I immediately had three ideas that could happen but I wonder how realistic those would be:

Average temperatures would drop (inverse Greenhouse effect) (but how far?)
Plants would eventually be unable to produce sugar through photosynthesis and die off
Instead of acidifying, oceans would become increasingly alkaline. Lime might drop out of the oceans rapidly which could, perhaps, have cancer-like effects on coral reefs and anything that heavily depends on lime.

And besides those, are there any other obvious notable effects?

The average global warming due to greenhouse gases corresponds to a 33 Kelvin temperature increase.  If you remove all greenhouse gases the average global temperature would then decrease 33 Kelvin (from 288K to 255K).

You might want to check out:
http://www.nasa.gov/topics/earth/features/co2-temperature.html
 which estimates the CO2 portion of global warming to be about 80%.

  "... it is the 25 percent non-condensing greenhouse gas component, which includes carbon dioxide, that is the key factor in sustaining Earth’s greenhouse effect. By this accounting, carbon dioxide is responsible for 80 percent of the radiative forcing that sustains the Earth’s greenhouse effect."

Simple math might suggest then that the average global temperature of Earth would be ~262K if CO2 were completely removed.  There are always sources of CO2 though, so you could never remove it all as it is constantly being replenished when animals breathe and things burn.


Does the Coriolis Effect affect a wind from East to West? I'm studying meteorology for a pilot license and there I was taught as a rule of thumb that wind at higher altitudes is approximately turned 30° clockwise to the wind on the surface due to the Coriolis Effect.

The explanation I got is that if an air parcel moves e.g. towards the pole, it started with a higher velocity around the earth's axis than the destination point has, so it will arrive ahead of the destination point on the earth's surface.

While that totally makes sense for winds e.g. from south to north, or the other way round - why does the Coriolis effect also impact a wind that's blowing exactly from East to West? Shouldn't the origin and the destination of that wind have the same speed around earth's axis and therefore no Coriolis force should act on the wind?

There have been a number of answers here that answer slightly different questions. As I understand it the question is "Why does the Coriolis force apply to objects (or air parcels) moving east and west, as well as those with a north/south component?"

It's a good question. The common intuitive explanation of the Coriolis effect, which you describe, considers only the horizontal forces acting on an object. That isn't quite right. This diagram adds two more forces that matter:

The arrow marked "g" is the force due to gravity, and is directed towards the centre of the planet.
The other arrow represents the centrifugal force that results from the earth's spin. Notice that it does not directly oppose gravity, but instead acts away from the earth's axis of rotation. In the absence of aerodynamics, buoyancy, etc, the vertical components of these forces must cancel out so that our particle maintains its altitude, but there is a resultant horizontal force towards the equator.

Let's assume that our red dot is stationary with respect to the earth's surface (the horizontal component of the centrifugal force must be balanced by something else). If the red dot accelerates to the east (away from us), meaning that its angular speed around the axis of rotation of the earth is increased, then the centrifugal force will increase, while the gravitational force will remain (very nearly) the same. Thus it's no longer in equilibrium. This has two effects: the vertical component of this is a force upwards which I believe is known as the Eötvös effect, and the horizontal component is a force towards the equator (a right turn in the northern hemisphere), which is Coriolis.

Similarly if the dot accelerates to the west (towards us), its angular speed decreases, the centrifugal force decreases, and it is pushed down and away from the equator (a right turn in the northern hemisphere).


Insert points into a 2d grid I have a list of single point values that I want to insert into a grid.

point_values = [1, 4, 5, ...]

point_lats = [-12.101, -12.1023, -12.1031, ...]

point_lons = [155.511, 155.520, 155.533, ...]

the grid latitudes and longitudes are currently in 2d arrays of 2030 x 1350

latitudes = array of shape 2030 x 1350 of latitudes

longitudes = array of shape 2030 x 1350 of longitudes

how could I insert the points into the 2D grid if a point falls within the grid boundaries?

Technically, this is a mathematical modelling problem. You just happen to be using earth science data - satellite LIDAR readings.

Ore reserve geologists constantly deal with this, but in three dimensions when they are required to create a block models of a geological deposit from drill hole data.

Scientific fields that use 2D data would include: forestry, meteorology and ground contamination studies looking into pollution effects of smelters.

Methods you need to consider are Inverse Distance Weighting and possibly variography and kriging. Variography and kriging are elements of geostatistics, also known as the Theory of Regionalized Variables.

With inverse distance weighting, the distance variable is usually raised to a power n, i.e. ${1/d^n}$. Choosing the appropriate value of $n$ is the tricky part. When geologists used inverse distance weighting, prior to primary using geostatistics, typically the value of $n$ used was 2, but values between 1 and 3 have been used for different deposits.

Given that you are using two dimension data, you may need to use GIS software or other modelling software that offers grid interpolation methods, such as I have mentioned to achieve what you want.


What are these Gizmos at Mauna Loa Observatory? Artist Rosten Wu's Vimeo channel has a video title Bridging Time and there is discussion about the Keeling Curve and the site where it all began in Hawaii.

In the video there is a shot of a weather observation station (shown below), and I'm assuming this is Mauna Loa Observatory where these accurate and systematic measurements of CO2 began.

In the foreground there are several gizmos and I was wondering if someone can identify them.

I've included a cropped section, sharpened it a bit, and added annotations A, B, C below the three types of instruments that caught my eye.

I am going to take a guess here because I have not used these instruments in real life but given the content of this Mauna Loa Observatory I Exploratorium video - fast forward the video to 3:43 and see the yankee name on that instrument.

Then I did a google search on that and got this link - Yankee list of products

So A is a Pyranometer and B is a  Ultraviolet Multifilter Rotating Shadowband Radiometer. I am not too sure on C and it probably is a actinometer. You can take a look of that here - Actinometer

The respective data sheets give information on both of those products.

1) Ultraviolet pyranometer

As this AMS glossary definition mentions a pyranometer measures both direct solar radiation(radiation that has not been scattered or absorbed) as well as diffuse sky radiation(radiation that is scattered)

Specifically this ultraviolet pyranometer measures both UV-B and UV-A rays.
This link covers the difference btween UV-B and UV-A rays. Specifically UV-A rays penetrate deeper into the skin than UV-B rays.

2)  Ultraviolet Multi-Filter Rotating Shadowband Radiometer

This one measures the diffuse and total global irradiance and computes direct irradiance at four or seven narrow bandwidth wavelengths(hence the term multi filter). One can see real time data for sites across the US  at this site - UV-B monitoring

3) Originally I thought C was a actinometer but when I look at this image Downwelling SURFRAD instruments I am going to say it is a LICOR PAR sensor(PAR is  Photosynthetically active radiation). The reason is because of the instrument inventory provided in this URL - SURFRAD BOULDER CO. If you notice in the NOAA ESRL image there is an instrument that  has a shape of a long column(in grey and to the right of the black colored instrument that is actually a MFRSR) that looks very similar to OP's C instrument.

You can now guess why that observatory has these set of instruments. It is at an altitude and that is a good place to study effect of Solar irradiance(less pollution)


How acidic waters make rocks disappear? I was working on this science project.

I was on step 11, day. 4. Since day 2, I found out that my pH and the mass of the rock (limestone) stopped changing. This project should proves acidic water makes rocks disappear.

I think I did something wrong. Did I?

First of all, the rocks do not disappear they dissolve, so they are still there only dissolved into the liquid.

You are using an acid (vinegar), this has a low pH.

The rocks you are using (limestone) they have a high pH (alkaline).

The alkaline rock you add to the acid will dissolve but only until the acid is neutralized. The reaction stops when the pH reaches close to 7,0.

If you had used less limestone or more vinegar the rock will be fully dissolved but the pH of the liquid will stay low. To neutralize the vinegar you must then add more limestone.

So you did nothing wrong except maybe using too little acid.

I will stop my answer here, but if you had taken this reaction one step further you would have made marble (the bubbling you might have seen was carbon dioxide CO2).


If the accuracy of measurement of the earth's volume is not known, how can scientists assert that the earth is not expanding? Volcanic eruptions, undersea earthquakes, fissures in the crust, meteoroid accumulation could all be seen as empirical evidence of expansion of the earth. Sink holes and other phenomena could be contrary evidence. Subduction of crustal layers and changes in the earth's rate of rotation could be cited as evidence one way or the other. But the net effect, if measurable at all, might well fall within the range of inaccuracy of the earth's volume estimate.
Moreover, nuclear fission produces elements of lesser density. Could this process not produce a reduction of density in the mantle, and hence provide a mechanism for expansion of the earth?
I realize that the effect of these factors, although large on a human scale, may well be tiny when compared to the total earth volume.
Nonetheless, whatever the measurement or estimate of these factors, how can their effect on the earth's volume, over eons, be considered insignificant, if the accuracy of the total volume of the earth is not known to a degree of certainty?

In short, the current volume of the earth is known to great precision and modern measurements show no significant expansion at meaningful scales.

Facing 20th century evidence that points on the globe -- such as the edges of continents -- that are now distant from each other were once adjacent, some scientists argued that the only explanation was the ongoing expansion of the earth's surface. That argument collapsed by the 1960s, as overwhelming evidence accumulated for the theory of plate tectonics -- that is, roughly, there are relatively rigid continental plates that move across the surface of the earth, with the ocean floor between them created at the mid-ocean ridges and destroyed by subduction under the continental margins. Broad calculations showed that the volumes of the two processes were close enough to cancel each other out.

In the modern era dependent on the accuracy of satellite positions for GPS, sea-level rise measurement, and other detailed geodetic measurements, there was a need to resolve the question of whether the earth's volume was changing in a more conclusive and precise way.

One of the studies that addresses that is the 2011 paper Accuracy of the International Terrestrial Reference Frame origin and Earth expansion, published in Geophysical Research Letters, a journal of the international American Geophysical Union. Most of the paper discusses the technical processes and calculations, but it concludes:

  A possible secular change in the mean radius of the solid Earth has
  long been suspected from various scientific disciplines. The problem
  was not settled due to lack of a proven theory and the inherent
  difficulty in actually determining such a change. By using the data
  combination and the simultaneous global inverse approach, the issue of
  aliasing from the geophysical processes due to network sparseness is
  largely overcome here. In fact, our uncertainty in the mean expansion
  rate determination is dominated by an ITRF [International Terrestrial Reference Frame ] scale drift uncertainty of
  0.16 mm yr−1 estimated from comparing VLBI [Very Long Baseline Interferometry] and SLR [satellite laser ranging]. In conclusion, no statistically significant present expansion rate is detected by our
  study within the current measurement uncertainty of 0.2 mm yr−1.


Does ground-to-cloud lightning create crystals as well? I've read that cloud-to-ground lightning can create fulgurites.  Does ground-to-cloud lightning also create crystals within the earth as it surges  through the minerals?

I would assume that any lightning bolt connecting to the ground would be capable of producing a fulgerite in the soil, regardless of the direction that the bolt "flows". Fulgerites are caused by the extreme heat of the lightning bolt, which fuses the soil (sand mainly) together into a type of glass. Since the extreme heat of a lightning bolt also causes the sound of thunder, it's safe to assume if you hear thunder from a ground to cloud strike, it can also cause a fulgerite.

Most ground to cloud lightning seems to flow from the highest points of very tall objects, such as sky-scrapers, radio towers, etc. Since the best fulgerites are formed in sand, it may be very hard to find a fulgerite caused by ground to cloud lightning. Perhaps on a sandy mountain peak?


Why does climate change generate desertification? According to IPCC:

  Climate change can be a significant driver of desertification and land
  degradation and can affect food production, thereby, influencing food
  security.

  Source: IPCC

My concern is if greenhouse gasses increase the temperature, there is more evaporation, so more clouds, so more rainfall.

Why does climate change generate desertification instead?

Most arid and semi-arid regions are normally far inland. Often those also have terrain features that don't allow for the moist air to reach, such as mountain ranges, etc.

So now if global temperatures increase, the evaporation in semi-arid regions increase as well, reducing the amount of water available for plants. At the same time moisture coming from the ocean still precipitates as rain before reaching those regions.


Not able to open .f000 file formats in pygrib I've been working with GFS data in Python using pygrib, and have been able to download and process data stored in .grb and .grib2 file formats from the NCEP archive ftp site. When I switch over to try to open grib files from the real time analysis, however, I'm not able to. I've tried downloading manually and changing the ending of the file to .grib2 and .grb, but neither has worked. Here's the ftp site that I'm trying to access for reference: http://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.2017061300/

Figured out my error: I was assuming that I needed to alter the filename endings / type in order to save as a genuine .grb or .grib2 file. The files are already in grib2 format despite the ending in .f000 so you should be able to leave them as that.

My other error was not double checking the exact filename and path when dealing with multiple grib files across the GFS datasets. Some have slight differences in the naming convention, and when loading on pygrib it will throw the same generic "import error" as if the file couldn't be read.


What is the mechanism for deep-sea volcanism of the Gakkel Ridge in the Arctic? Related to an earlier question, What is the geochemical source for the helium detected in deep Arctic explosive eruptions?, where it is stated in the linked article that there is evidence of explosive volcanism deeper than 3km depth - the evidence coming from both seismic and petrological observations.  The article Hotbed of Volcanic Activity Found Beneath Arctic Ocean suggests that, as the article title alludes to, that the region has many hydrothermal vents and explosive centres.

These types of eruptions are not thought to be able to occur at depths greater than 3km, according to the article Arctic Volcanoes Found Active at Unprecedented Depths.

What is the mechanism for deep-sea explosive volcanism of the Gakkel Ridge in the Arctic?

There is some considerable uncertainty as the exact mechanisms. However, the recent seismicity and pyroclastic deposits detected around the ridge provide a unique opportunity to observe and model the baheviour of ultraslow spreading ridges.

According to the article Explosive volcanism on the ultraslow-spreading
Gakkel ridge, Arctic Ocean (Sohn et al. 2008), to overcome the pressure of the seawater, it becomes a question of the amount of volatiles (particularly $\ce{CO2}$ available in the magma chamber to cause fragmentation resulting in the glassy pyroclastic deposits observed around the volcanic centres on the Gakkel Ridge.

Sohn et al. hypothesise that the ultraslow spreading nature of the Gakkel Ridge would cause long intervals between volcanic events, which in the article, Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85°E (Pontbriand et al. 2012) suggest to be around 10,000 years.

The long interval times allow for the accumulation of large volumes of volatiles in the upper part of the magma chambers. These would erupt periodically when the pressure in the magma chamber exceeds the deep sea-water pressure.  Models from Sohn et al. suggest that a weight fraction of 14% $\ce{CO2}$ (~75% volume fraction) would be required - a value considerably higher than those measured at most mid ocean ridges.  Pontbriand et al. estimate that $\ce{CO2}$ supersaturation in the magma chambers of the Gakkel Ridge to occur around 1500-2000 year timeframes (i.e. well within the estimated volcanism interval).

Pontbriand et al. go further and suggest that one of the most important implications of the observations (and modelling) of explosive volcanism on deep-sea ultraslow spreading ridges challenge the hypothesis that eruption volume varies inversely with mid ocean ridge spreading rates.


Is the Arctic sea ice volume increasing? According to the graph below, Arctic sea ice volume has been decreasing from 1979-2012:

Though this graph from the ESA’s CryoSat satellite show that the volume of Arctic sea ice increased 50% from 2012 to 2013:

What is the explanation for the difference accounts of Arctic sea ice volume trends?

This question has already been answered on Skeptics.SE:

Did the Arctic Ice Sheet grow by 60% from 2012 to 2013?

The short answer is that those two graphs are consistent with each other. The first shows a 33 year trend of declining Arctic sea ice (summer minimum, I think), whereas the second highlights inter-annual variation in Arctic sea ice over the last four years.  We don't expect long-term trends to be strictly monotonic increases or decreases, so both positive or negative year-on-year differences, such as those between 2012 and 2013, can be consistent with the trend.


What is the lateral ground acceleration, at the fault line, during a strike-slip earthquake? I've read that peak lateral ground acceleration for magnitude 7 - 8 earthquakes is ~1 g at the epicenter (is that correct?), but I'm wondering if it might be significantly higher right at the rupturing fault itself. This paper compares theoretical models of this motion but, in scanning through it, I didn't find any empirical measurements:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JB009097?fbclid=IwAR0yy3vmLouk8jNz8FlIqPddj-HA4Npyh6rHQSS_qZ12aR29aM2jkkqK1EU

What is the approximate range of lateral ground acceleration (and peak velocity), as a function of earthquake magnitude, right at the fault, for strike-slip earthquakes?

It can be high but is bounded because the slip velocity on fault (as it slips during an earthquake) is usually of the order of 1-3 m/sec.

Kaikoura earthquake (M7.8 strike slip event) had a max PGA of 3.1 g (second highest ever recorded) but it is attributed due to flapping effect. See here for more details.


Does the global temperature vary daily (hotter and colder days)? Earth's current average global temperature (i.e. including hot deserts and cold polar caps) is reported be somewhere between 14°C and 16°C (depending on sources and methods).

This temperature varies on a long-term basis due to climate change.

But does it also vary (substantially) on a daily basis ?
I.e. are there hotter and colder days (worldwide) ?
Or is it exactly the opposite, namely a zero-sum game: A hotter-than-average day in – say – Australia inevitably goes along with a colder-than-usual day somewhere else on the planet to make up for the difference, so that the global temperature stays the same from one day to the next (because energy is not created but only transferred from one region to another) ?

As an example, below are the relative temperatures (i.e. colder/hotter than expected/average) for 3 Feb 2014. Would the hotter and colder temperature regions balance out (compensate one another), so that the global temperature on 3 feb 2014 is the same as on 2 feb 2014 and 4 feb 2014 ?

source: https://robertscribbler.com/2014/02/03/arctic-heat-in-winter-february-2-temperature-anomaly-hits-13-f-for-entire-arctic

(Please note: The image doesn't exactly illustrate my question, because it doesn't depict the air temperature difference between 3 Feb 2014 and the previous day, but between 3 Feb 2014 and the average for [3 Feb, I assume] 1979-2000. So due to global warming, 3 Feb 2014 was obviously warmer than 3 Feb in previous decades – by 0.45°C to be precise, as the sum of northern hemisphere + southern hemisphere = -0.01°C + 0.45°C = +0.45 °C. But my question is not about global warming or long term trends, but daily variations. I just couldn't find a similar heat map depicting temperature differences between one day and the next, so I just took this image for illustration purposes, although it doesn't perfectly relate to the question asked.).

As Earth surface temperatures don't necessarily
correspond to the air temperature (see below), please distinguish both cases in your answer, i.e.:

Can global average Earth surface temperature vary from one day to the next ?
Can global average air temperature vary from one day to the next ?

  Andreas Schmittner, Oregon State University: "It is not the average temperature of Earth that is reported but the average air temperature near the surface (2 m) of the Earth."
  source: researchgate.net/post/It_it_misleading_to_report_the_average_temperature_of_the_Earth

I would appreciate if your answer included both a source for your claim AND an explanation (i.e. WHY the global temperature can or cannot vary on a daily basis).

The best answer would include a diagram or table of global average air and Earth surface temperatures for any given month, since this couldn't be argued with.

Example:
+-----------+--------------------------------+----------------------+
|           | avg. global Earth surface temp | avg. global air temp |
+-----------+--------------------------------+----------------------+
| 01 Feb 14 |           15.1 °C              |       15.2 °C        |
| 02 Feb 14 |           15.1 °C              |       15.3 °C        |
| 03 Feb 14 |           15.1 °C              |       15.7 °C        |
| 04 Feb 14 |           15.1 °C              |       15.2 °C        |
| 05 Feb 14 |           15.1 °C              |       15.1 °C        |
|   ...     |            ...                 |        ...           |
+-----------+--------------------------------+----------------------+

tags: thermodynamics

The site http://www.karstenhaustein.com/climate.php comes closer to answering your main question with a daily anomaly graph:

Indeed it's still not the actual average temperature... and I was quite interested to see if there are annual global fluctuations in global mean temperature.  Surprising how much focus is on anomalies, but how little most sites note the mean temperature itself.  But eventually I found NOAA's monthly global climate reports, and was able to piece together the "globally averaged temperature over land and ocean surfaces" for each month and put together this graph:

(One trouble to point out in global totals such as these require the whole globe... so observation of the full far reaches... but we still have a somewhat limited surface observation networks in spots, and each satellite can only see a portion of the globe at one time, and all it's put together by varying data assimilation methods, so there will be some limitations\variation in any global estimates of it [as you can see later down that Karsten Haustein's page in the section comparing CFSR-GFS, NCEP reanalysis, and GISS temperatures])

But Karsten's graph above and all the other plots from their site are useful in showing real-time and the past that there are definitely some real oscillations day-to-day, but also that there is indeed quite a bit of stability whereby large regions of hot temperatures will tend to be balanced quite a bit by reduced temperatures elsewhere.

This conceptually would seem to make sense to me, as in the end the guiding framework would be that the energy put into the Earth system (by solar radiation) must equal the energy coming out in the long run.  That in itself wouldn't prevent fluctuations in the radiating temperature/energy sent out to space (related example: if you put your food in the oven, it takes in some of the energy, radiating less than it receives, and thereby gaining temperature until it gets up to temp).

This is one reason I should expect the global average temperature as a whole does shift some through the year: because water changes temperature more slowly than land, and the NH and SH have different coverage, there should probably be differences/lag in temperature and energy absorption/emission depending upon which portion of the Earth is receiving more sunlight.  Additionally, while the sun's energy is very constant, and the tilt only changes which region receives the energy but not the total amount incoming, there will actually be some overall change in how much energy we get into the lower parts of the atmosphere/to Earth's surface globally day-to-day and over longer periods due to variation in how much snow, cloud cover, and aerosols absorb/reflect some of the energy before reaching near the surface.

Overall, this would make sense to see a global peak in July (NH summer), when both more of the "warm Hemisphere" receiving increased energy is land, and more less of the "cool Hemisphere" is land able to hold snow cover.

When it comes to any specific layers within the Earth system, be it the surface ground/water, or the atmosphere at 2 meters above the ground, or any other height for that matter, I'd expect the answer would likely be the same: there is some fluctuation both daily and seasonally.  It's indeed not a zero-sum game because of the variations in the makeup of the globe.  But because the overriding principle is net energy balance of the Earth, those daily/seasonal changes are likely kept to a few degrees tenths of a degree in the short-term and a few degrees Celsius innerannually.
The ground/ocean are the primary heat source of air near the ground (air itself doesn't absorb much solar energy).  So generally fluctuations in global average air temperature (at 2 meters) should connect very well to changes in global average ground/water temperature... though differences in heat capacity and absorption spectra between air/soil/water/etc likely cause the sizes to be different, and probably small differences in the synchronization as well.  But overall, they should have very similar patterns.


Phase relation for mantle? I have information about temperature, pressure, normal and shear stresses, viscosity, conductivity, density, heat capacity and adiabatic heating for a particular area of mantle in the form of 2D matrices. I want to show phase relation for this region of mantle. Is there an equation (group of equations) which relates phase relation for mantle with these properties?

Perple_X (http://www.perplex.ethz.ch/) is software designed to do exactly that.

It has thermodynamic and mineral property databases for phases in interest. This is pretty much automation of method 3 given by the other answer.

In short, the way it works: you input your bulk composition, pressure, and temperature, and it spits out the phase relations.

A bit of warning: this software is very poorly documented with many tutorials and guides referring to older version that don't work exactly like the new one. I recommend going on their discussion forum which is very active, and the developer himself is commonly there. He is usually very responsive and can fix bugs pretty much on the spot (time-zone constraints permitting).


Did the Neolithic Revolution have an effect on the earth's climate? I imagine that human agriculture had a major effect on the composition of flora across the planet's surface.

Did the transition from gathering to growing have a measurable effect on climate? If so, what was it?

Raising herd animals would likely contribute more than mere farms.  Many farms simply produce feed for animals anyway, and this can lead to an inflated population which can wreck havoc when released in the wild to graze.  That said, with the exception of Egypt and a few rare cases, every agricultural society eventually failed because they could either could not keep up with the deposits of silt clogging their water works, or they could not contend with the the rising salinity of soil, caused by prolonged irrigation.  The evaporation of water leaves behind an excess of mineral salts, and eventually a field's production drops and the desert takes over.  The usual method people employ to contend with these issues is to build more canals and irrigate more land elsewhere.  So for a few thousand years agriculture societies have been converting land to desert and this no doubt this would have effected the climate.  But probably only a scant iota when compared to the last 100 years of agriculture . . .


Where can I find a list of snow fall recording stations in my zip code? Where can I find the locations on snow fall recording stations in a particular United States county or zip code? Is there a way that I can find an hour by hour recent history of snow fall? Hour by hour for the last 7 days would be interesting but even the last 24 hours would be very helpful. I need to to know where and when to dispatch crews to remove snow from office and apartment buildings, often in the middle of the night when I don't have eyes on the ground.

I may have to resort to installing web cams so I can personally review the conditions remotely.  The lake level stations are so accurate and easily accessible, I thought they might have sometime for precipitation as well.

I would prefer reports in inches of precipitation rather than inches of snow, but either would work. I find the former to be more accurate for my needs. It's the amount of water that needs to me moved that matters, no matter if it is densely packed or loosely packed.

Were to find hourly data will depend on your location, as you will probably need to access the national weather network of the country of your interest. Global climatic databases usually record data on daily basis. Like the Global Historical Climate Network, you can search for all the station in that network and query snowfall data in the KNMI Climate Explorer. This is a example query of all the stations between 50 and 51° North and 120 and 122° West (to convert ZIP codes to coordinates you can use geocoder or other similar services):

It returns 39 stations, each one with a record like this:

And you can also download the raw data.


How likely is Earth to naturally reverse climate change in the next 2 decades? A new decade question: given that the “mini ice ages” were triggered by volcanic activity, how likely is it that we will experience similar levels of volcanic activity over the next 20 years?

In other words, if earth is capable of naturally saturating atmosphere with cooling sulphates, how likely is it that another series of such events will reverse climate change?

Bonus question - can such event be forced through interference with volcanic regions or tectonic plate seams?

Very unlikely, especially as the major industrial nations will come nowhere near to meeting their greenhouse gases emission targets. Major volcanic eruptions, like major earthquakes, are random and unpredictable. The last really big volcanic eruption we had was Tambora, on the Indonesian island of Sumbawa in 1815. That caused climate cooling for a few years, but it didn't cause a mini ice age. It may have helped the Little Ice Age which was already in progress, to last until the middle of the century, but that's all.

Tambora was the biggest eruption in recorded history, dwarfing Pinatubo, Krakatoa and Thera (Thera erupted in the Med near Crete 3.5 thousand years ago and destroyed the Minoan civilisation), so an eruption big enough to cause another Little Ice Age would probably need to be as large as the Toba eruption of about 75,000 years ago on the Indonesian island of Sumatra. The chances of such an eruption within the next 20 years are virtually nil. The Little Ice Age, which lasted about 400 years and ended about 1850, is not believed to have been caused by volcanic eruptions, though such eruptions may have from time to time intensified it and prolonged it.

There is no way of inducing major eruptions short of detonating 50 megaton hydrogen bombs in sites known to be volcanically unstable, but that would not only violate international treaties about nuclear explosions in the atmosphere but would in any case be unacceptable. Fifty megatons is the world record for thermonuclear explosions, by the way, held by the Russians.


How does vertical wind change over time? My question is about how vertical component of wind may change over time; in particular, as I am interested in simulating the effect of vertical wind on flight mechanics, I'd like to know whether I should consider vertical wind as a deterministic function of time or a stochastic one. Furthermore, should I consider vertical wind persistent over time or having a limited duration (e.g. few seconds)?
Note that I am not interested in horizontal wind.

There are a number of causes, for a variety of scales.
Generally speaking, you can boil it down to convergence/divergence, as a continuity of mass problem, or buoyant motion.

You can refer to the vertical component of the Navier Stoke's equations.
$$
\frac{Dw}{Dt}=\frac{∂w}{∂t}+\vec{v}\cdot\nabla w + w\frac{∂w}{∂z} =-\frac{1}{ρ}\frac{∂P}{∂z}-g+\nu\nabla^2w
$$
Additionally, it must also be constrained by the conservation of mass.
$$
\frac{∂P}{∂t}=-\nabla\cdot(\rho\vec{v})
$$
The Quasigeostrophic Omega Equation may also provide you some insight. This equation is filtered down from the above Navier-Stokes equation, though it may not seem like it. Omega is vertical velocity in pressure coordinates.
$$
(\nabla^2+\frac{f_0^2∂^2}{\sigma∂\Phi^2})\omega=\frac{f∂}{\sigma∂p}(\vec{v}\cdot\nabla(\frac{1}{f_0}\nabla^2\Phi+f)) + \frac{1}{\sigma}\nabla^2[\vec{v_g}\cdot\nabla(-\frac{∂\Phi}{∂p})]
$$


Sun's Highest Point on June 21 Where would you have to be for the sun to be highest overhead at noon on June 21?

Since the rays of the Sun are perpendicular to the Tropic of Cancer on June 21, shouldn't the Sun be overhead in this location at noon?

Well, kind of, depending on what you really mean.

We're being rather vague with our terms, and so it shouldn't be surprising if the answer doesn't meet our expectations.

We could interpret all these terms to conclude that such a situation will only rarely, or even never, happen.
But allowing some reasonable latitude (pardon the pun) in our definitions, we can come up with a reasonable response of "yes".

The Sun can only be "directly overhead" of one spot at a time, where the line between the Earth's center and the sun intersects the Earth's surface. Because the Earth is spinning on its axis and also moving in its orbit,  that spot is constantly changing latitude and longitude.

The Tropic of Cancer isn't a single-point "location" but a circle that stretches around the Earth.

At the exact moment of the summer solstice, the Sun is directly overhead one point on the Tropic of Cancer and one point only. That point slowly spirals down through the tropics until it reaches a corresponding point on the Tropic of Capricorn at the winter solstice. And then it begins the trip back up.

That's what happens in the geometrically-idealized definition of "directly overhead".  We can allow a small tolerance, and as the tolerance gets bigger, the spot of "direct overheadness" spreads out into a disk, which covers more and more of the Tropic of Cancer around the moment of the Solstice, due to the spot's E-W motion being much greater than its N-S motion.

Although the spot's change in latitude over time isn't linear , it's a reasonable approximation for this exercise.  The spot moves about 0.18 degrees north or south in a day, all the while circling the Earth. Around the Solstice it will move 0.09 degrees north and 0.09 south. The Sun's angular size in the sky is 0.5 degrees, so, it's reasonable to conclude that yes, the Sun is directly overhead every point of the Tropic of Cancer at some time around the summer solstice.

(The solstice does't always happen on June 21, but depending on the tolerance, some degree of direct-overheadness will be the situation  for a few days before and after the solstice).

So now, we get to your last two tricky terms: "noon" and "June 21" , which believe it or not are in conflict for this example.

There is a local "noon" (defined by when the Sun is the highest in the sky it can get) and a clock "noon" (defined by your time zone). Only people at lucky longitudes in their time zones get to have them coincide.  But "June 21" is defined by those very time zones.  And so the sun can be "directly overhead" at "noon" on June 21 only around those lucky meridians. Elsewhere the sun will be directly overhead at some time other than noon.


What are the factors that dictate a given topology for seismometer placement around a volcano? The image below (borrowed from [#1]) shows the topology of the seismometers around the volcano Stromboli.

In the text, they explain the following:

  The seimometers were set on the
  flanks of the volcano, forming three rings around the crater
  area at different altitudes (top, middle and bottom ring indicated
  on the map with the letters T, M, B, respectively). The
  distances of the stations from the crater zone ranged from 0.3
  to 2.2 km.

What are the factors that dictate a given topology for seismometer placement around a volcano?  There are probably some obvious rules of thumb in terms of placing them at different elevations and placing them outside of any lava paths or areas showered with debris.
Is the soil around the volcano homogeneous enough to produce a response that radiates outward at the same rate?  If not, shouldn't the sensors be placed in concentric circles to capture the arrival times for the waves?

  Reference:

  De Lauro, E,De Martino, S, Falanga, M, and Palo, M. (2006). Statistical analysis of Stromboli VLP tremor in the band [0.1-0.5]Hz: some consequences for vibrating structures. Nonlin. Processes Geophys., 13, 393–400. [DOI] [PDF] (freely available)

A general statement about the placement of seismometers around a volcano is provided on the USGS page Monitoring Volcano Seismicity, that a significant factor in their placement is to detect 'microquakes':

  Seismic networks are made up of several instruments. Having enough of the right instruments located in strategic places is especially important for detecting earthquakes smaller than magnitude 1 or 2; sometimes, these tiny earthquakes represent the only indication that a volcano is becoming restless.

They state that detection of these microquakes requires seismometers to be placed near the crater.

Placing them in rings around the volcano (in accessible and safe areas) allows scientists to accurately model the seismic changes, hence changes in the nature of the underlying magma chamber and the movement of magma and fluids.

An example is presented in the presentation Deploying a Sensor Network
on an Active Volcano using Tungurahua and Reventador volcanoes in Ecuador, seismometers are typically separated by at least 100m, across and up-and-down the volcano - this allows the identification of where the movement is occurring (whether the event is from the cone or deep within the volcano).

Practically speaking, according to the article A wireless sensor network for monitoring
volcanic tremors (Pereira et al. 2013), the spacing ought to be

  The sensors must cover a region where the entire
  phenomena can be evaluated. Therefore, the coverage area must comprise, at least,
  one wavelength of distance between the two sensors farther away from each other.
  Since both the direction and speed of the tremor wave need to be estimated, at least,
  two sensors in each one of the cardinal points are required.

The authors emphasise the need for the networks to be flexible in terms of their location.

The authors also state that cost is a major factor - not only of the instruments, but of personnel to monitor and analyse the data.