What equation should I use in this isostasy problem? I have this problem, and I am not sure where to start.  The only Airy equation in my text is $r_1= \frac{h_1 \cdot p_u}{p_s - p_u}$.  This doesn't seem to apply, or if it does it isn't obvious.  Is there some other equation I should be using?

A mountain range 4 km high is in Airy isostatic equilibrium. (10 points)

(a) During a period of erosion, a 2 km thickness of material is removed from the mountains. When the new isostatic equilibrium is achieved, how high are the mountains?

(b) How much material must be eroded to bring the mountains eventually down to the sea level? Use the crust and mantle densities of 2800 kg/m3 and 3300 km/m3, respectively.

C) How High would they be if 10km of material were eroded away?

As this is a homework problem I don't think I can answer what you have posted.

I think you have confused Airy's stress function with his concept of isotasy.  For some helpful information to get you pointed in the right way try the Wikipedia article on isostasy:

https://en.wikipedia.org/wiki/Isostasy


Are the other causes of an earthquake (e.g. volcanic eruptions) the cause of the "sudden slip" which is the main cause of an earthquake? I am to deliver an informative speech about earthquakes in class. However, I was not the first to talk about earthquakes and his discussion of the cause of earthquakes is different from mine.

He mentions that there are multiple causes of earthquakes like a volcanic eruption, release of seismic waves, and tectonic plate movement.

However, from the information I gathered from the United States Geological Survey, it states that the cause is the movement of tectonic plates. The roughness of the plate boundaries cause them to get stuck; thereafter, when the plates move far enough, the boundaries unstick, releasing seismic waves, causing an earthquake.

Is the movement of tectonic plates one of the causes or the volcanic eruptions, etc. are the cause of the sudden slip or the part when the boundaries unstick which cause the earthquake?

When you look at a table of all the major historic earthquakes they are all related to plate tectonics, either directly or indirectly. These are all of the magnitude 7 to 9 events, and most of the magnitude 4 to 6 events. The linkage with volcanic eruptions is real, but weak. Again, most but not all, of the world's volcanoes are generated by plate tectonic processes, the main exceptions being intra-plate movement over mantle hot spots. As we get down to lesser magnitudes we are getting into greater frequencies. It is roughly a logarithmic relation ship, so for every major earthquake, there are thousands of low to medium level earthquakes and millions of small micro-seismic events - the latter being so small that nobody notices - except for geophysicists. There is a host of processes which give rise to low-level seismicity, such as submarine slope failures, turbidites, sedimentary compaction, thermal contraction, magma redistribution at depth, erosive load shedding, after-shock adjustments, landslides, mudslides, rock-falls, rapid draw-down in reservoirs, mining subsidence, fracking, and probably a load of other stuff that I can't think of right now.

So it's roughly a matter of scale. The USGS is correct that serious earthquakes are all caused by plate tectonics. On the other hand, your other source was right, that some seismicity can be caused in a multitude of ways.

Afterthought: Probably someone will point out very rare exceptions, such as major bolides crashing into Earth and causing shock waves right through the planet. But such are extremely abnormal.


What controls how quickly groundwater gets recharged from rainfall? This is a follow up question to an earlier question I asked about how groundwater gets mapped. I have read that our groundwater is getting exhausted as people drill to deeper depths and lift prehistoric water, water that got trapped and stored before humans walked the Earth. The same articles also talk about the millions of years it takes to refill those reservoirs, and then extoll about how we need to use less water.

My question is this: What controls how quickly they refill with rainwater? Could these reservoirs be refilled faster if an outside pump refilled them using rainwater? What are the energy economics on doing this for a place like Nebraska or Bangladesh?

What controls how quickly they refill with rainwater?

Really it depends on where the aquifer is. Letting rain top off a Hawaiian aquifer may take a few weeks. However, refilling the aquifer beneath the Atacama desert may take tens of millions of years. That assumes that the recharge source is actually overlying the aquifer; in many cases, it's not, thus adding lateral distance that recharge must travel.

Regardless, drawing down an aquifer does lasting damage and they will never refill to the same reservoir capacity. Once groundwater is pumped out, the solid materials are then free to further compact and reduce the pore spaces that would be re-filled. In the case of California's San Joaquin Valley this sediment compaction, or, surface subsidence, has caused a permanent loss of nearly %10 of the aquifer's recharge volume.

  Could these reservoirs be refilled faster if an outside pump refilled
  them using rainwater?

In one sense, sure, there are groundwater recharge systems that work as closed-loop systems: groundwater is pulled out of the ground for use by a community, treated by the waste-water system after being used, then pumped back underground some distance upgradient. Aurora, Colorado, for one, has such a system in place. Note that the system isn't used to filter the used groundwater, but to keep it from being wasted when draining it to a local river. Furthermore, groundwater levels must be kept stable lest compaction ruin reservoir capacity.

  What are the energy economics on doing this for a place like Nebraska
  or Bangladesh?

They may be entirely manageable, but the politics would be NUTS! After all, rainwater is a "surface" resource that is promised to users downstream from where it falls. Diverting it underground for the exclusive use of a community would be like trucking parts of Himalayan glaciers to Delhi with no regard to downstream users who depend, for example, on the Ganges.

You could fill a couple of academic libraries with proper answers to your questions, by the way!


Transferring water using underground channel I heard in tv show, there are water channels in underground like rivers or small channels! So I just wondered why don't we use such underground water channels to recharge the underground water of one area from another area, incase there are connections?

I'm sure if there are channels, scientists would have been done some research about it?

So, Do we have any underground water channels maps for world wide?
Do you think its possible to recharge lakes few miles away from river using this idea?

This is already used in some cases. The one I'm familiar with is California's Coachella Valley, best known as the home to Palm Springs.

Farms, golf courses, other businesses, and homes pump far more water out of the region's aquifer than is restored by normal rainfall, so the Coachella Valley Water District pipes in water from the Colorado River and, basically, pours it into the sand at the high end of the 15-mile-long valley.

This water then percolates through the sandy soil down the valley; it's retrieved through local wells. One advantage to delivering the water through the aquifer is that it avoids loss through evaporation.

  The Coachella Valley’s groundwater basin can be imagined as a tilted
  bathtub filled with sand and gravel and topped with a layer of clay;
  water fills the spaces under the clay and in between the sand and
  gravel. --Coachella Valley Water District

This system works because:

There is a (relatively) plentiful external source of water.
The local geology allows water to flow.
The replenishment is largely powered and directed by gravity, which makes it cheap and avoids having to pump water into a system that already has liquid in it and having to worry about whether the water is going where you want.

This Stanford University project talks about the opportunities and challenges for aquifer recharge projects.


Can the Air Mass Factor (AMF) be negative? I am using a untraviolet-visible spectrometer to measure Vertical Column Densities (VCDs) of trace gases up to the stratosphere. It is physically impossible to have negative VCDs. I have observed some of the measurements of slant column densities (SCDs) to be negative. mathematically, VCD = SCD/AMF. I was wondering whether AMF could be negative or the negative SCDs should be filtered out.

No, AMF is always positive. Depending on the retrieval algorithm, negative SCDs can occur as artifacts. You should look at your retrieval algorithm but in general I'd treat negative values in such a situation as "below detection threshold" values. Depending on what you are doing replacing them by 0 might be a valid course of action.


What do weather forecasters mean when they say "50% chance of rain"? What do weather forecasters mean when they say "50% chance of rain"?
Even more confusing: weather report often says something like "30% chance of rain. >10mm", then the next day "70% chance of rain <1mm". How should I deal with this information, for example, if I'm planning a picnic?

In the US, meteorologists forecast the probability of ANY amount of precipitation falling.  The minimum amount of that we deem acceptable to meet this criteria is .01".  So, we are forecasting the probability of one hundredth of an inch of precipitation to fall at a location.

We look at observational data from ground stations, satellites, and computer models and combine it with our knowledge of meteorology/climate and our past experiences with similar weather systems to create a probability of precipitation.

A 10% chance of rain means that 10 times out of 100 with this weather pattern, we can expect at least .01" at a given location.

Likewise, a 90% chance of rain would mean that 90 times out of 100 with this weather pattern, we can expect at least .01" at a given location.

Similarly, the Storm Prediction Center issues severe threat probabilities.   You can see things like 5% chance of tornado or 15% chance of severe hail.

This simply means 5 times out of 100 in this scenario we can expect a tornado.  Or 15 times out of 100 you can expect severe hail with thunderstorms.

By definition, there is no difference in the amount of rain forecast by a 10% chance or a 90% chance.  Instead, that information is defined elsewhere, typically by a Quantitative Precipitation Forecast (QPF).

Meteorologists are still struggling with the best ways to inform the public about the differences between high chance, low QPF events versus low chance, high QPF events, and everything else in between.

Meteorologists are still human and have their own wet or dry biases that can hedge the chance of precipitation you see.   Recently, forecasts are relying more on bias-correction techniques and statistical models to remove the human bias from precipitation forecasts.


The position of magma chambers Where do magma chambers exist? Is it necessary that they exist in the asthenosphere where the circumstances of temperature and pressure are suitable for the rocks to be molten? Or they exist in places of shallow depth?

Magma chambers can exist at a range of depths from very deep to very shallow.  Only requirement that is really necessary is that there be enough pressure from overlying rock strata to keep the magma chamber from reaching the surface and erupting/exploding.  Volcanoes typically represent a slow leak of molten magma.
Even large Volcanic eruptions will only expel a fraction of the magma available.

There are several important geological factors that will control the size. location, and depth of a magma chamber:

Magma buoyancy: Density of the magma (Dissolved gases/liquid and chemical composition vs density of the surrounding host rock.
Integrity of the overlying host rock: tectonic settings, fault and fracture patterns, how seismically active is the local region.
Rate of melting: dependent upon source rock composition, heat flow, depth of source material.

Back in the early 1990s, Japanese researchers imagined magma plumes near the lower mantle  / outer core boundary.

Here is an article discussion shallow and deep Magma sources for the kilauea, Hawaii. As this article suggests, magma can originate at depth and migrate upward and supply shallow chambers.

Facts on the Yellowstone volcanic complex.


What is meant by Massif? In India, Panchchuli, Kun Nun and Shilong only these mountain are claimed to be massif. Why other mountain formations are not termed as massif...? What are the characteristics of massif..?

Anybody pls explain.

A massif is an undisturbed solid rock mass, which is demarcated by e.g. faults. Massifs keep their internal structure and are displaced as a whole. Only mountains of mountain ranges fulfilling this criteria are called massifs.


Difference between thermal and contact aureole Are therms "contact aureole" and "thermal aureole" synonyms?

I found some sentence at A. M. PATWARDHAN (2012):

  "The peripheral extent up to which the thermal effect of the intrusion
  is observed is referred to as the contact or thermal aureole of the
  intrusive body."

Contact aureole, thermal aureole and metamorphic aureole are all synonyms referring to the peripheral aureole of recrystallized rocks around an intrusion of an igneous body due to the heat flux between the intrusion and the box rock.

You can read several examples quoting both terms as synonyms:

The Wikipedia article on metamorphic types includes a section heading of

  "Contact (thermal)"

And another example is frontiersin.org where the subject regularly interchanges the terms to prevent monotony in the writing.


How bad is geo-engineering? It is just curiosity that forced me to ask this question. At some point in time, if we can't control global $\sf{CO_2}$ emissions, temperature will increase until a tipping point and it will be a complete catastrophe. However, if we could prepare ourselves through geo-engineering (e.g. carbon removal, blocking solar radiation), then we may return the temperature back to normal. I am not saying that we have to experiment with mother Earth, but if we may do weather-engineering experiments in controlled labs just like the Large Hadron Collider(LHC), we may some day be able to save the planet from catastrophe.

So, my question is, how bad does geo-engineering go as far as controlled experiments done in totally isolated labs?

In NWP models, it is mostly possible to control the evolution of $\sf{CO_2}$, solar radiation, moisture, temperature etc. Given the current computation power is better than in the past and will most likely be better in the future, once we have calibrated and validated those climate/weather models, can we use them to fight extremes of weather like floods, drought, hurricanes and all other wind storms?

The accuracy of current weather predictions is better for forecasts 5-10 days ahead. So, this may give enough time to do controlled simulations before and after our intervention. Based on that we may act on to, for example, increase precipitation (e.g. through controlled spraying of condensation nuclei) where there is drought, hit and disperse hurricanes or change their directions before they hit and damage cities etc. How wrong can one be to think like that?

The bad part about geo-engineering are the unknown unknowns, to paraphrase a certain US politician.

Our climate models are wrong.  All models are wrong, but some are useful..  Our models are useful, but not quite useful enough to trust them when they tell us massively spraying stuff into the stratosphere or the oceans is mostly harmless.  Our models can't properly reproduce our current climate.  They agree about some trends, but there's lots of stuff that they're missing.

We used to use lots of toxic chemicals in our fridges.  That was a bad idea, so we found some stuff that wasn't toxic.  Great, no?  Decades later, scientists realised this was destroying ozone above Antarctica.  At first the measurements were rejected because they didn't make sense.  Contrasted with our understanding of the atmosphere, and why would ozone suddenly disappear anyway?

Our climate system is complex.  Very complex.  Mess with one of the symptoms, and who knows what side effects are going to be?  It's a risk that we cannot quantify, and those are probably the scariest risks out there.  If even with stuff that doesn't seem remotely connected to each other (fridge coolants and ozone) we almost messed up very seriously, who is to say actively messing with our atmosphere or ocean isn't going to have nasty unintended consequences?

Better than offsetting one set of geoengineering (deforestation, ocean acidification, enhanced GHG emissions) with another equally radical one, it might be safer — from a risk management point of view — to try to not do any geoengineering at all.  Certainly as long as our understanding of climate is just starting.

To borrow an analogy from medicine: preventing is better than curing.  Patients are sometimes prescribed medicine where the side-effects are so bad that they're almost lethal by themselves, but only when the patient is surely terminally ill, so there is "nothing to lose".  We do have a lot to lose on Earth.

Note that weather models are initial value problems and climate models solve boundary value problems, so mathematically speaking, the two are completely different.


What is this geographical feature? (as seen in maps) Can someone help me identify this peculiar geographical feature I've noticed in satellite imagery?

This particular screenshot is from satellite imagery of northern Russia, however this kind of geography appears extremely common in the northernmost latitudes of both Russia, Canada, and the United States.
The below image is from Alaska.
.
I've always wondered how this landscape would be described. Is this marshland, or swamps, or something else in particular?
Thank you!

The dark color of the water masses make me think they are peatlands in tundra.

Peatland is a terrestrial wetland ecosystem in which the production of
organic matter exceeds its decomposition and a net accumulation of
peat results.
The largest known concentrations of peatland are found in Canada and
Alaska, Northern Europe and Western Siberia, Southeast Asia, and parts
of the Amazon basin, where more than 10% of the land area is covered
with peatlands.

Source: peatlands.org


What is this island or reef 600 km east of Marianas Islands? This map shows an island a bit east of the Marianas. I took a screenshot of the relavent part.

I hunted around for it in Google Earth with no luck, but I did find a promising candidate here:

I could not get any sort of label to appear, but the terrain data from Google Earth says that thing has a minimum depth of -42 meters. It's about 600 km east of the Marianas. You can see the coordinates at the bottom of the picture.

Does anyone know what it's proper name is?

To better pin down the location, I georeferenced the map getting good match of all land and sea features with a reference map. The figure below shows it overlaid over a reference map with seafloor releif:

And the location of your mystery Island is were the red dot is, plus a 25 km search radius.

And the coordinates are (Lat/Lon): 17.0619° N, 152.177° E.

It nicely coincides with a seamount, so it might be more than an error on the map (but that seamount acoording to the data in Google Earth is more than a kilometer under the surface). What definitely seem to be an error, is including such island as part of the Northern Mariana Islands, because in all the references and maps I saw, that denomination only covers the 15 islands on the chain to the west.

I did a search for something in that location first looking as MODIS images (250 m resolution) on WorldView I had to browse trough months of images to get cloud free images, but I couldn't identify any island

Therefore, if there, it must be tiny.
After looking at the catalogs for higher resolution images, there are no Landsat images there at all (something that suggest there is no land there) but there are two Sentinel-2 scenes (10 m per pixel), and happily the cloud cover is not too bad.
I did a search in those two images within the 25 km radius displayed above.

This is the first image

And this is the second

And again I didn't found anything.
Therefore I'm inclined to think that there is nothing. But I can't rule out that something very small can be hidden by the clouds. However, I doubt it.
If you want to perform the search yourself over a larger search radius, just let me know and I can give you the images.

I also searched the seamount catalog for those coordinates and the only one that show up is Vlinder Guyot about 224 km to the East. So there is no information on the one below your mystery island.

However, in this publication. It is refereed as "I'l Ichev" and is part of the "Magellan Seamounts".

I also looked over the seamount you suggested ("Pegas" in the above map and located at 16.136° N, 151.968° E approximately), that is about 100 km away from the location pointed on the map you posted, but I didn't found any island there either (on a search box 22x26 km):

After browsing many other maps, I've also failed to find other map showing that Island. However, in a relatively similar location some old maps show "Los Jardines" Island. It is a know "phantom" island, some more info on its wikipedia page. Here a 1932 German map showing it:

Despite it is not in the same location, it might be the source of the confusion.

Here a list of good quality maps that DO NOT show that island:

https://www.interkart.de/media/catalog/product/r/e/re01020331_1_1.jpg
https://www.maps.com/media/catalog/product/cache/1/thumbnail/17f82f742ffe127f42dca9de82fb58b1/p/a/pacific_ring_of_fire_wall_map_42x31.jpg
https://www.nationalgeographic-maps.com/media/catalog/product/cache/7/image/8ecabcfb697832bc77ac7e2547ded39f/x/n/xng196910a.jpg
http://www.melbmap.com.au/site/resources/overseas_map_samples/hema_asia_west_pacific_thumbnail_image.jpg
http://universoguia.com/wp-content/uploads/2012/12/mapa_politico_oceania.jpg
http://www.gifex.com/images/0X0/2009-11-11-10993/Mapa-Fsico-de-Oceana.jpg
http://www.xxlmaps.com/maps/1/map3.jpg


Question about the sign of the shearing deformation terms I have the following equation for the shearing term of the deformation zone in meteorology. The reference is this link:
http://www.zamg.ac.at/docu/Manual/SatManu/main.htm?/docu/Manual/SatManu/CMs/Def/backgr.htm

Shearing = dV/dx + dU/dy

U and V are the zonal and meridional winds, respectively.
X and Y are the longitude and latitude,respectively.

I would like to know what does it mean to have if:

a). dV/dx < 0 (dU/dy > 0)

b). dU/dy < 0 (dV/dx > 0)

c). both dV/dy and dU/dx are less than 0.

d). both dV/dy and DU/dx are greater than 0

I'll appreciate any help.

Did you try to sketch one of those situations? Try a square grid, define x and y, and then put $U$ and $V$ components onto one of the grid points, which you choose as starting point.

Now proceed to implement a). For example, from your starting arrows, go to the next grid point eastwards, and implement $\frac{dV}{dx}<0$, i.e. the upwards pointing arrows become smaller as you go eastwards. Do the same for U. Repeat for enough grid points until you see a pattern. Now connect $U$ and $V$ components into the final, two-dimensional velocity vector $\vec v$.

In this way you will possibly self-answer your question. I don't know if I can help you more, because I don't know what you mean with \

  I would like to know what does it mean to have

The end result will be the graphical representation of a vector field. The shear tensor simply measure the amount of shear in each vector field. You will discover that some field structures surprisingly possess shear, while others don't.


What's really happening with "stormquakes"? The PBS Newshour article Scientists discover big storms can create ‘stormquakes’ says:

A stormquake is more an oddity than something that can hurt you, because no one is standing on the sea floor during a hurricane, said Wenyuan Fan, a Florida State University seismologist who was the study’s lead author.
The combination of two frightening natural phenomena might bring to mind “Sharknado ,” but stormquakes are real and not dangerous.
“This is the last thing you need to worry about,” Fan told The Associated Press.
Storms trigger giant waves in the sea, which cause another type of wave. These secondary waves then interact with the seafloor — but only in certain places — and that causes the shaking, Fan said. It only happens in places where there’s a large continental shelf and shallow flat land.

Unfortunately the article does not link to or identify the published study.
Question: Are there more technical terms or clarifications for the following items?

stormquake
storm-triggered giant waves
another type of wave (secondary waves)
"certain places"

The article can be found here in Geophysical Research Letters:
Fan, W., McGuire, J. J., Groot‐Hedlin, C. D., Hedlin, M. A. H., Coats, S., & Fiedler, J. W. ( 2019). Stormquakes Geophysical Research Letters, 46. https://doi.org/10.1029/2019GL084217

Abstract
Seismic signals from ocean‐solid Earth interactions are ubiquitously recorded on our planet. However, these wavefields are typically incoherent in the time domain limiting their utilization for understanding ocean dynamics or solid Earth properties. In contrast, we find that during large storms such as hurricanes and Nor'easters the interaction of long‐period ocean waves with shallow seafloor features located near the edge of continental shelves, known as ocean banks, excites coherent transcontinental Rayleigh wave packets in the 20 to 50 s period band. These “stormquakes” migrate coincident with the storms, but are effectively spatiotemporally focused seismic point sources with equivalent earthquake magnitudes that can be greater than 3.5. Stormquakes thus provide new coherent sources to investigate Earth structure in locations that typically lack both seismic instrumentation and earthquakes. Moreover, they provide a new geophysical observable with high spatial and temporal resolution with which to investigate ocean wave dynamics during large storms.
Plain Language Summary
Large storms such as hurricanes and Nor’easters generate strong long‐period ocean waves, which can interact with shallow seafloor features located near the edge of continental shelves known as ocean banks. Such interactions produce seismic sources with equivalent earthquake magnitudes that can be greater than 3.5. These seismic sources are termed “stormquakes”, and they can excite coherent seismic wave fields that are well recorded across the North American continent. Stormquake is a newly identified geophysical phenomenon, which involves interactions of atmosphere, ocean, and the solid Earth. Therefore, stormquakes can provide useful information to investigate the Earth structure and ocean wave dynamics.

At the moment the link there to the PDF works and is not paywalled.


Roughly how much Co2 is generated per kWh of electricity generated I’m interested to know how much Co2 is generated by a coal fired power station to produce 1kWh of electricity for electrical grid

About 900 grammes of CO2 for each 1kWh of electricity.

There is some variation: very modern super-critical coal plants can be lower. But 900g is a reasonable central estimate.

Note that that's just CO2 from combustion. It can be higher, when we include CO2 and CH4 emissions from the rest of the coal supply chain too.


What Keeps the Earth Cooking? If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?

If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?

Mostly it is residual heat energy from when the Earth was very young. The biggest source came from the kinetic energy of all the bodies, big and small, that collided to form the Earth being converted to heat. The differentiation of the Earth added even more heat energy to the Earth.

In addition to radioactive decay, the on-going freezing of the outer core material onto to the inner core adds a bit more heat to the system, but neither one compensates for heat transported through the mantle and crust and then out into space. Note that this heating from below is but a tiny portion of the overall energy budget for the Earth's surface.

Even the Earth's surface was very hot shortly after the formation and differentiation of the Earth. While the surface cooled quickly (geologically speaking), the interior has not. The key reason is that 2,890 km of rock makes for a fairly thick blanket.


What is the value of calculating the elevation of mountains in the past? (paleoelevation) I would like to know if knowing the history(elevation, temperature, etc) of montains has any application, different from killing curiosity of scientist.

Compared to some other fields in geology, this one actually has immediate practical implications.

By "knowing the history of mountains", you can learn a lot about processes that involve erosion, weathering, seismicity, etc. This is important for risk management and mitigation. Landslides and rockfalls are a significant risk in some countries. There are many ways of studying these processes, one of them being the interpretation of past events: their causes and effects. This is also true for earthquakes (which as you know, move mountains up and down).


Does human body temperature impact climate change? The human body temperature is about 37 °C (99 °F), so as the population increases does this cause the Earth's temperature to rise?

Does human body temperature impact climate change? Directly? It's not even a blip. The Earth's population is 7.6 billion. With each person radiating about 80 watts (basal metabolism), that's about 600 gigawatts, or 760 gigawatts using a round figure of 100 watts. That sounds like a lot, but it's only a tiny fraction of the 18 terawatts consumed by humanity, which in turn is a tiny fraction of the 174 petawatts the Earth receives from the Sun.

Indirectly, yes. A growing population and the desire for greater wealth by a growing population (third world nations and developing nations want to move themselves out of those categories) are key drivers of climate change.


Can minimum relative humidity be greater than maximum relative humidity? I am trying to calculate minimum and maximum daily Relative Humidity values given a min/max Specific Humidity and min/max Temperature.

I found some equations here that work with the given variables, but I have noticed that occasionally the value calculated for Minimum Relative Humidity will be greater than the value calculated for Maximum Relative Humidity. Is this accurate? It feels incorrect that a lower specific humidity and temperature would lead to a higher relative humidity, and it also doesn't seem right to say that, for example, the minimum RH was 80% while the maximum RH was 50%.

I verified my results with this online calculator, and while it is unclear what equations are being used here, the same scenario occurs.

Here are my C# functions for calculating RH. Specific Humidity is given as kg/kg, and Temperature in Celsius:

    public static double CalculateRHmin(double MinSpecificHumidity, double MinTemperature)
    {
        double RHmin = 0.0;
        double es = 6.112 * Math.Exp((17.67 * MinTemperature)/(MinTemperature + 243.5));
        double e = MinSpecificHumidity * 1013.25 / (0.378 * MinSpecificHumidity + 0.622);
        RHmin = 100 * (e / es);
        return RHmin;
    }

    public static double CalculateRHmax(double MaxSpecificHumidity, double MaxTemperature)
    {
        double RHmax = 0.0;
        double es = 6.112 * Math.Exp((17.67 * MaxTemperature) / (MaxTemperature + 243.5));
        double e = MaxSpecificHumidity * 1013.25 / (0.378 * MaxSpecificHumidity + 0.622);
        RHmax = 100 * (e / es);
        return RHmax;
    }

Sample execution:

Tmin(Celsius) = 12.71    SHmin(kg/kg) = 0.007672     RHmin = 84.71%

Tmax(Celsius) = 23.71    SHmax(kg/kg) = 0.010929     RHmax = 60.33%

I think you might be getting confused. There is relative humidity. If you put in different values, you will get different results. For instance, if you replace the variable names of one of your functions (say replace Min with Max), you will have the same exact function.
Relative humidity is a ratio of the amount of water vapor in the air to the amount of water vapor that could be in the air (saturation vapor pressure $e_s$): $$RH=100\%\times\frac{e}{e_s}$$ Since the saturation vapor pressure decreases with increasing temperature (Clausius Clapeyeron equation):$$e_s=611 \exp\left(\frac{L_v}{R_v}\left[\frac{1}{273.15}-\frac{1}{T}\right]\right)$$ it is conceivable, and also not uncommon, for the maximum relative humidity to occur when the temperature and specific humidity is at a minimum.
So can the minimum relative humidity be greater than the maximum relative humidity? By definition of minimum and maximum, no. But the times that the minimum and maximum relative humidity occur are often counter-intuitive.


Why are CO2 sensors so expensive when CO sensors aren't? Please excuse me if Earth Science is not the correct place to ask this question.

I read a New York Times article about increasing $\small\mathsf{CO_2}$ levels in the atmosphere: "Carbon in Atmosphere Is Rising, Even as Emissions Stabilize" (26 June 2017)

According to the article, there are not enough $\small\mathsf{CO_2}$ monitoring stations for scientists to have a detailed understanding of where $\small\mathsf{CO_2}$ is being emitted/absorbed (e.g. by landmasses and oceans)

This got me thinking, would it be possible to design a dual-use product that integrates a $\small\mathsf{CO_2}$ sensor (e.g. a solar powered garden lamp) from which we could crowd source $\small\mathsf{CO_2}$ data for scientists? Perhaps a bit naive, since the sensors may not be accurate enough for scientific studies, and if it's a consumer product they would likely have a dense install base in metropolitan areas and less in the countryside/oceans.

But that isn't the biggest flaw in this idea. No, that came when I looked up $\small\mathsf{CO_2}$ sensor prices:

 (click for full size)

I was able to find some Arduino compatible sensors from a Google search for around 50USD at the low end, but looking at electronics distributors, a more reasonable price for a raw $\small\mathsf{CO_2}$ sensor seems to be at least 70USD.

Carbon Monoxide detectors which you are encouraged to install in your home are much less expensive!

 (click for full size)

How can it be that $\small\mathsf{CO_2}$ sensors are so expensive compared to CO detectors?
Is this due to the fact that carbon monoxide sensors use a detection
method which cannot accurately determine the PPM of CO?

Carbon monoxide (CO), natural gas & hydrocarbons, VOCs, ammonia, etc.

In this Chemistry SE answer and this Electronics SE question I discuss how the family of MOS gas sensors work. They can measure a large variety of different gasses that can react with atomic oxygen (O rather than $\small\mathsf{O_2}$).

  I'll quote from this question:

    ...sintered composite based on the semiconductor material $\small\mathsf{SnO_2}$, which is the metal oxide. The different sensors have different admixtures and operating conditions to achieve different sensitivities to different gasses.

    The principle of operation of MOS-type gas sensors is explained in Figaro sensors' Operating principle; MOS type.

  The Figaro link shows the operating principle in the GIF below:

   GIF (Source: Figaro)

  When the $\small\mathsf{SnO_2}$ is heated by the (usually 5V but not always) heater supply, oxygen in the air will dissociate at the surface and oxygen ions will stick to the surface, depleting the semiconductor and cutting off the flow of current. When a carbon-containing gas (e.g. $\small\mathsf{CO}$ or $\small\mathsf{C_xH_y}$ (but not $\small\mathsf{CO_2}$)) comes along, it will combine with the adsorbed oxygen and remove it from the surface. The more gas, the lower the equilibrium concentration of adsorbed oxygen and the higher resulting current flow through the semiconductor.

Carbon dioxide ($\small\mathsf{CO_2}$)

The $\small\mathsf{CO_2}$ sensor works on a totally different principle because $\small\mathsf{CO_2}$ is fully oxidized carbon, it will not react further with atomic oxygen.

Instead the $\small\mathsf{CO_2}$ sensors are either solid electrolyte chemical cells like the MG-811 or newer versions (see this question) or they are Non-dispersive Infrared Light sensors (NDIRs) based on optical absorption of a certain wavelength of infrared light, using a hot filament or other light source to produce IR and a narrow multilayer optical filter to select one of the strong absorption lines of $\small\mathsf{CO_2}$. The more $\small\mathsf{CO_2}$, the more the reduction in the transmission of light in the optical path of the sensor.


Does the extension of the absorption line of $\text{CO}_2$ with temperature play a role in the climate change? I've read not long ago that the absorption line of the $\text{CO}_2$ becomes larger with temperature thanks to Doppler effect (if it's false it would be great to tell me). My question is the following: Does this imply, like I think, that more energy is "stored" on Earth (thanks to greenhouse effect) and so play a role in climate change?

If the answer is yes, how big is this role?

No. Not in a significant way.

The full width at half maximum (FWHM) of a spectral line widened by thermal Doppler broadening is

$\Delta f_{\text{FWHM}}={\sqrt{\frac{8kT\ln(2)}{mc^{2}}}}f_{0}$

where $m$ is the mass of the emitting particle, $T$ is the temperature, $f_{0}$ is the frequency of the spectral line, and $k$ is the Boltzmann constant.

Let's look at the CO$_2$ absorption lines:

(Image from Wikipedia commons, source)

Let's take for example the band roughly between 12 and 20 $\mu m$. That corresponds to frequencies from 15 to 25 THz, with a mean of 20 THz.

If we solve the above equation for the mass of a CO$_2$ molecule ($44.01/6.02\times 10^{23}$ g), a frequency of 20 THz and an Earth's mean temperature of let's say 15°C (288.15 K) we get 1158 kHz broadening, and for an scenario 2°C warmer it would be 1162 kHz.

Therefore, the width of the absorption band would grow 8 kHz (4 kHz on either side). Which considering the original width of 10 THz corresponds to a 0.00008% increase. This could be roughly equated to an analogous increase in absorbed energy, which is absolutely negligible for all practical effects.


Doesn't Increase of Potential Temperature with Height contradict Adiabatic Nature of Processes within Troposphere? I refer to this question, I asked recently in the physics board:
https://physics.stackexchange.com/questions/578308/doesnt-increase-of-potential-temperature-with-height-contradict-adiabatic-natur
It doesn't make sense to type it again, so I link to it.
Maybe the question can be answered here.

If we'd be living in a dry atmosphere your reasoning is indeed correct. Air would rise adiabatically and air would loose about 9.8 °C/km (dry adiabatic lapse rate). This means constant potential temperature. However, Earths atmosphere isn't dry. As soon as a rising, moist air parcel reaches saturation, it will rise with a moist adiabatic lapse rate (6-7 °C/km). Potential temperature will rise (because if the parcel falls down again it will be warmer at the same level - see below). This causes clouds and sometimes rain and thus, reduces the overall water content in an air parcel.
If such a parcel is now going to fall again it will gain temperature according to the dry adiabatic lapse rate (because it lost water during ascension). Lets say initially a parcel starts rising with moist adiabatic lapse rate with temperature $T(t=0)$ and then falls down again and reaches the same level at $t=1$. You will then observe that $T(t=0)< T(t=1)$. Thus, potential temperature must have increased as the parcel was rising.


What is the difference between mineral groups and series? It seems to me when reading about minerals, groups and series are spoken about interchangably in similar types of contexts. Is there a difference? If so, what?

Yes, there is a difference.

A mineral series represents mineral which have a well defined solid solution. One of the most known examples is olivine: olivine is not a strictly defined chemical composition for a mineral, but rather a series between the forsterite end-member (Mg2SiO4) and fayalite end-member (Fe2SiO4). Note that if you find a pure end-member in nature, then you have a mineral species. Quite rare for olivine though. There's also the olivine group, which consists of other minerals that do not form a solid solution with the forsterite-fayalite series (for example monticellite CaMgSiO4) or minerals that do form a solid solution, except that it's extremely rare in nature (for example tephroite Mn2SiO4). Here's a comprehensive list of the minerals in the olivine group: http://www.mindat.org/min-29264.html

Another example is the pyroxene group. So for simple Ca-Mg-Fe pyroxenes, you have the clinopyroxene and orthopyroxene series, which consist of the end-members (species, if you find them pure) diopside (CaMgSiO6) - hedenbergite (CaFeSiO6) and enstatite (MgSiO3) - ferrosilite (FeSiO3), respectively. Intermediate clinopyroxenes are also called augite.

The distinction is not always clear. For example, the feldspar group traditionally has the plagioclase series (albite-anorthite, NaAlSi3O8-CaAl2Si2O8) and the K-feldspar species (KAlSi3O8, either microcline, orthoclase or sanidine, depending on structure). But in some cases there is a solid solution between albite and K-feldspar, forming the alkali-feldspar series. Nature doesn't always behave according to our rules, and it's important to remember that our classification systems work well with ideal systems but break down often.

Further reading


Long-term Wind Speed Forecasting: reality or wishful thinking? I have been studying/working with Wind Energy for a while and, one of my main responsabilities right now is to search for adequate long-term wind speed forecasting models.

However, 2 things strike me about this quest.

Wind speed forecasting is a task of great complexity for wind speed itself is highly stochastic. It depends on climate patterns, regional weather behavior, topography and atmospheric stability, or the lack of thereof, just to mention a few.
The very own idea of "long-term" varies from researcher to researcher. So far I've found authors who claim that 1 to 7 days can be considered long-term (Current status and future advances for wind speed and power forecasting,Jung & Broadwater, 2014); but also those who say one full year is the minimum threshold for long-term forecasting (The quality of weather information for forecasting of intermittent renewable generation, Sokolowska & Hossa, 2014). It's clear that forecasting horizon is highly linked to the aim of your research; therefore, when topics change, so will their forecasting horizons.

a. Isn't there a consensus about what long term means when it deals with wind speed forecasting?

b. Can it be assumed year(s)-long wind speed forecasting withsignificant accuracy  is still some far-fetched, wishful thinking?

c. What are some efficient models out there yielding meaningful results?

I would like to hear your ideas/points as long as they can be backed by scientific reasoning. If you could point me out in the direction of research (proofs to your rationale) in long-term wind forecasting, I'd be downright grateful.

In case you have worked with this topic, then I'd enjoy hearing from your own experience.

Thank you so much in advance for all inputs.

Warning: "long-term wind-speed forecasting for generation" has (at least) two very different meanings. One refers to forecasting a distribution of wind speeds; the other refers to hour-by-hour (or half-hour by half-hour) forecasting of wind speeds.

Generally, when we talk about long-term forecasting of wind speeds for wind generation, we're talking about estimating the distribution of wind speeds over the next few years. That is to say, we're not talking about what the wind speed will be exactly two years from today, at 15.00 UTC. We're talking about what the shape of the distribution of the wind speeds will be - maybe in terms of the two parameters of a Weibull distribution, together with some indication of how the distribution varies by time of day, and by season of the year.

There is some skill in hour-by-hour wind speed forecasts up to about two weeks away. But for longer than that, there's very little skill in the models at all. In that regard, if we are talking about hour-by-hour wind speed forecasts, then short term is the next 0.5 - 4 hours, and long-term is 1-2 weeks.

In both cases, I'd look at recent publications from Reading University - David Brayshaw and others - and specifically on the accuracy of wind forecasts for wind generation, I'd also recommend work by Henrik Madsen and Pierre Pinson.


Are we experiencing lower level of gravity now compared to past? Whole civilizations have been buried underground and we have built new landscapes over them.

The fact that tall buildings and houses are being excavated from under the ground means that we are living very much away from earth's core than the past.

Does this mean that we are experiencing less gravity compared to past Since we are further from the earth's core that causes the pull?

Note: Parent question
 Was the Earth's sea-level significantly lower in ancient times?

asking as separate question as per community suggestion

Earth's radius is about 6400 kilometres. That's 6400000 metres. Let's say that you have a mound 20 metres high, burying an older settlement. Your new "radius" is now 6400020 metres.

Let's say that $g = 9.8\ \rm m/s^2$ at 6400, your new gravity will be $g = 9.799939\ \rm m/s^2$.

Clearly, this is hardly "lower level of gravity".

To make this even less significant, the 20 metres of extra dirt underneath you have their own contribution to the gravity. Even though the overall mass of the Earth is the same, local mass variations cause gravity anomalies. Not much, but $g$ changes by a bit. So adding more dirt directly underneath you will increase $g$, counteracting the fact that you're 20 metres farther away from the centre.


Ice Coverage on the Laurentian Great Lakes Currently (April 2014), the fraction of the Great Lakes covered by ice is more than ten times the median amount for this time of year, the median amount being indicated by the green line in the below graph and representing the 1980-2010 time period.  The source of the graph is the Canadian Ice Service.

(in the graph, the x-axis is year, 1980-2014; the y-axis is percent ice cover 0-40%; Link to graph)

While the data in the graph are only back to 1980, looking at data from the NOAA Atlas of Great Lakes Ice Cover it can be seen that the amount of ice for this time of year is unprecedented back to 1973, the earliest year in the atlas.

My question is, how far back would one have to go to find a year with an equal or greater amount of ice coverage on the Great Lakes at this time of the year?  Obviously the Great Lakes were glaciated thousands of years ago :), but is there any historical record of a similar ice coverage event?

update 4/29/2014:

(x-axis is year, 1980-2014; the y-axis is percent ice cover 0-30% Link to graph)

As we close out April, the amount of ice remaining on the Great Lakes is more than 4 times greater than any other year in the 1980-2014 time period, and about 50 times the median value for this time of year.

Vast areas of Lake Superior which were considered by Canadian Ice Service as having a zero-probablity of ice-cover at this time of year are in fact covered in very thick ice:

update 6/2/14

A small amount of ice still remains on Lake Superior.  This is the first time in the satellite era (1973-) that ice has been present in June.

April and later ice cover is primarily on Lake Superior, since this lake is in the coldest region and also because it is the largest lake.

Raymond Assel analyzed the Great Lakes ice coverage for the winters of 1897-1982 in AN ICE-COVER CLIMATOLOGY FOR LAKE ERIE AND LAKE SUPERIOR FOR THE WINTER SEASONS 1897-1898 to 1982-1983 INTERNATIONAL JOURNAL OF CLIMATOLOGY, VOL. 10,731-748 (1990).

According to table IV of Assel, in the winter of 1911-12 Lake Superior had an ice cover of 80% or greater for 74 days.  No other winter had more than 52 such days.

According to this NOAA file in the winter of 2013-14 Lake Superior has an ice cover of 80% or greater on 68 days.

Assel also studied Lake Erie, and finds that 1911-12 had 72 days with 80% or greater ice cover.  This compares to 70 such days in 2013-14.

Based on the above, it is very likely that 1911-12 was the most recent winter with similar April ice cover to 2013-14.


Thunderstorms in Mountains When you’re in the mountains for example like in the Appalachian Mountains, is thunder heard more easily from further away in the mountains rather than if you aren’t in the mountains?

I presume you mean if one were a substantial distance away from a lightning strike in the mountains, would it be heard better or worse by another observer the same distance away in the plains and foothills? It depends whereabouts in the mountains this lightning strike occurs and where the observers or listeners are.

If it occurred between two rocky ridges forming a V shape with the open end directed toward the plain, it is likely that the observer on the plain would hear it more clearly than an observer or listener the same distance away in the mountains. The very mountain walls which reflected the sound toward the plain would act as barriers to listeners placed, let's say, 10 miles away in the mountains to either side. This is called acoustics.

One can also imagine an acoustic layout in which the mountain observer would hear the strike more clearly and loudly, but on balance the plains observer would be more often in a position to hear the thunder clearly. My own observations of thunder in the mountains and coastal areas of Brunei and Sarawak would seem to bear that out


Identifying different parts of a cave Hopefully this is on topic here - I'm wondering if there are names for the different "biomes" that are present within a cave.

Some of these "biomes" include:

Open (no) ceiling, sunlit, potentially with trees growing (grotto?)
Dark, little to no natural light ("standard" cave)
Containing an underground stream or lake, potentially supporting aquatic life

I know little about caves, but they (can) have diverse areas that give rise to all sorts of interesting creatures. Are there any specific names given to the different parts of a cave?

Please let me know if I can edit this question to make it clearer or more on-topic.

The Karstic aquifer is vertically divided in several zones. These zones host caves that are typical for them and are also named after them. The zone closest to the surface is called epikarst that is commonly riddeled with karren and also most efected by outer conditions. Below it lies vadose zone that is from hydrological aspect unsaturated and hosts mostly shafts and vertical caves. Epiphreatic zone is flooded occasionally and caves in this part are mostly horizontal, some have water some do not. The lowest is the phreatic zone that is flooded all the time. Passages of caves here are jumping up and down in vertical profile along fissures and bedding planes.

This is only a general explanation to find out more i would suggest this book:

http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470849967.html


What exactly is wind velocity How exactly do we define wind velocity?

Obviously, I suppose this is something like "speed of displacement of a quantity of air", but this seems to be too imprecise.

For example, a cup anemometer measures this velocity, but any anemometer depends on a calibration function that depends on size of cups, material used, and so on. So how do we know this function?

Before defining wind velocity, I think it is necessary to explain the continuum assumption. The basic idea is that even though gases are composed of discrete molecules occupying a small fraction of the total volume filled by the gas, gas flows are made up of many individual collisions between gas molecules. In most applications, the flow field is assumed to behave as a continuum and the discrete molecular nature of gases is ignored. By doing so, fluid properties (e.g., density, velocity) can be defined anywhere in the flow.

In order for the continuum assumption to be appropriate, the length scale of the application must be much larger than the mean gas particle path length. In most atmospheric conditions, including in anemometers, the mean path length is on the order of micrometers, while the anemometer size is much larger.

While most anemometers (cup, vane, laser, acoustic resonance) measure wind speed some measure the wind's pressure (e.g., tube, plate anemometers). In the case of cup anemometer, like any other measuring device, there is an error associated with the measurement that depends primarily on the cup size. In general, the anemometer factor (the ratio of wind speed to the rotation speed of the cups) has a value between two and a bit more than three and it depends on the size of the cups and arms.


Available Matlab code to design Seismic Colored Inversion Operator? I want to apply seismic colored inversion technique to my datasets. Is there a Matlab code available that I can easily use? Are there any other recommended codes to apply seismic colored inversion?

Here is a link to a colored inversion operator design code written and provided by Peter Zahuczki.

This code requires that you provide a P-impedance log amplitude spectrum; he uses the open-source interpretation software OpendTect to compute this spectrum.

Peter has a easy to follow tutorial on how to use his code with OpendTect. Good luck!


How to deal with a pond silting up I live in a town that has a sizable pond that is dammed with a concrete overfall spillway. Decades ago the state demanded that the dam be installed to guarantee that the surface height of the pond remain the same when a culvert was being built at the outfall of the pond.

This is a problem because the pond is slowly silting up, and as it silts up it is becoming larger and larger and shallower and shallower, basically it is slowly turning into a marsh which is infiltrating into people's backyards (not mine, but those of some neighbors).

How can this problem be solved?

That is what lakes and ponds do , fill with silt. Serious earth moving equipment is needed to slow Mother Nature. Our community has recently removed some silt with draglines, bulldozers , trucks , etc. I don't know the cost but certainly significant . They concentrated on certain areas to facilitate flow as we have a dammed stream that made roughly a 300 and 100 acre lake and the costs of general silt removal would be overwhelming.  On the upside , bushes on a new island have become a egret rookery,


What are the usable minerals that can be found in our daily life? Can anyone tell me what are the minerals that can found at home or something that can be seen in yard or in waste/trash bins.

This question is somewhat vague & broad. It almost looks like a homework question.

For starters, in the kitchen there's salt, NaCl.

In the bathroom, talcum powder, which is ground up talc.

In the garden shed there's fertilizers.

In the yard, soil contains a numerous minerals, which will differ from location to location because of different types of soil. Locations with sandy soils will contain silica.


Is snow less likely to appear at a coastal area? Is it true that a coastal area is less likely to see snow compared with inland area nearby? If so, what are the reasons?

I don't know if someone has conducted statistical research on this. It certainly depends on the situation. Here are some situations:
More snow in coast

Like @gerrit commented, elevation increases precipitation as air is forced to lift up and thus cools condensing water vapor -> rain/snow. This is true when predominant winds are from the sea.

Lake-effect snow situations

Less snow in coast

The air temperatures are affected by nearby bodies of water so situations where temperatures are freezing, but the sea isn't frozen yet will keep the coastal temperatures higher. Thus melting falling and fallen snow faster than in inland.


Extreme rainfall events Extreme rainfall events have different intensities at different places depending on the availability of water to precipitate. Can anyone explain how do we define/determine extreme rainfall events in a particular region with an example?

We define rain events in terms of the probability of reccurrence. For example, we call a certain rainfall the "10-year rain event," meaning that this amount of rain would only be expected to occur once every 10 years. We usually like to have at least 30 years of data before calculating recurrence intervals.

Note: Just because we call something the 100-year storm event does not mean that it will only occur every 100 years.  Sometimes they occur much more frequently.  Sort of like winning the lottery twice in a row when the odds of winning at all are quite low.  Unlikely, but possible.

The 100-year storm also changes with the available data.  If we were to have several "100-year storm events" in the span of 10 years, we might need to go back and determine a new 100-year event that takes recent data into account.  This is especially important with respect to climate change.  In Boston, the 100-year flood event is projected to occur every 2-4 years by 2050 or so.  Obviously we then need to go back and calculate what a new 100-year event is.

USGS Q&A on flooding

NE Aquarium Climate Change page


What instrumentation and/or measurement is likely being shown in this video of giant Siberian craters/sinkholes? The RT video The Permafrost Mystery: scientists explore giant Yamal Sinkhole (with English subtitles) shows scientists exploring the formation. In one scene after about 14:00 two scientists are deploying a device made of two perhaps 30 meter or more long wires(?) separated by about 1.2 meters, held apart by a rigid brace. One scientist holds some electronic equipment with a cable going down to one side of the brace.
Two screenshots are shown below. I can't tell if these long green wires go down into the hole as well or if those are something different, but I think they do, eventually.
Can anyone identify this instrument and what it measures, or at least provide some insightful educated speculation?

Potentially related Detecting and Mapping Gas Emission Craters on the Yamal and Gydan Peninsulas, Western Siberia

It looks like a geophysical method. But a wide variety of such methods have been applied to the Yamal crater by Olenchenko et al. (2015):

The complex of geophysical survey techniques included electrical resistivity tomography (ERT), near-field transient electromagnetic sounding (Transient Electro Magnetic (TEM) sounding), magnetic survey, and radioactivity survey.

I'd say it looks like the first one (ERT), but it's just an "educated speculation"! :)


Solution for the coexistence of overpopulated human species with nature Is there any solution to deal with the overpopulation of our species at the same time protect the natural environment of ours? (other than finding a inhabitable planet?)

It's important to understand that this problem is a bit more nuanced.
Population growth in every species is exponential (as much as exponential growth can exist, in reality almost nothing is proven to grow infinitely, therefore at some point stops growing exponentially).
Check out this for a description of carrying capacity. In a lot of ways it shows that human population growth is not much different than any other species... but we do it on such a grand scale, and that is something to consider. https://en.wikipedia.org/wiki/Carrying_capacity#:~:text=The%20carrying%20capacity%20of%20an,water%2C%20and%20other%20resources%20available.
The biggest problem in the future may not be our exponential growth, but our increase in carrying capacity for our specific environment (which for humans is the entire Earth). The most significant cause of this is the Green Revolution (agricultural improvements, not environment).
https://en.wikipedia.org/wiki/Green_Revolution
We certainly don't want to see that carrying capacity drop.


Typhoon in December of 1864 in Japan? In "20,000 Leagues Under the Sea" by Jules Verne there is a reference to a "tempest" that destroyed Yeddo (Tokyo) in Japan:

  They are they which, in the tempest of December 23, 1864, after
  destroying the town of Yeddo, in Japan, broke the same day on the
  shores of America.

Was this a real event or just fiction?

Yeddo seems to be a version of Edo, which is today Tokyo. Though it has had its share of disasters, nothing seems to come up concerning any storms in the 1864. Fires and earthquakes seem the more typical catastrophes. A horrible fire in 1857 seems to be the closest event timewise that I find. It was apparently still in existence in 1868:

  In 1868, when the shogunate came to an end, the city was renamed Tokyo
  ("eastern capital"). The emperor moved his residence to Tokyo, making
  the city the formal capital of Japan


Where did the carbon, neon and nitrogen go? It is interesting to compare estimated Earth abundances with estimated Milky way abundances.

Obviously the hydrogen and helium were gaseous and too light for Earth's gravitational field (other than hydrogen in molecules like H2O).

Oxygen is the second most abundant element on Earth. Even though it can exist in the gaseous O2 form, I assume this is because of how it combines with so many heavier elements and is trapped in the ground.

Carbon, neon and nitrogen however have a much lesser abundance in the Earth than cosmic abundances. Can we assume that this is proof that there was a solar event that blew most of the gases away during early planetary formation. (Carbon because of its gaseous form in CO and CO2)?

The reason Carbon and Nitrogen are rare on Earth compared to their abundance in space is because elements containing carbon and nitrogen didn't survive the heat of the sun at Earth's distance during the protoplanetary disk stage.   Carbon can form carbonate rock, but only under certain circumstances.  Carbonate rock is rare in space and most of the carbon is in the form of Carbon dioxide.

Oxygen, unlike Carbon or Nitrogen, bonds readily with Silicon, Magnesium, Iron and other heavy elemets, which is why Oxygen is very abundant in rocky planet formation.  It's one of the elements abundant in space-dust, unlike CO2, H20, CH4, NH3, which can form, in colder regions, ice or snow like formations as they begin to clump together, but only in cold regions of space.

The sun didn't precisely have an "event", though young stars after formation can be much more violent.  The initial heat of formation can be very bright and very hot, and young stars are usually rotating very fast and prone to much bigger solar storms and very large mass ejections.   Pretty much all stars go through a violent youth.  It's not a unique event to our solar-system.

Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region.   This is true for all 4 inner planets and likely all rocky worlds.   Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.

Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.

The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line.  Different gases have different frost lines depending on their freezing point.

It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed.  There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.

Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass.  In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium.   That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.

Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40.   Earth's Helium is also present as a result of radioactive decay.


Resources on Andean geology I would like to begin studying the geology of the Andes, with particular respect to the tectonics and paleogeography of the region.

I have been searching on-line resources for some time and I would like to start reading a book on the topic, but I am not finding any titles focussing on the geology, tectonics and paleogeography of the area. Would anybody have any suggestion, if possible in Spanish?

Since I have found the reference-request tag, I hope this question is not off topic here and, if it is, I will delete it. I thank you for any answer!

Some books are about specific parts of the Andes, for example - The Geology of Chile (Mareno and Gibbons - editors). This book represents a culmination of research in tectonics, geology and such from researchers across Chile.  Given the location of Chile, this is definitely an apt reference.

A comprehensive resource is the book Tectonic Evolution of South America (edited by Cordani et al. 2000), this brings together data, information and observations from dozens of scientists across South America.

A paper that is involves a study related to your query is Andean tectonics as a cause for changing drainage patterns in
Miocene northern South America (Hoorn et al. 1995) - this looks at the palaeodrainage of the northern portion of South America in the relation to the mountain building and tectonics of the region at that time.

Another paper, is The proto-Andean margin of Gondwana: an introduction, this introductory paper reviews the evidence for Andean tectonics and palaeotectonic regimes, stretching back to the Neoproterozoc.


What do cumulonimbus clouds signify? When I saw huge cumulonimbus clouds in the sky I thought the weather would be just fine, but in the evening it started raining. So I just wanted to know what do these clouds really signify.

Cumulonimbus clouds are thunder clouds, they are heavy and dense clouds that come in large heaps, these clouds produce precipitation or rain, Cumulonimbus clouds also produce hail and tornadoes.


Could the earth be much older than the currently accepted number? According to wikipedia, the Earth is about 4.543 billion years old. If I understand correctly, this number is based on radiometric age-dating of meteorites. So basically, the logic is this:

We've got this material
We can show that it's about 4.543 billion years old
We haven't found anything older.
Therefore this is probably about the age of the Earth

However inference 4 seems a bit problematic. How do we know that the Earth isn't significantly older? Could it be 5 billion years old? Could it be 8? Discounting the big bang theory, could it be 13 or even 15 billion years old, using only what we know about the science of the Earth?

The age of the solar system is 4.6 billion years.  We know that because almost all meteorites are 4.6 billion years old¹.  Therefore, that puts a very solid upper boundary to the age of the Earth.

According to solar system models, it took between 10 million and 100 million years for the Earth to form in the early Solar System.  That result is consistent with the independently estimated age of the Earth of 4.54 billion years old.  The Earth could maybe be 10 million years older, but it certainly couldn't be older than the solar system.

None are older.  We've never found a meteorite from outside the solar system.  I expect some scientists would have given an arm and a leg for the opportunity to sample some rocks from interstellar Oumuamua but it was not possible.


What makes pollen varieties useful index fossils? What makes pollen varieties useful index fossils? Should pollen not be a poor index fossil?

Depends upon the species. If the pollen spores are large enough, and of wide spatial distribution, and easily recognizable, and preserves well in sediments, and of distinctive age range (geologically), then it could be used.

There have been mistakes in the past where modern pollen collected in microscopic pores in older rock, giving the illusion of rock ages much younger than they really are, so precautions against sample contamination are of paramount importance.


Height of Everest from base to top It's relatively well known that Everest is the highest mountain above sea level, and that Mauna Kea in Hawaii is the tallest mountain from base to top.

But how tall is Everest from base to top? Or to put it another way, how high is Everest's base?

The 1954 recorded height of 8,848 m remains the accepted figure for height. As for the elevation of Everest's base, it is 5,380 m (at 17,600 ft).


What is the total weight of mineral extractions from Earth per year? I am writing a somewhat realistic space game, and instead of the commercial 3 or 4 commodities model, I am making my players suffer with all 118 elements. I have gathered the data needed to create templates for several types of planets, but when it comes to a template for extraction rates I am finding it surprisingly difficult to come up with some statistics I thought everybody loved, and despite the dozens of pages, I cannot find a site that would give me the total number of tons of minerals extracted from Earth per year. Any working number would do, if you can make a guess.

I read 55 billion tons per year somewhere, but that hinted as including organic production as well. The issue is specially sensitive in my case because what is extracted is taken out of the planet...

Since I am here :D , I am also looking for an estimate of: (1) number of mines in the world (2) number of people working (anyhow) in them (3) Number of factories in the world. Though some of these might better suit some other subject, I'd appreciate if you can point me at some direction. Thanks in advance.

EDIT Only to clarify something about the 118 element model I was asked,as to the mining and usability of some elements:
We humans haven't yet discovered all the possibilities, but then Tc didn't have a chance to have its possibilities fully explored because we didn't find any during most of our existence :) However, once you find the technology to perpetuate Tc in a Bose-Einstein state, it is noted that the very properties that make it unusable now makes it the best energy dispersor in existence (important in shield technology). As to mining, yes, on Earth, and Earth minerals, S is a result of Cu mining, but on the gaseous planet Pioi there is no Copper, but plenty of free floating Sulphur, CRUCIAL in terraforming barren planets :) and all mines mine all there is in a body by abundance, not separate mines for each element, or that would be a micromanagement nightmare! I mean, if a settlement has, say, 10000 mines, the output is proportional to abundances of this moon/planet settled (which takes into consideration multiple mining). That is actually why I need the numbers in question!
(Incidentally I just remembered that an Rb surface is a great catalyst for alpha particle cycling during the first phases of ignition in star construction :P (It is 'realistic', but still as a sci-fi game)

This may give you some useful information. You can download the World Mineral Production (2011-2015) produced by the British Geological Survey at this link. This publication has data for approximately 70 different commodities by country and world totals (tonnes).


Is there any possible future for high energy geophysics? If so how it is going to revolutionize our knowledge about Earth's interior? How practice is to map/image the subsurface of the earth using the high energy particles like neutrinos?
https://www.geosci-instrum-method-data-syst.net/special_issue2.html

I don't think neutrinos will be much good for mapping the interior of the Earth, the reason being that they rarely interact with matter and are said to be able to pass through 11 light years of solid lead without being stopped (though I would take that claim with a pinch of salt). However, so many pass through the Earth from the other side that  a tiny number will interact and muons from these interactions have been detected coming upward through the ocean!

Muons seem to be more useful, and have already been used to detect secret chambers in the Great Pyramid. They undoubtedly have applications to volcanology, but don't have the penetration powers of neutrinos. Muons are very transient charged particles which decay in a minute fraction of a second to become electrons or positrons. Because of their ultra-brief lifetime and electric charge they can't penetrate very far, hundreds of metres rather than hundreds of miles, so although they are a useful tool I don't think they will revolutionise geology in general. They might revolutionise the more limited field of geophysics.

Cosmic rays are high energy protons and atomic nuclei originating in the sun and other stars, sometimes in supernovae, but their energy is very variable. Most are stopped high in the atmosphere, but their secondary radiations, which include muons, often reach the surface of he Earth. Owing to their randomness and unpredictability, they are unlikely to prove very useful.


Relative dating of intrusion I am quite new to geology and have a realtive dating problem which I am a bit unsure of. I know very well the principle of superposition, principle of cross-cutting, etc., but am still a little bit unsure on one part.  The problem is illustrated in the following picture:

My question is about the intrusion (E).  Obviously the intrusion must have occurred later than the deposits of layers B, C and D, but how can I tell if the intrusion occurred before or after the deposit of layer A?  In my opinon, both of these scenarios are possible.  The intrusion does not appear to cross through A, so I suppose it is possible that A was deposited after the intrusion.  But isn't it also possible that A was deposited before the intrusion, and the intrusion simply did not make it past layer B?

If anyone can let me know if there is any certain way of reasoning whether A or E occurred first, then I would greatly appreciate it.

It does seem like it's impossible to know unless you have additional information. However, I think there is a hint in there. See this white halo around the intrusion? My guess (and I could be wrong here) is that it's not there for artistic reasons but rather it's there to provide a very strong hint.

My feeling that this is some kind of metamorphosed contact zone (or aureole), which transforms sedimentary rocks into their low pressure and high temperature metamorphic equivalents (shales to hornfels, limestone to marble, sandstone to quartzite, etc).

It's hard to see, but I think I can see (when zooming in ) some of the white halo extending into the bottom of layer A. That would mean A was present when E intruded, because you can't metamorphose something that's not there. Otherwise, the metamorphic aureole would be cut by layer A.

Again, I'm not sure because the image is low resolution. Maybe you should ask your teacher or if that's not possible try to figure out if you should already know about metamorphic contact zones in your stage of geological education.


Why deep ocean didn't freeze during snowball Earth? I know that at least twice in its history Earth was totally frozen. I also know that the last time it happened there were already life on Earth, and it survived. In deep water, under the ice, which was transparent enough for light to penetrate it and support life.

My question is, why didn't all the water freeze? AFAIK Earth was frozen for 10 million years, so I think it was enough time. Something must have kept deep water from freezing, what was it? Geothermal warmth? Underwater volcanoes? Both seem to be too weak sources of energy for keeping deep ocean liquid.

The same about Antarctica. I know there was a lake found deep under thick ice, why didn't it freeze?

At least four things combined to prevent solid freeze-up during Ice/Slush Ball Earth periods:

It takes a lower temperature to freeze water under pressure. Deep sea pressures are enormous.
Ice floats. If it sank and new ice kept forming at surface, the seas might fill with ice.
The surface freezes first and acts as an approx zero-degree C barrier, slowing the progress of the ice penetration.
Thermal heat from the ocean floor at hotspots, island arcs, subduction zones, and mid-oceanic rifts is substantial, especially locally.


Are there significant amounts of rare earth elements on Iceland? The rare earth elements form in magmatic rocks. The Iceland is very active vulcanic region, and it's, to my knowledge, entirely build from magmatic rocks.

So it wouldn't be surprising if there were large amount of rare earth elements there? Are such deposits already documented?

The simple answer is no.
There are not any significant rare earth elements (REE) deposits in Iceland. This question: What are rare earths and why do they cluster near alkaline magmatism? gives a list of possible formation mechanisms.
Basically, to form a magmatic deposit of rare earth elements, simple magmatic activity is not enough. It would have to be magmatic activity related to one of two processes (or both):

Magma formed due to very low degree of mantle melting. REE are incompatible elements, meaning that they concentrate into the liquid during melting. If the mantle melts to a very low degree (let's say less than 1%), REEs are concentrated in it. Once the melting proceeds, the REE-rich liquid is diluted by further REE-poor melt. Rocks that form in this process are, or example, carbonatites and alkaline magmas. They do not exist in Iceland (and if they do, very scarce).
Magma that has evolved and differentiated. Let's say we take the REE-poor magma from 1. Now it starts crystallising. Remember that REE are incompatible and will stay in the liquid. So the residual melt eventually gets enriched in the REE. Think salt water being evaporated - the salt remains inside the water making it more saline. Pegmatite is one type of rock that forms in this process. Similarly, it does not occur in Iceland.


How to interpret the negative (actual) evapotranspiration values? I am exploring FLUXNET sites for actual evapotranspiration (ETP) data (I convert the energy balance closure-corrected latent heat to ETP).
I am interested in the half-hourly data. During the night we see negative values. I would like to know the reason or physical process behind this.
Can physically-based hydrological models handle this situation? (: estimating negative half-hourly ETPs)
There are some discussion in web about how to handle the negative values of potential ETP, but not easy to find a solid discussion about the actual ETP in this case.

Negative values for the ET, both potential and actual, usually refer to condensation.
See also "ERA5 mean evaporation rates data - Why is that negative?"
Regarding the ability of the physically-based hydrological models to handle condensation, I'd say that it's difficult to give you a general answer: it will depend on the specific math behind the model, but my general guess would be that they do.
Even a simple Bucket Model, would integrate condensation in the water balance equation. While a more sophisticate Earth System Model would probably process it in the soil moisture and/or canopy component, in order to better represent these dynamics in the water-energy balance of the specific system. See for instance Longo et al 2019


Pangaea - Why did all the land mass form in one area? The thing I find most interesting about Pangaea is that, if all the landmasses were connected, it leaves a massive amount of uninterrupted ocean everywhere else. It seems to suggest that there is a significant difference between the two areas of Earth; one area being where Pangaea was located, and the other area being the rest of Earth.

Why would only that portion of the Earth be above water? Is there something significant about where Pangaea was located which made it different from the rest of the Earth?

The formation and break up of supercontinents have happened throughout Earth's history in almost a cyclical manner. There may have been many others supercontinents before Pangaea and the total number of such is uncertain. The 4 last supercontinents are: Nuna (some other people call it Columbia) that was present in the period 2.0–1.8 Ga (billion years ago or 1000 million years ago, if you use the long notation); Rodinia that formed around 1.1 Ga and lasted until about 750 Ma; Pannotia that lasted 650-560 Ma; and finally, Pangaea.

The location of the supercontinents seems to have varied throughout Earth's history and it doesn't seem likely that there was something special about the location of Pangaea, except the underlying forces of plate tectonics.

Here is good animation of the evolution in time of the different supercontinents.


Why does it rain during the sunny day? What are factors that cause rainfall while the sun is still shining. The phenomena is known as sunshower?

The information I found so far is very limited. Please help me answer this question if you know anything about it.

I think Wikipedia explains quite well. It is the wind that transport the airborne water droplets from a nearby showering cloud. It is quite common in UK especially near the coast which is often very windy. Usually the weather forecast will say that it has scattered shower with sunny spell.
https://en.wikipedia.org/wiki/Sunshower


TRMM rainfall measurement for synoptic systems I have gone through the website of TRMM that explains how the TRMM satellite gather precipitation data- http://pmm.nasa.gov/node/158.  During the Indian Summer Monsoon (ISM), we have synoptic systems that deliver rainfall during the months of June through September. These systems are spread over days and often provide continuous rainfall i.e. they are continuous atmospheric processes. How does the TRMM satellite, which I do not believe is a geostationary satellite, 'continuously' measure the rainfall over a wide region of space?

Now one way they could overcome that is they mention they have a dozen such satellites that measure the precipitation but do those dozen satellites coordinate their work as in a A-train satellite constellation? If they do not coordinate their work they probably return to the same location every few hours to make a measurement.

If that is true what sort of assumptions are made  about what happens between these observations from a algorithms perspective to derive precipitation values?

The Tropical Rainfall Measuring Mission (TRMM) satellite is a single satellite, carrying multiple instruments on board, as described here. It makes a total of 16 orbits/day at a low altitude of 400 km, with different swath widths for each instrument. Thus, the measurement product that you get is not a "continuous" measurement of a single atmospheric phenomenon, but a composite of multiple orbital passes and instruments, where the density of coverage will depend on the time period over which the composite is made.

If you take a look at TRMM data access page, there are 3 levels of data, each level depending on the amount of processing and quality control:

Level 1: Precipitation radar (PR) reflectivity
Level 2: Combined rainfall profile - PR + Microwave interferometer (TMI)
Level 3: 3-hourly composite of the above + additional data from other instruments (satellites, ground measurements, ground radars), with extended range to 60S - 60N.

Level 1 and 2 data are nearly raw, and are not composites - they give you data from all 16 orbits/day, and each swath cross-section along the orbit will have a timestamp associated with it. Level 3 data will be the most spatially "continuous" of the three, but one must be aware that this is a composite of multiple orbital swaths and multiple instruments, so it is more suitable for slowly evolving (larger scale) systems.

Related: Is there a database of global rainfall time series?


How can agricultural ammonia lead to PM2.5 production in the atmosphere? The NPR News article Growing Corn Is A Major Contributor To Air Pollution, Study Finds talks about all sources of pollution associated with growing corn, and it singles out the application of ammonia to the soil as a surprisingly polluting aspect.
The article says that the ammonia which escapes the soil and is released into the atmosphere ultimately leads to the production of PM2.5 and is a major source of pollution harmful to people. It links to the new paywalled paper in Nature Air-quality-related health damages of maize.
Question: What would be the chemical and/or physical processes by which traces of ammonia in the air would lead to PM2.5 production?
From the article:

The study estimates that "4,300 premature deaths can be attributed to corn production," says Hill. "That's about a quarter of all [air pollution-related] agricultural deaths. That's significant."
The vast majority, 86 percent, of PM2.5 emissions happen on farms, with the rest occurring elsewhere in the supply chain, according to the study. The main culprit?
Fertilizer application.
"Ammonia from fertilizer application accounted for about 70 percent of attributable deaths," says Hill. The nitrogen in fertilizers helps fuel plant growth, but not all of it can be used by the plant. "Some of that nitrogen washes into waterways, and some of it gets released into the atmosphere as ammonia," says Hill.
Once ammonia hits the atmosphere, it reacts with other particles, mostly nitrogen and sulfur oxides, to form PM2.5, according to Hill.

From the question in Biology SE Why do soil bacteria produce nitrous oxide as a result of anhydrous ammonia fertilizer application?:

below: Anhydrous ammonia tanks in a newly planted wheat field. Walmart has promised big cuts in emissions of greenhouse gases. To meet that goal, though, the giant retailer may have to persuade farmers to use less fertilizer. It won't be easy. TheBusman/Getty Images. From here.

Acid/Base Chemistry

Gaseous ammonia (NH$_3$) acts as a base when it dissolves in water. The reactions are below.

NH$_3$(g) + H$_2$O(l) $\rightleftharpoons$ NH$_3$(aq)

NH$_3$(aq) + H$_3$O$^+$(aq) $\rightleftharpoons$ NH$_4^+$(aq) + H$_2$O(l)

The end product is an ammonium ion. We also have gas phase species SO$_2$ and NO$_2$ in air. They dissolve in water to form the conjugates of the acids H$_2$SO$_4$ and HNO$_3$ (e.g. SO$_4^{2-}$).

The protonized ammonium and the deprotonized acids (e.g. NO$_3^-$) are not gaseous anymore. They are also NOT solids. They are dissolved ions.

Precipitation and Nucleation

Ammonium cations react with the acid anions in an acid/base reaction to form a salt complex. An example is ammonium sulfate (NH$_4$)$_2$SO$_4$. When the concentration is low, salts remain as dissolved species in water. As the salt concentration increases, at some point, the salt condenses to a solid (it precipitates out of solution). Salt concentrations increase as the water droplets in the air take on more acid and base species. Salt concentrations also increase as the water droplets evaporate. This causes the water droplets to act as sites for the formation of solid salt particles.

Air also contains other solids as ultra-fine particles. Think ... dust.

All solid surfaces in water act as sites to catalyze the further capture of dissolved salts. They act as proton exchange mediators, better than the liquid phase itself.

The process of formation of a solid particle or capture of a dissolved species onto a solid surface is called nucleation. Nucleation is followed by growth. Some of the solid salts can alternatively redissolve when the conditions are reversed ... e.g. the concentration of the salt in solution surrounding it decreases.

The figure below illustrates the entire process using ammonia and nitric acids (formed from nitrogen dioxide).

Image caption: The compounds in green colored font are located at (mostly wet) particle surfaces or are dissolved in droplet water. Compounds written in black colored font are gaseous. A second arrow head is missing at the arrow connecting gaseous $HNO_3$ and particle-bounds $HNO_3$. Gaseous $NH_3$ is missing in this figure.

Because proton-exchange favorably takes place at surfaces or in droplets, the particles grow favorably rather than redissolve (see below).

References

An exemplary particle size distribution is shown below (own work (Neumann, 2016, Fig. 2.1) but content based on Seinfeld and Pandis (2006a, Fig. 2.7,p.59) which is based on Whitby and Cantrell (1976)). The Y-axis shows particle abundance (roughly; please see Fig 2.2 in the linked document above for details).

The major source of the coarse particles on the right are primary emissions of particles (dust, sea salt, ...). The accumulation mode particles in the center are partly caused by primary emissions (fine sea salt, combustion processes, ...) and partly grown from smaller particles (Aitken mode or ultra-fine particles). Actually, the ultra-fine particles are grown from so called nucleation mode particles by the condensation of further atmospheric gaseous compounds. The nucleation mode is missing here (and merged with the Aitken mode). Nucleation mode particles are those particles, which are formed by ammonia and atmospheric acids.

Other sources for these nucleation mode particles are gaseous organic compounds, which lump together to form particles. The latter particles are also called SOA (secondary organic aerosol). Isoprene is one of the compounds that forms SOA.

Health Impacts

When we combine air polluted by combustion emissions ($NO_X$) with air affected by agricultural emissions, we can expect the formation of ammonium nitrate particles ($NH_4^+$ + $NO_3^-$). Ammonium nitrate can irritate the eyes, nose and lungs. As stated in a comment and to the best of my knowledge, ammonium nitrate particles are not as harmful as e.g. fine soot particles. But I am not a expert on this field.

Ammonium sulfate (from $SO_2$ from combustion emissions) have been shown to have negative health impacts on the respiratory system but also on the cardiovascular system (heart etc.; if the particles are sufficiently small to pierce the lung-blood barrier).

Ultra fine ammonium nitrate particles can be nuclei for condensation of further gaseous compounds -- e.g. VOC (volatile organic compounds) --, which might have harmful impacts on our respiratory system.

notes

Commonly, atmospheric particles are not dry spheres/lumps of matter but somehow associated with water: water droplets with dissolved compounds or a solid core with water attached to the surface; whereas dissolved compounds might be dissolved in the water of the latter type.

The atmospheric life time of gaseous acids is very short because they tend to get attached to water (and deprotonize -- reducing the pH value of the water). Partly, the reaction from precursors to acids takes place in the wet particle/droplet phase. E.g. most of produced sulfuric acid ($H_2SO_4$) takes place in the wet phase.

tl;dr

Thus, we foster the growth of ultra-fine nuclei by the condensation of ammonia (as base) and condensation/formation of acids.

References:

Seinfeld and Pandis, 2006: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change.
Whitby and Cantrell, 1976: Fine particles in Proc. Int. Conf. Environ. Sens. and Asses.


Why is the colour gradient in the sky at sunset on an angle? Below is a picture of a typical sunset that I have been observing lately at an undisclosed location in the Southern Hemisphere:

Given that the base of the picture is parallel to sea level, you can see that the line where the dark blue meets the red in the sky, is on an angle of elevation of approximately 7 - 8 degrees.

Is there an explanation for this phenomenon (which I have observed for the past few days) and is it related to my position on the Earth, or the time of year?

Looking at your picture I would say it was most likely not taken facing in the direction of the setting sun, but perpendicular to it. What you see as a colour gradient is most likely the shadow of the Earth. I suspect if you took a series of pictures you'd see the shadow (your gradient) moving upwards and becoming steeper while the sun sets deeper behind the horizon.


How are thermals really released? Sailplane, paraglider or hang-glider pilots are used to say 'thermal is released by trigger'.

The zones with contrasting albedos (land/water, plowed field/forest) or locations where terrain profile changes abruptly are dubbed as triggers/release points. There are even legends about maneuvers of last hope when glider pilot dives down, makes a low pass above the overheated wheat field and thus releases thermal.

There is also a tendency to divide thermals behavior regarding the area - either it is a flatland or mountains - as if laws of nature were different.

There are two things here which I do not like.

1) The claims are not supported by or at least reference any scientific proof.
2) My own humble experience of thermal soaring partially contradicts with common beliefs.

I have many times witnessed long living dust devils. They are good examples of a non stationary point of detachment of hot air from the land surface. They actively move instead of being fixed to some special point like top of the heel.
Dust devils (not tornado) also can appear above water surface, so it looks like unstable layer of overheated air can magically ignore heat contrast between land and water.

Large thermals also behave similarly...Well, at least some of them.

In springs, when people burn old leaves, the smokes of fires converge and literally show you the point where thermal is. Being 1500 meters above the ground allows you to notice that the lowest part of the thermal moves quite noticeably even without background wind and do not stop where forest begins.

The only practically useful book about thermals I have read so far is Scorer R. S. Environmental aerodynamics, Ellis Horwood Limitid Publisher Chichester. — N. Y., 1978.
Though Scorer writes much about thermals structure (jets, plumes, thermals), he says almost nothing about how exactly unstable air is perturbed to give a birth to a thermal.

I fly too, so I have first hand experience with movement of air below 13000 feet (Cessna 172). I have my simple version: in an otherwise calm weather a thermal has three stages which looked from profile looks like a tree. Base level near earth is the roots. Rising column is trunk. And cooling off and dissipating at high altitude is the canopy.

The part that has lifting power most is column because it picks up speed and momentum while it spins and whirls like the water draining into a sinkhole. The rising column can be pushed and swivel around by wind or topology of area surrounding it. The source of energy is dark surface or topology or local climate that can create layered temperature gradient from hot near ground to cold at altitude. Of course as we pilots of small planes know there are many other factors involved specially in mountains. Fire fighters are keenly aware of the tunneling effect and unpredictability of thermal near the canyons.


I am not sure about your R code or your snippet of data.  However, you could do an ncdump on the file and direct the output to text to get it "from the horses mouth" so to speak.

In general, the lat/long export of the WRF grid will not have a linear pattern.  WRF uses a spatially projected grid, likely an equal area lambert method or something similar. The curvature of the Earth creates non-linear grid values in geographic coordinates, but the projected grid coordinates (which you can also export) are linear. See the example WRF domain below plotted in geographic coordinates.

image credit: Zhongfeng Xu and Zong-Liang Yang


Did an impact crater influence the formation of uranium deposits in South Australia? As a supplementary question Did an impact crater cause the formation of the gas fields in north eastern South Australia . South Australia is a well documented uranium province. Could an impact crater, as announced in early 2015 have created conditions that would have allowed South Australia to be the uranium province that it is?

Sort answer: from what we already know, NO.
A comet (or asteroid) impact can influence mineral composition near the crater (high pressure and temperature) but this impact is small and diminishes quickly in respect of the radius. There is no documented quantitative difference of a mineral deposit versus its radius from an impact crater (not in cm and meters scale, but in km scale). Thus, we cannot assume that there is correlation between uranium deposits of Australia (or any other country) and impact craters.
Uranium deposits can be formed in many ways:
As you can see from the list, 7 out of 15 ways of uranium formation, occur in Australia. None of them due to comet impact.

1. Intrusive deposits
In South Australia, Radium Hill was mined 1954-62, and large bodies of low-grade mineralisation occur in the Olary Province.

2. Granite-related deposits
The dimensions of the openings have a wide range, from the massive veins of pitchblende at Jachymov deposit (Czech Republic), to the narrow pitchblende-filled cracks, faults and fissures in some of the ore bodies in Europe, Canada and Australia.

3. Polymetallic iron-oxide breccia complex deposits

4. Volcanic-related deposits
In Australia, they are minor – Ben Lomond and Maureen in Qld are the most significant.

5. Metasomatite deposits
Valhalla and Skal (Australia)

6. Metamorphite deposits

7. Proterozoic unconformity deposits
Australia (the Alligator Rivers region in the Pine Creek Geosyncline, NT and Rudall River area, WA).

8. Collapse breccia pipe deposits

9. Sandstone deposits
Basal channel deposits – wide channels filled with permeable sediments. Examples are Dalur and Khiagda (Russia) and Beverley and Honeymoon (South Australia).
Mafic dykes or sills in Proterozoic sandstones – Examples at Matoush (Canada) and Westmoreland (Australia).

10. Palaeo-quartz-pebble conglomerate deposits

11. Surficial deposits

12. Lignite-coal
Mulga Rock (Western Australia).

13. Carbonate deposits

14. Phosphate deposits

15. Black shale deposits