Would ultra-efficient carbon sequestrion produce immediate results in global temperatures? So, imagine a new technology were introduced that was incredibly efficient at carbon sequestration, lets say removal of ~90% of carbon in processed air and processing 10 tons of gas per minute (these numbers can be fudged, the basic gist is extreme carbon sequestration that would be visible on a global scale in a very short order of time, like, less than a decade or so).

Earth is warming, and it's obvious in our longer spring/fall seasons and shorter winters. If we were to quickly remove atmospheric CO2 using the above mcguffin, would the seasons revert to pre-industrial levels relatively quickly, or would earth have trapped a significant amount of solar energy that would need to radiate away before we began to see normal seasons?

The issue of the lag time between carbon addition to the atmosphere and maximum warming that results from it, is probably pretty divisive. I had previously heard estimates around 50 years, but the most recent work I could find (that was available for free) indicates that 10 years is about right, with Figure 1 of the linked paper being the best graphical evidence. This 10 year response is for a one-off injection of carbon, so we can't assume it would work the same for a one-off removal of carbon, but we can go with that number for now.

So, looking at Figure 1, if we started rapidly removing carbon from the atmopshere, the temperatures should reflect within a year or two, and if we removed ALL of the anthropogenic delta-CO$_2$, we could expect temperatures to go back to pre-industrial revolution plus or minus any natural changes since then in about 10 years.

A side note: supposing we could sequester as much carbon as we put into the atmosphere every year. That would be great! But how much energy would it take to sequester that carbon? And where would we get the energy to sequester the carbon. Sequestration seems like a great idea, but I don't think it would work, even if an excellent method of sequestration could be found, until the world's energy demands are met from non-fossil fuel sources.


How to make wind forecast like Predictwind.com? Which mathematical model has been used? PredictWind.com is able to make wind forecasts on a very precise 8 km scale. For educational reasons I would need the mathematical model used or at least one very similar.

Searching on the internet I did not find much. Do you have any suggestions?

It seems like that particular website is a commercial forecasting website and requires login/registration information, so I will take your word for the output.

The general equation of motion is described by the Navier-Stokes Equations, which is $$\frac{\partial \vec{u}}{\partial t}+(\vec{u} \cdot\nabla)\vec{u}=-\frac{1}{\rho}\nabla P+g\hat{k}+\nu \nabla^2\vec{u}+f\hat{k}\times\vec{u}$$ where $\vec{u}$ is the atmospheric motion vector (wind + vertical motion), $\rho$ is density, $P$ is pressure, $g$ is gravity, $f$ is the coriolis parameter, and $\nu$ is the kinematic viscosity.

This very complicated equation currently has no analytic solution (if you have one, you can win $1,000,000 from the Clay Mathematics Institute), but is instead discretized and solved using even heavier mathematics. Additionally, some mathematical tricks are played on the equations to 'simplify' them, but it usually results in other problems.

While 8 km seems like a fine scale, it actually isn't. Smaller phenomenon (called eddies) affect the weather significantly, so research that tries to mimic the effect of those eddies is applied, but there are still problems. Cutting edge research tries to reduce that 8 km (called resolution- think of the resolution of your television) down to tens of meters, but at a significant cost- one that limits the domain.

Likely, the data that your website comes from a weather model, which attempts to solve the above equation. Such models could include the ECMWF, GFS, and other global models.


Geology: facies v. formations Can someone please explain the difference between sedimentary facies and formations?

A formation is a unit of stratigraphy. It refers to a set of sedimentary layers which are somehow distinct from those above and below them in the stratigraphic sequence. This may be because they have a different lithology, different sedimentary structures, or different fossil assemblages, or something else entirely.

A sedimentary facies is a set of rocks which where deposited in the same sedimentary environment. Typically deposition in this environment will leave behind distinctive signatures in the rock which can help to identify the environment of deposition.

Within a formation the facies can change both vertically and laterally. Equally, the facies may not change at all over several formations.


Does vegetation contribute to long-term carbon sequestration? So we know that vegetation sequesters carbon dioxide into its leaves. Much of this carbon sequestration is temporary, since when the plant dies, much of it is released as CO2 back into the atmosphere. If it dies in a frozen region, it could be sequestered in permafrost, but even that can be released back.

What if it dies, and some of the carbon gets carried into a river, which could then deposit its carbon into the ocean basins?

Unlikely but theoretically possible.
As the bits of tree work their way down to the sea, they are going to oxidise and release CO2. This would appear to our eyes as "rotting" and breaking down. Leaves aren't going to make it, although they might get buried in river sediments.
Trunks might. Once they reach the open sea, they are going to have to become water logged and sink to the bottom of the sea or ocean. They are going to then have to either fall into an area of anoxic bottom waters (restricted water flow => very little oxygen if any), or be quickly buried by sediment that cuts off the oxygen.

Speaking generally, when I look at ocean sediments, I have yet to see fossil wood. I do see fossil wood in places like river deltaic sediments though (eg. the Carboniferous sandstones of West Yorkshire).


How are data from tiltmeters used to monitor volcanic activity? I've just learned in this answer that tiltmeters (which I assume measure changes in tilt) are used near active volcanos. (Saw a mention in item 4. here also.)

What kind of geological (volcanological?) information can be learned from tilt data? Can it also offer predictive benefits, trigger evacuation warnings?

Tiltmeters placed on the flanks of an active volcano can measure changes in the slope angle of the flank. These changes are often inferred to be related to changes in the shape and activity of the magma chamber.

This article provides a quick and dirty example of how these instruments can be used, as well as their limitations.

In this case, the tiltmeters were able to capture the deflation of an erupting magma chamber, but not the precursory inflation. This leads to some inferences about the nature of the magma's ascent through the subsurface.

The article also references studies that were able to detect magma chamber inflation as well.

These kinds of observations definitely add to the body of evidence volcanologists use to assess risk of an eruption, but it's far from a slam dunk.

Here are some examples from that paper, both the long-term trend, and a higher time resolution display during a small eruption:

Fig. 2. Tiltmeter data from V-net (KRMV, KRHV) and Hi-net (MKNH, SUKH) stations during the period from January 23 to February 2, 2011. From here.

Fig. 10. Enlarged view of tiltmeter data during the period from 0:00 to 21:00 on January 26, 2011. Vertical line shows the occurrence time of the small eruption at 7:31 and the beginning of the sub-Plinian eruption, when the amplitude of the seismic tremor increased at 14:49.  From here.


How quickly can coral fossilize? On a trip to Honduras a few years ago I visited one of the islands off its north coast with a friend and went to a section of it mostly with nothing but residences which looked far less visited by tourists and which had no live coral off the coast in that section of island unlike other parts of it. While in that area we saw what looked like a rocky protrusion a little off from a small beach, about 50 or so yards offshore, so my friend and I waded out to it and we were stunned to discover that it was a rather large exposed section of coral that had been completely fossilized. It was pitted in parts, reminding me a bit of the surface of the moon, but we clearly saw amazing varieties of coral and their fossilized contours and patterns in the "rock".

But more puzzling is that it protruded at its base a good 1-2ft above sea level on average (though erosion made the edges gradually slope down to the water) and up to probably betweeb 5 to 7ft above sea level in some other areas where the coral [or mass it was on] protruded), which made the higher sections clearly higher than the beach we had just waded from. That seemed to indicate that the ocean level may have been quite a bit higher when it was still alive and parts of the island may have been more submerged at some point in the past if I had to guess.

Ignoring for a moment my imprecise measurements and notes about its exposure relative to sea-level, how long would it take any portion of alive and healthy coral to fossilize once exposed directly to the sun outside of/above water at its quickest, turning rock-grey and becoming firm, even if the fossilization process is not completed to its utmost extent? Can it happen in a few thousand years, or does it happen only at a significantly slower rate than that? Has any such process of fossilization actually been observed (as proceeding through its stages) at any point throughout recorded human history, and what would intermediate stages look like in terms of color, firmness, etc.?

I am not an earth scientist so you'll have to go easy on the explanation here.

Edit: I have now uploaded some photos to Flickr of the particular coral I saw. The "mini island" (I'll call it) was quite alien-looking and bizarre in places, also overgrown with some plants on the main mass, but you can, for example, see the close up I took of one fossilized bit of brain coral that was firmly set in the rock.

I also found a similar photo on Flicker taken by someone else taken from San Salvador (Bahamas) at what is identified as the Cockburn Town Fossil Reef, and the photo has an interesting scientific essay with citations in the image description.

First thing is that the sea-level wasn't necessarily that high when the reef was growing, Hondurus is on the edge of the Caymen Trough Fault Zone and experiences quite high rates of uplift, (relatively speaking, your fingernails actually grow faster but over long periods it builds up). So the Coral reefs you're seeing high and dry could be quite recent in geological terms and laid down at or close to current sea levels.

Live Coral is a thin skin of either algae or tiny animals called polyps over what is essentially already Limestone. The live coating builds up this Limestone in order to 1. protect itself and 2. gain advantageous position as far as sunlight and nutrient rich currents etc... Once the coral builders die, which can happen within minutes of exposure to the air for some species (for others the water just has to get too warm, or too cold), the "skeleton" is already effectively a fossil and pretty well as hard as it's going to get.

Any reef is largely made of Limestone from dead Corals that have either simply been grown over or have been broken, ground down and then the coral sand concreted together because of biological and/or chemical processes to form bulk Limestone in which most or all of the old coralline structure is invisible. The primary mechanism for removing coral structure is actually fish that crush coral chips into sand or even finer grains while feeding on surface dwelling algae. The hardening of these grains into a homogeneous whole is usually a combination of the action of coralline algae creating lime on the grain surfaces that bridges individual grains together and the chemical precipitation of dissolved minerals, particularly calcium carbonate from the grains themselves, into the lime sand beds due to daily fluctuations in water temperature and the associated calcium carbonate solubility shift. As the temperature of the water drops at night more lime can and is dissolved into the sea, during the day this process is reversed by the rising water temperature. This process is ongoing with coral sourced lime being added to the limestone reef steadily all the time it's growing.

In terms of the grey colouration you've observed a lot of that will be land derived sediment that was incorporated into the reef while it was still growing and is the natural colour I would expect from an exposed reef deposit so close to shore. Some of it may also be surface in nature though and the rate at which that will accumulate will depend on the wind, the amount of dust in the environment and the surface porosity of the exposed deposit. The higher the winds, the dust count, and/or the surface porosity the faster that surface will be discoloured by dust. There might be a little bit of chemical staining from water percolation but that's normally in the form of Iron and is yellow, red, or orange in colour, similar to this image from Spain.

Short version not much has actually happened to the reef deposits you're seeing since they were laid down except that as the land has risen they've been taken along for the ride and are now above sea level.

If I missed anything or wasn't clear somewhere along the line give me a shout in the comments and I'll update accordingly.


Why are there 5 oceans? Like many people, while in school I learned there were four Oceans on Earth - Pacific, Atlantic, Indian, Arctic. In general I think it was described that the currents and the surrounding continents are what divided them into different oceans.

Now there is a Southern (Antarctic Ocean). I thought (when I was taught) that that area was just Southern Pacific and Southern Atlantic, but I'm sort of fuzzy.

How (or why) was it determined the Southern Ocean is an Ocean?

The Southern Ocean does have its own current, the Antarctic Circunmpolar Current.

It helps generate the Circumpolar Deep Water due to density gradients. Ice melts and thus salinity decreases. Differences in salinity are the reason for bulk water movements in the ocean.

Thus the Southern Ocean contributes to cool the Earth.

Geographical criteria may be open for discussion, but oceanographically speaking it is a separate system from its neighbors, the Atlantic, Pacific and Indian.


Are there any effects on the atmosphere comparable with ebb and flood of the oceans? Due to the attraction of our moon (and Sun) our oceans undergo an up and down movement every day. So the water rises or falls by a couple of meters. But does this type of effect also occur with our atmosphere?

Yes, they are called atmospheric tides. They can be caused by the gravitational effect of the moon on the atmosphere (lunar tides) and also differential solar heating (thermal tides). I believe you are asking about the former which is much weaker than the latter.

You can find more about it here: https://www.springer.com/us/book/9789027726308
and https://physics.stackexchange.com/questions/201973/are-there-tides-in-the-atmosphere


A human foot impression on a rock There is a rock that I have been climbing ever since I was a kid to get a magnificent view of an escarpment. One of the things that was part of our rock tour among other things was a perfect human child foot impression on top of the rock. It looks like the rock was molten or wet and someone just stepped on it before it dried.

Is this even possible?

As @kwinkunks and @Gordon Stanger say, it's not possible to comment usefully on your particular observation without at least a picture and further information about the site. However, if you're asking “Is this even possible?” as a general question, the answer's yes, but under special circumstances. As an example, picture a scene in ancient East Africa: some individuals made their way across a layer of volcanic ash on the ground, leaving footprints in the process. Whether the ash was already wet or later rainfall fell on a dry ash layer (light enough not to destroy the evidence), the wet ash hardened and the footprints were buried under more ash fall - the “Laetoli” footprint tracks, discovered in Tanzania in the 1970s by Mary Leakey and her team, are remarkable evidence of bipedalism in our ancestors of ~3.7 million years ago.

References:

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

http://www.sciencedaily.com/releases/2011/07/110719194356.htm


Is the Mid-Atlantic Ridge a ridge or a trench? I am confused after reading conflicting text from different sources. For example, I read that divergent oceanic plates form ridges. National Geographic calls Mid-Atlantic Ridge a valley!

On the other hand, Wikipedia states this:

  The Mid-Atlantic Ridge includes a deep rift valley that runs along the axis of the ridge along nearly its entire length. This rift marks the actual boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava and producing new crustal material for the plates.

As per Wikipedia: a rift valley is a type of trench!

Trench has a specific meaning in plate tectonics. It doesn't just refer to any valley; it specifically refers to the features formed at subduction zones by the flexure of the downgoing oceanic plate. A classic example is the Marianas Trench which is the location of the deepest point in the ocean

Fast spreading ridges do indeed have valleys at their centre but these are not usually referred to as trenches to avoid confusion. In slow spreading ridges the valley is often filled up with erupted lavas. However, the valley sits on top of a much larger ridge, which is the surface expression of hot mantle upwelling below the spreading axis.


Aspiring Geophysicist I am interested in becoming a geophysicist. I am currently doing my undergraduate degree in the UK but have not chosen a specialisation. Is it better to specialise in Earth Sciences as an undergrad or go with Physics?

I like quantitative fields but I feel that undergraduate Earth Sciences does not offer such quantitative aspects. I also really like physics but feel that applying it in the context of the earth is really interesting. As becoming a geophysicist would probably require me to go to grad school, would an undergrad degree in Earth Sciences or Physics better prepare me to study Geophysics in grad school?

I would recommend to do an undergraduate in physics.

I work at a department of Meteorology.  When faculty hire a new PhD student or postdoc, they often prefer those with an undergraduate in Physics than with an undergraduate in Meteorology.  The Physics degree gives a better preparation for doing science.  It has more maths and physicists are more likely to have some programming experience than meteorologists.  For most scientific positions, such programming experience is highly valuable.  It appears the meteorologists are more likely to end up in jobs like weather forecasting or energy trading, rather than science.

Although this experience may be quite localised, a physics undergraduate degree does give you a more generic background.  It's easier to catch up on the specifics of geophysics when you have a physics background, than the other way around.


Tidal flow in an estuary I am working on a project. Where this bacteria has been deposited at a port in the Humber Estuary. Where it has been deposited has been marked in red. I am trying to work out the limits of where this bacteria can get moved to. I know that the input of all freshwater by the rivers is 250 m3 per second so I could calculate the movement of the bacteria as it leaves the estuary. However, I want to work out if it can be moved inland by the tide. I have found some information that looks at tide velocities. However, the velocity seems pretty low compared to the amount of freshwater entering the estuary. The thing is the points of tidal incursion are marked on the map so I assume the tide reaches there, especially as the tide can increase the height of the river by metres in some places. I am struggling to know what information I need to calculate this because I am more a biologist by training.

Any help would be appreciated!

Thanks

James

The tidal flow velocity is not the same thing as the mass movement. Think of the tidal flow as a pressure pulse that moves up the river. It moves much farther than the actual salt water movement. The extent of the brackish zone is much shorter. The relationship depends on the river flow and the shape of the estuary.

In your case, your source area is within the limit of saline intrusion so there is some mass movement upstream. Given that you are studying bacteria particles rather than dissolved salt, I would say that the limit of saline intrusion marked on your map is an upper limit for the distance it could move upstream. That is assuming that the bacteria haven't established a stable population that can reproduce and grow outward.


Does temperature affect partial pressure of gas dissolved in water? I am trying to understand the behavior of oxygen dissolved in seawater. I have always been under the impression that if a gas is in equilibrium between its gaseous and aqueous forms, that it will always have the same partial pressure in the air as in the water. For example, both air and air saturated seawater have a pO2 of 21.227 kPa (101.325 kPa x 20.95%). I recently, however, came across this tool from a company that creates dissolved O2 measuring devices which indicates that temperature has an effect on this relationship. It indicates that if atmospheric pressure is 101.3 kPa (pO2 in the atmosphere = 21.222 kPa) then the pO2 in seawater could be anything from 21.094 kPa at 0*C to 20.331 at 30*C.

If this is true, what causes this relationship? How can I calculate expected seawater pO2 given atmospheric pressure and temperature?

Bonus if you know of a function or package in R that could do this. Perhaps in the marelac package?

have always been under the impression that if a gas is in equilibrium between its gaseous and aqueous forms, that it will always have the same partial pressure in the air as in the water. For example, both air and air saturated seawater have a pO2 of 21.227 kPa (101.325 kPa x 20.95%).

That's a very bad impression, and your example is just not the case. Oxygen solubility in water at 0°C at one atmosphere of pressure is 14.6 mg/liter in fresh water, 11.2 mg/liter in salt water (35 g/kg salt). Those values correspond to 1036 pascals and 794 pascals, respectively.

Oxygen solubility in water is highly temperature and pressure dependent. Like most (but definitely not all) gases, oxygen solubility in water is greatest at 0°C.

Oxygen solubility comes very close to following Henry's law for typical pressures. Henry's law says that "at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." The constant of proportionality is not constant. It instead is a function of temperature and the nature of the liquid.


Calculation of river width in relation to contributing area I'm looking for a mathematical method to estimate the river width based on the basic topographic information of the specific sections of stream under consideration.
Is there a formula to estimate the river width in a specific point based on the upstream contributing area (or any other relation with the geo-morphological characteristics of flow accumulation)?
Could you please also refer to the corresponding literature?
Thank you

It's a function of flow volume rather than catchment area. The flow rate can be vary by an order of 10 to 100 for the same catchment area, https://www.google.com/search?q=average+river+width+based+on+flow+volume&tbm=isch There's so many variables like flow speed, inclination, bedrock type, flow rate.
This document includes the river width, it says there are too many variables.
https://www.nature.com/articles/s41598-019-44347-4
https://link.springer.com/article/10.1007/s11629-014-3265-0
here's a cool reference:
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082027
Did you know that a given type of rock gives mountains with all the same slope angles, i.e. there are mountains with ravines averaging 23 or 14 or 33 or 50% for the same mountain group, and screes inclines are rarely an irregular mix.


Street and road data Where do companies like Google and Yahoo and Mapquest get their street and road data? Is this a data source that the public has access to?

Google Maps and MapQuest have gathered data and information through subcontractors and their own internal efforts. Their information is proprietary and is very hard to gain access to (and most methods of scraping this data would violate their Terms of Service). It's generally not considered a reliable source for getting anything beyond geocoded addresses.

An alternative method for getting more specific geographic data (e.g. building footprints, forest extents, roads/highways, POIs, etc.) is through the OpenStreetMap Project. This information is Open and crowd-sourced with very few limitations. Specific information can be grabbed through their Overpass API or can be downloaded as a whole in their pbf format which can then be converted to shapefile/GML.


What are these basal rip up clasts in North Dakota? Ther's an graph that appears that the KT asteroid turned the rocks into rubble 3000 km away, else there was a rain of big rocks from the sky.

What are the rip up clasts and what is the way they were generated?

It's at the base of the formation, section 1, lower left.

Log from Tanis Site, North Dakota. Document from PNAS 1

Robert A. DePalma, Jan Smit, David A. Burnham, Klaudia Kuiper, Phillip L. Manning, Anton Oleinik, Peter Larson, Florentin J. Maurrasse, Johan Vellekoop, Mark A. Richards, Loren Gurche, Walter Alvarez, (2019):
"A seismically induced onshore surge deposit at the KPg boundary, North Dakota"
Proceedings of the National Academy of Sciences Apr 2019, 201817407; DOI: 10.1073/pnas.1817407116

Short answer: They are clasts from adjacent hillside deposited
inmediately after the Chicxulub impact.

The log you posted represents a sudden onshore inundation event due to the impact.
The paper you provided clarifies it [1]:

Tanis site, which documents a turbulently deposited, rapidly emplaced
sediment package directly overlain by the Cretaceous–Paleogene (KPg)
boundary tonstein. The site, situated in the continental Hell Creek
Formation in southwestern North Dakota (Fig. 1), displays
inland-directed flow indicators and holds a mixture of Late Cretaceous
marine and continental biota, implying that its emplacement is related
to sudden onshore inundation surges.

Figure 1: Tanis Site, North Dakota.

Figure 2: Log of Tanis Site, North Dakota.

The unit 1 is described bellow. The contact between conglomerates and the point-bar is non gradational, and the rip-up clasts come from Hell Creek strata above the river (1C).

The base of unit 1 comprises a matrix-supported, massive coarse-sand
conglomerate, with angular pebble- to small boulder-sized rip-up
clasts derived from the underlying Hell Creek strata. As shown in Fig.
2, the massive sand (1a) at the base of unit 1 has a sharp
non gradational basal contact with the underlying point-bar surface and
vertically grades into a thin (∼3-cm) zone of plane-parallel bedding
of interlaminated sand–silt (lower 1b); climbing ripples (mid 1b);
sinuous, wavy lamination (upper 1b); low-angle cross-lamination (lower
1c); fine, discontinuous subparallel lamination (upper 1c); and nearly
structureless fine silt/mud near the top (1d). Flow-direction reverses
180° toward the east—seaward—near the top of unit 1

My guess is they were transported to the sand-bar from the hillside because of the sudden event, before the conglomerate clasts started to fall from the sky.

The whole depositional unit took place shortly, and before the iridium layer.

Because the Tanis deposit contains ejecta throughout and is also
capped by the KPg tonstein, the depositional event took place
during a narrow window of time: after impact but before deposition
of the fine-grained KPg tonstein. Given this constraint, we can
deduce that the Event Deposit was emplaced within a matter of hours
after the Chicxulub impact event.

The subsequent conglomerates are aerial deposits .The event is nicely described at the paper.

We assume a scenario in which ejecta-curtain material, launched at
about a 45° elevation angle and seen as the glassy or altered-glass
spherules at Tanis, arrived before the shocked quartz that was
launched at steep angles in a “warm fireball” produced by release of
CO2 from shocked limestone after departure of the ejecta curtain

 1    Robert A. DePalma, Jan Smit, David A. Burnham, Klaudia Kuiper, Phillip L. Manning, Anton Oleinik, Peter Larson, Florentin J. Maurrasse, Johan Vellekoop, Mark A. Richards, Loren Gurche, Walter Alvarez, (2019):
"A seismically induced onshore surge deposit at the KPg boundary, North Dakota"
Proceedings of the National Academy of Sciences Apr 2019, 201817407; DOI: 10.1073/pnas.1817407116


What is this fossil found in flint in Kent? My 7 year old son found this fossil whilst cracking open flint in Deal, Kent.
The fossil (assuming it is) looks like scales/cells/shell and is chalky. The oblong lines are raised and well defined and tough to the touch. It certainly looks like a natural biological pattern.
It looks very a little smaller than a golf ball stuck in the flint. Its edges disappear under the flint with the appearance that it is a sphere.
Be glad if anyone has an idea. Thanks[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/ye4XU.jpg![enter image description here](https://i.stack.imgur.com/byNAu.jpg)

That is a sea urchin (echinoid) or at least part of one. the pattern of plates is fairly distinctive. 2 rows of small plates alternating with 2 rows of large plates. I am not familiar enough with urchin phylogeny to give you species but you might be able ot get it from the biology stack.


Are these clouds exhibiting gravity waves? This is a GOES visible channel image from 2017-01-27, about 9 a.m. local time. It's the Atlantic coast of the US. The coast is visible towards the bottom of the image. The scale is large.

This question is referring to the wavy structures that appear in the clouds. Are these 'gravity waves'?

These are rotor clouds, and are manifestations of "Lee Waves", a particular kind of internal "gravity wave" (better defined as "buoyancy effect").

Forced convection helps form these clouds as warm, moist air is forced upward by both wind from behind and the mountain barrier in front. The upward movement forces cooling and condensation of vapor into clouds. Once past the mountain barrier, this instability dissipates it's momentum through a series of less intense waves as a function of distance away from the mountain range. The clouds themselves are "standing": they do not move, but are constantly regenerated by the windward moist air mass; nor do they build increasingly larger as they are dissipated on their lee side.


Horizontal momentum flux in the surface layer Given the question below, how would the kinematic momentum flux be at the surface layer?
For letter a, why would it be that way (positive, negative, or 0)?

Based on the answer below:
I’m not sure if I’ve done it correctly, but this is how I answered it based in your comment below.

First, I assumed that $\overline{u’w’}$ = $\overline{w’u’}$. So is this something like the mixing of horizontal momentum into areas of lower wind speed (as is the case in the surface layer)?

Instead of just giving you the answer to a textbook problem (which would make SE a version of Chegg that future students would use to cheat on homework), I'll guide you in getting an answer.

Which variable does $\overline{u'w'}$ affect most?
For that variable, identify the surface layer.
Imagine that you are on the line. If you go straight up (that is, $w'>0$) what would the difference be between the $M$ traced out and the graphed $M$? What is the sign of $w' \times u'$?
Do the same as number 3, except start at the top and go down ($w'<0$).


Why is Venus so cracked? Wired.com's Space Photos of the Week: Perfectly Safe Celestial Coronas includes radar images of the surface of Venus taken from spacecraft in orbit around it. One of them shown below.

What causes this peculiar cracking? It reminds me of ice somehow.

  In 1991 NASA’s Magellan spacecraft captured the cracks and corona on the surface of Venus. You can see some younger impact craters, as well as cracks from plate tectonics; that main circular feature is a corona created by past volcanic activity.PHOTOGRAPH: NASA/JPL

I found the picture with a small write up on a JPL site.

It's a picture of the Aine Corona with pancake domes.

  P-38340 MGN-48
  5/21/91

  This Magellan radar image shows a region approximately 300 kilometers (180 miles) across, centered on 59 degrees south latitude, 164 degrees east longitude and located in a vast plain to the south of Aphrodite Terra. The data for this image were obtained in January 1991.The large circular structure near the center of the image is a corona, approximately 200 kilometers in diameter and provisionally named Aine Corona. Just north of Aine Corona is one of the flat-topped volcanic constructs known as "pancake" domes for their shape and flap-jack appearance. This pancake dome is about 35 kilometer (21 miles) in diameter and is thought to have formed by the eruption of an extremely viscous lava. Another pancake dome is located inside the western part of the annulus of the corona fractures. Complex fracture patterns like the one in the upper right of the image are often observed in association with coronae and various volcanic features. They are thought to form because magma beneath the surface follows pre-existing fracture patterns. When eruptions or other movements of the magma occur, the magma drains from the fractures and the overlying surface rock collapses. Other volcanic features associated with Aine Corona include a set of small domes, each less than 10 kilometers (6 miles) across, located along the southern portion of the annulus of fractures, and a smooth, flat region in the center of the corona, probably a relatively young lava flow. The range of volcanic features associated with coronae suggests that volcanism plays a significant role in the formation of coronae.

Apparently, pan cake domes are on found on Venus.


What other graphical methods can be used to represent weathering? Context:

For one of my reports I have taken samples of a rock from an adjacent creek. I have done XRD analysis to get compositions of calcium, potassium and aluminium.

My question:

I know about ternary diagrams, this is the base graphical method I will be using. However, what other basic methods could I employ to emphasize the effects of weathering in this experiment? The following data is what I plan on using.

First of all, you probably used XRF, and not XRD. XRF is a method used to obtain chemical compositions. XRD is used to obtain crystal structures.

A ternary diagram would be indeed very useful in this case. Another thing you might want to try is ratios: a plot of Al vs. K/Ca or something similar. Potassium and calcium likely behave differently in different weathering regimes, so it could be useful to show it.


Was volcanic activity more prevalent when the dinosaurs roamed? Popular film culture often depicts much volcanic activity during the time of the dinosaurs.

Assuming "time of the dinosaurs" as the Jurassic (200 million years ago) until the end of the Cretaceous (66 million years ago):

Are there any geological theories that support such an assumption?

There seems to be indeed reasons to believe in an enhanced volcanism during the Cretaceous at least.

The Cretaceous timescale is indeed peppered by the formation of large igneous provinces (known collectively as LIP; short review in Ogg & Hinnov 2012a): Parana at ca. 135Ma, the Ontong-Java Plateau at ca. 125Ma, the Kerguelen Plateau at 118Ma, the Caribbean Province at 90Ma and of course the famous Deccan Traps at the K/Pg boundary. In addition to those large events, they were as well other more minor pulses of large-scale volcanism during the earliest Cretaceous (Shatsky Rise), and at ca. 87Ma (Madagascar Traps) and ca. 73Ma (Sierra Leone Rise).

The 5 LIP, though localized to a specific region each time, had a global impact on the climate and on the oceans, as seen on $\delta ^{13}C$ curves for instance, or during the different episodes of Oceanic Anoxic Events.

As far as the pop culture trope is concerned, most of these volcanic events were partly underwater (Shatsky Rise, Sierra Leone Rise, Kerguelen Plateau, Ontong-Java) so I doubt dinosaurs were roaming around active volcanoes. It is probable that the trope originated instead in the idea that the Deccan Traps triggered the end Cretaceous mass extinction (i. e. the disparition of non-avian dinosaurs, in particular).

In comparison (see Ogg & Hinnov 2012b), there were only one LIP forming during the Jurassic in the Karoo Basin (South Africa); if we ignore the Central Atlantic Magmatic Province which formed just below the base of the Jurassic (it may or may not have caused the end-triassic mass extinction).

Ogg, J. G. & L. A. Hinnov, 2012a. Cretaceous. In F. Gradstein et al (Eds), The Geologic Time Scale 2012, Elsevier, Amsterdam: 793-853.
Ogg, J. G. & L. A. Hinnov, 2012b. Jurassic. In F. Gradstein et al (Eds), The Geologic Time Scale 2012, Elsevier, Amsterdam: 731-791.


Why don't we store carbon by storing used plastics under ground? Some types of used plastics are very stable.
They also contain a significant amount of carbon.
An example is polyethylene (PE).
When waste is collected for recycling, not every plastic part can be reused. There is a fraction that is usually burned, creating CO2.
We want to avoid accumulating CO2 in the atmosphere, and look for methods to store carbon under ground.
Why don't we store used plastics under ground, in a long term stable way?
I am not sure how normal mixed waste dumps behave in the long term, but they have drawbacks. For example they can leak substances from the other parts of the mixed waste and they can burn.
But other methods seem stable to me: Solid PE blocks of standard pallet size, stacked underground in abandoned mines should be long term stable, I think. But it is not about the specific place of storage, a mine is only an illustration to argue that it is possible.

Some locations don't have the available space to dump rubbish underground and those that do are running out of suitable dump locations.
Similarly, the location of abandoned mines and the available dumping space is also limited. Prior to using abandoned mines, many will need to be made safe by implementing ground control measures to prevent injuring from falling rock and to prevent cave in.
Some mines, particularly coal mines have been mined to subside shortly after coal has been removed, making such mines unusable.
Some mines were constructed underneath the water table and are now flooded. Such mines would need to be de-watered and made safe. The water would need to be dumped somewhere, which and may need to be treated prior to dumping because of metals that may have leached into the water from minerals in the abandoned mine.
Once such mines have been backfilled the ground water will again flood the mine. The question of how any plastics would behave when submerged needs to be investigated to mitigate against deleterious environmental effects.
Some old mines were established using manual methods and have short height and narrow width tunnels which would require a lot of manual handling to make the mines safe and to dump plastics in them. Alternatively, the tunnels may need to be enlarged to allow the used of heavy machinery in dumping the plastics. This would be expensive and may not be practical in some cases.
The location of some mines is far from population centers which would required expensive haulage to the mines.
It would be to reuse plastics in another way, if possible, or to stop using them or significantly reduce their usage.


Why are most minerals so rare? There are 4,660 known minerals, so why are most of them so rare?

Is it to do with the structure of minerals?

Mineral rarity is dependent on several factors that include these:

Distribution of elements within the earth

The mass-abundance of the nine most abundant elements in the Earth's crust is approximately: oxygen 46%, silicon 28%, aluminum 8.2%, iron 5.6%, calcium 4.2%, sodium 2.5%, magnesium 2.4%, potassium 2.0%, and titanium 0.61%. Other elements occur at less than 0.15%. (reference)

So minerals composed of elements other than (O, Si, Al, Fe, Ca, Na, Mg, K, and Ti) represent far less than 0.15% chemical composition of the earth.

Redistribution of elements by natural processes.

Consider the top 9 elements (O, Si, Al, Fe, Ca, Na, Mg, K, Ti), notice Chlorine is not in the list but by mass Cl should be in the top 9 for the surface of the earth.  Natural processes will alter the distribution of elements.

Top elements in the oceans (71%) of earth's surface are:
Oxygen, hydrogen, chlorine, sodium, magnesium, sulfur, calcium, potassium, bromine, carbon, and boron.

Atmospheric elements are: Oxygen, Carbon, Hydrogen,Nitrogen ,Calcium, Potassium

Stability (physical and chemical characteristics) of mineral species can affect how common a mineral may be.

Example: Water soluble mineral species - There are at least 90 mineral species that readily dissolve in water.  (reference)

Some minerals are solution readily affected by acidic or alkali solutions.

Some minerals are inherently unstable are near surface conditions.

Some minerals readily oxidize  (native iron)
Some minerals can slowly altered by humidity and oxygen (marcasite)
Some minerals are only stable at high tempature and/or pressure.
(It depends on the crystal structure of the mineral how long the mineral remain at surface conditions (1 atm pressure 25'C)
Diamonds are resilient but alpha-Quartz can rapidly alter to beta-Quartz.

Mineral formation environments impact mineral distribution.

Minerals that commonly form in the mantle of the earth are naturally going to hard to find at the surface regardless of the chemical position.

Volcanic mineral assemblies require a volcanic activity which is typically limited to plate boundaries and isolated mantle hot spots.

Lastly thermodynamics (Gibbs free energy) can be used to measure the how probability of specific chemical reaction is occur.

Consider:  Fe + S = FeS2  (pyrite)  verses Fe + S = FeS2  (marcasite)
Free energy state of an environment can be used to explain why pyrite or marcasite will form.

Some chemical reactions are very improbable due to elements involved with in a specific environment.

Consider:
   Cubic zirconia (CZ) is the cubic crystalline form of zirconium dioxide (ZrO2). It is not found in nature because there are no stable environments for formation where Silicon is absent.   Zircons are formed instead. (zirconium silicate (ZrSiO4).


Which are the mechanisms of the correlation between atmospheric carbon dioxid and global warming/cooling? In the end of glacial periods there seems to be an increasing release of carbon dioxide as the global warming increase and at the end of these global warming periods the content of carbon dioxide in the lower atmosphere seems to decrease in correlation to the temperature. Except from the obvious that carbon dioxide is more soluble in cold water and perhaps that some carbon dioxide is trapped in glacial ices, which are the known mechanisms?

Except from the obvious that carbon dioxide is more soluble in cold water and perhaps that some carbon dioxide is trapped in glacial ices, which are the known mechanisms?

Those obvious mechanisms, particularly the first, are the primary mechanisms. Atmosphere carbon dioxide content gradually drops to very low levels during a glaciation precisely because cold water can dissolve much more carbon dioxide than can warm water.

When the Milankovitch cycles reaches a stage where the Earth starts warming up at the end of a glaciation, the Earth's waters start warming up, too. The warmer waters cannot hold as much CO2 as they held during the glaciation. The CO2 comes out of solution, adding to the Milankovitch-driven warming. This is one of the key reasons why the exit from a glaciation is much more abrupt than is the entry into one.

Based on comments by the OP, the OP appears to doubt that carbon dioxide and other polyatomic gases are greenhouse gases. The three principal components of the dry atmosphere, nitrogen (N2), oxygen (O2), and argon, are not greenhouse gases. Electronically neutral monatomic gases and diatomic gases comprising two atoms the same substance have zero dipole moment. These gases have essential zero cross section to low energy (e.g., thermal infrared) photons.

On the other hand, polyatomic molecules have many more degrees of freedom than do the homogeneous diatomic molecules and monoatomic gases that comprise the bulk of our atmosphere. Some such as water vapor have a marked permanent dipole moment. Others such as carbon dioxide nominally have a zero dipole moment, but transients due to thermal vibrations can temporarily given them a non-zero dipole moment. The combination of increased degrees of freedom and a non-zero dipole moment make these polyatomic gases very good at absorbing some parts of the thermal infrared spectrum.

All other things being equal, adding greenhouse gases to the Earth's atmosphere increases the Earth's equilibrium temperature. It's important to note that this greenhouse effect is essential for life. Without it, the Earth would be a frozen icefall, from pole to pole. In fact, during the Cryogenian (850-635 million years ago) the Earth apparently was covered or nearly covered with ice from pole to pole.

The end of a glaciation adds significant portions of the two most important greenhouse gases to the Earth's atmosphere. Water vapor increases because a warmer atmosphere can hold more water vapor than can a cold one. Carbon dioxide increases because a warmer ocean can hold less carbon dioxide than can a cold one.

While the OP asked about the end of a glaciation, the real question being asked was about what is happening now. What happened at the end of glaciations and what is happening now are one and the same thing. Adding greenhouse gases to the Earth's atmosphere increases the Earth's equilibrium temperature. The end of a glaciation added greenhouse gases to the Earth's atmosphere, making the subsequent warming very rapid. Humanity is adding greenhouse gases to the atmosphere, carbon dioxide in particular, resulting in an even more rapid warming than that that occurred at the end of a glaciation.


Is this a former volcano in the Hamad Plateau, in the Syrian desert? On my random explorations of google maps, I came across this interesting terrain:

(link to map here)

Apparently, this is part of the so-called Hamad Plateau, in the Syrian desert. If so, the rock would be limestone, which I read is not directly related to volcanoes. But it just kind of look like it from above.

Anyone has some information on what this geological area is? I can find little about it, eve it even is the Hamad Plateau. I must say that I have zero knowledge of geology. Zooming in you see a lot of rock and desert, and not so much height variation, so maybe it's not a volcano. Still, it's interesting by the colour and shape. Any help is more than welcome!

My Rand-McNally Atlas shows the signature for lava fields in that area. The elevations in Google Maps indicate concentric contour lines with only small differences in elevation, rising from 600m at the outer perimeter to 700m in its center. This a shallow cone-shaped formation. Best I can tell from Wikipedia (compare the picture there), this feature is:

  As-Safa (Arabic: الصفا, Aṣ-Ṣafā), also known as Tulul al-Safa (تلول
  الصفا, Tulūl Eṣ-Ṣafā), Arabic for Al-Safa hills, is a hilly region
  which lies in southern Syria, north-east of Jabal Al-Arab volcanic
  plateau.  It consists of a basaltic lava field of volcanic origin,
  covering an area of 220 square kilometres, and contains at least 38
  cinder cones.

NASA Earth Observatory provides a satellite view as well and gives a few more details regarding the very noticeable dark area:

  Es Safa contains numerous vents that have been active during the
  Holocene Epoch (beginning approximately 12,000 years ago). The most
  recent recorded activity was a boiling lava lake observed in the area
  around 1850. The dark lava flow field (center) likely represents the
  latest activity of the volcanic field, and is emplaced over older,
  lighter colored flows.


How this sedimentary rock is made? Apologies in advance for a beginners question. Different rock types make me curious and recently went to an area where interesting sedimentary rock is all over. As the area is on the coast, sea has washed away some soil and is making it easy to observe rocks.

This sedimentary rocks is composed of different pieces. Sometimes the pieces are in different color, while other times are white. I took an image of a typical rock:

How such sedimentary rock is made? In which period of crust formation? Can you point me to links where I can learn more about it?

The rock you show is a conglomerate - it contains a substantial amount of clasts (your pieces) that are gravel or larger size. The pieces have been cemented together into a new rock - kind of like concrete.

There are a couple of additional things that can be seen in your pictures. First the clasts are very angular. This means they haven't been rounded be wave action or transport to the location where the rock formed. It was very likely formed close to where you found it. If you look at the clasts, the grey ones look like the rock to the lower left and the light ones seem similar to the rock to the lower right. This suggests that the conglomerate formed by eroding those rock types followed by cementation very close to the source. Then a new phase of erosion formed the pieces you see.


Cloud Formations Near Capetown Why do clouds form a 'tablecloth' which exactly fits the top of Table Mountain near Capetown, South Africa? Something about the table top tailors the clouds to fit it exactly. The thickness is smooth and even, at a rough guess about ten metres thick.

This is adiabatic compression of descending air. The air warms and clouds dissolve. The air is blown by a wind that's roughly perpendicular to the ridge, causing it to rise, cool and eventually condense on the windward side and sink and warm on the leeward.


Adding time dimension and corresponding new variable to a netcdf file I have created a x,y netcdf file and now want to add additional time energy variable. So that for each grid cell I have a energy time value.

My script is like this in Python:

value = loadtxt("countries.txt",skiprows=0) % countries
data = loadtxt("energy.txt",skiprows=0) % energy

The energy.txt file is like:

[country id]    ...   51      52      54      55      56      59       60      62    ...
[time step 1]   ...  nan     649     nan     nan    1083    9979      nan   13602    ...
[time step 2]   ... 5743    1283    9062    4026     nan    6365    43444     nan    ...
[time step n]   ...  ...     ...     ...     ...     ...     ...      ...     ...    ...

etc (till 87648 steps), where cells of interest are the first row:

cellsOfInt=data[0,:]

For some cells I have nan values since there are not values for those time steps.
Each row correspond to one time step so for cell of interest 51,
in the first time step we have nan value, in the second time step we have 5743 and so on till 87648.
All cells of interest are in countries.txt file that is 950 X 1000 with cells of interest ids or nan when there is no value.

My code:

y = nc.createDimension("y", 950)  #y
x = nc.createDimension("x", 1000) #x
time = nc.createDimension("time", 87648) #time

latitude=nc.createVariable("y", "f8", ("y", ))
longitude=nc.createVariable("x", "f8", ("x", ))
time = nc.createVariable("time","f8",("time",))
countries = nc.createVariable("countries", "f8", ("y", "x"));
energy = nc.createVariable("energy", "f8", ("time", "y", "x"),
                           fill_value=-9999, chunksizes=(1, 950, 1000));

time.standard_name='time'
time.units ='hours since 2006-01-01 00:00:00.0'
time.calendar='proleptic_gregorian'

lats =  np.arange(5497500,747500,-5000)    #y
lons =  np.arange(2502500,7502500,5000)    #x

# Fill variables
latitude[:] = lats
longitude[:] = lons

countries [:]=value

UNTIL HERE WORKS FINE I have my 2d country but then it does not give any result for energy:

for i in xrange(0,950):  #rows
    for j in xrange(0,1000):    #columns
        for n in xrange(0,87648):  #rows
            for m in xrange(0,1):    #columns
                if data[1,m] == countries[i,j]:   #correspondance
                    nc.variables["energy"][n]=data[n,m]

Any idea how to fix this so I can have in country.netcdf file time dimension with energy values at each time step? Thanks a lot!!

There are two issues (and one optimization) with/for the code above:

Array indexing starts with 0 (not 1) in Python. Therefore, it should be if data[0,m] == countries[i,j]: because you are interested in the first row;
m goes from 0 to 1 (for m in xrange(0,1):) but it should go from 0 to number_of_countries so that all columns of the energy are iterated.
The order of the n and m for loops seems to be quite ineffective. Better would be: for m ...: if data[1,m] == ...: for n in ...: nc.variables...=.... Or replace latter for loop by nc.variables["energy"][:,i,j]=data[:,m]

This could work (please improve => community Wiki) but I cannot test it due to missing input data:

y = nc.createDimension("y", 950)  #y
x = nc.createDimension("x", 1000) #x
time = nc.createDimension("time", 87648) #time

latitude=nc.createVariable("y", "f8", ("y", ))
longitude=nc.createVariable("x", "f8", ("x", ))
time = nc.createVariable("time","f8",("time",))
countries = nc.createVariable("countries", "f8", ("y", "x"));
energy = nc.createVariable("energy", "f8", ("time", "y", "x"),
                           fill_value=-9999, chunksizes=(1, 950, 1000));

time.standard_name='time'
time.units ='hours since 2006-01-01 00:00:00.0'
time.calendar='proleptic_gregorian'

lats =  np.arange(5497500,747500,-5000)    #y
lons =  np.arange(2502500,7502500,5000)    #x

# Fill variables
latitude[:] = lats
longitude[:] = lons

countries [:]=value

for i in xrange(0,950):  # grid rows
    for j in xrange(0,1000):    # grid columns
        for m in xrange(0,int(max(countries))):    # countries
            if data[0,m] == countries[i,j]:   #correspondance
                nc.variables["energy"][:,i,j]=data[1:87648,m]


What would happen if we removed Earth's moon? This question is an object of fascination of mine. There are a few different angles to take to it. My favorite is blasting the moon out of existence while its moving away from Earth.

What would happen if Earth's moon was removed?

This has sat untouched for a while, so I did a quick search and found this article which sums it up nicely.

They key factors with regard to earth science would be:

1) Less extreme tides. The tides would only be linked to the sun and would not be as strong. They would also peak at noon. This has obvious implications for any coastal processes that rely on the tides. Many industries would be impacted. For one, the Bay of Fundy wouldn't be quite the tourist attraction it is.

2) Day length would potentially shorten at a greater rate. Our tidal lock to the moon helps to stabilize the slowing rotation of the Earth. In terms of Earth Science, this would have implications on any diurnal processes (weather), with compounding long-term effects (the climate).

3) The axial tilt of the Earth would change quite a bit. The moon helps to maintain our reasonably stable tilt. Greater tilt would result in more extreme seasonal changes, which in turn would affect all sorts of processes.

Those are the bigger ones from an Earth Science perspective.


Is there an atmospheric data database somewhere on the web? For a personal project, i wanted to develop a global atmospheric database, to compile data like wind speed and direction, temperature, etc. from different sources.

My question is this :
Does such a database exist? either in a free or paying format.

By your edit, it seems you are more interested in the "big data" side of the science. Model reanalyses contain large amounts of historical weather data, so that is a safe bet for ample amounts of data. NOMADS, which is a service provided by the National Weather Service is a good resource for model data. There is another version of NOMADS for operational data; I'd recommend that. For generic data, RDA has data. NASA has a server that also has a lot of data.

You can also generate your own weather data for prediction and the like, by using models like WRF or SPEEDY.

Departing from model data, you have observations, you can access ground-based observational datasets via NCDC. NCDC also has satellite data, radar data, and so on down the line (you don't need me to explore the site for you).

Other countries have other datasets, though many come with a price. ECMWF, for example, has reanalysis products, operational datasets, etc. The same is true for JMA, and other countries with their own weather service.


During an average winter, what part (if any) of the Mississippi River becomes unnavigable? What part of the Mississippi River becomes unnavigable (either freezes or accumulates too much ice to navigate) during an average winter? Perplexingly I could not find this through Google. I suppose no part could become unnavigable all year-round? But that seems unlikely to me as the Mississippi reaches well into Minnesota.

Upper Mississippi river near St Paul Minnesota is closed December - March.  US Army Corp of Engineers is responsible river navigation in the United States.  From winonapost.com, (from 2015) the article states that all vessels need to be south of Lock and Dam 9, near Lynxville, Wisconsin.  Sounds like the upper river is closed so locks can be dewatered and maintanence performed.

My guess is most of the Mississippi river remains open to navigation south of Wisconsin during the winter.

US Army Corp of Engineers river navigation site.


Is seismology really the only way to measure the thickness of Earth's layers? Answers from these two questions:
How can we guess the size of the earths inner core?
&
How can we measure the thickness of the earths mantle?
use seismic waves as the method for detirmining size and thickness of sections in the earth.

Is this the only way of measuring the inner sections of the earth?

Bonus Points: Where did the idea of using seismic waves to measure earth's layers start?

Robert Mallet is sometimes referred to as the "father of seismology." He was helped (around 1850) by the newly created science of photography, which enabled him to create seismic "maps" of the earth, at different depths.

He has started life as an iron engineer/manufacturer, but turned his talents to seismology after a number of devastating earthquakes in Europe. His earlier work with iron gave him a background in the use of explosives to "open up" the earth at critical points.

Paleoseismology is a related field that relies on paleontology to form estimates of various properties of the earth.


Does thermal bubble initiated in WRF dissipate over time? I am running idealised supercell simulation using WRF model. The supercell storm is initiated with a thermal bubble. I just wonder if the thermal bubble is only affecting the initial temperature.

I ask because I am trying to calculate CAPE, and needed to set the parcel temperature. Parcel temperature is normally set to the environmental temperature at the surface. But since my simulation is initiated by a thermal bubble, I wonder if I should add the perturbed bubble temperature to the environmental temperature as my parcel temperature. Hope my question is clear.

After initialization the model calculates forward in time ncluding all physical processes represented by your setup of WRF. This probably means that the warm air will rise and thereby trigger the supercell thunderstorm. Cape can be calculated for a parcel starting at any height. If the bubble (warm anomaly) is present at the surface, and you are interested in the so-called surface-based Cape, then I would set the temperature to the environmental temperature + the warm anomaly. Why not try out both and see what the difference is? This would give you an idea of the vertical forcing magnitude of the warm anomaly.


Can ocean temperatures affect groundwater storage capacity ? In a paper published in Nature Geoscience (paper)  the authors conclude :

  Declining precipitation in northern India is linked to Indian Ocean
  warming, suggesting a previously unrecognized teleconnection between
  ocean temperatures and groundwater storage.

What could be the physical explanation for such relationship . I understand that sea water intrusions can take place in coastal regions ,  but how does temperature come into the picture ?

I think the abstract of the article addresses your question. Working backwards, it presents two direct causes of change in groundwater storage. The first is climatic - greater precipitation tends to increase storage and a decline in precipitation will reduce recharge and thus reduce storage. The second is the anthropogenic response to changes in climate (they focus on changes in precipitation but there may be a second effect of changes in air temperature). When there is less rain, more water will be pumped for irrigated agriculture.

These two effects are then related to the way the change in precipitation is affected by change in ocean temperature. So changing ocean temperature changes the rainfall amounts and patterns. The rainfall reduction in northwestern India increases the amount of groundwater pumping needed for agriculture and decreases groundwater storage.

Methods have been developed to separate the climate and pumping effects on waterlevels (Shapoori, V., et al. 2015).


Is there a quick way to roughly estimate how quickly a flood will move downstream? At the time of this post, there was urgent danger of spillway failure at the Oroville Dam in California, with evacuations in place for hundreds of thousands, and even larger populations further downstream in the Sacramento metro area.  There's 300 large dams in the world.  So it would seem quite useful to have a method to quickly estimate how quickly a large flood might move downstream.

Obviously detailed hydrological models are the only way to properly incorporate the varied topography and other unique factors in each situation.

But it would seem useful for a lot of folks, whether tens of miles downsource of a mountain stream (such as might've been vital as the Big Thompson flood started), dozens of miles down a valley from a dammed waterway (like those further down the Feather/Sacramento Rivers tonight), or hundreds of miles down a flooding major river (such as the 1993 Mississippi Flood), especially given the varying warning networks in place around the world, to have a rough scale of how quickly an unexpected flood might translate downstream their way.  Is it a matter of hours, days, weeks?  A rough worst-case scenario of how quickly they may have to react is what is desired.

Would seem a reasonable formula for a loose estimate might reasonably include the volume of water flowing, the expected channel size, and the elevation change (or alternatively, just the speed of the water... but if you knew that, you really don't need any special formula!).

Does such a formula like this exist?
Or are there good empirical estimates for those different situations I presented?
Or is each case just so unique that there's no hope of such an estimate?

My first thought would be to use Manning equation as an approximation. It does not take into account the effect of a dam burst providing excess water and immediate flooding, although for larger scales (in terms of river reach) this is likely less important.

Detailed hydrologic models may not be the right answer by the way, especially for the tradeoff of the work involved to build them. A detailed forecasting system with a model and real-time data would be the best, but a quick approximation is often a good guess for the work involved.


Why do gold deposits form only in certain areas of the earth? In the map above you can find that most elements are spread evenly throughout Earth's crust and that they are available all around the Earth. However, gold can only be found in certain areas of the planet such as Australia and Canada. Is there a specific reason to why gold can only be mined at these locations or is it just a coincidence?

I'll take the form of the question given by another person here and attempt to provide a different answer.

So what you are asking is: "How did gold become so concentrated in certain parts of the world?"

So yes, gold is all around but the concentration is too low to make extraction of it worthwhile. You need some process to take small amounts of gold from a large volume and turn it into large amounts of gold in a small volume where it is convenient to build a mining facility and get it from the Earth.

One of the most common process to concentrate gold is through the action of hydrothermal fluids. This is basically heated water flowing through the Earth's crust. Heated water with certain properties such as acidity (pH) or dissolved anions (think chlorine-rich seawater is more corrosive than your tap water) can dissolve solid gold and put it into solution. Just like regular water can dissolve table-salt or sugar and put it into solution.

So you have this hydrothermal fluid flowing through huge masses of rock (mountain-like, but underground) for a very long time, and when it goes up to the surface, it is channelled into thin conduits of fluid flow. During their ascent the conditions change (be it temperature or pH, etc.) and the water are not capable of carrying gold with them anymore. This results in the deposition of gold in that specific region.

I made an example, that I hope will help you understand this in a clearer way:

So in here you have rain water, entering the Earth in a large area and getting hotter as they descend down. It becomes possible for them to dissolve the gold from the large volume of rock.  But also, because the water (now steam or a supercritical fluid) are hot they start to ascend upwards, usually through a narrow zone. When they cool down again, gold forms as a solid. For example, gold associated with quartz veins commonly forms through this process.

Now, what happens if these gold-bearing quartz veins are exposed on the surface? They may erode by rain and snow and get concentrated in river beds. So you can either mine the original quartz vein or the nearby river bed.


How to convert the units of specific cloud liquid water from ERA5 (kg/kg) to kg/m2? I am trying to initialize my model with the cloud liquid water data from ERA5. My model IITM-ESM which evolved from CFSv2 takes in the cloud liquid water information in $\small\mathsf{kg/m^2}$. However the ERA5 specific cloud liquid water data is in kg/kg. I have the following questions

Am I right in trying to derive cloud liquid water in $\small\mathsf{kg/m^2}$ for specific cloud liquid water in kg/kg
How do I go about this ? I found a way to convert kg/kg cloud liquid water content to $\small\mathsf{g/m^3}$ in the link https://www.nwpsaf.eu/site/download/documentation/rtm/docs_rttov12/rttov_gas_cloud_aerosol_units.pdf
After getting the cloud liquid water in $\small\mathsf{g/m^3}$, will multiplying by layer thickness (data is 3D with lat, lon, levels and the level information is in pressure levels i.e. Pascals) and $\small\mathsf{10^{-3}}$ be okay to convert it to $\small\mathsf{kg/m^2}$

I got the solution https://www.researchgate.net/post/How_to_convert_the_units_of_specific_cloud_liquid_water_from_ERA5_kg_kg_to_kg_m2

and

https://www.nwpsaf.eu/site/download/documentation/rtm/docs_rttov12/rttov_gas_cloud_aerosol_units.pdf

In the above link the conversions between $\small\mathsf{kg/kg}$ , $\small\mathsf{g/m^3}$ , $\small\mathsf{kg/m^2}$ can be explicitly derived

EDIT
The summary of the first hyperlink is:

  $\small\mathsf{kg/kg}$ stands usually for kg liquid water per kg air.
  Multiplying the term with the calculated air density within the field will result into $\small\mathsf{kg/m^3}$, which means kg liquid water per $\small\mathsf{m^3}$ air. Then you have to multiply with the thickness of the liquid cloud, which will result into $\small\mathsf{kg/m^2}$."


Is it true that "[sand] grains in the Coconino Sandstone come from the Appalachian Mountains"? The Creation Museum is a terrifying place for scientists of all stripes. One of their exhibits is the "Flood Geology" exhibit, which purports to explain how a flood of (literally) Biblical proportions circa 6000 years ago explains all the features of the Earth we see today. One panel at that exhibit is titled "Evidences of the Flood in the Grand Canyon":

(photo taken by John Scalzi; click for larger, more-readable version - if you think you can handle it)

This is obviously boneheaded in so, so many ways, but anyway - this panel makes the following claim:

  Sand grains in the Coconino Sandstone come from the Appalachian Mountains.

Three related questions:

Is this claim true? (The Creation Museum is not beyond telling outright lies, so I have to ask...)
If so, how did it get there?
How do we determine that a particular grain of sand originates in the Appalachians?

Jeffrey Ralh of Yale and coauthors published Combined single-grain (U-Th)/He and U/Pb dating of detrital zircons from the Navajo Sandstone, Utah, which concludes that Navajo sandstone originated from the Appalachian Mountains.  A review of the article is found here: http://www.geotimes.org/nov03/NN_navajo.html.

Rahl et al. propsed that a large river system transported the sediment.

However, Ralh's research concerned only Navajo sandstone, not Coconino sandstone as far as I know.

U–Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA: paleogeographic implications does investigate Coconino Sandstone and other sandstones from the region and discusses what fraction are of Appalachian origin and transport mechanisms.

34% of Coconino Sandstone zircon grains are reported to be of Appalachian origin in table 4.


Question on the derivation of a prognostic equation for the mean concentration (Assume horizontal homogeneity in X) In deriving the prognostic equation for the mean quantity of pollutant C, as shown in my solution below:

Am I right in that I do not need to separate T (temperature) into its mean and turbulent parts (like $T = \overline{T}$ + t’)? If I am right, is it because T does not depend on anything in this equation?
When assuming horizontal homogeneity in the x-direction, this means that the change in c with respect to x (dc/dx = 0) is zero. So does that leave the final prognostic equation with no advective terms since I aligned U to be in X also?

Thanks for any help!

In the question, T was not specifically mentioned to be a constant. So by also expanding $T = \overline{T} + t’$, we end up with the following answer. Where, the covariance term containing $\overline{c’t’}$ reflects that turbulence still plays a role in determining the mean quantity of C.


Why exactly did the use of Greek letters as names for Hurricanes happen the first place, despite the fairly obvious and predictable impracticalities? The Washington Post article Hurricanes Eta and Iota brought disaster to Central America. Officials can’t retire their names. describes a complicated situation, aspects of which are:

Eta roared ashore in northern Nicaragua on Nov. 3, followed by Iota exactly 13 days later and just 15 miles to the south. Both were Category 4 hurricanes at landfall, though Iota had attained Category 5 status offshore. The pair brought flood disasters across Central America, in addition to extreme wind and storm surge near the coast.
They’re the textbook candidates for having their names axed from the Hurricane Center’s six-year rotating name list. Just as Katrina was replaced by Katia, Michael with Milton, and Sandy with Sara, there would ordinarily be little question that the name of a deadly and destructive Category 4 hurricane would be retired. But in the case of the Greek alphabet, there’s no easy replacement.
“The Committee … agreed that it was not practical to ‘retire into hurricane history’ a letter in the Greek Alphabet,” read a news release from the World Meteorological Organization, which oversees hurricane naming across the world’s oceans.
Instead of removing a letter from the list, Greek letters can only be symbolically retired. Under the current policy, “Eta 2020” and “Iota 2020” would be listed as retired storms if the WMO voted accordingly, but the names Eta and Iota would remain in circulation for future storms. Some meteorologists fear this defeats the purpose of retiring names, while others find that assigning Greek letters to storms is impractical to begin with.

Question: Why exactly were Greek letters used as names for Hurricanes in the first place, despite the fairly obvious and predictable impracticalities? Certainly this exact problem was brought up, how was it dismissed?
Related but different (because the current question is backward-looking), and also in need of answers:

In the future, is the World Meteorological Organization going to allow Hurricanes Zeta, Eta, and Theta to exist simultaneously?
What will happen if the Greek letter names were exhausted for naming tropical storms?

Well for one major reason, the assumption was that seasons with so numerous hurricanes were rare. Canonically, tropical cyclones typically follow a Poisson Distribution. If you consider that, of the English alphabet, only 21 of 26 letters are used for names, and if you assume that the average number of hurricanes from the past decade were to stay unchanged compared to this decade (155 tropical storms/10 years= 15.5 tropical storms per year), then the probability of going over 21 tropical cyclones is about 6.96%. Such a view is backed up by the World Meteorological Organization.
But if you say, "aren't the number of tropical cyclones supposed to increase under climate change?" to challenge my assumption of constant tropical cyclones per decade, I will argue that canonically, the frequency that tropical cyclones form should decrease, but the intensity should increase. So the assumption doesn't actually hold, but should actually overestimate the probability of more hurricanes in the long term.
So why use Greek letters? Well, to be consistent, something has to be used to draw attention to the storm. Cycling back to the A's sends the wrong message. And the Greek alphabet was used previously, without major consequence.
Arguably, it may be easier to only name storms that make hurricane strength. However, that would be inconsistent, and may miss strong, rain-heavy storms. For example, Tropical Storm Allison was retired without making the hurricane wind requirement.


Is the magma in one volcano different from the magma in every other volcano? First off, a confession:  I'm asking this question because of The Lord of the Rings.  If you're not aware already, in the story, a magical ring can only be destroyed in a specific volcano.  The reason for this is presumably "because magic".

But the issue got me wondering if this volcano is any different from every other volcano on the planet.  Is there a significant difference between the magma in different volcanoes?  If so, why?

Doesn't all magma come from the same place if you go down deep enough?

In keeping with your Lord of the Rings inspiration, the first reference is from New Zealand, where the Lord of the Rings movies were made.

There are three main types of magma that volcanoes currently produce: basalt, andesite and rhyolite.

Basalt magma has a high temperature, around 1200ºC, it is poor in silica, has a low viscosity and a low gas content. When basalt erupts it produces a flowing magma.

Andesite magma has a mid range temperature, between 800ºC and 1000ºC, it also has a mid range silica content and moderate viscosity and gas content. When andesite erupts it flows but it is also moderately explosive.

Rhyolite magma has a low temperature, between 750ºC and 850ºC, it is silica rich and it has a very high viscosity and high gas content. When it erupts it is very explosive.

Other forms of magma which are much rarer are carbonatite melts and komatiite melts. Carbonatite melts may be cool, as low as 600ºC, whereas komatiite may have been as hot as 1600ºC.

Unlike the other forms of magma that are composed of silicate minerals, carbonate melts are composed of carbonates and can be confused with marble and may have to be geochemically analysed.

Most komatiites are very old, up to  4 billion years old. It is speculated that komatiite magma formation was possible when the Mantle was at least 500ºC hotter.


Dry atmospheric temperature profile (dry adiabatic vs. isothermal) I'm trying to understand why there are differing predictions of the atmospheric temperature profile. It is well established that the dry adiabatic lapse rate (DALR) is:

$$
\frac{\mathrm{d}T}{\mathrm{d}z} = -\frac{g}{c_p} \approx -9.8\ \mathrm{K/km}
$$

This is derived by assuming adiabatic process and hydrostatic pressure gradient:

$$
\mathrm{d}s = c_p\mathrm{d}\ln{T} - R\mathrm{d}\ln{p}\quad(= \frac{\delta q}{T} = 0)\\
\quad \frac{\mathrm{d}p}{\mathrm{d}z} = -\rho' g
$$

where $\rho'$ is density of ambient air, and pressure of an air parcel is the same as ambient pressure ($p = p'$). It is essenitally the cooling an air parcel will experience due to change in ambient pressure when risen adiabatically in the atmosphere.

However, when using the principle of maximum entropy (i.e. looking for the equilibrium profile) we get isothermal profile, as predicted classically by Gibbs and Boltzmann.

Apparently, the actual atmospheric profile (where there is no moisture condensing) is consistent with the dry adiabatic lapse rate much more than with the isothermal profile. The actual profile is of course subject to continuous thermal cooling of the atmospheric layers, thermal warming by radiation from the Earth's surface, heating from the surface by conduction (by turbulence and molecular diffusion), and during the day to solar heating. These factors can obviously affect any equilibrium.

My question is:

What causes the discrepancy? Is there a consensus?
If there was initially a DALR profile, would it eventually turn into an isothermal profile if there was no influence (no radiation, no surface, no dynamic phenomena).

My impression is that when radiative processes (thermal cooling and thermal heating from surface) are included in the maximum entropy calculation, one might get some sort of lapse rate, i.e. something between a pure thermal radiative profile and the isothermal profile.

I found some papers discussing the issue, esp.:

Verkley WTM., Gerkema T, 2003. On Maximum Entropy Profiles. Journal of atmospheric sciences.
Akmaev RA., 2008. On the energetics of maximum‐entropy temperature profiles. Quarterly Journal of the Royal Meteorological Society

where they treat potential temperature as something which is conserved when applying the maximum entropy principle in order to reach a profile with a lapse rate. But it is not clear to me why such an assumption should be made, or if there is any general consensus that this is the right approach.

The two articles you found are spot-on. An isothermal atmosphere is indeed the condition that maximizes entropy for a given amount of energy. Yet a positive lapse rate is almost always observed. Temperature typically decreases with increasing altitude. The key to resolving this apparent paradox is how heat flows into and through the Earth's atmosphere. The Earth's atmosphere is a system that is very far from equilibrium.

If the atmosphere isn't in that maximum entropy state (and it never is, at least not from very bottom to very top), heat transfer will set up to put move it toward that state. Very key: That entropy-driven heat transfer rate is rather low. If other heat transfer processes are in play (and they always are), it is very easy to overwhelm that low entropy-driven heat transfer that would nominally equalize the temperature. The Earth's troposphere is heated from below and cooled from above. This alone overwhelms the entropy-driven heat transfer, and by multiple orders of magnitude.

The other factor is how heat flows through the atmosphere. The presence of greenhouse gases in the atmosphere set up the conditions that make a positive lapse rate possible. By way of analogy, imagine a perfect blackbody heat source that generates heat at a rate $Q$ and has a surface area A. If that heat source radiates to the dark sky, the equilibrium temperature will be given by the Stefan-Boltzmann law, $T_\text{top} = (Q/(\sigma A))^{1/4}$. (Note: I'm assuming that $Q$ is much, much greater than the tiny amount of heat coming in from the cosmic microwave background.) If you put a perfect blackbody blanket atop that heat source, the blanket will radiate at a rate $Q$ outward and inward. The heat source will receive heat from above and below, making the equilibrium temperature of the heat source with one blanket equal to $(2Q/(\sigma A))^{1/4}$, or $2^{1/4} T_\text{top}$. Yet another blanket makes the thermal equilibrium equal to $3^{1/4} T_\text{top}$, and so on.

The atmosphere with its greenhouse gases that are optically thick in the thermal infrared acts as a bunch of blankets. Obviously not perfect blackbody blankets, but blankets nonetheless. This is what favors the development of a positive lapse rate.

This favoring isn't universal. There are times when weather creates conditions where the lapse rate is negative, that is, temperature increases with altitude. This turns out to be a very stable condition (the name for this is a "very stable atmosphere"). This negative lapse rate precludes rising and falling parcels of air. With calm air as well, the only thing that can transfer heat is diffusion, which is a very slow process in the atmosphere.


Which equations describe complete (or near complete) behaviour of magma moving through rocks? Yes this is a bit broader question but I want to know which processes play their role in movement of magma. If one wants to model magma movement through rocks, which processes should one not miss at all and which equations discuss these processes?. As a starter I can that we can use Navier Stokes equations for velocity fields, continuity equation for pressure distribution and etc.

From McKenzie's original 1984 paper and from Spiegelman & McKenzie (1987) paper the equations that govern the conservation of momentum and mass of a low-viscosity fluid melt (magma) in a deformable matrix (rocks) are:

${\partial\over\partial t} (\rho_f\phi) + \nabla \cdot (\rho_f\phi{\bf v})=\Gamma$

${\partial\over\partial t} [\rho_s(1-\phi)] + \nabla \cdot [\rho_s(1-\phi){\bf V]}=-\Gamma$

${\bf v}-{\bf V}=-{k_\phi\over\rho \mu}\nabla \mathscr{P} $

$\nabla \mathscr{P}=\eta\nabla^2{\bf V}+(\zeta+{\eta\over3})\nabla(\nabla\cdot{\bf V})+(1-\phi)\Delta\rho g\hat k $

$k_\phi \sim \alpha^2{\phi^n\over c} $

where $\rho_f$ is the density of the magma, $\phi$ is the porosity or the volume fraction occupied by the magma, ${\bf v}$ is the magma velocity, $\Gamma$ is the "melting function", which gives the rate of mass transfer from matrix to magma, $\rho_s$ is the density of the solid matrix, ${\bf V}$ is the matrix velocity, $k_\phi$, is the permeability, $\mathscr{P}$ is the piezometric pressure (the pressure in excess of hydrostatic pressure, $\mathscr{P}=P-\rho_fgz$), $\Delta\rho=\rho_s-\rho_f$ and $\hat k$ is the unit vector in the $z$ direction with $z$ increasing downwards. The permeability, $k_\phi$, can be expressed as a non-linear function of the grain size $\alpha$, porosity, and a dimensionless coefficient, $c$.


Optimized interpolation method with fixed-location sample data points? I'm trying to find an optimized spatial interpolation method that deals with fixed-location sample data points. Say if I have fixed-location sampling sites and collect data daily, and then use these data to create interpolation surfaces. Is there a method that pre-process the spatial relationships among those sampling sites and then integrate this spatial relationship into the interpolation method to speed up the whole interpolation process? I googled some information but couldn't find what I want. Can anyone put me on the right direction? Thanks.

Welcome to an interesting and important field of research!

Interpolation is a large topic and there are many techniques. I agree that the GIS or math forum could be more initiated, but for completeness, I'll post some thoughts here.

The choice of method depends on the type of data you are using and the implementation depends on your environment. GIS software should always have a number of methods and parameters to adjust. It's also rather easy to create a script in e.g python or matlab to test and evaluate interpolation methods (E.g this).

Some questions to answer before you chose your method are:

Can I trust all my data? How much noise do I have?
Should only the nearest points be considered for the interpolation? How far should I 'feel' the values from data points?
How many dimensions should be interpolated? E.g. should I take time  into consideration?
Should the curves be as smooth as possible?
Should all interpolated values be in a specific range, within min-max of the whole data set or between the nearest points?
Do I know the total value? E.g. when interpolating population density I might know the total population and this could help me find the right interpolation method.
Process speed, that is an issue in your case might force you to choose a simpler technique.

Wikipedia has an overview and Caruso, C., and F. Quarta. "Interpolation methods comparison." Gives a rather good introduction of the techniques and there are some good webpages on GIS and interpolation.

The most important step is to test the method you choose. Again, there are various ways to do so, but the easiest is to simply leave points out from you data set and interpolate the values without them. Try to make the interpolated value as close to the data value as possible.

Kriging are methods based on the actual data instead of a curve. It's often a good first try on spatial data but also in other application like this.
Spline methods produces smoother curves. People doing computer graphics are experts on this, but there can also be applications where you'll aspect smooth changes in a model.

Naturally, more complex methods (e.g. kriging) take longer time to process, whiles simpler algorithms (e.g. bilinear or nearest-neighbor) are faster. Lower resolution of your output raster (array) would also speed up the process. You can let your resolution depend on the variance of the data, so that you interpolate less points in a flat surface and more points for a surface with higher relief. This techniques are common practice in signal processing and the experts are here.


Origin of Andaman and Nicobar islands Are Andaman and Nicobar islands in Indian ocean a continuation of Alpide-Himalayan orogeny or are they volcanic in origin?

The Andaman and Nicobar Islands are neither orogenic or volcanic in origin. They are in fact an accretionary wedge, i.e. an accretion of sediments and oceanic crust "scraped" from the subducting Indian plate. See for instance the description in the first chapter of the aptly titled The Andaman–Nicobar Accretionary Ridge:

  The islands are an exposed segment of the accretionary wedge (outer arc) of the Sunda subduction system, where the Indian Plate subducts beneath the Sunda Plate. Ongoing uplift of the sediment-dominated accretionary wedge has exposed, over a relatively small area, a diverse range of rock types associated with the subduction complex (dismembered ophiolites, volcanic-arc rocks, trench-slope deposits, submarine fan turbidites, pelagic sediments and the sediments of shelf and reef environments), making it an ideal area for investigating subduction processes.

(Unfortunately, other chapters with more detailed descriptions are not open access.)

Note that if some of the sediments are indeed volcanic in origin, it does not mean that volcanism is responsible for building the archipelago, like it was for the Chagos-Laccadives ridge for instance, to stay around India. It is the accretion of sediments in the subduction trench, and their subsequent uplift above the sea, that created the islands.


where to download NASA-NEX daily downscaled datasets? I'm looking to download a small geographic area of the CMIP5 models part of NASA-NEX dataset. Previously I relied on the Planet OS OpenNEX GDDP website which had a great tool for selecting geographic areas, models and time periods, saving in this way a large amount of downloading time and disk space. The problem is that OpenNEX is gone and I haven't been able to find a similar tool.

Is there another tool/website/script that can be used similarly?

Google Earth Engine's NASA NEX dataset (or this) might be of interest to you. It is an online repository, where you can do your analysis using the GEE platform without having the need to download to local machine.


How much land does it take to support New York City? New York City has about 8.5 million people living in an area of 300 square miles which gives a population density of 28,300 people per square mile.  The food required to support such a high population density is mostly grown outside of that 300 square mile area.  Likewise, the fresh water required to support that population is not collected within that area.

How much land outside of NYC is effectively dedicated to supporting it?  More generally, how much reasonably productive land does it take to feed and hydrate a human being on average?

The average ecological footprint of a US citizen has been estimated as 8.00 global ha.

Multiplying 8.5 million by 8.00 hectare gives 680,000 km², or around 5 times the area of New York state.

Of course, this calculation contains a lot of assumptions and simplifications.  This doesn't mean you could simply allocate 680,000 km² around New York City and use this to support the lifestyle of their inhabitants.  There is a considerable uncertainly around the calculation, and the land is spread all over the world (New Yorkers want their bananas, almonds, and iPhones too, even if none of those are local).


Appearing of Weird Cornered Cloud in Sky? It was about 6'o Clock in the Evening. Suddenly I noticed A wierd Cloud in the middle of the sky.

Is there Natural Phenomenon responsible for creating such prefect clouds? & What it is?

or

Human activities like Climate Change?

or

Just a Coincidence ?

The left edge of the cloud is a real edge, irregular and fuzzy as expected. However, the lower sharp edge is just an illusion due to illumination. Just before sunrise or after sunset, the sun can illuminate the upper clouds but not the lower ones. If a cloud happen to be in the limit between illuminated clouds and shaded clouds, it will have its upper side illuminated and the lower one in the shade. That is what you are seeing, the lower edge is not the edge of the cloud, is just the limit of the illuminated part of it.

If you pay attention you can follow the contrast in illumination even outside of the cloud to the left. Where the illuminated air above the line have a glow not visible in the part under the illuminated part.


Is there any intuitive and easily understandable way to help students understand the triangular facet of outcropted stratigraphy? I find it difficult to teach college students about using the triangular facet on remote sensing images to judge the dip direction of sedimentary formations. Is there any intuitive way that can help?

This is a tale of two three dimensional coordinate systems. You may need to take a bit of a side track if your students are not already familiar with the concepts of three dimensional coordinate systems, three dimensional vectors, the three dimensional dot and cross products, and transformations between coordinate systems. The image below portrays two such coordinate systems, with axes in blue and red,

I'll denote one of those coordinate systems as the East, North, Up coordinate system (ENU for short), with unit vectors $\hat E$ (East), $\hat N$ (North), and $\hat U$ (Up), and the other as the dip, strike and outward normal coordinate system (dsn for short), with unit vectors $\hat d$ (dip), $\hat s$ (strike), and $\hat n$ ((outward) normal). In terms of the above diagram, imagine the trio of blue vectors corresponding to East, North, and Up while the trio of red vectors corresponding to dip, strike, and (outward) normal. As an instructor, you might well want to create a better diagram, with labels.
There are singularity issues with both of these sets of coordinate systems. East/North/Up doesn't make sense at the Earth's poles as all horizontal directions are south at the North Pole and north at the South Pole. The dip/strike/normal doesn't make sense wherever the surface is flat. I'll ignore those issues. (Bonus question for your students: Address those singularities.)
One way to define local ENU coordinate system for a point on the surface of the Earth is to use the Earth's reference ellipsoid. The "up" unit vector is normal to the ellipsoid, with "up" pointing outward. The east unit vector is orthogonal to the $\hat U$ unit vector and the Earth's rotation axis. Use the cross product and divide by the norm. The north unit vector is the cross product of the up and east unit vectors.
Regarding the dip/strike/normal coordinate system, one direction, the outward normal, can be determined from the coordinates of the three points in a triangle in a vector-based triangular network digital elevation model. The coordinates of the three points in a triangle ($\vec A$, $\vec B$, $\vec C$) are supposed to be arranged such that $(\vec B - \vec A)\times (\vec C - \vec B)$ points outward. This points in the direction of $\hat n$: $\hat n = \frac{(\vec B - \vec A)\times (\vec C - \vec B)}{||(\vec B - \vec A)\times (\vec C - \vec B)||}$.
Aside: This is not always the case; there are DEMs that do not follow this rule. Those are DEMs one should toss in the nearest digital trashcan.)There are also some DEMs that do follow this rule but occasionally have triangles whose outward normal has a downward rather than upward component. An example is an extremely detailed DEM that models not only the topside but also the underside of an overhang. Satellite-based DEMS typically don't do this as satellites cannot see the underside of an overhang. (Extra credit: Have your students address such cases!)
We're looking for $\hat s$ and $\hat d$, the unit vectors that point in the strike and dip direction. Both of these vectors lie in the plane of the triangle formed by $\vec A$, $\vec B$, and $\vec C$. This means that both $\hat s$ and $\hat d$ are normal to the outward normal $\hat o$. The strike vector is horizontal, which means that it is also normal to the unit upward normal. To find $\hat s$, compute the cross product of $\hat U$ and $\hat n$ and normalize. (Note: Normalization is impossible if $\hat U \times \hat n \equiv 0$. This only happens if $\hat n$ is parallel or antiparallel to $\hat U$, in which case strike and dip are not well-defined.) Finally, the dip unit vector, which is what we're after, is the cross product of the strike and outward normal unit vectors: $\hat d = \vec s \times \vec n$. Bonus: Ask your students to show that if $\hat d$ exists, it always has a downward component.


Does nitrate take a particular long time to percolate from surface into groundwater? In a recent discussion with a farmer, the (at least in northwestern Germany) "popular" topic of nitrate infiltration into groundwater came up. The general view is that lots of fields receive more nitrate fertilizer than the plants can use, this then percolates through the ground and eventually shows up in the groundwater that is also used as drinking water. So far so plausible. Raised nitrate content in groundwater is indeed often observed.

One should probably add that in this area, a lot of agriculture is raising of hogs and cattle, consequently much of the fertilizer is manure that has a (compared to commercial fertilizer) low NPK content and is thus not worth to transport over far distances. So there's an incentive to dispose on ones own fields, nearby.

Now, this farmer claimed that the nitrate content we see now is decades old, that the bylaws and controls as well as agricultural practices in place now work. Is this true? Does nitrate penetrate ground so slowly? The only mechanism here I could think of that nitrate is adsorbed and desorbed on minerals in the ground, sort of like in chromotography column.

If neccessary, I can provide more figures for nitrate content of specific wells, groundwater table etc - but I don't think it's neccessary since I want a qualitative answer wether or not such a slow infiltration is plausible at all.

I know in New Zealand we have a number of soils you can't raise dairy herds on because the nitrate in their urine strips too many nutrients too fast, to the point where one can tell where the cow urinated a couple of weeks ago because that patch of grass is dying from several different deficiencies simultaneously. My understanding is that dairy cows are, hands-down, the worst farm animal for this because they stand still when voiding and dump up to 15 litres of moderate-high nitrate liquid waste at a time which all goes effective straight down through the soil column robbing it of nutrients along the way. On the other hand there are also some soils, generally in more arid areas, where nitrate doesn't migrate right through the soil column at all but concentrates in the subsoil as a visible, white, salty, horizon.

As a rule the more water retentive the soil the longer water soluble compounds like nitrate will take to work down into the ground at a given water input. There are also some chemical interactions that will bind nitrate and slow it down more than you might expect we need study them in my soil fertility papers but I can't think what they are right now.

But to answer your question, usually soluble soil ions (which nitrate is) move on a timescale of days, weeks or maybe months, but not decades. We wouldn't need to apply slow-release nitrate fertilisers annually if it didn't migrate through at least the top-soil relatively rapidly.