Latent heat and global circulation What is the relation of latent heating and the global circulation of the atmosphere?
Do you know some references about this relationship?

Latent heat is released when water vapor turns to liquid\solid water.  So latent heat is released where there is precipitation.  So you're looking primarily at places where there is lots of moist convection... the ITCZ near the equator and then the midlatitudes.

I would believe that all of that latent heat release aloft should mean more heat is moved Poleward in the upper atmosphere branches of global circulation than would be moved by dry convection.  And would therefore make the circulation more efficient, perhaps having a long-term effect of allowing reduced horizontal wind magnitudes in comparison to a dry world (the resulting reduction in instability means weaker updrafts and the better transport Poleward means smaller temperature\pressure imbalances and thus less wind than a world without moisture).

Offhand I don't know the literature well... Google Scholar helps though you run into a lot of climate model parameterization articles using most terms.

The nature of the global circulation of the atmosphere should be fairly stalwart, as Lorenz was pretty big in the field I believe.  It talks about how latent heat in the tropics enhances the updraft winds in the ITCZ on page 17 a small bit.  The paper seems to suggest it would increase the global circulation strength by increasing those velocities.

Response of the Hadley Circulation to Convective Forcing in the ITCZ
looks like it might have potential too.

My most successful search term set seemed to be
"global circulation" "latent heat" -simulation -co2
though it still wasn't amazing.  But probably some other good articles to find if you thumb through them.

I'm certainly not a top expert in the field, but hope these thoughts and links add at least a little potential help or a starting point for you.


Sand on the beaches of Kanyakumari, India I recently visited the southern tip of India (State of Tamil Nadu) - it is called Kanyakumari. The beach was beautiful and one thing that struck me was that the sand was multicolored. The local legend is that the Pandava (of Ramayana epic) princess spilt food on the beach which turned the sand multicolor. I'm hoping for a more scientific explanation. Could it be due to particular minerals? I'm certain the striking white sand is due to quartz. Would love to hear the views of this community.

There are a few studies looking at different aspects of the magnificent colours observed at the Kanyakumari region. The colours, according to the research are due to the mineral content therein.

According to the article Hydrogeological Studies of the Coastal Areas of Kanyakumari to Colachel after Tsunami, South Tamil Nadu, (Perumal et al. 2010), it is common for zircon, rutile, ilmenite and garnet to be observed in the sand - this can acount for reddish hues.

In some places, monazite has been noted, also noted in radiological studies in Baseline Assessment of dose due to Natural Radionuclides in soils of coastal regions of Kanyakumari district in Tamil Nadu, India (Sarojini, 2014).

According to a Geological Survey of India (GSI) report of the region, there are also small amounts of sillimanite and leucoxene.  They also state that there is between 10-25% silica sand content.

The presence of zircons, causing some of the brilliant lustre, was confirmed by XRD analysis discussed in the article Observations on the reported incidence of micro-diamonds in the beach sands of the Kanyakumari Coast, Tamil Nadu (Dinesh et al. 2011).

Much of the beach sand sources are likely to be weathered from the surrounding gneissic (including garnetiferous gneisses) and charnockites, as described in Perumal et al. and the GSI report.  Additionally, the report Post Tsunami Heavy Mineral Distribution
Between Cuddalore to Kanyakumari Along the
Tamil Nadu Coast, India – A Review  that also suggest some offshore and alongshore sources of the heavy minerals.


Minimum sea-level pressure and maximum wind speed intensity relationship in Hurricane Katrina (2005) Hurricane Katrina was one of the deadliest and most destructive hurricane to hit the US. After looking into the minimum sea-level pressure (MSLP) and maximum wind speed (MWS) intensity data from NOAA's HURDAT database, I am confused with the pattern or whether there actually is one.

For Katrina specifically, is there a pattern in the relationship between MSLP and MWS intensity? What role does a low or high air pressure system play in the velocity vector of the hurricane?

Generally the relationship is the lower the air pressure the more intense the hurricane. For example during the same hurricane season as Katrina (2005) which also happened to be a record breaking season for the number of hurricanes recorded in the Atlantic basin, hurricane Wilma was recorded as being the most intense hurricane ever to form in the Atlantic. It reached a minimum air pressure of 882 millibar which was a record low. The corresponding maximum wind speed during this period of intensification was 185 mph. Hurricane Katrina was also a category 5 hurricane and reached a minimum air pressure of 902 millibar with maximum wind speeds at this pressure of 175 mph. Katrina of course striking where it did caused far more destruction even though it was the less intense hurricane of the two:

http://en.wikipedia.org/wiki/Hurricane_Wilma

http://en.wikipedia.org/wiki/Hurricane_Katrina


Why does the road appear wet on a sunny day? Whenever I'm travelling by road on a hot sunny day and I look towards the horizon, it appears as though there is puddle ahead but as I approach it, it disappears. Why does this happen?

This optical illusion is due to refraction of visible light due to density gradients near the surface and the fact that the index of refraction in a medium is dependent on the density of the medium.  In an atmospheric density gradient light will bend toward the direction of increasing density.  When it is cool at the ground and warms up with height this effect bends light toward the ground and when it is hot near the ground and cools with height this bends light toward the sky.  This is particularly strong over a road surface, which can be much hotter than the surrounding land surface.  This produces a sensible heat flux that warms the air over the road and can produce exceptional temperature gradients near the surface.

This strong temperature gradient near the ground is also a significant density gradient and when you look through it toward the horizon you are actually seeing the sky.  Photons that would normally illuminate the surface of the road are instead refracted by the density gradient and are bent toward your eye.  This only works for specific angles determined by the actual density gradient and this is why the mirage always appears at a certain distance.  You never really get closer or further from the "water" and you may be able to see road surface beyond the illusion.

Here is an image that describes the effect:

 Image licensed CC-BY by The School of Physics UNSW

This illustrates a the effect of a near-surface density gradient that is low density (warm) at the ground and increases (gets colder) with height.  The photons from the sky that pass close to the road are refract toward the observer and you see a false image of the sky as an inferior mirage.  The other photons do not pass through the strong density gradient and are not bent and you see the true positions of the objects.


What is a reasonable forecast of sea level in 2100? The IPCC 2013 Physical Science Basis Report says 0.4m - 0.6m.  That is somewhat dated and now http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.html seem to have contested it.  Is it save for local governments etc to plan on the basis of 0.4 - 0.6 or is there another level that would be better?

Their abstract is summarized below for reference.

  There is evidence of ice melt, sea level rise to +5–9 m, and extreme storms in the prior interglacial period that was less than 1 °C warmer than today. Human-made climate forcing is stronger and more rapid than paleo forcings, but much can be learned by combining insights from paleoclimate, climate modeling, and on-going observations. We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters. Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years. Paleoclimate data reveal that subsurface ocean warming causes ice shelf melt and ice sheet discharge. Our climate model exposes amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability. Ocean surface cooling, in the North Atlantic as well as the Southern Ocean, increases tropospheric horizontal temperature gradients, eddy kinetic energy and baroclinicity, which drive more powerful storms. We focus attention on the Southern Ocean's role in affecting atmospheric CO2 amount, which in turn is a tight control knob on global climate. The millennial (500–2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change, thus the time scale for paleo global climate, ice sheet and sea level changes. This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human-made climate forcing. Recent ice sheet melt rates have a doubling time near the lower end of the 10–40 year range. We conclude that 2 °C global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous. Earth's energy imbalance, which must be eliminated to stabilize climate, provides a crucial metric.

An important aspect of this is location.  Sea-level rise will not be exactly uniform across the globe and tides/storms will cause a lot of regional variability in terms of coastal change.   Local governments should not necessarily be planning for an average global sea-level rise but instead develop a regional understanding of the coastal effects they will likely experience.  For instance, see California's recent CALIFORNIA COASTAL COMMISSION
SEA LEVEL RISE POLICY GUIDANCE here:  http://documents.coastal.ca.gov/assets/slr/guidance/July2015_Full_RecFinal.pdf
which says

Sea level at the San Francisco tide gauge has risen 8 in (20 cm) over the past
century, and the National Research Council (NRC) projects that by Year 2100, sea level in
California may rise by 4 to 56 in (10 to 143 cm) for areas north of Cape Mendocino and 17 to 66
in (42 to 167 cm) for areas south of Cape Mendocino (NRC 2012). While the California coast
regularly experiences erosion, flooding, and significant storm events, sea level rise will
exacerbate these natural forces, leading to significant social, environmental, and economic
impacts.

The estimate of 0.6 meters has increased as recent research shows Greenland's melt rate is a bit faster than previously estimated and ocean warming, which causes expansion, is also happening more rapidly.
Below  is some useful information from the 2014 US National Climate Assessment ( http://nca2014.globalchange.gov/report/our-changing-climate/sea-level-rise ).

Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100.
Projecting future rates of sea level rise is challenging. Even the most sophisticated climate models, which explicitly represent Earth’s physical processes, cannot simulate rapid changes in ice sheet dynamics, and thus are likely to underestimate future sea level rise. In recent years, “semi-empirical” methods have been developed to project future rates of sea level rise based on a simple statistical relationship between past rates of globally averaged temperature change and sea level rise. These models suggest a range of additional sea level rise from about 2 feet to as much as 6 feet by 2100, depending on emissions scenario.
Recent projections show that for even the lowest emissions scenarios, thermal expansion of ocean waters and the melting of small mountain glaciers will result in 11 inches of sea level rise by 2100, even without any contribution from the ice sheets in Greenland and Antarctica. This suggests that about 1 foot of global sea level rise by 2100 is probably a realistic low end. On the high end, recent work suggests that 4 feet is plausible.,,,, In the context of risk-based analysis, some decision makers may wish to use a wider range of scenarios, from 8 inches to 6.6 feet by 2100., In particular, the high end of these scenarios may be useful for decision makers with a low tolerance for risk
In the next several decades, storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many of these regions. Sea level rise will not stop in 2100 because the oceans take a very long time to respond to warmer conditions at the Earth’s surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than that of the current century

The discussion paper, which is still undergoing peer-review at the time of this post, brings into question the semi-empirical methods used to calculate the rate of sea-level rise on the decade-scale.  As an alternative, they use paleo-climate data and doubling times to make their own approximation, which predicts faster sea level rise.  Let us be clear, though, the amount of possible net sea level rise over the next few hundred years or so is not really in question. The timing of how fast the sea will rise over the coming century is what is less certain.  So, a coastal community doing long term planning could consider sea-level rise even further in the future.  Most of Greenland could melt over the next few hundred years, which would contribute nearly 6 meters of sea level rise. If we are strictly talking about the year 2100, though, that is a difficult forecast to make. For planning purposes, it would be wise to assume at least 1 meter of sea level rise by 2100, with definite continued increases.


Where can I find data for annual high and low temperatures? I am comparing the climates of a handful of cities and I would like to find the average of all recorded yearly high and low temperatures, but all I'm able to find is the average of all monthly averages.

For example, if I look at climate data for Portland Oregon, it tells me that the average high temperature for the month of July is 81(F), but I know that the temperature regularly climbs into the 90s in the month of July (occasionally into the 100s). I know that for 2015 the highest recorded temperature in Portland was around 104(F), 2014 was 98(F) and 2013 was 93(F), which for this small sample would put the average annual high temperature at around 98(F).

Where can I find this type of information?

You can find this data from NCDC.  You can find the data for Portland, OR here.  These are annual summaries (ancsum) and for Portland they have extreme minimum daily temperature (EMNT) and extreme maximum daily temperature (EMXT) dating back to 1910.  From the linked page you can request data in various formats and select the date range and the specific variables you want.  They will put together the requested data and email you with a link to download it.  Here is some example data from the dataset:

COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201301  55  23
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201302  61  30
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201303  77  29
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201304  78  36
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201305  85  40
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201306  97  49
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201307  92  53
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201308  91  57
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201309  95  47
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201310  74  32
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201311  60  24
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201312  57  12
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201401  58  25
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201402  58  19
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201403  69  32
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201404  83  39
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201405  91  42
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201406  85  48
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201407  99  54
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201408  99  54
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201409  94  51
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201410  85  47
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201411  63  26
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201412  64  21
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201501  60  24
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201502  64  32
COOP:356751 PORTLAND INTERNATIONAL AIRPORT OR US    201503  73  30

These are extreme max/min temperatures for each month, so for this station you have annual maximums of 97 F and 99 F for 2013 and 2014.  You have annual minimums of 12 F and 19 F for the same two years.  There are multiple stations and they have varying temporal coverage.  You can request this data for each of the cities that interest you.


Why is Great Oxidation Event associated with Iron oxidation but not Aluminum or Silicon? Just to build up on my previous success with oxygen origin in the atmosphere, I want to expand the question as was advised in the answers. The official heresy, despite denied in the comments and answers here, says that the atmosphere oxygen was produced by plants. Meantime, the oxidation of the atmosphere was delayed by oxidation of the iron, which was free at that time. Yet, if we look at the geology, we find very few Fe oxides in the crust. There is much more aluminium oxide Al2O3 (aka clay) and quartz (SiO2 aka sand). I wonder, when did the clay with sand were formed so that no phytoplankton was necessary for their formation and why was iron delayed its oxidation?

PS I have later realized that Ca oxidation is also an issue of this kind.

Because Al and Si were already oxidised to begin with.

When the Earth formed, it had some amount of metals (Fe, Si, Mg, Al, Ca, etc) and a fixed amount of oxygen to bond with those metals. Certain metals with bond with oxygen preferentially. Mg and Ca are usually the first to take up oxygen, followed by Al, Si, and then Fe comes last (out of the short list I just provided). Turns out that there is not enough oxygen left for all of the Fe!

As you probably know, Fe oxides come in two states, ferrous iron (Fe2+) and ferric iron (Fe3+). So to put it simply, the amount of oxygen left in the Earth after being used up in the other more-easily-oxidised metals was enough to oxidise just a small part of the Fe0 to Fe2+. That's why Earth has a metal core - that's where all of the Fe0 is. The crust, however, had only Fe2+ in it. Once you start pumping out oxygen to the atmosphere, this Fe2+ starts oxidising to Fe3+, which is the stable form of iron in the Earth's surface in the presence of oxygen (as you can tell by iron rusting everywhere quite rapidly). This buffers the amount of oxygen you had in the atmosphere until you run out of Fe2+ and then oxygen can really increase.

Some corrections:
Al2O3 is not clay. It is an important component of clay minerals, but it is definitely not clay. Clay minerals have both Al2O3 and SiO2 in it.


Less pollution: moving hurricane debris to other regions for use, or burning? When a big hurricane hits, it can create debris on the scale of $\mathrm{10^8 yd^3}$.  Cities in Florida, Texas, and other affected areas are struggling to hire enough trucks and drivers to pick it up quickly.  But aside from that, I noticed many of the areas have started to burn the debris once it starts building up.

Got to wondering... typically mulch comes in modestly pricey, and when free mulch is offered, it often goes quickly.

So assuming a fair portion of debris is mulchable and is of interest to other areas, and that we can acquire typical transportation resources, then we'll set up transfer from collection sites to those other regions rather than burning it.  What would be the net pollution result?

If removed for mulch and such: trucking pollution + decomposition (- trees saved locally??)
If burned: the burning pollution.

Obviously it's about approximation rather than exacts, it's probably hard to appraise the different byproducts from burning versus decomposition, and a lot probably depends upon the way it is burned.  But as a whole, can we get a rough estimate of comparable quantities/damage done... is it less pollution/damage even to truck it an average of 3000 miles?  1000 miles?  100 miles?  10 miles?  Should it be burned on the spot (if done safely)?  Would think there's got to be some way to get a very rough idea.

Certainly the best option if viable might be leaving it in place to decompose.  But considering how upset people are getting at having debris around these parts a month later, exclude that option from the possibilities.

Trucking or burning, how do they compare?

As the question was changed, my answer attempts to evaluate only the difference between burning and transporting. Please correct my values if my quickly found sources are inaccurate or you find more representing. I know there is quite a few unwritten assumptions that simplify this problem.

On average transporting via trucks emit 161.8 $\frac{CO_{2}}{short-ton-mile}$ (according to this Environmental defense fund handbook). Short ton equals to 2 000 lbs.
The amount of $CO_{2}$ equivalent from burning wood is $1900 + 200 + 70 = 2170 \frac{CO_{2} eqiuv.}{kg}$ from carbon dioxide, nitrous oxide and methane respectively (according to this article, the link to the source of these numbers fails so please comment if these numbers aren't correct).

Now we can write an equation out of this and solve for the kilometer distance that produces equal amount of carbon dioxide equivalent.$$\frac{2170\frac{CO_{2}eq.}{kg}}{161.8\frac{CO_2}{short-ton-mile} \cdot 0.0011\frac{short-ton}{kg} \cdot 0.6213\frac{mile}{km}} \approx 20000 km$$
This is quite a large number in my opinion. I would've expected less. So quite a long distance is needed until transporting produces more $CO_2$ pollution than burning.


What factors explain mountain glacier retreat variability? It is well known that the majority of the world's mountain glaciers are retreating, but looking at a few LANDSAT images from the 1980s and today I am able to see glaciers that have retreated kilometers in that time frame, and others which have hardly changed at all within the same region.

I am wondering what variables could be responsible for this? Bed rock lithology? Precipitation differences? Mountain slope? Etc.

There is indeed a large variability in glacier behavior, even between neighboring ones. If you look harder, you will even find advancing glaciers right beside others receding quickly. There are multiple factors that can explain such variability, I will list the most important ones:

Orographic control: A climatic change can affect differently neighbouring glaciers. If the wind, air moisture or temperature changes, the corresponding changes in precipitation or solar irradiation can vary on different areas of a mountain massif due to its topography, therefore affecting differently each glacier. A classic and illustrative example is the orographic precipitation illustrated by the figure below. It explains why the windward side of a mountain range could have bigger glaciers than the other. Now, in the case of an increase in -let's say- temperature and air moisture content (that usually come together), the associated  increase in precipitation might benefit snow accumulation in one side more than the other, while the temperature will affect both more or less in the same way. Leading to leeward  glaciers receding faster than windward ones.

Topographic controls: All glaciers flow downhill, and the speed of such flow depends on the resistance the bedrock, valley walls, moraines, etc. A glacier that is in steady state (i.e. not advancing nor receding) is in balance between snow accumulation in its upper reaches and melting in its lower areas. Even if there is no changes in accumulation or melting, this balance can be broken if the speed of the glacier changes. If the ice is taken faster from its cold head to the warm front, that will increase the melting and more snow would be needed to offset the additional melting.
Most of the resistance to flow is provided by constrictions of the valley walls or protrusions of the bed. As in the figure below (from here), taking a floating ice tongue as example (a.k.a. ice shelf) where most of the resistance to flow comes from the bed protrusion below the "ice rise", in this case such protrusion is called a "pinning point".
Now, going back to your question: Even if two glaciers that are receding at the same rates, eventually one could recede behind a constriction, therefore its speed will increase, pushing it further out of balance, so it will start loosing mass faster than its neighbor and at some point that will show up as a more pronounced shrinking in images like the ones you were studying.
In the case of ice shelves (like the one in the figure), loosing contact with a pinning point can lead to the collapse and breakup of large sections of the floating tongue in very quick and dramatic events.

Reaction time scales: Neighbouring glaciers can have huge differences in mass. And that means that they don't react with the same speed environmental changes. In a very small glacier, you will see advance after a few years of high accumulation. However, in a very large glacier, a few years of high accumulation doesn't make much of a difference. And the glacier can still recede after such events, perhaps due to a few decades of low accumulation that happen a hundred years ago.
Area is not volume: What you see in the images are changes in area not volume. So even if two glaciers are loosing the same amount of mass per year. If one is thinner than the other, you will see that the thicker one shrink less that the other.
Hypsometry: It  refers to the distribution of values of surface elevation of a glacier. For example if two of the glaciers you are observing span from 1,500 to 2,500m of elevation, but one of them have 90% of its surface above 2,000m of elevation, and the other only a 30%. You will observe that a change in temperature that push the average freezing line from 1,800m to 2,000m will affect the second glacier much more than the first, because it will suffer a larger increase in the fraction of its surface exposed to melting temperatures.
Surging glaciers: Some glaciers undergo what is call a glacial surges. They show a cyclical behavior in which they advance very quick over few years and then recede slowly over decades to then start over again. I won't go in detail about this process that is very complex and still poorly understood. But in the images you observe, they might be some variability also to the presences of glacier surges.

Other factors could be more complex weather redistribution patterns, bed topography, bedrock lithology, basin divide migration, frontal wasting (calving) for lake and marine terminating glaciers, etc.


Where did the sand in the Sahara come from? If the Sahara used to be fertile and has since experienced minimal rainfall causing the current desert conditions, where did all the sand come from?
I assume the original dirt is still there, just underneath the sand.

The sand IS the original dirt, or at least what's left of it.
Sand is one of the major constituents of soil. Soils are roughly half minerals by volume and those minerals are silt, sand, and clay. In fact sand is often the largest single constituent of most common soils. Silt and clay are smaller and lighter, and can be moved by wind much easier when dry, this leads to the removal of everything but the heavier sand particles in very dry conditions.   What has happened is that without water and life to bind the material together, wind has removed all the lighter particles leaving nothing but sand and pebbles. Wind is good at sorting grains by size so each area tends to only have one grains size.
Where it came from originally
. Sand is just weathered rock, if you look at a map of the sahara there are quite a few scattered mountains and highlands in the desert. That is where the sand (and the original silt and clay) came from originally, weathering of rock, and the sahara is mostly exposed rock, with sand only making up a minority of its surface.
I suggest the wiki for getting started on soil science, if you are interested, https://en.wikipedia.org/wiki/Soil
More on what sand is, http://www.sandatlas.org/sand/
More on wind driven sorting, https://people.ucsc.edu/~jzachos/migrated/eart120/lectures_08/LECT7B.pdf


Where does the water from rain in rain forests come from? When discussing a hypothetical world without oceans and just forest it occured to me that I wasn't so sure there would be any rain in the first place, due to the lack of oceans. Searching on Google however I found out that trees transpire a whole lot more than I thought, but I was unable to find a run down of how much water in rain forest rains come from the oceans and how much comes 'directly' from the rain forest itself.

Leaves, mostly. Photosynthesis requires carbon dioxide, and it gets it via stomata - small controllable pores in the leaf. When the stomata open, water goes out, because the air is generally drier than the interior of the leaf. Water in the leaves is drawn up from the roots, via the xylem, using the suction from the lost water in the leaves, and also acting as a capillary.

As for how much water comes from transpiration, Brustaert (2005) includes a list of estimates of global annual evapotranspiration from the land that range from 0.42-0.54 my$^{-1}$ (averaged over all 1.49×10$^8$ km$^2$), and 1.18-1.4 my$^{-1}$ for the ocean (3.61×10$^8$ km$^2$). That 6.22×10$^{13}$-7.99×10$^{13}$ tonnes of water or 62.2-79.9 petatonnes, compared to 425-505 petatonnes for the ocean.

So, for Earth, the land is something like an sixth of the total evaporation. Keep in mind that that includes desert areas. A rainforest planet would have significantly higher evaporation than that, per square meter. For example, Malhi et al. (2002) calculate evapotranspiration over the rainforest in the Amazon at 1.12 my$^{-1}$. That is much closer to ocean rates than average land rates.

Brutsaert, W., 2005. Hydrology: An Introduction, Cambridge University Press.
Malhi, Y. et al., 2002. Energy and water dynamics of a central Amazonian rain forest. Journal of Geophysical Research: Atmospheres, 107(D20), p.8061.


Where does water vapor go/what does the sun do? For instance, coastal areas are often foggy in the morning. Then the sun “burns it off”. Where does the moisture go? I’m curious of the star’s (i.e. Sun) influence on evaporation effects.

Simplistically, fog consists of water droplets.  The sun provides energy, which heats the droplets and evaporates them, and also raises the air temperature.  The water is still there, it's just in the form of (transparent) water vapor, rather than light-scattering droplets.

PS: Maybe a similar example would help make things clear.  Say you've just washed some clothes, and hang them on the line, and some time later they're dry.  There was water in the clothes when you hung them out, it didn't drip off the bottom, so where did the water go?  Into the air, as vapor, no?  Same with fog, when the sun raises the temperature a bit.


How are minor tributaries of a river determined? What are the criteria to determine if river A is a major or minor tributary to another River B?

Is stream order the only deciding factor i.e. the highest order is the main stem, one less order is a major tributary and one more lesser order is a minor tributary?

I haven't been able to find any literature on this online.

This is a question of topology. There are three major attempts to order streams from small to larger.

The first was established by Horton (1941) who established the concept of drainage composition. To establish the relative importance of streams in a network Horton suggested to investigate each junction and to set the stream that entered the junction at the highest angle as a stream of lower importance. By starting at the mouth of a river, one can thus establish which would be the main trunk of a river and which are tributaries of smaller and smaller significance. The order number of streams cannot be determined until the entire tree of streams have been ordered. In the figure on Strahler stream order the diagonal would be the main trunk of the river and have order three. The only order two trunk would be the one labelled two turning down from three in the figure.

Strahler, 1952 took the concept further and established the concept of stream order. In this approach the basic stream is the smallest source tributaries. When two streams of order one meet they form a stream of order two. It takes two of the same order to make a stream of a larger order so a stream of order two and one will not increase the order number, the result is still two. The following image provides an example of Strahler's stream order:

Strahler stream order concept. Image from Wikipedia commons

The stream order allows one to calculate an assortment of statistical measures that characterizes a drainage basin and it is possible to use these characteristics in, for example, flood prediction.

Shreve (1967) took the ideas of Horton and Strahler further by introducing magnitude, now called Shreve Magnitude. This concept differs from Strahler's in that all streams are additive so that as soon as one stream is added to another the resulting stream is the sum of the two tributaries. The result is that the system can be seen as reflecting discharge, assuming all first order streams are of similar size. In the figure above the largest magnitude would be six, this is also the sum of all order one streams.

So establishing the main trunk of a river is not necessarily simple. Hortons method does this but is at the same time relying on geometry and rivers may be heavily influenced by geology  to generate odd river patterns.

References:

Horton, R.E., 1945. Erosional development of streams and their drainage basins: Hydrophysical approach to quantitative morphology. Geological Society of America Bulletin, 56, 275-370. doi: 10.1130/0016-7606(1945)56[275:EDOSAT]2.0.CO;2

Shreve, R.L., 1967. Infinite topologically random channel networks. Journal of Geology 75, 178–186.

Strahler, A.N., 1952. Hypsometric (area-altitude) analysis of erosional topology. Geological Society of America Bulletin, 63 (11), 1117–1142, doi:10.1130/0016-7606(1952)63[1117:HAAOET]2.0.CO;2.


Temperature Advection using finite differences with gridded data Advection of a scalar quantity, such as temperature (T), by the horizontal wind, is defined as follows:

$-\textbf{U}\cdot\nabla T$

where $\textbf{U}$ is the horizontal wind vector, $\textbf{U}=(u,v)$, being $u$ and $v$ its zonal and meridional components, respectively (source).

To compute it with gridded data, it is convenient to use finite differences (or similar numerical approaches), as pointed here.

Using this method, the following lines written in Python calculate the advection of temperature (TAdv):

dy=111000 # [m]
lonres=lon[1]-lon[0] # constant
tadv=np.zeros(np.shape(T)); tadv.fill(np.nan)
for t in range(np.shape(T)[0]):
    for x in np.arange(1,len(lon)-1):
        for y in np.arange(1,len(lat)-1):
            dx = abs(111000*np.cos(lat[y]*(2*np.pi/360))*lonres)
            tadv[t,y,x] = -(u[t,y,x]*(T[t,y,x+1]-T[t,y,x-1])/(2*dx) +\
                              v[t,y,x]*(T[t,y+1,x]-T[t,y-1,x])/(2*dy))

I would expect a similar result from scaling the wind components by the temperature, at each grid cell, which is done as follows:

ut  = np.zeros(np.shape(T))
vt  = np.zeros(np.shape(T))
UT  = np.zeros(np.shape(T))
for t in range(np.shape(T)[0]):
    for x in range(len(lon)):
        for y in range(len(lat)):
            ut[t,y,x] = u[t,y,x]*abs(T[t,y,x])
            vt[t,y,x] = v[t,y,x]*abs(T[t,y,x])
            UT[t,y,x] = ((ut[t,y,x]**2 + vt[t,y,x]**2)**0.5)*np.sign(T[t,y,x])

The magnitude of the scaled wind vectors (UT) would be then similar to this "amount of transport of T". It is multiplied by the sign of T (-1 or 1), because T are anomalies (there is T<0), in order to keep its the sign.

However, the results are totally different. What I am missing here? Is it a mistake in this assumption (that both results should look fairly similar)? Or is it a coding problem?

In the figure below, I show the original T, u and v fields (left), and the results of the two above calculations: Tadv with u and v (middle), and the magnitude of the scaled vectors, UT, with the scaled vectors themselves uT and vT (right). TAdv is multiplied by 24*3600, so that the units are K/day.

Here is a link to a Dropbox folder, where the full script and sample data are available for download: https://www.dropbox.com/sh/kcrb08h72jjj3rn/AAAIAUgKVrRrICAQtXhOHS2ta?dl=0

When I look at problems like these I first check to see if there is a well tested and well documented implementation already rather than reinventing the wheel.  In this case MetPy temperature advection is a well tested software that does many of the things meteorologists want including calculating finite differences with the right map scale factors. Since you are using Python I would at least look at their implementation first and correct your code even if you are not going to use their code.

Please do this first and validate your data before you attempt any downscaling operation.

And finally AtmosphericPrisonEscape is correct. If you are using lat,lon grid and calculating finite differences you need to include map scale factors. And if you are using global grids the finite differences will not work at the poles. If you are using regional grids that is not a problem. Please include as much  detail as possible when you ask a computational question.


Carbon Dioxide levels appear to be linked to the Milankovitch cycles according to Ice Core data but what is the mechanism? As in ice core data shows that $CO_2 $ levels have fluctuated on levels correlating to the temperature and ice levels, but I couldn't think of a mechanism for what might be the link between the release of carbon dioxide and other gases, and presumably orbital geometry?

Is it to do with gases dissolved in the oceans? Or the melting of permafrost?

The link between orbital parameters and CO2 levels is, as you wrote, the temperature.

Orbital parameters may change, via feedback mechanisms, the atmospheric temperature. To my knowledge the most important feedback mechanism with respect to the Milankovich cycles is the ice-albedo feedback.

The temperature, however, is an important player in geochemical feedbacks which influence the concentration of gases like CO2 or methane. For CO2, again to my knowledge, you named the most important feedback; the exchange of CO2 between atmosphere and ocean.

The exchange of CO2 between ocean and atmosphere in turn depends on the partial pressure of CO2 in the atmosphere and the surface layer of the ocean; there is uptake, release according to the pressure gradient.
Now, the partial pressure of CO2 in the surface layer depends also on the amount of carbon transported or received from the deep sea layers. There is way more CO2 stored in the cold water of the deep sea. So the exchange of CO2 does depend on the vertical circulation pattern of the ocean.

There are, to my knowledge, three major mechanisms that transport carbon between the surface and the deep sea and they all depend on temperature.

Solubility pump: Cold water can store more CO2 than warm water. Therefore at the poles, where cold water is sinking into the deep sea, you have CO2 rich water. The CO2 stored in the deep sea can, as far as I know, remain there for hundreds of years, before it comes up again in the warmer upwelling regions at the equator. The temperature dependence of that mechanism is obvious.

Biological pump: In the surface layer you have photosynthesis of algeas etc., so carbon is withdrawn from the layer and stored in biomass. A portion of dead plants is not reused (eaten) but sinks into the deep sea. The process is temperature dependend since biological activity depends on temperature.

Carbonate pump: The amount of carbonate and CO2 are linked to each other via marine chemistry. Animals building shells etc. need carbonate thereby also influencing the amount of CO2 present in the water. Again, a portion of this carbonate is withdrawn from the short term cycles once the animals die and sink to the deep sea. Again this mechanism is temperature dependend since biological activity is.


What is the Carbon Footprint of not changing car oil? I am on my second vehicle that I have stopped changing my oil after the car has been broke in or around 90k. The first car I made it 400k miles before the rear end went out. The second car I'm at 130k with no oil change from 90k and runs just as good when I got it.

Does not changing the oil decrease the vehicles carbon footprint then changing it?

I watched the Discovery Channel and a Japanese Engineer said their engines are built efficiently enough not to need an oil change ever. I still add an oil stabilizer like Lucas every 4th quart when I top it off. I am not interested whether it is bad for an engine to do so. I just want to know if it more environmentally friendly not to change the oil?

This is an interesting question, and a life cycle emissions analysis can give a pretty good answer.  Obviously there are a lot of variables, so some basic assumptions have to be made.

We start with the CO2 equivalent emissions from building and driving a car over its lifetime.  There are various analyses out there, but here is one that I found which gives the following values for a typical gasoline powered automobile over a "typical" lifetime of 150,000 km (93,000 miles): 24,000 kg of CO2e emissions total, of which 5600 kg is from the fabrication of the car.

For the oil, I found this, which gives a range of 2.5 to 13 kg CO2e per gallon of motor oil.  The lower value assumes the new oil is made from recycled oil, and the waste oil is sent to a recycler.  The higher value assumes the new oil is not from a recycled source, and the waste oil is not recycled.  For the most extreme case, we can assume virgin oil, and assume the oil is changed every 3000 miles, and that the car holds 4 quarts (1 gallon).  That makes 31 oil changes in the car's lifetime, which gives 403 kg of CO2e from oil changes.  Another perfectly reasonable value might be to assume recycling and assume an oil change every 7000 miles which results in 33 kg CO2e emissions.

So the oil changes are contributing something in the 30 to 400 kg range over the life of the car, compared with 24,000 kg from building and driving the car.  Skipping all oil changes in the most extreme case results in less than 2% reduction in total CO2e emissions.  You can get almost exactly the same result by changing the oil every 7000 miles instead of every 3000, and by using recycled oil and making sure that your used oil is recycled.

Even though you're not asking about it, I have to add that I think you have been exceptionally lucky if you drove 400,000 miles without changing the oil.  I don't think you should expect that result again.  And note that the emissions associated with building a car are 5600 kg - 10 to 100 times greater than the emissions contributed by changing the oil.  If you don't change the oil in any car again for your entire life, and end up ruining just one car as a result, you will cause far more emissions than you saved.


Equation for solar radiation at a given latitude? I'm trying to find equations that would help me determine the amount of solar radiation hitting a certain latitude on a certain planet given the following inputs:

the degrees of latitude of the location in question
this hemisphere's current season (winter or summer)
size of the planet
luminosity of the star(s) the planet orbits

Without taking into consideration wind, air pressure, or any atmospheric effects.

Ideally I would like to determine the average solar radiation of a given location in both the winter and summer.

My end goal is to determine the average surface temperature of a given latitude on a planet using the base solar radiation and the effects of wind, air pressure, and surface ocean currents.

Ignoring meteorological factors and any dust or satellites, this is still an incomplete problem. You would also need to know the rotation axis. For example, Uranus rotates completely on its side (i.e. it rotates at 97.77 degrees, while earth rotates at 23 degrees, 26 minutes and 21.4119 seconds). Such things become important for factors like the Arctic Circle. You are also missing the distance between the planet and the star. That becomes important when you consider that Pluto is colder than Mercury. This is needed for the formulation of the sterdian.

In your question, you said to ignore atmospheric effects. However, the atmosphere also acts as a secondary source of radiation (the infamous greenhouse effect). Even if you neglect eddies, advection, etc. you also need to consider that the atmosphere can absorb radiation and emit it back to the surface, otherwise you would find the average temperature of the surface to be the same as the average temperature of the earth.

Edit: I found a decent approximation (approximation being the key word).

Let $Q_S$ is the incoming solar radiation flux
$$Q_s= S(1-\alpha)(\frac{\bar{d}}{d})^2cos(\zeta)\tau_s $$
Where $S$ is the solar constant, $\alpha$ is the albedo, $d$ is the distance of the earth from the sun, $\bar{d}$ is the mean distance of the earth from the sun and $\tau_s$ is the transmissivity of the atmosphere (including any clouds above).

The last factor, $cos(\zeta)$ can be computed by$$cos(\zeta)=sin(\psi)sin(\delta)+cos(\psi)cos(\delta)cos(h)$$ where $$\delta=23.45\times\frac{\pi}{180}cos(\frac{2\pi\times(d-d_{solst})}{d_{year}})$$
Where $d$ is the Julian day, $d_{solst}$ is the julian day of the solstice (173) and $d_{year}$ is the number of days in the year (365.25)

Additionally, $h$ is the local hour, as defined by $$h=\frac{(t_{UTC}-12)\times\pi}{12}+\frac{\lambda\pi}{180}$$ where $\lambda$ is the longitude and $t_{UTC}$ is the time in UTC (in hours).


shortwave and longwave radiation terminology, direct, beam, PAR, flux? Some reanalysis data sets provide different components of shortwave radiation (near infrared and visible) and longwave. They are referred as radiation or flux. Also there is no mention of "direct" radiation but only "beam". Are these two considered the same? And does the word flux imply something in addition to radiation? Also what is the difference between the long wave and solar fluxes? Here are some examples taken from the NCEP reanalysis site:

Visible beam downward solar flux
Visible diffuse downward solar flux
Upward longwave radiation flux
Near IR beam downward solar flux
Downward longwave radiation flux
Downward solar radiation flux

Beam radiation is direct radiation, e.g. photons that have not been scattered.  Diffuse radiation is indirect and has been scattered.  Examples of beam radiation from the sky would be from the sun directly to your eye.  Diffuse solar radiation would be the blue sky (scattered out of the direct beam by the atmosphere), clouds and anything you can see that is illuminated by the sun.

Shortwave radiation refers to radiation of solar origin, which is primarily in the visible and shorter wavelengths.  Longwave refers to radiation of terrestrial origin, which is typically in the infrared and longer wavelengths (dependent on temperature) and is radiated by the earth, us, clouds, the atmosphere, etc.

A flux is the "rate of flow of a property per unit area" and for radiation is generally expressed in watts per square meter, Wm$^{-2}$.  A watt is 1 Joule per second, so this is an energy flux, a or the mount of energy flowing through a 1 m$^{2}$ surface every second.

To apply this to your variables:

Visible beam downward solar flux

This is the direct radiation in the visible spectrum from the sun expressed as a flow of energy.  This is generally given either at the top of atmosphere or at the surface.  For ToA, this would be the rate of energy through a 1 square meter patch just above the atmosphere.  For the surface, this would be the rate of energy into a 1 square meter area on the earths surface.
Visible diffuse downward solar flux

This is a measure of radiation in the visible spectrum that isn't directly from the sun.  At the surface of the earth this flux would be the rate of energy flowing into a 1 square meter patch of earth from reflection of sunlight (scattering) and from the rest of the sky and clouds that isn't the direct path from the sun.
Upward longwave radiation flux

This is the rate of energy flow from the sum of all terrestrial emission.  At the top of the atmosphere this would be the terrestrial energy escaping to space (per square meter).
Near IR beam downward solar flux

This is the same as the visible beam downward solar flux except it is in the near IR band (infrared wavelengths longer but close to that of visible red) rather than in the visible spectrum.
Downward longwave radiation flux

This flux is terrestrial emission sources that send energy downward toward the earth.  This energy would come from clouds, the atmosphere (greenhouse gasses), etc.
Downward solar radiation flux

This is the total shortwave flux (visible + IR + UV, etc; beam and diffuse) downward through the top of atmosphere or at the surface.


Rossby radius as horizontal scale In the introduction of "Geographical and monthly variability of the first baroclinic Rossby radius of deformation in the South China Sea", the authors states:

  In both theoretical and observational studies of large and meso-scale oceanic processes, the first baroclinic Rossby radius of deformation (R1) is an important quantity in determining horizontal scales which characterize eddy sizes, trapping scales for coastal jets and equatorial flows.

I am familiar with the fact that R1 can determine eddy sizes (e.g., this answer), but I am having an hard time to find references about trapping scales for coastal jets and equatorial flows.

Can someone, please, give me some explanations and/or references?

The Rossby radius of deformation tells you the distance when the Coriolis effect becomes just as important as the buoyancy or gravity.

Let the Rossby radius of deformation be denoted as $L_R$. According to Holton's Fifth Edition of "An introduction to Dynamic Meteorology,"  $$L_R=\frac{NH}{f_0}$$ where $N$ is the Brunt-Vaisala frequency, $H$ is the scale height, and $f_0$ is the Coriolis parameter.

For phenomena with length scale $L$, buoyancy can be neglected if $L<<L_R$.

In statically stable equatorial flows, $$\lim_{f_0\to 0} L_R=\infty$$

In certain coastal flows, $L \approx L_R$

So the author is saying that in equatorial flows, buoyancy can't be neglected, since the Rossby radius "blows up" and for coastal flows $L\approx L_R$


Is there a standard definition of the term "mountain"? Is there any standard internationally recognizable definition of the term "mountain"?

If international texts describe some terrain as mountains, do they use some international definition of the term, or do they use the local definitions?

For example, in Poland geographers usually agree that terrain is called mountains when its peaks are at least 600 meters above sea level. This makes, for example, the Świętokrzyskie Mountains 'mountains', although only a single peak is above 600m. But there are other definitions that are bases on the geological structure of the terrain, not on the height.

Germans, from what I know, use a definition based on 'Reliefenergie', so the relative height difference for every square kilometer, independent of the absolute height.

What criteria are usually used to call a terrain 'mountains' in international community? For example, what would we use on this site?

There does not appear to be an agreed international definition of a mountain.

In the UK there is a colloquial definition that a mountain must be "a thousand feet high". This definition is sufficiently firmly established in a "folklore" sense that the 1995 film "The Englishman Who Went Up a Hill But Came Down a Mountain" centred around it for its plot, and this plot is allegedly based on an older story in the region.

According to the UK's Ordnance Survey,

  There is no precise international definition of a mountain... However,
  it is generally agreed that the minimum height is 610 metres (2 000
  feet). (Source)

This definition does not make clear whether a 2000' rise from the surroundings is required, or whether a peak must simply be 2000' above sea level.


Which geological processes will destroy plastic? The geological record at the end of the Anthropocene will undoubtedly contain large volumes of plastic.  However, some geological processes will completely destroy plastic (e.g. magmatic or chemical processes).  I assume that sedimentary rocks will contain plastic pellets at the least and that igneous rocks will not.  Which geological processes that create metamorphic rock will be able to completely destroy plastic molecules?

Some simplifying assumptions

This is quite a broad and complex question to answer, so I'm going to simplify it shamelessly to make it a little more answerable.

Firstly, there are a huge number of different plastics with a huge variety of physical characteristics. You mention that you're interested in ‘the most common type of plastics’, so I'm going to ignore exotic, high-temperature specialist polymers.

Secondly, you specified that by ‘destroy’, you mean ‘chemically convert the plastic to a molecular form that is found in "nature"’. This could be tricky to guarantee completely: to be really sure you'd have to do a thorough analysis of all the molecular structures in the altered plastic, and make sure that none of them occur in nature. I'm going to reference research on pyrolysis of plastics which classifies end products as gas, wax, oil, and char, and assume that these products contain little or no material which couldn’t be found in nature.

Thirdly, I’m going to ignore metamorphic conditions other than temperature. Temperature will, I’m fairly sure, have the biggest effect on the breakdown of plastics. The chemical environment might make the plastic break down more quickly (by providing reactants), but I don’t think that it will make the plastic break down any more slowly than it would at the same temperature in an inert atmosphere or vacuum. I’ll also ignore any pressure effects.

Grades of metamorphism

Here’s a helpful diagram of metamorphic facies, temperatures, and pressures (source: Wikimedia).

The chart cuts off at 900°C, by which point the rock will generally be melting, putting it into the igneous rather than metamorphic category.

Effects of heating on common plastics

Fortunately for this question, efforts to dispose of waste plastic have led to a lot of research on the effects of heating. Williams and Williams (1997) is a particularly useful reference. They report the effects of heating a sample of mixed plastic waste (low- and high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyurethane) in an inert nitrogen atmosphere at temperatures ranging from 500°C to 700°C. Here’s what they got out of it (yields are in percentages):

(I assume that there's a typo somewhere in the 650°C column, since it implies a 110.5% yield.) The yield is 78.91% at 550°C, so maybe we could expect some identifiable plastic residue (though probably no actual plastic) to remain at that point. By 600°C, there's already a 95.51% yield; unfortunately the missing char figures prevent us from quantifying the yield at higher temperatures, but it seems likely that we’d be approaching 100% by 700°C.

There are a few pages of analyses of the products, but they’re mainly focused on their suitability as fuels rather than whether they’re found in nature. Considering the wide variety of compounds found it crude oil, I think it’s plausible that all the plastic pyrolysis products have naturally occurring counterparts, but it would be a significant research project to establish this beyond all doubt.

Putting it together

Referencing the pyrolysis temperatures back to the metamorphic facies, it looks as though the amphibolite facies corresponds reasonably to the range over which common plastics are completely, or near-completely, decomposed by temperature. So, when the aliens land in a few million years and start investigating the Anthropocene, they might well find some of our old rubbish in prehnite-pumpellyite (P-P) facies rocks, but there won't be much to see in the granulites. Here are some examples of metamorphic rocks from those grades.

Liberty Gulch Broken Formation, a prehnite-pumpellyite facies metasandstone. Source: Raymond and Berro (2015).

Amphibolite facies (staurolite zone) metasediments from the Scottish Dalradian. Source: Dave Waters, Dalradian Metamorphism album.

Strongly deformed high- to medium-pressure pelitic granulites from the Qianlishan Complex. Source: Yin et al. (2014).

References

Loren A. Raymond, David A. Bero (2015). Sandstone-matrix mélanges, architectural subdivision, and geologic history of accretionary complexes: A sedimentological and structural perspective from the Franciscan Complex of Sonoma and Marin counties, California, USA. Geosphere, 11(4), pp. 1077–1110. doi: https://doi.org/10.1130/GES01137.1

E. A. Williams & P. T. Williams (1997). Analysis of products derived from the fast pyrolysis of plastic waste, Journal of Analytical and Applied Pyrolysis. 40-41, pp. 347-363.

Yin, C., Zhao, G., Wei, C., Sun, M., Guo, J., & Zhou, X. (2014). Metamorphism and partial melting of high-pressure pelitic granulites from the Qianlishan Complex: constraints on the tectonic evolution of the Khondalite Belt in the North China Craton. Precambrian Research, 242, pp. 172-186.


How can we distinguish fold and cycle of sedimentation on a remote sensing image or in the field? A fold is composed of stratigraphy that is symmetric and repeated. Cyclic sediments (also called rhythmic sediments) are sequences of sedimentary rocks that are characterised by repetitive patterns of different rock types (strata) or facies within the sequence (wiki). A cycle of sendimentation is usually composed of transgressive and regressive deposition, so the sequences can be also likely symmetric.
One method to distinguish them, I think, is the stratigraphic occurrence. Is there other methods that can help distinguish them on a remote sensing image? Thank you.

You need to take a look at lithology changes and stratification.
On a fold the stratification is parallel to the fold, while on a transgressive-regressive cycle it crosses the v form.

Source: Own work with Inkscape.
At the field the best is to look up to lithology changes and define how is stratification spatially related with the main shape.
You can easily distinguish stratification on a 2D log. From a remote sensing image it would be distinguishable if you have an outcrop that crosses the shape.


Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement Why increasing transmitter-receiver coil separation in EM survey (EM31, also here) increases depth of penetration?

Suppose there is a horizontal flat conductive layer underneath a flat resistive layer. Why receiver coil records stronger signals at 4 m transmitter-receiver coil spacing compared to 2 m transmitter-receiver coil spacing? What us the physical explanation of this?

As described in the question there are two similar coils, one radiates the AC magnetic field ("transmitter") and the other picks up the weak radiated AC magnetic field produced by subsurface electrical currents induced by the primary field.

Sensitivity vs. Depth

There are two modes of operation. The following two figures are from Section 4.1 of GEONICS Technical note #6; Electromagnetic Terrain Conductivity Measurement at Low Induction Numbers. (more technical notes here) In both figures the two coils are separated by a horizontal distance $s$ which is typically a few meters.

In Horizontal mode the axes of the two coils point in the horizontal plane. In this orientation the sensitivity always peaks near the surface, and falls off to about 30% at a depth of $0.4 s$.

In Vertical mode the axes of the two coils point "up" or vertically. In this orientation the sensitivity is low near the surface and peaks at depth of $0.4 s$.

In either case, if $s$ is twice as big (the coils are twice as far apart) these two shapes will be stretched by the same amount. If $s$ is 2 meters, the vertical method will have peak sensitivity at 0.8 meters. If $s$ is 5 meters, vertical sensitivity peaks at 2.0 meters.

The two plots can be seen on the right side of Figure 1. in The Application of EM38: Determination of Soil Parameters, Selection of Soil Sampling Points and Use in Agriculture and Archaeology Kurt Heil and Urs Schmidhalter, Sensors 2017, 17(11), 2540; https://doi.org/10.3390/s17112540

That article also links to Comparison of the EM38 and EM38-MK2 electromagnetic induction-based sensors for spatial soil analysis at field scale which may cite further references but it's paywalled.

  Figure 1. (Left) Relative cumulative contribution vs depth for vertically (RV(z)) and horizontally (RH(z)) orientated dipoles; (Right) Comparison of the relative responses for vertically (FV(z)) and horizontally (FH(z)) oriented dipoles.

Yes, that's all fine and dandy... But Why?

I can't come up with a simple model for why this is true, so I'll have to read further. It's possible someone else will be able to provide a better answer. I think it's related to how the phase of the signals are process, but I'm not sure about that yet.

However, the Computers and Electronics in Agriculture paper Accuracy issues in electromagnetic induction sensing of soil electrical conductivity for precision agriculture (also available here) K.A.Sudduth, S.T.Drummond and N.R.Kitchen, Volume 31, Issue 3, May 2001, Pages 239-264 https://doi.org/10.1016/S0168-1699(00)00185-X happens to give equations for these shape, and a clue to where these are from.

Those equations are close but $\color{red}{wrong!!}$ they are missing a division "/" sign.

  Fig. 2. Relative response of EM38 sensor as a function of distance (adapted from McNeill, 1992).

The equations in the figure have obviously been typed incorrectly, but if I make some simple adjustments they work nicely

$$\phi_V(z) = \frac{4z}{(4z^2+1)^{3/2}} $$

$$\phi_H(z) = 2 - \frac{4z}{(4z^2+1)^{1/2}} $$

where z has to be unitless, so is almost certainly given by:

$$z \equiv \frac{\text{depth}}{s}$$

where $s$ is the separation between the two coils as before.

Possibly helpful links:

The use of electromagnetic induction techniques in soils studies (also available here)
Comparison of Electromagnetic Induction and Direct Sensing of Soil
Electrical Conductivity


How and why did the oceans form on Earth but not on other planets? Earth is the only planet in our solar system that has copious amounts of water on it.  Where did this water come from and why is there so much water on Earth compared to every other planet in the solar system?

Your assumption that there is not a lot of water elsewhere in the solar system is incorrect.  According the this article on NASA's website;

Missions in recent years have overturned our view of a dry solar system, returning mounting evidence of ample water from a vast array of locations.
Comets from the remote corners of our solar system are made of water and other ices. Orbiters, landers, and rovers reveal Mars as a watery world in the distant past -- a world that today may contain entire underground oceans of frozen water.

It also points out that

Jupiter's moon Europa has a frozen crust of water, covering a thick global ocean. By current estimates, it has twice as much water as all of Earth's oceans and rivers!

The perception that the rest of the solar system does not have a lot of water is probably due to the fact that the Earth is in the 'Goldilocks zone' where water can exist in all three phases at the surface of the planet.  The temperatures on the rest of the planets in the solar system are either so hot that it can only exist in a vapor phase or so cold that it can only exist in ice at the surface or liquid beneath.


Sun and moon anomally Below is a photo that my son took in Scotland showing the sun and moon at the same time. I immediately noticed this anomaly that the light illuminating the moon could not possibly come from the sun. I sent the photo to 4 University astronomy departments and only one responded and that was Cambridge University which is near where I live. The response came from the department librarian (not an astronomer) who said he had never heard of this before. He gave me two possible solutions, one was was from an engineer (not an astronomer) in which he got confused between perspective and light ray tracing and the other was referring to Einstein's theory of light bending by gravity. I check out Einstein and the effect was so small as to be almost immeasurable.

I have looked at the various 'complex' explanations for what to me is a very simple model.  What need is there to introduce 'curved planes' and 'starry sky domes' all of which do not exist in reality?
It is only referred to as an 'illusion' because observation doesn't fit the conventional model hence the complex explanations to try and make it work.
The anomaly is acknowledged to exist with or without photos. Since everyone believes that the moon is illuminated by the sun then simple normal physics do not seem to work. Either the physics is wrong or the sun does not illuminate the moon. I realise that is a heavy statement!

Therefore I state once again:

The sun and the moon are two objects (like a torch and a football) that are suspended in a 3 dimensional space and size should not matter.
The moon/football are illuminated by the sun/torch and a perpendicular line or light ray can be drawn between them.
It doesn't matter where in space you choose to view them, a perpendicular line or light ray can still be drawn between them.

This drawing explains my doubts:

I'm very surprised that some of you have never noticed it before hence the suggestion asking me to post a video. This is a very common occurrence and I have seen it many many times as I go for my morning walk at about 8.00am every morning. I have never thought of actually tabulating my observations.

The apparent anomaly, known as the Lunar Terminator or Moon Tilt Illusion, is indeed a matter of perspective. A brief explanation can be found here: http://chrisjones.id.au/MoonIllusion/

The essence: 'The illusion occurs when the moon and sun are separated by a wide angle, so that they are perceived relative to the horizon, as if in a panorama. A panoramic photograph is a cylindrical projection. In this projection, most straight lines project as sinusoidal curves. The moon-sun line is curved, unless the moon and sun are on the horizon or directly above one another.'

A long, technical explananation is in the PDF The moon tilt illusion. Quoting from page 21:

  Modern cameras use lenses whose properties are designed to deliver a rectilinear
  or curvilinear image.  Rectilinear lenses reduce barrel or pincushion distortion from
  the image but such lenses are difficult to manufacture for the wide angles (90°
  and above)  needed  to  record  both  the  sun  and  the  moon  on  a  single  photograph.   A
  photograph [3]  of  the  moon  and  sun  at  an  azimuth  difference  of  80°
  containing  a
  leaning  tower  and  unnaturally  leaning  trees  illustrates  the  difficulty  of  eliminating
  distortion in a wide-angle photograph

That reference [3] is to A Different Moon Illusion on Jerry Lodriguss astrophotography site Catching the light where he shows and explains the exact same situation (picture taken from there):


Have meteorites been found in the oldest sedimentary rocks? Dropstones sometimes occur in sedimentary rocks. These are foreign rocks and boulders that happened to "drop" into a sediment and were fossilised when the sediment was lithified.

(source: Michael C. Rygel via Wikimedia Commons)
But what about meteorites? You can find meteorites here on Earth, and while such large blocks as pictured may be extremely rare, they do exist somewhere. We don't have a lot of meteorites now, but it seems to me that if we go back billions of years, it makes sense that somewhere, sometime, a meteorite has been incorporated into the rock record.
I suppose that it is also unlikely because most meteorites fall in the ocean is then subducted and the meteorite "dropstones" are lost to the mantle.

EDIT
I found this recent (2020) paper talking about 20 cm large meteorites in Ordovician sediments, that came from the breakup of a larger asteroid:
Absolute dating of the L-chondrite parent body breakup with high-precision U–Pb zircon geochronology from Ordovician limestone

A main source of meteoritic origin in sedimentary strata could have been likely to have been placed in a marine sedimentary environment as debris from a larger impact. Evidently, as you stated, the older the sediment, the greater the chance of alteration or even complete destruction of any trace of the fragments.

In addition to the micrometeorites found in Sweden (as per DavePhD's linked articles), the article Cosmic-ray exposure ages of fossil micrometeorites from mid-Ordovician
sediments at Lynna River, Russia. (Meier et al. 2014), report of observations of chondrite micrometeoritic dust occurring in mid-Ordovician (~ 470 million years ago) sediments found around the Lynna River, Russia, as well as localities in China.  The authors state that the composition of the micrometeoritic sample makes them largely resistant to weathering and diagenesis.

The authors of the article Noble gases in fossil micrometeorites and meteorites from 470 Myr old
sediments from southern Sweden, and new evidence
for the L-chondrite parent body breakup event (Heck et al. 2008) concluded that it was 'remarkable' that the solar gases trapped in the chromite grains from the Ordovician-aged 'fossil meteorites found in Sweden (and according to Meier et al. 2014, also in Russia and China) have survived not only the heat up due to entry into the Earth's atmosphere, but also the long residence time in the sediments.

Further back, finding pristine sedimentary layers, let alone intact meteorites within the strata become increasingly difficult to find, so there incorporation into the geology would be in the form of geochemical traces.

A couple of examples of this include the following, the Nature article (Abstract only - paywalled), Tungsten isotope evidence from approx 3.8-Gyr metamorphosed sediments for early meteorite bombardment of the Earth (Schoenberg et al. 2002), suggest that Archaean aged metamorphic rocks found in Greenland and Canada contain tungsten anomalies that can, according to the authors, only be meteoritic remnants in the metamorphosed sediments.  Chemical traces of possible chondritic origin have been hypothesised to have been included in Archaen spherules in metamorphosed sedimentary strata in South Africa, according to the article Geological and Geochemical Record of 3400-Million-Year-Old Terrestrial Meteorite Impacts (Lowe et al. 1989) (Abstract only -paywalled).


What is seismic stretch in geophysical method? What is seismic stretch in geophysical method ?

I believe you are referring to - as @ye-ti-800 has already pointed out - the apparent stretch that results from the NMO correction applied to CMP gathers. There is a great tutorial supplied by a Leading Edge article that may be accessed here: https://wiki.seg.org/wiki/Step-by-step_NMO_correction. It is important to note, though, that the article does not go into details about stretch mute. The article just goes into the specific details of the "mechanics" occurring during a conventional NMO correction and accompanied stretch that results from it.


How is it possible for rocks to be trapped within another type of rock? More specifically, I would like to know how the rocks in these pictures have formed:

If this is because magma has melted and trapped the other rocks inside, do they have a different melting point then?
Images are from St. Blaize Trail in Mossel Bay, South Africa

There are three major types of geological formations that contain or are composed of various rocks:

breccia
conglomerate
xenoliths

Breccia
The word breccia comes from the Italian word for rubble. There are various forms of breccia:

sedimentary
tectonic
igneous
impact
hydrothermal

The clast (rock fragments) within breccia are angular in shape and generally randomly orientated, a opposed to a conglomerate which is composed of rounded fragments.
Sedimentary beccia generally formed in ancient stream beds. Igneous breccia forms as a result of rocks being torn away during volcanic eruptions. Impact beccia results from the impact of meteorites. Hydrothermal breccia results from fissure opening up due to seismic or volcanic activity & hydrothermal fluids (hot water) entering the fissure causing the sides of the fissure to collapse inwards.
Conglomerate
Conglomerates contain rounded rocks bound within a sedimentary unit. They form either within ancient stream systems or in marine environments. They can also form as a result of glacial activity.
Xenolith
Xenoliths are fragments of rock contained with igneous rocks. Their spacing with the host rock is much greater than that of beccia or conglomerate - they are more isolated. They generally result from volcanic eruptions.


What is the concentration of silver in tap or freshwater in the United kingdom Can anyone tell me the concentration of silver in uncontaminated water ways, or treated tap water in the united kingdom? sources would be desirable too

Monitoring results from UK groundwaters 1996-2007, Silver:

Sites 2929

Samples 19420

Min <0.04 µg/l

Max 79.6 µg/l

Average 0.457 µg/l

Source - Defra

  Routine monitoring for trace elements in drinking water is only
  conducted for the elements specified in the Water Supply (Water
  Quality) Regulations. Specified elements include antimony, arsenic,
  boron, cadmium, chloride, chromium, copper, fluoride, iron, lead,
  manganese, mercury, nickel, selenium and sodium. Monitoring for other
  elements will only normally be conducted in response to specific
  identified risk. Recently DWI has funded investigations of uranium1
  and molybdenum2 in drinking water in response to recent developments
  in WHO guideline values. Both these studies showed a good level of
  compliance should the WHO guideline value be adopted as a standard.

Also...

  Water companies also conduct raw water monitoring and these results
  are reported to Drinking Water Inspectorate. Preliminary analysis suggests most of the
  raw water monitoring relates to elements already covered by the
  regulations but a few companies monitor for additional elements in raw
  water. A summary of the additional elements and (number of companies
  monitoring). Silver (4).

Source - Defra 2

  Average silver concentrations in natural waters are 0.2-0.3 µg/litre.
  Silver levels in drinking-water in the USA that had not been treated
  with silver for disinfection purposes varied between "non-detectable"
  and 5 µg/litre. In a survey of Canadian tapwater, only 0.1% of the
  samples contained more than 1-5 µg of silver per litre. Water treated
  with silver may have levels of 50 µg/litre or higher; most of the
  silver will be present as nondissociated silver chloride.

Source - WHO


Given a 3 box model of the atmosphere,determine fraction of mass transport from lower layer P = 300mb, Pot. Equiv. Temp = 375K

P = 600mb, Pot. Equiv. Temp = 325K

P = 900mb, Pot. Equiv. Temp = 350K

(surface)

Given that a deep convective plume sends a portion of the bottom layer to the top:

What fraction of the mass of the lower layer must rise in order to just barely stabilize the lower layer with respect to the middle layer?  How many millibars of environmental subsidence does this imply?

I need direction on how to begin this.  Which equation will assist with this answer.

My attempt:

If I remove a chuck sized $\alpha$ from the bottom layer, it will contain $\frac{3m}{2}$ the mass of the middle layer of same size.  So, is the answer simply $\frac{2}{3}$ of the mass must move out of the lower layer?  I believe I am wrong, it seems to be more involved than this, but I cannot grasp this concept.

My results:

If an $\alpha$ sized chunk was moved up, then what remains is $(1-\alpha)$.  Because each layer is 300mb thick, they have equal parts mass.  What goes up must be compensated, and due to conservation of mass, there is no gain or loss of mass in my system.  Potential temperature is a conserved quantity, so I can say:

$$350K(1-\alpha)+325K\alpha = 325K(1-\alpha)+375K\alpha$$
$$\alpha = \frac{1}{3}$$

Further,
$\frac{1}{3}$ mass movements equates to $\frac{1}{3}$ of a $300mb$ layer, which is $100mb$ subsidence.


How does the synthesis of Kaolinite (and it's by products) influence porosity in granodiorite? I started studying the effects of weathering on granodiorite (see previous posts) and plan on referencing the link between the chemical weathering of feldspar plagioclase leading to kaolinization, a process I am relatively unfamiliar with. In brief terms, how would this reaction reduce the porosity of the rock? Also, how would the release of $Ca$ and $K$ influence further degradation of the rocks porosity?

Kaolinite "grains", for want of any better term, are swollen with chemically bonded water compared to the crystals they weather out of so porosity is decreased by particle expansion while at the same time overall density drops. Kaolin also has very strong particle-particle adhesion so any mechanical deformation of the material tends to compress it leading to further reductions in bulk porosity. The influence of Calcium and Potassium on the ongoing weathering of the rock and it's overall porosity depends greatly on the weathering regime; for example if weathering is continuously under wet conditions then Calcium and Potassium will be mobilised in ground water and removed. On the other hand in a wetting-drying cycle Calcium and Potassium liberated from the parent rock become oxides when the material dries out, those subsequently react strongly with water in the next wetting cycle acidifying the environment and accelerating rock decomposition.


Are there water molecules in the oceans which will almost never fall down as rain? Some oceans are very deep. But is there also current (convection) deep in the ocean so that all water molecules will ones be evaporated and fall down as rain or is it very quite at the bottom so some water molecules will stay at the bottom for decades?

Never is a very, very long time.  Almost never is a vague term.

The age of deep ocean water has been studied with both models and observations, and both indicate a lower limit age in the order of thousands of years, rather than decades.  Here, age is defined as elapsed time since contact with the surface, which would be the only opportunity for evaporation.

On a geological timescale, all ocean water has ample opportunity to evaporate and fall back as rain again and again.  On a human timescale, not so much: for some water in the ocean, it has been well over a thousand years since the last time it was near the surface.

For an example of a recent study into the topic:

  Gebbie and Huybers (2012): The Mean Age of Ocean Waters Inferred from Radiocarbon Observations: Sensitivity to Surface Sources and Accounting for Mixing Histories.  in: Journal of Physical Oceanography.  http://dx.doi.org/10.1175/JPO-D-11-043.1

From the abstract (emphasis mine):

  A number of previous observational studies have found that the waters of the deep Pacific Ocean have an age, or elapsed time since contact with the surface, of 700–1000 yr. Numerical models suggest ages twice as old. Here, the authors present an inverse framework to determine the mean age and its upper and lower bounds given Global Ocean Data Analysis Project (GLODAP) radiocarbon observations, and they show that the potential range of ages increases with the number of constituents or sources that are included in the analysis.
  (...)
  The authors find that the North Pacific at 2500-m depth can be no younger than 1100 yr old, which is older than some previous observational estimates.
  (...)
  Subject to the caveats that inference of the mixing history would benefit from further observations and that radiocarbon cannot rule out the presence of extremely old waters from exotic sources, the deep North Pacific waters are 1200–1500 yr old, which is more in line with existing numerical model results.


What does the precessional parameter measure? I am wondering what is measured in the plots of change of precession, e.g. when describing Milankovitch Cycles. The values typically vary between .06 and −.06. I am also wondering about what the different values for extreme points mean, but that will probably be answered with the first question.

What is usually shown in cyclic plots showing precession is the precession index ($e \cdot \sin\varpi$ where $e$ is the eccentricity and $\varpi$ is the moving longitude of the perihelion). It is dimensionless ($e$ and $\sin \varpi$ being ratios).

Here is the precession index for the last 2 Myrs that I plotted using data from Laskar et al. (2004) (in the data file, first column is the age, second the eccentricty, third the obliquity and fourth the longitude of perihelion from moving equinox):

As for the range of values, by definition a $\sin$ can only take values on the range [-1,1], while the eccentricity (at least during the last 100Myrs) has values ranging from 0 to 0.067; hence a resulting precession index ranging in theory from -0.067 to 0.067.

References

Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428(1), 261–285.


Minimum flow duration curves It is common to prepare flow duration curves from a set of daily river flow data, but does it make sense to build a flow duration curve from a set of monthly minimum flow data? I searched on internet, but the key word "minimum flow duration curve" does not return any relevant document.

I believe it is not very useful while FDC's  are mostly interesting for the entire discharge record. You can zoom in to the lower part of the curve and analyse it. The problem with the FDC is that it give no indication of sequences of low flows.
You can imagine a river with no discharge (=0) during a couple of months for example. With monthly minimum values this problem is smaller.

In the end I believe it's more useful to use probability distributions for frequency analysis of extreme values like low flows. In literature you can find that the Gumbel distribution of the smallest value is one of the most reliable for annual minimum flows.


How do we know the rate of decay for radiometric dating is constant? http://www.purdue.edu/newsroom/research/2010/100830FischbachJenkinsDec.html

The link above talks about a research paper from Purdue University that the researchers had detected slight fluctuations in radioactive isotope decay rates and  might affect how we uses radiometric dating. Young Earth creationists did used this to claim that radiometric dating is not accurate and that it is base on assumptions. https://www.discovercreation.org/blog/2012/10/26/80-years-of-scientific-fact-wrong-radioactive-decay-rates-not-constant/ Could the rate of radioactive decay be different in the past that today?

First of all, you shouldn't take creationists seriously; like flat earthists, their views are totally out of touch with reality. Rates of radioactive decay have been tested many times in the laboratory and found to be accurate. However, there have been some instances where a substantial change of temperature or the formation of a chemical compound involving the radioactive isotope produces a small change in the rate of decay. When used for radiometric dating, this is not a source of error. The main source of error is the minuteness of the samples that labs have to work with. For example, only one potassium atom in 100 is potassium 40,the half life of which is I,300,000,000 years. In argon potassium dating the volcanic tuffs the lab has to analyse contain only a tiny amount of potassium 40,and only 11 percent of that decays to form argon 40 (the remainder forms calcium 40). The lab has to detect and measure the tiny trace of argon which has formed in the sample since it was emitted by a volcano a few million years ago.

Sometimes several dating methods are used on the same fossil or artefact, and if they are in rough agreement the dating is reliable. If you are looking for pin point accuracy, you won't get it with radiometric dating, but if accuracy to within a few percent is good enough, then that is usually achievable. The colossal orders-of-magnitude errors which creationists try to convince you of never happen.


What is the characteristic time of the loss of the Earth atmosphere, how can it be calculated? Somewhere I've read it is in the order of some tens of billions of years, but unfortunately I can't find any reference with it in Google.

I suspect, the losses are coming mainly from analyzing the statistical distribution of the upper atmosphere, extending with the interaction of the Solar Wind. The result is probably a finite element model and not an analytical solution. Am I right? What is the result?

Even in the exosphere, at 1800 deg centigrade, the only components of the Earth's atmosphere that can currently attain escape velocity are hydrogen (3 kg per sec), and and helium (next to nothing). The notion that the Earth's atmosphere would be stripped away by solar wind but for the protective magnetic shield, is a myth. So there is no 'characteristic time of loss of the Earth's atmosphere' in the sense of slow decay. There is certainty that, as the sun approaches the red giant stage, several billion years from now, there will be catastrophic heating of the atmosphere such that oxygen and nitrogen will be stripped away, leaving Earth to overheat in runaway carbon-dioxide. Unless, that is, if gravitational mayhem, caused by galactic collision with Andromeda, flings Earth substantially further from the sun.

Oxygen, nitrogen and inert gasses can escape from bodies the size of the moon, Venus and Mars because the thermal process, 'Jeans Escape', in less massive bodies incurs substantially lower escape velocities.


How does the influence of clouds on climate vary with height? It is generally assumed that clouds affect climate by reflecting sunlight back to space and therefore decreasing the total warming of the Earth.  However, stratospheric ice clouds are said to have a net warming effect, due to (I think) the insulation properties of clouds and the low reflectivity of ice clouds.

How do various clouds affect climate?  Specifically, what is the relative energy balance effect clouds have as you go up in the atmosphere?  Is it just stratospheric ice clouds that have a net warming effect?  What really are the insulation properties of a cloud and how do they compare to the reflectivity?

There are a few things that come into play when you talk about the radiative forcing of clouds, or their effect on the climate budget. "Cloud" is a pretty wide-sweeping definition. Scientists are still trying to fully understand and quantify these effects. Clouds do not vary only in where they are in the atmosphere but also in their phase (ice versus mixed phase versus water) and their depth--the combination of these two affect the cloud's optical depth. All of these different properties affect the net effect (whether positive, negative, or neutral) of clouds on the climate system.

High clouds are generally ice crystals, yes, because they are in areas of the atmosphere that are far colder than the freezing level. They are also generally geometrically thin. These high clouds have little effect on the shortwave energy and instead mainly reduce the amount of longwave radiation leaving the planet.

Clouds in the middle parts of the atmosphere are usually tall cumulus clouds that are full of liquid and mixed phase precipitation. These will be very bright to shortwave radiation and thus reflect much of that incoming radiation. They also provide some trapping of longwave emission from the surface and radiate less longwave radiation for a given level in the atmosphere than would normally be the case. The anvil regions of these clouds, on the other hand, are full of ice crystals which again don't reflect much shortwave radiation but do reduce the amount of longwave radiation leaving the planet.

Compared with the high atmosphere, completely ice phase clouds near the surface are thicker and their shortwave reflection is therefore a bit stronger than their thinner counterparts in the middle and upper atmosphere; they also trap longwave radiation from the surface. Mixed and liquid phase clouds' effects have similar effects as ice phase but are stronger in both the short- and longwave spectra.

Another thing special about clouds near the surface is because of that proximity they can actually have a strong influence on the surface which can cause a climate feedback. If you have a deck of clouds overlying a bright surface, it can actually warm the surface a bit since it is reflecting less shortwave than the highly reflective underlying surface would otherwise. For example, it has been hypothesized that the Greenland Ice Sheet melting is enhanced when cloud cover is present.

A good resource on this topic is available here. There have been many hypotheses over the years as to how these clouds and their effects will change in a changing climate. You can search for things like the "Iris hypothesis"--and subsequent refutation--as a good example of this still-evolving science. Climate models are still struggling to cope with correctly representing all of the feedbacks associated with clouds, which causes such high uncertainty in cloud effects in the IPCC reports.

One last thing to keep in mind is that these forcings are relative to a column with no cloud in the current climate. But what if our distributions or regimes of clouds greatly shift? If the planet warms so much that ice clouds can never exist, the relative forcing of ice clouds in that climate would then be null. So akeep in mind the point of reference you are using when thinking about the forcing of clouds.


If planting trees is ineffective to tackle climate change, why do people plant them? I've read answers that outline how if we afforested large (continental-scale) masses of land, it would do little in the way of tackling climate change. While it would sequester $\small\mathsf{CO_2}$ for about a century after it was planted (while growing) before reaching equilibrium, the planting of large quantities of trees would also sufficiently decrease the albedo of the land in which it was planted, that it would hold in a lot more heat than the land it replaced (likely desert or otherwise barren land). This means that, all things considered, it would make a negligible, if not negative impact, in tackling global warming.

If this is the case, why do we associate "planting trees" as a good thing, on the scale of individuals planting individual trees? Is it because generally, these trees improve ecosystem vitality/diversity, or for some similar reason unrelated to climate?

Planting trees has a short term benefit in carbon sequestration but will not offset the carbon from fossil fuel burning. However, in some places trees provide a benefit of increasing soil carbon which can have a longer lasting effect. Thus, one benefit is to increase the time needed to implement replacements to fossil fuels. Trees can increase cooling through greater evapotranspiration than grassland, in some climate zones. That, however, may have an impact on water resources. Wood and paper products that are not recycled remove carbon from the natural system, although the effect is small.

Burning wood instead of fossil fuels has a positive impact on the carbon budget where the carbon is recycled back into tree plantations.


How to read Seismic Survey? Recently I am tasked to create a POC on detection of patterns using a neural .
But I am from a computer science background so I know about neural networks but I don't have any knowledge about geology or how to read those surveys.

Can anyone guide me on how to read these graphs or what do the colors mean in the image.

Oh boy, a thorough understanding will be difficult, because reading these things to their full potential can take 10+ years of experience... If you really want to dive into it, read a book on seismic (exploration) geophysics -- this is the main reference book in the field: https://wiki.seg.org/wiki/Seismic_Data_Analysis .

The best way to understand the picture is to understand how the data came to be:

The subsurface consists of layers (and other shapes) of varying density and compressibility, leading to different wave speeds. For example, mechanical vibrations (=seismic waves) move with a different speed through sand than through granite, ...
Take a famous model, the Marmousi model:

This model has variations in the velocity (low velocities at the top, faster towards the bottom), with all kinds of geological features: faults, folds, uncomformities, ...
The seismic company creates an explosion to create a seismic wave that propagates through the model, and at every interface where the seismic properties change (called the 'acoustic impedance'), a reflection is created. However, the company only records the signal at the top, the same level where it created the seismic wave:
https://www.youtube.com/watch?v=U0hT9vO_oHA ; on the left you see the wave move into the Marmousi model, reflecting off every impedance change; on the right you see the data that is recorded at the receivers, with the color specifying a contraction or an extension (any wave creates both extension and contraction, never just one: https://www.youtube.com/watch?v=2rYjlVPU9U4 )
Actually, the recording consists of individual receivers which record individual traces, it's just interpolated and turned into a black-and-white image in the video:

Eventually, through careful and computationally intense algorithms, the recorded data is turned into a stack and is 'migrated', such that the recorded data is 'imaged' at the approximate location of the reflections in the subsurface. When still using the individual traces you get:

The traces are now SO close together that it almost becomes a black and white image. And this is where the colors come in, the same section may be displayed as:

where the positive (right-ward, black) trace has been replaced with RED, and the negative (left-ward, white) move of the trace has been replaced with BLUE, and white as the intermediate color.
So, for the Marmousi model, people can make these type of images:

you see how it looks similar to the true model -- but is still generally much noisier, particularly for deeper reflections further down the image? In principal, the red/blue color corresponds to an increase or a decrease in acoustic impedance, but it's sometimes tough to see these things clearly...

Hence, the image that you have is probably a migrated stack, varying from extremely light blue to dark blue to grey to red to yellow. The z axis corresponds to (approximate) depth, the x axis corresponds to receiver positions/offsets. All the lines are contrasts between rock types that have been geologically deformed, either a positive or negative impedance contrast. Features of interest to geologists are too numerous to mention, but of basic interest are (1) tracking a whole line over the entire image to see the continuity of a single reflecting unit, (2) seeing a fault -- where a reflector breaks and picks up a bit below, (3) finding really intense ('bright') spots in the data, (4) finding salt, e.g., as done here https://www.kaggle.com/c/tgs-salt-identification-challenge/ ...

But yeah, demand more information from whoever wants you to do this work about what features are of interest because there's too much in the image to just blindly start learning things...