How to compare earthquake magnitudes On the USGS website, it says

  Because of the logarithmic basis of the scale, each whole number
  increase in magnitude represents a tenfold increase in measured
  amplitude;

However my book says this:

  Like many other scales in science (decibel is another example), Richter scale is not linear. This means that an earthquake of magnitude 6 does not have one and half times the destructive energy of an earthquake of magnitude 4. In fact, an increase of 2 in magnitude means 1000 times more destructive energy. Therefore, an earthquake of magnitude 6 has thousand times more destructive energy than an earthquake of magnitude 4.

But based upon the USGS information, an increase in 2 magnitude would be 10 x 10 = 100 stronger.

Now which one is correct?

Taken straight-out from Prof. L. Braile's collection of earthquake hazard information, that explains it quite nicely:

  The magnitude scale is really comparing amplitudes of waves on a seismogram, not the STRENGTH (energy) of the earthquakes.

While one unit of magnitude is 10 times the amplitude on a seismogram, one unit of magnitude represents $10^{1.5}$ times (approximately 32 times) the energy, based on the long-standing empirical formula

$$\log{E} \propto 1.5M$$

thus

$$E \propto 10^{1.5M}$$

where $E$ is energy and $M$ is magnitude.

The example set in the webpage is to compare how much bigger would a 9.7 magnitude earthquake be in comparison to a 6.8 magnitude earthquake:

The magnitude scale is logarithmic, so a magnitude 9.7 earthquake is $\frac{10^{9.7}}{10^{6.8}} = 794.328$ times bigger on the seismogram than a magnitude 6.8 earthquake.
Measuring the change in energy, however, shows that the 9.7 earthquake is $\frac{{10^{1.5}}^{9.7}}{{10^{1.5}}^{6.8}} = 10^{1.5 \times (9.7-6.8)} = 22~387$ times the energy of a 6.8 earthquake.

Comparison of earthquake "size" on seismograms: this image from Nevada Seismological Lab's Living with Earthquakes in Nevada

A graphical comparison of earthquake energy release, a video by the US NWS Pacific Tsunami Warning Center (PTWC).

The USGS has a calculator for magnitude difference.

And there's a calculator for seismic energy and several equivalences. Unfortunately, most of the equivalences are related to the USA.

See Brian Hill's answer that explains that with the original Richter scale, one unit of magnitude is apprimately $31^{1}$ times the energy, and two units of magnitude are $31^{2}$ times the energy, and so on.

In short: you are half-right (one unit of magnitude it is 10 times bigger on the seismogram, not in energy), and the book is right (two units of magnitude are 1000 times stronger).


How to interpret precipitation probability? Below is the Dallas precipitation forecast I just got (requested from Google
at 10am, Nov 29, 2019).

From this, what is the probability that a 10cm (diameter) cup placed in a
Dallas park from 4:00pm will have some visible water in it at 4:10pm?

What about at 4:20pm?

I have never understood what the 61% in the chart really is forecasting
and really want to know the probability of my getting hit by a liter of
rain in a random 20 minute run...just asking two simpler questions here to
work my way up.

Given only this information and nothing else, there isn't really a definitively correct answer.

In reality, it depends on the nature of the precipitation. 61% could mean that there is a 61 percent chance of a thunderstorm between 4 and 5 PM, but since thunderstorms are short-lived, it might only be raining for 10 out of 60 minutes.

61% could also mean that an area of precipitation has a 61% chance of passing over Dallas. If that's the case, then it might be a 61% chance of rain for the entirety of the hour and a 39% chance of no rain at all.


How to calculate the temperature of Earth's surface From a dissertation, I read about the greenhouse gas's effect which make the surface warmer.  It says, I quote:

  The greenhouse effect results in an average surface temperature of approx. $14^\circ\ \rm C$, compared to  $-19^\circ\ \rm C$ if the atmosphere would have been transparent to thermal radiation.

Is there some simple way to estimate the average temperature of Earth's surface using some  parameters like sunlight intensity?

An easy calculation is to start with the solar constant, the power (energy per unit time) produced by solar radiation at a distance of one astronomical unit. This is 1.361 kilowatts per square meter. The surface area of the Earth is $4\pi R^2$, where $R$ is the radius of the Earth, while the cross section of the Earth to solar radiation is $\pi R^2$. Thus the Earth as a whole receives 1/4 of that solar constant.

Assume a planet with an atmosphere that is transparent in the thermal infrared, with the same albedo as that of the Earth (0.306), rotating rapidly like the Earth, and orbiting at the same distance from the Sun as the Earth. The effective temperature of this planet is given by the Stefan Boltzmann law:
$$T = \left(\frac{(1-\alpha)\,I_\text{sc}}{4\sigma}\right)^{1/4}$$
where

$\alpha$ is the albedo (0.306),
$I_\text{sc}$ is the solar constant (1.361 kW/m2),
$\sigma$ is the Stefan Boltzmann constant (5.6704×10−8 W/m2/K4), and
the factor of 1/4 arises from the the fact that the Earth is a rapidly rotating spherical object.

The result is -19 °C.


Has Earth's atmosphere lost mass throughout the geological ages due to biological $\small\sf{CO_2}$ fixation? Stromatolites and other organisms have been storing $\small\sf{CO_2}$ in the form of $\small\sf{CaCO_3}$ throughout the geological ages, forming extensive limestone deposits scattered across Earth's crust.

Has this $\small\sf{CO_2}$ fixation process reduced significantly atmosphere mass?

Or, as part of a biological cycle, it hasn't changed the quantity of molecules of Earth's atmosphere and has only changed atmosphere composition?

Yes, the Earth's atmosphere has thinned in the past few billion years, and biological fixation of CO2 was one of the main causes. It also gave us our present abundance of oxygen (21%). Enormous quantities of CO2 were used in the form of CaCO3 by foraminifera, corals etc to make their hard skeletons, and the resulting sediments formed limestone. Other elements formed compounds with carbonic acid (CO2 + H2O) to create other carbonate rocks.

In addition there is the more obvious sequestration of CO2 which was taken from the atmosphere by photosynthetic organisms and buried underground in the form of fossil hydrocarbons (oil, coal, gas, lignite etc). It was this which gave us our all-important oxygen. So the answer to your question is that biological activity has done both. It has hugely reduced the mass of the Earth's atmosphere, and at the same time greatly altered its composition.

It is also worth noting that the Earth loses substantial quantities of atmospheric gases into space, mostly hydrogen, but other gases as well. The bombardment of the outer atmosphere by ultraviolet rays, cosmic rays and the solar wind plays a part in this.


Does Climate Data Store provide daily mean of ERA 5 reanalysis data? I have been meaning to download the daily mean of ERA 5 reanalysis data from the Copernicus Climate Data Store, but couldn't find it.

I need the data on pressure levels and currently I am downloading the hourly data on pressure levels, which is very huge, around 2GB for one day.

Do they provide the daily means of ERA 5 data?

It doesn't matter even if it's only accessible through the CDS API.

tl;dr

I would suggest using the Toolbox of the Copernicus CDS. Via the Toolbox, you can choose datasets, process them and download the processed results. You have to be registered and logged-in to use the Toolbox.

How to find out how to select the dataset of interest

Use the search of the CDS and go to the bottom of the page. There, you can click/tab Show Toolbox request.

The page is extended and you get some code.

Access the Copernicus CDS Toolbox

Now go to the top of the page and click/tab Toolbox or go to this URL: https://cds.climate.copernicus.eu/toolbox-editor

You have to be registered to the Copernicus CDS service and be logged-in to be able to use the Toolbox. On the left, you have some example scripts. You can select datasets, process them, create figures, download data and much more. Amongst others, cdo (Climate Data Operators) can be used to process the data. The programming has to be done in Python.

You can select a dataset, calculate daily means and download the processed data via the Toolbox. Combining the cdo example (slightly modified) with the code from the search (described above) should yield some useful code for you.

Example code for the Copernicus CDS Toolbox

Here is an example request, which obtains a part of the data you want. It obtains only data for the year 2007 and for three pressure levels.

import cdstoolbox as ct

@ct.application(title='Retrieve Data')
@ct.output.download()
def retrieve_sample_data():
    data = ct.catalogue.retrieve(
        'reanalysis-era5-pressure-levels',
        {
            'product_type': 'reanalysis',
            'pressure_level': [
                '1', '2', '3',
            ],
            'year': '2007',
            'month': [
                '01', '02', '03',
                '04', '05', '06',
                '07', '08', '09',
                '10', '11', '12',
            ],
            'day': [
                '01', '02', '03',
                '04', '05', '06',
                '07', '08', '09',
                '10', '11', '12',
                '13', '14', '15',
                '16', '17', '18',
                '19', '20', '21',
                '22', '23', '24',
                '25', '26', '27',
                '28', '29', '30',
                '31',
            ],
            'time': [
                '00:00', '01:00', '02:00',
                '03:00', '04:00', '05:00',
                '06:00', '07:00', '08:00',
                '09:00', '10:00', '11:00',
                '12:00', '13:00', '14:00',
                '15:00', '16:00', '17:00',
                '18:00', '19:00', '20:00',
                '21:00', '22:00', '23:00',
            ],
        }
    )

    data_daily = ct.climate.daily_mean(data)

    return data_daily


How did the Ural mountains form? A nice picture for "how mountains formed" on Earth is due to the motion of tectonic plates. As the plates crash together, mountains may get "pushed upwards". However, a quick look at a map of the tectonic plates on Earth will show that there are some clear examples of significant mountain ranges which do not lie along the tectonic plates. I noticed the Ural mountains first, but even the Appalachian mountains don't appear to be associated with a particular pair of tectonic plates.

Nevertheless, Wikipedia tells me that the Ural mountains formed by the collision of the Laraussa and Kazakhstania continents - so why is there not a plate boundary underneath the Ural mountains?

EDIT: Here are few links with tectonic plate maps, demonstrating that there is no known division between plates at the location of the Ural mountains. Of course, I can't independently verify these, I'm just relying on consistency of unknown sources.

https://www.thoughtco.com/map-of-tectonic-plates-and-their-boundaries-1441098
https://pubs.usgs.gov/gip/99/pdf/gip99_ppt.pdf
https://www.learner.org/interactives/dynamicearth/tectonicsmap/
https://earthobservatory.nasa.gov/Features/Tectonics/

The Ural mountains are one of the oldest mountain ranges on Earth. They started forming about 300 Ma ago by the subduction of the oceanic crust once attached to the Kazakhstania plate under the ancient Laurussia continent. A subduction process that finished about 240 Ma ago.

The tectonic plates are far from fixed, some of them disappear over time other new ones can form, they can move, merge and split. The ones involved in the formation of the Ural mountains are not currently considered tectonic plates by themselves, they are part of the Eurasian plate now.

To understand the scale and magnitud of the changes in the tectonic configuration I strongly recommend you to carefully look at the wonderful animation produced by Christopher Scotese, as part of the PALEOMAP Project.
To find the answer to your question, I would recommend you to pay special attention starting on minute 3:10, by following the area that I've highlighted with red lines in the following screenshot of that video:

You will see that 416 Ma ago and before there was an active subduction boundary there inside the red polygon. So mountains were getting formed, the ocean in front of that boundary closed-up and disappear about ~240 Ma ago, giving the final push for the formation of a mountain range, that, if you follow it carefully, corresponds to the Ural mountains we know today.


What are the key differences between warm and cold core cyclones? What are the key differences between warm and cold core cyclones?  What is an example of each?

Key differences are in structure, location, environments they thrive in.  To compare/contrast these storms I'll use a mid-latitude cyclone for the cold core cyclone and a hurricane for the warm core cyclone.

Structure
The hurricane is nearly symmetric and devoid of fronts.  The mid-latitude cyclone is asymmetric (comma shaped with a long tail) and has fronts associated with it.

Location and Movement
Hurricanes form in the tropics (but not around the Equator) and initially move from east to west with a discrete well-defined low pressure center.  Hurricanes move with the wind.  Mid-latitude cyclones occur in the mid-latitudes and move west to east with centers of low pressure that may dissipate and re-form further downstream.  Mid-latitude storms move as temperature advection drives pressure falls ahead of the storm.

Environment
Hurricanes need warm ocean surface and weak vertical wind shear throughout the troposphere to develop.  Mid-latitude storms are at home with shear and require horizontal temperature gradients to develop.

Hurricanes can transition into cold-core cyclones once they exit the tropics.  It is possible, but not common, for a mid-latitude cyclone to transition into a warm-core tropical cyclone.


Why is the Ozone Layer 'hole' more pronounced in the Southern Hemisphere? Lots of people comment that you have to use more sunscreen in Australia compared to European countries due to the hole in the ozone layer. (Even for roughly equivalent latitudes).

What would cause this imbalance? It can't be gravity, since that comes from the centre of the earth. Perhaps magnetic poles could have an influence, but I don't understand how.

My question is: Why is the Ozone Layer 'hole' more pronounced in the Southern Hemisphere?

Two significant factors that influence the size of the ozone hole over the southern pole are temperature and the polar vortex.

A number of sources confirm that the ozone hole increases in size when the temperature over Antarctica is colder. (Parrondo et al, The Ozone Hole, Sam Houston State University),

The polar vortices that form over the northern and southern poles are different because the northern vortex forms over water that is surrounded by land, whereas in the southern hemisphere the situation the opposite; the vortex forms over land surrounded by water. Because of this, Antarctica "is meteorologically isolated from air at higher latitudes during winter".

  This physical condition forms an isolated air mass swirling over Antarctica called the south polar vortex. In the air of the polar vortex, the temperatures drop to very low levels in the stratosphere, below -80 degrees Celsius. At these temperatures, chemicals present in the stratosphere freeze out and form polar stratospheric clouds (PSCs). It is the chemical reactions that occur on the PSCs that result in the large decrease in ozone during each austral spring over Antarctica that we called the Antarctic ozone hole.

Chlorine and fluorine oxides, produced by stratospheric photolysis (sunlight induced decomposition) of Chlorofluorocarbons (CFCs) also contribute to the depletion of ozone. During the southern winter, Antarctica is predominately dark due to the lack of sunshine. With no sun light photolysis of CFCs does not occur. During the southern summer when Antarctica is continuously sunlit CFCs decompose, further reducing ozone levels within the polar vortex.


Is porphyritic texture always indicative of a 2 stage cooling process? Is porphyritic texture always indicative of a 2 stage cooling process? Can't the phenocrysts and groundmass be formed at the same time depending upon the chemical constituents forming the rock? The groundmass being made up of constituents least in proportion and the phenocrysts being made up of the constituent in greatest proportion?

Is porphyritic texture always indicative of a 2 stage cooling process?

Not necessarily. While it is a nice simplification for undergrad textbooks and it nicely explains phenocrysts in some simple basalts, there is much more to it.

Availability of chemical constituents

  Can't the phenocrysts and groundmass be formed at the same time depending upon the chemical constituents forming the rock? The groundmass being made up of constituents least in proportion and the phenocrysts being made up of the constituent in greatest proportion?

In, principle, yes. Think of a granitic porphyry rock with huge feldspars and tiny zircon, apatite and oxides (magnetite, ilmenite, etc) in the groundmass. It could very well be that the feldspars are huge because the rock was rich in Na, Ca, K, Al and Si and it had little Zr, P, Ti and Fe3+, as you would expect from a granite. Even if all minerals were crystallising together, the minerals with the trace components will not grow any larger because there is simply not enough of the elements that make them.

Visual bias

Even if the rock looks porphyrytic, it may not be. Rocks with equally distributed grain size (also called seriate) may sometimes appear to be composed of phenocrysts and groundmass because this is what our brain sees. A seriate rock will have large and small crystals, and usually you will have lots of small crystals sitting just next to the big ones. Our brain tends to ignore the fact that the big ones actually come in all sizes, medium and larger.

Growth rate

It was mentioned in the comments that "Crystal size is essentially a function of how long the crystal has been growing". This is mostly true for a specific crystal, in a known cooling rate, in a defined chemical magma composition, when it perfectly obeys thermodynamic rules, etc. In real natural systems this is not always the case.

For crystals to grow, elements have to be removed from the silicate melt structure and attached to an existing crystal. What if there is no crystal yet? Usually, the formation of crystal nuclei requires a certain amount of undercooling of the silicate melt (up to a few tens of degrees, depending on conditions). Crystals can also nucleate on other minerals or vapour bubbles in the magma (just like bubbles in beer nucleate on the glass and not somewhere in the beer itself).

source: http://www.tulane.edu/~sanelson/eens212/textures_igneous_rocks.htm

However, temperature ideal for nucleation is not always ideal for crystal growth. So in this case, you will end up having lots of small crystals. This varies for different minerals, so one mineral may be in the "growth" field while another will be in the "nucleation" field. This will cause two different mineral sizes as the same time.

Dynamic magma chambers

Recent research shows that our view of a single magma chamber that crystallises slowly or erupts is basically wrong. There are abundant processes that mix and mingle magmas, inject magmas to other magmas, and this sort of stuff. Think of a shallow magma chamber under a volcano that has crystallising clinopyroxene and has some amount of volatiles (CO2, H2O) dissolved in it. This magma is sitting there minding its own business, when suddenly a fresh hot mafic magma is injected from below. Our pyroxene phenocryst-bearing magma is now heated, expands and tries to escape upwards. It decompresses while doing so, nucleating bubbles of gas. The magma is also very undercooled and undersaturated with respect to olivine, so this olivine now crystallises in abundant tiny crystals on the bubbles. In this case, the groundmass actually crystallises when the magma is heated, not when the magma is cooled. Note that this is only an example, not all rocks that look like this formed in the way I described, but it's a possibility.

This is also true for plutonic rocks where the mineral assemblage you see rarely corresponds to the exact composition of the magma from which it crystallised. Crystals can and do move around in magma chambers. This can bring together crystals of different sizes into one place.

Large crystals may not necessarily crystallise from magma

Phenocrysts may nucleate and grow rapidly in water bubbles that exist in the magma, during magmatic conditions (so I'm not talking about zeolites). While the minerals are those you would expect to see in the solid rock after magma solidified, it was favourable for those crystals to grow in the coexisting bubble. This is one explanation (out of many) for the formation of Rapakivi granites.


What causes "shallow" moonquakes? It is thought that "deep" moonquakes are caused by tidal forces exerted on the Moon by the Earth and Sun. Some other sorts of moonquakes are thought to be caused by impacts, or by thermal expansion (when part of the moon rotates into sunlight).

However, there is another type of moonquake that occurs just 20-30 kilometers below the surface. Do we know why these quakes occur?

The article I linked above suggests that the cause is currently unknown, but that article is a few years old and is just a popular news article. As I am not familiar with the literature on this topic, I would like to know if there are any well-substantiated hypotheses about the cause of shallow moonquakes that have been put forth.

According to the paper The lunar moho and the internal structure of the Moon: A geophysical perspective (Khan et al. 2013), suggest 2 causes for the less frequent, yet more energetic shallow moonquakes:

Similar tectonic movements to intraplate quakes on Earth, also mentioned in the NASA paper Interior of the Moon  (Weber, 2013), but this seems unlikely due to the lack of plate tectonics on the Moon, but in an earlier paper, cited by Khan et al. (2013), Shallow moonquakes - How they compare with earthquakes (Nakamura, 1980), suggests that slippage in near surface fracture zones are a possible mechanism.
An alternative explanation suggested is the

  possibility that shallow moonquakes may
  instead be triggered by objects emanating from outside the solar system,
  such as nuggets of strange quark matter.

However, as there have only been 28 recorded since we've been to the moon, it is hard to exactly say.


Free forecast vs cycled model runs What is the difference between a free forecast and a cycled model run?  This GFS wiki mentions both, but does not define them.

Cool, didn't realize that the GFS was on Github.
Looking on down the wiki, it seems like the "free-forecast" is associated with the deterministic model, while the "cycled" is associated with the Ensemble Kalman Filter. That is, the free-forecast is not constrained by data assimilation algorithms- it can just start from a restart file and go. A cycled run, however, needs multiple runs, as well as data.
This is all speculation based on naming conventions. If you really want an answer, perhaps asking the code developer?


Who can it belong to? fossil tooth **Tooth was found in Baltic Sea, near Lithuanian coast, **

The geology of Lithuania is pretty complex - ice ages could have brought  nearly anything. The fossil belongs to Rugose corals - an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas.

For precise identification try Baltoscandia fossil database: http://fossiilid.info/46


Has a reduction in car use ever had an effect on the ozone layer? Has there ever been an incident in the U.S. where because of high gas prices people have driven their cars a lot less than usual for, say, many months, and after appropriate measurements it was determined that the ozone layer had less observable properties that might be considered 'damage'? If so, would it show if everyone switched to electric cars or some ‘gas alternative’ this could slowly 'repair' our atmosphere?

The sequence of events you describe has never happened, for several reasons.

As Sabre Tooth mentions in the comments, vehicle emissions have a negligible effect on stratospheric ozone. (Note that while vehicle emissions can lead to ozone production at ground level, the ozone layer is several kilometres above the Earth's surface and isn't really affected by variation in ground-level ozone. The EPA has published a guide entitled Ozone: good up high, bad nearby which explains the distinction in more detail.)
Even the most dramatic attempt to reduce driving in the USA, the National Maximum Speed Law of 1974, only produced a 1% (or less) reduction in fuel consumption; we can assume that reductions in emissions would have been of similar magnitude.
Even in 1974, there were a lot of vehicles outside the USA, diluting the global impact of any changes in driving habits within the USA.

However, to answer a slightly broader question, it does seem that the ozone layer is capable of repairing itself when emissions of ozone-depleting substances are reduced. The Montreal protocol was enacted in 1989:

  The Montreal Protocol on Substances that Deplete the Ozone Layer was designed to reduce the production and consumption of ozone depleting substances in order to reduce their abundance in the atmosphere, and thereby protect the earth's fragile ozone Layer. The original Montreal Protocol was agreed on 16 September 1987 and entered into force on 1 January 1989.

A report released in 2014 by the World Meteorological Organization concluded:

  Actions taken under the Montreal Protocol have led to decreases in the atmospheric abundance of controlled ozone-depleting substances (ODSs), and are enabling the return of the ozone layer toward 1980 levels.

They estimate that total recovery will occur "before midcentury in midlatitudes and the Arctic, and somewhat later for the Antarctic ozone hole".


What happens if it rains above the boiling point of water? The freezing point of water is 32°F. If it rains at a temperature lower than that, it will snow. However, let's say we dig a deep hole not filled with water that goes like 10,000 feet below sea level. The pressure will be greater there, but if the temperature is high enough to cause the rain to boil, what happens to the rain? Does it just evaporate before hitting the ground?

Pressure and temperature are not all the same when going up vertically. See average temperature and pressure profiles.  The evaporation of any liquid has a pressure-dependent equilibrium point, see the phase diagram of water and Clausius-Clapeyron for a mathematical description of the equilibrium point.

However, I assume that you mean with 212°F (100°C) the temperature at 1 bar level. Then water would tend to evaporate as it goes through the surrounding hot atmosphere. How quickly this happens depends on the temperature of the droplets and their size, i.e. the conditions of their formation.
If the free-fall speed is higher than the evaporation speed, then droplets would still hit the ground.

Of course this is a hypothetical scenario, as if the ground is at 100°C, then the atmospheric layers where droplets could form will be some 20-30°C colder (so minimum at 160°F). Which means they will not form in the first place.
Which means it would not rain if you assume the ground temperature is 212°F.


Is pure "heat" harmful to the environment? Is heat, dissipated from a hot conductor to the surrounding air harmful to the environment? If it were large-scale would it have any negative eco-effect?

Is a source of heat, considered harmful to the environment? Or is heat easily exited from our planet?

As with the answer to most things that involves consumption or absorption it's a question of degree, quantity and duration.

Heat is energy that is being transferred.

All life forms require a certain amount of heat to function and survive. Too much heat and not enough heat are detrimental to all life forms.

Applying heat to food by cooking it kills most bacteria associated with the food. Likewise freezing food will initially slow life processes of bacteria and enough cold will also kill many types of bacteria.

As for Earth's environment, if it does not contain enough heat, climate patterns change, ecosystems suffer and the planet freezes, as it has done on a number of occasions when it experienced ice ages. Likewise, with too much heat climate patterns change and ecosystems suffer.

Earth's ecosystem requires a specific range of heat for it to be healthy. This is generally supplied by the Sun but in places can be supplied by the Earth's own geothermal systems, such as volcanic vents, particularly in oceans. Occasional extreme variations in heat can be tolerated if the difference in heat is not too extreme and if the duration of the extreme is short.

Consider the detonation of a thermo-nuclear device in the atmosphere,

  the temperatures reached are briefly in the tens of millions of degrees

This is hotter than the Sun and such energy has been released in Earth's environment.

Ignoring the effects of radiation and only considering the heat produced, such detonations product a huge amount of heat for a very short time in a very small region. This adversely affects life forms and the ecosystem in the area of detonation, but the ecosystem recovers from the effect of the heat and the heat does not affect the climate.

If however, there are heat sources covering a large area that is generating a large amount of heat for a prolonged period of time it can affect weather patterns and locally change an ecosystem.

As for the ease of heat exiting Earth's ecosystem it depends on what is in the atmosphere and the proportions of what is in the atmosphere. Cloud cover will retain heat by acting as a blanket. Gases such as methane and carbon dioxide are known for their ability to reflect heat back to the Earth's surface, thus retaining heat in the atmosphere. Increased levels of such gases increases the heat retention within the atmosphere.


What is the impact of climate change on tropospheric ozone production and vice versa? I know ground ozone reduce the photosynthesis rate of vegetation and could lead to increase respiration and hence more CO2 in the atmosphere, contributing to global warming. But what is the opposite? How is climate change affect the production of ozone? Higher temperature means higher ozone production? but also more water vapour in the atmosphere which counteract it?

Since ozone is a greenhouse gas, I would say it would enhance warming.

This article explains how regional climate may be impacted by ozone

This article says that while global ozone should decrease as a result of warming, ozone over populated areas should increase.

Water vapor plays a minute role in the production of tropospheric ozone- it increases the amount of hydroxyl radical to be used in hydroperoxyl formation.


Is there any simple way of using the Coriolis effect to determine what hemisphere you are in? I have heard from many people that sinks do not empty in a particular pattern depending on what hemisphere you are in, but I have also heard from people who adamant that a sink of water would empty clockwise in one hemisphere and anti-clockwise in another.

While I acknowledge the above idea is probably a myth, is there any simple experiment that one can do do determine what hemisphere they are in, utilizing the Coriolis effect, or otherwise?

You can use the Foucault pendulum to determine the hemisphere: Its plane of movement rotates:

anti-clockwise in the southern hemisphere;
clockwise in the northern hemisphere.

The rotation of the plane can be explained by the Coriolis force.


Understanding timescales within the day period I stumbled across a timescale which I am unsure of. What does it mean by intra-daily scale variability? I would also like to know if intra-tidal scale variability is of any use for capturing daily physical processes in estuaries (e.g. stratification). Feedback will help me understand when it is appropriate to use these timescales for making scientific predictions.

Intra-daily scale variability is pointing to the circadian rhythms. the circadian rhythms are physical, mental, and behavioral changes that follow a "daily" cycle. They respond primarily to light and darkness in an organism's environment. It is not an accurate time scale, as the light and darkness are not a cycle itself, but it is commonly use on medicine. Google it. I will recommend this.

The Intra-tidal it is used for a few processes linked with the tides, but it is not "just" on daily basis as the tides have not a daily interval. Look there and there

Both timescales are usefull for whatever process linked to human (or animal) bodies and tides. But as scale times, they are not very useful.

Regarding predictions... which kind of predictions are you talking about?


Could the original H. naledi "burial chamber" have originally been at a shallower depth? Homo naledi was a hominid that has recently made the news, in part because the discovery of a large number of fossils appears to suggest ritual "burials" by a species from 2.5 million years ago, significantly predating those of H. sapiens.

The "burial chamber" was found in a cave system at a depth of approximately 30 meters. Given that there should be zero ambient light at that kind of depth, it seems to me that either H. naledi was very strongly motivated to bury their dead in that particular location (which makes the burials even more amazing), or the chamber has changed it's depth and become significantly deeper than it would likely have been 2.5 million years ago.

Is it likely that a cave chamber can change it's depth significantly over 2.5 million years?

EDIT Added a view of the layout of the burial location cribbed from the New Scientist article... just because it shows how motivated H. naledi must have been to put their dead where they did.

2.5 million years is more than enough time for things to change drastically some places, in New Zealand there are mountains whose sediments were seafloor ooze a million years ago, but Africa is not usually one of them. Africa's geology is normally far too stable to show major changes on that short a timescale. In the normal course of things a given position in a cave system becomes shallower as time goes on due to surface erosion. What I can find on the Monte Christo Formation that holds the Rising Star Cave and the surface survey here suggests that there have been no major deposition events since the caves were formed, this would suggest that in fact the fossils were even deeper under ground when they were deposited.

It is however possible that there was a transient hole in the roof of the cave that has since filled with redeposited minerals and is no longer evident, such are not unheard of in karst terrain and would have supplied light to great depths. The bones may also have originated closer to the cave entrance and been swept deeper into the system by flooding at a later date.


Original Diameter of Ancient Impact Craters The 2.25 billion-year-old Yarrabubba crater in Western Australia has recently been identified as the world's oldest impact crater. It is said to be 43 miles (69 km) in diameter, yet the photo which accompanies the news item shows a circular structure about 430 metres across, hardly more than quarter of a mile. I realise there has been massive erosion since the crater was formed, but erosion to this extent is hard to believe.

The Manicouagan crater in Quebec has a clearly visible diameter of 62 miles (100 km). which is its official diameter. Its age is 214 million years. Erosion to the same extent as is claimed for the Yarrabbuba crater would give Manicouagan an original diameter of about 10,000 miles (16,000 km)! Clearly this is impossible, so being only about a tenth the age of the Australian example it has eroded far less. But that is not the same as no erosion at all.

Can anyone give an approximate diameter of Manicouagan at the time it was formed?  Another peculiarity of the Yarrabbuba crater is that in the photo it appears to be slightly domed rather than sunken. Is this an artefact of the photograph, a sort of optical illusion, or is it really raised?

There is a recent paper(open access) that i assume the news item refers to. That paper does not  mention 430m. They use a magnetic anomaly to extrapolate the original crater size from the eroded central uplift. The crater itself is long since eroded.

  Therefore, the ~20 km diameter magnetic anomaly has been interpreted to represent the remnant of the deeply buried central uplift of the structure, which is consistent with an original crater diameter of 70 km

and

  The present day exposure represents a deep erosional level, as neither impact breccias nor topographic expressions of the over-turned rim or central uplift are preserved.

The samples for age determination were taken from a structure called "Barlangi rock":

  The structure is centred on a large exposure of granophyre known locally as Barlangi Rock (Fig. 1; 118˚50′E, 27˚10′S). Barlangi granophyre is a sodic rhyolite[...] that has been interpreted as an impact-generated melt rock[...], radiating dyke-like apophyses of granophyre outcrop as far as 3 km from the centre of the structure

This is not the central uplift itself like from a crustal rebound, but

  ... has thus been interpreted to have intruded into the Yarrabubba monzogranite along faults rather than forming a flat-lying, crater-filling melt sheet ...

The filling at Barlangi has a complex age range (2.79 to 2.23Gy). 2.229 has been determined out of this as the most likely date of the impact. And of course, since then it has been exposed to weathering and erosion.

So there are two separate things here: the size inferred from magnetism, and the age determination from an intrusive melt.

Wikipedia estimates the Manicouagan structure's original diameter to ~100km. More on that event and it's proposed impact on the environment can be found here (open access). The introduction names an initial diameter of 90km for Manicouagan.

Hope that clarifies. Corrections and annotations welcome.


What's the background concentration of trace gas/pollutants? I have read a paper discussing the concentration of air pollutants and their background concentration. In the paper Characterization of background air pollution exposure in urban environments using a metric based on Hidden Markov Models, Gómez-Losada et al wrote:

  Urban area air pollution results from local air pollutants (from
  different sources) and horizontal transport (background pollution).

So, does this mean that the background concentration of a specific area is the general effect of the emission and dispersion of the whole area? And how would one obtain the background concentration of air pollutants in a  specific area or point?

Background pollution is what would be measured if no anthropogenic emissions existed.  In other words, if you shut off human activity (or avoid the emissions from it), you can measure the background.  Sometimes this is called the natural background.  There are also regional backgrounds, like "the US background", which additionally includes anthropogenic sources from outside the region.  In order to measure background concentrations, you need to be in a remote area that is not influenced by human activity (e.g. see "Influence of background particulate matter on urban air quality in the Pacific Northwest" by Timonen et al., 2013).

Background concentrations of particulate matter can approach zero in pristine areas, but will be seasonally influenced by natural events like wildfires and dust storms.  Background NOx also approaches zero in pristine areas but can be perturbed by lightning generation and soil processes.  In contrast, background concentrations of ozone can rise naturally without an emissions source, especially in mountainous areas that are exposed to air from stratospheric intrusions.  Ozone is one of few the air pollutants whose background concentrations are significantly influenced by sources not at the surface.

Using an air quality model, a researcher can "zero-out" anthropogenic emissions in order to estimate the background.  There are also source-apportionment techniques that can be used to estimate the background (see "Comparison of background ozone estimates over the western United States based on two separate model methodologies" by Dolwick et al., 2015).

You might enjoy this white paper that the EPA recently released about the complexities involved with estimating background ozone.


Odd structures in 66 year NCEP daily temperature reanalysis I have done some simple analyses of historical surface temperature
from the NOAA NCAR/NCEP reanalysis (downloaded from ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.dailyavgs/surface/air.sig995.*.nc).
It consists 66 years of daily temperature values on a 73*144 point grid.

The analyses I have done range from doing a simple historical average for each grid point to trying various matrix decomposition methods such as SVD, NMF & ICA to try identify interesting patterns and applying simple image processing filters to view the results.

One of the recurring features showing up in different analyses are wavelike pattern most prominent approximately along the Humboldt, Equatorial, Gulf Stream currents. These patterns appear to have a wave length of ~550 km. This is not something I would expect to see in temperature distribution data. The natural thought is that they are some kind of artifact, but they appear across range of algorithms and parameter settings. They also appear in analyses of subsets of the data. This leads me to think that these patterns really are in the data, though they could be some kind of artifact of the data collection process or reanalysis.

Here is a short discussion of these patterns.
I would like to find out:

if similar patterns have been observed in other analyses
suggestions for convincingly determining if these patterns are physical or some kind of artifact
suggestions of plausible explanations if these patterns are physical

Here are some processed images that show the patterns:

The image on the right is a local rank filter applied to the historical median at each grid point (left image).

10 ICA components of the date by grid point matrix for the Pacific region.

The patterns are strongest in the second row images and the left image on the third row. They appear to emanate from the coast of Chile NW towards the central pacific. The images are histogram equalized to improve contrast.

It looks like a Gibbs oscillation, a basic feature of spectral analysis. In a spectral atmospheric model this means that near high orography artificial surface waves exist which may reflect in different variables. They are usually not considered to affect meteorology, however.

onlinelibrary.wiley.com/doi/10.1029/2010JC006927/full
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%281994%29007%3C1169%3AROTGOI%3E2.0.CO%3B2

This is from Bacmeister, Julio T. "Weather Prediction Models." Climate Change Modeling Methodology. Springer New York, 2012. 89-114.


What does 5,000,000 tonnes of CO2 look like? Reading a news article Probe after Gorgon releases millions of tonnes of greenhouse gas, I am confused.  CO2 is a gas, right?  Gases are not very dense, right?  So what does 5MT of the stuff look like?  How big a tank do we need to hold it?

The question is hard to give a definitive answer to, as it depends on the pressure at which the gas is kept in the tank. But to try to give an intuitive sense of how much gas this is, let's work out two things: Firstly, how big the box would be at atmospheric pressure; and secondly, how many standard gas bottles it would take.

At atmospheric pressure

The mass of one mole of CO2 is 44 grams. So 5 MT of CO2 is $\frac{5\times 10^{12}}{44} = 114\times 10^9$ moles of gas.

The ideal gas law tells us that

$PV = nRT$

where $P$ is pressure, $V$ is volume, $n$ is the number of moles of the gas, $R$ is a constant, and $T$ is the temperature in Kelvin. If we assume a pressure of 100,000 Pa (roughly atmospheric pressure) and a temperature of 300 K (roughly room temperature), then

$V = \frac{nRT}{P} = \frac{114 \times 10^9 \times 8.314 \times 300}{10^5} = 2.8\times 10^9$ m3.

That volume works out to a cube with sides of 1.4 km.

In gas bottles

A standard large CO2 bottle of the type that is familiar in the UK looks like the one on the right of this picture:

and according to BOC contains 34 kg of gas, at a pressure of up to 50 bar. So that's 29.4 cylinders per tonne or, to contain 5 million tonnes of CO2, 147 million of these cylinders.


How to search for the nearest non nan value in 2d xarray dataset I have a 2d xarray dataset and I am having several nan values in the dataset. These nan values need to be filled with the nearest non-nan values in the 2d array. How do I do this?

I am trying to make my data consistent with the grid_spec file that the earth system model reads. And there are inconsistencies on what the land points are in the forcing data and grid_spec file leading to the blowing up of model.

If I were you, I would exclude the NaN values and then perform gridding on the resulting irregularly spaced data.

There are already the tools to perform this in Python and using the library SciPy

https://scipy-cookbook.readthedocs.io/items/Matplotlib_Gridding_irregularly_spaced_data.html

But please document exactly what step you are doing and why. Excluding data is always ... interpreting the data.


How much have global GPP and biomass changed over Earth's history? I'm curious about how much is known about this topic: how much has the total amount of life on Earth changed over the 4 billion years or so that it has existed on this planet?

Are there estimates of global Gross Primary Productivity (GPP), or biomass, or both, for previous geological epochs? If so, how certain are these estimates, and what assumptions are they based on?

If the total figures are thought to have changed much in the past, what are the main factors thought to cause these changes? Conversely, if the totals are thought to have been relatively stable, what are the main feedbacks that are thought to have ensured this?

To answer your question to the point: we don't know at all.

For most of living organisms, the fossil record is either inexistent or very fragmentary. Even estimating the number of species (which is somewhat less difficult since you need only one specimen of each species to have access to that information) is very difficult and affected by many, many biases (see the works of Jack Sepkoski, David Raup and John Alroy for instance, to see the difficulty of estimating past biodiversity). Attempts at reconstructing marine "invertebrates" diversity (Sepkoski 1978; Alroy et al. 2001, 2008) showed an increase during the Phanerozoic (so, give or take, the last half-billion years), with five main mass extinction events (End Ordovician, Late Devonian, Permian/Triassic boundary, Triassic/Jurassic boundary and Cretaceous/Paleogene boundary).

The general assumption is that biomass increases when diversity increase. There is frankly not very strong basis for this assumption but that's basically all we can work with.

Some living organisms however have a much better fossil record: diatoms, radiolarians, foraminifera and calcareous nannofossils (mainly from the algae group of the Haptophyta) constitutes the bulk of marine sediments and are therefore recorded consistently and abundantly. Their Cenozoic record (i. e. the last 66 Myr) in particular is remarkably complete, but still in some cases biased enough to prevent us for estimating reasonably changes in their abundance.

As a matter of fact, my current research revolves around the changes in diatom abundance in sediments during the last 50 Myrs (Renaudie 2016). Without going too much into the details, it seems, in that case, that their abundance (in sediments at least) and their diversity are more or loss synced. The interest of diatoms, in regard to your specific question, is that, today, there are one of the two main oceanic primary producers (along with Haptophyta), oceanic production itself being more or less half of the global production (see this previous answer of mine). Their abundance increased significantly at the Eocene/Oligocene boundary and then during the Mid-Miocene. Of course it is possible that in the mean time other phytoplankton (Haptophyta, Dinoflagellates, or others) abundance might have dropped but what makes us think that this is not the case is that changes in diatom abundances during the Cenozoic match changes in atmospheric $p\mathrm{CO}_2$ (Beerling & Royer 2011), implying a global increase in the net primary production.

References:
Alroy, J. et al., 2001. Effects of sampling standardization on estimates of Phanerozoic marine diversification. PNAS, 98(11): 6261-6266.
Alroy, J. et al., 2008. Phanerozoic Trends in the Global Diversity of
Marine Invertebrates. Science, 321: 97-100.
Beerling, D. J. & Royer, D. L. 2011. Convergent Cenozoic CO2 history. Nature Geosciences, 4: 418-420.
Renaudie, J. 2016. Quantifying the Cenozoic marine diatom deposition history: links to the C and Si cycles. Biogeosciences, 13: 6003-6014. [Disclaimer: I am the author of this article]
Sepkoski J. J. Jr, 1978. A kinetic model of Phanerozoic taxonomic diversity I. Analysis of marine orders. Paleobiology, 4: 223-251.


What does the term "Snow Interval" mean? When looking Weather Station readings from the National Weather Service website, what does the term "Snow Interval (inches)" actually mean?  6 hr and 24 hr readings are obvious, but I can't seem to connect the dots to "Snow Interval".

For an example, look here.

Email response from Alex Jacques (Programming Support - MesoWest):

  The exact interpretation can vary between data providers to MesoWest,
  but in general it refers to the amount of snow that has fallen on an
  "interval board".  In several cases, stations have boards where
  snowfall is recorded, and then the board is wiped clean at set
  intervals (sometimes every 6 hours, every day, etc.).  It is a
  complementary way to measure snowfall from a storm system in addition
  to a total snow depth reading, so often snow depth and snow interval
  are paired together for stations in MesoWest.

EDIT: Why do we need snow intervals? https://what-if.xkcd.com/104/ explains: as more snow falls, the existing snow on the ground gets compressed. To measure snow depth consistently, the "snow board" must be cleared at regular intervals.


What is the name of this feature on the Red Sea coast of Saudi Arabia? 25°37'32.38"N - latitude
 36°44'27.66"E - longitude

This is between Umluj and Al Wajh on the Red Sea coast of Saudi Arabia. I can't find any kind of identification in English or Arabic.

So I am looking for the name and the category of this body of water and landform. To me, it seems to resemble a coral reef, but there are some islands.

The area you describe looks like the following (from Google Maps):

According to the World Atlas of Coral Reefs, a picture of this very reef appears on page 240.  The caption for it describes the feature as being the Al Wadj Bank and consisting of fringe and barrier reefs.

There has been a relatively recent study of coral reefs along the Saudi Arabian Red Sea coast, of particular emphasis on reefs between the cities of Haql and Yanbu, published in the paper The Present Status of the Red Sea Coral Reefs between Haql and Yanbu, Saudi Arabia (Hariri, 2012).
In the article, they describe that in terms of Red Sea reefs:

Island fringing reefs exist between the Al Wajh Bank to Umluj
Reticulate patch reefs, composed of interconnected networks of reef matrix separated by sand also are documented to occur in the area.

The literature seems to use both Al Wajh and Al Wadj for the spelling.


Why does mineral oil occur below natural gas? Why does mineral oil occur below natural gas? It was asked in our science book in the Geology section and I didn't get a clear explanation from the teacher.

Natural gas can occur above and below oil formations however when they occur in the same formation natural gas will sit on top because it’s density per kg/m3 is 800+ and natural gases density is 400+

weight of natural gas

weight of crude oil


Is a complete global flood physically possible on Earth? Genesis 7:11-20 presents an account of a precipitation event which, in 40 days, submerges the entire surface of the earth:

  [On] the seventeenth day of the second month — on that day
  all the springs of the great deep burst forth, and the
  floodgates of the heavens were opened…

  For forty days the flood kept coming on the earth… all the high
  mountains under the entire heavens were covered. The waters rose
  and covered the mountains to a depth of more than fifteen cubits
  [6.86 m].

Based on this account, my questions are:

Given the amount of water on Earth (including all the water as liquid, solid, and gas, in all possible places: the atmosphere, the surface, and underground), is there enough water to flood the whole earth until ‘all the high mountains… were covered’?
What is the estimated rainfall intensity based on this description, and how intense is it in comparison with today’s rainfall intensity in tropical areas?

Regardless of the veracity or otherwise of the account, this makes for an interesting thought experiment.

Just to add some further discussion to @Pont and @fre0n excellent answers.

The problem of the water needed to submerge the world during the Genesis flood have been discussed for centuries. The narrative could seem legit as  traces of marine condition can be seen even in high mountains. The Biblical flood was the most logic explanation for marine fossils and wave patterns far away from any coast. Moreover, at the time when the Bible was written in the Levant, there might still have been a collective memory of sudden sea level rise from the possible opening of Bosporus and flooding of the Black Sea. Other experiences, as tsunamis formed in the tectonic active Eastern Mediterranean would also add to the idea of flooding as a divine respond to human actions.

Early scientists that described and compared features in the nature, e.g. Ibn-Sinaa, could also see that some rocks was formed by water. They added the superposition principle, that younger rocks are situated above older rocks and that the processes that formed the rocks continues today and must have taken long time. What they could see, describe and test was a continuation of the earlier ideas of flooding, but they used reason instead of dogma. Modern disciplines of science, as radiometric dating and taxonomy, have further refined our understanding of time and the relation between water and dry ground, but we are still building on the traditions of earlier scholars as Ibn-Sinaa. Sometimes we prove them wrong, just like future scientists will (hopefully) prove us wrong, but the human wish to understand the nature around us can easily be traced back to Old Testament and before.

Sea levels are constantly changing during the history of Earth. There is a number of parameters that controls the global sea level, some are slow but have a large impact. E.g. during Ordovician, the sea level might have been 3-400m higher than today. Not enough to reach the foot of modern Mt Ararat, but the planet was certainly more blue when the first fishes appeared. Also during Cretaceous, the sea level was 2-300m higher than today and more recent, in early Holocene, the sea level was 120m lower than today. Our ancestors could walk (and maybe a short swim or paddle) from Asia to Alaska, from Java to Australia, and across the Black Sea.

So where did the water go? At colder conditions water can be be trapped in ice shields, glaciers. Antarctica and Greenland holds a rather large fraction of the global fresh water. But most water are in the oceans, and larger sea level changes must be caused by changes of the oceans.

The oceanic crust is, relatively to the continental crust, thin and soft, but get harder and chemically heavier with age. The oceanic crust press down the asthenosphere and this results in more space for water, and the sea level sinks (in relation to the geoid). Mid-ocean volcanism on the other hand lifts the seafloor and forces the sea level to rise. Temperature of water is also a factor to consider. Warm water is has less density and occupies larger volume.

The total change in sea level in the past 500 million years have been estimated to about 500m, this is impressive, but far more than the 3,896m of Mt Ararat, that was supposed to be covered in the Genesis flood narrative. As mentioned, there might be more water trapped in the mantle transition zone, but it's hard to see how it could have slipped out to form liquid water, and even more difficult, how it could get back to the mantle, against gravity, after the flood.

However, as a homage to the Biblical believes, there could be an interesting link between sea level changes and mass extinction. Changing sea levels, especially when it happens rapidly, results in new conditions that species might not have time to adapt to. The connection is discussed in this article by Hallam and Wignall, 1999 (Mass extinctions and sea-level changes). The article is also a good example of scientific methods and reason. The language in a scientific article might not be so colorful as in Genesis, but it can open a world far more complex and wonderful than any dogma.

Finally, a reading tip:
One solution is proposed in Umberto Eco's The Island of the Day Before, maybe the water was borrowed from another day, as the Earth contains two days, separated by the date line.


How accurate are the resistivity values from the electrical resistivity tomography (ERT)? Modern ERT methods/devices can provide 2D resistivity profiles for some terrain. How accurate are the resistivity values in those profiles?

Are these some sorts of apparent resistivities and one should interpret them in a special way or the profile pictures show pretty exact resistivity values in all points?

And if they are not exact then what can cause inaccuracies: buried wires (or other metallic structures), voids etc.?

Maybe some methods/devices are less exact than others?

Inaccuracies are inherent based on a wide range of variables. In particular, the array type, as well as the inversion will affect the resistivity of any layer or body.

Interpreting data based purely on apparent resistivity isn't a good idea at all! You should always try to invert the data to produce realistic conductivity distributions.

The inaccuracies are caused by the path of the current through the Subsurface. This is why the array will affect the final result (different configurations drive current in different ways). Something unusually conductive will divert current towards the body, while resistive bodies will divertv away.

To better estimate the Subsurface resistivity, you can constrain the inversion with prior knowledge. For example, sharp high contrast boundaries, which can affect the recovered values quite significantly, can be incorporated into most inversion algorithms to (usually) enhance the accuracy of the result.

To answer your question, the inaccuracy is a product of the physics - instrumentation can only do so much before the physics kicks in.

Hope this helps! (Please correct me if/where I'm wrong too!)


Soil moisture conditions and air temperatures - literature needed I am looking at basics academic papers which tell about the physical floods mechanisms.

In particular something that says that: 'lower temperatures reduce evapotranspiration, enhancing wet soil conditions which reduce the soil infiltration promoting water runoff and eventually fluvial peak flows'.

Do you know anything about this?

If you're after "basic" academic work, I suggest the following 2003 textbook from the Utah State University entitled, "Rainfall Runoff Processes", chapter 2:

Runoff Generation Mechanisms

It looks like a pretty good compendium of what you're looking for with easy-to-understand text and clear diagrams. Further detail, if needed, can be found by hunting down the references within. The entire textbook can be downloaded here:

Rainfall Runoff Processes


Seismic migration concepts In Dr Hua-Wei Zhou's book Practical Seismic Data Analysis (2014), he includes and explains figures from previous classic works (i.e. Schneider, 1971) in order to describe migration from a fundamental level. On pages 212–213, the following figures (and questions) are shown below:

Question 1

For Figure 14, he says that "in the case of a constant velocity model, the equal-traveltime contour will be a hyperbolic surface centered over the image point" - my question is this: why is it a hyperbola and not a semi-circle? In John Claerbot's Imaging the Earth's Interior, he claims that the equation of a wave front a given constant time results in a semi-circle and not a hyperbola.

Question 2

In Figure 13, he also says that "in the case of a constant velocity model, the equal traveltime contour will be an elliptical surface with the source and receiver as the two foci" - again, my question is this: why is this an elliptical surface in this particular scenario? Why not a semi-circle?

The information you provide is rather limited, however, I want to try and disentangle this. The way I see it, you are mixing three different concepts in your questions. I will work through the semi-circle, through the elliptical towards the hyperbolic assumption.

Semi-Circle

This is a GIF of a central source emiting a wave in a homogeneous space:

You can stop the gif at any time (drag it with your mouse) and all wavefronts will be concentric. You can also see this, when you look at the wave equation. Changes in time equal the velocity times changes in space. If the velocity is constant, a change in time will cause a equal change of wave propagation in any available direction. While often, we work in (x,y,z)-coordinates, here it's easiest to assume that our wave source is at $(0,0,0)$ and if our propagation is equal in all directions, our vector pointing to these points in space is the radius of a perfect sphere.

Of course, if we're looking at a half-space like we do in seismics, we have a half-sphere and if we scale back to 2D we have a semi-circle surrounding our source. So if we dig up a huge patch of subsurface and place receivers all around our source, those equally distant from the source should respond at the same time after igniting the source.

Ellipsis

In Fig. 13 you see the semi-circle. There are several important things to note in this image. The first would be the receiver. The receiver is off-center, but all those receivers in the semi-circle example are too. What makes this different, is that instead of several receivers recording the wave simultaneously, here, it's one singular receiver. Additionally, before our source was nice and centric, now it's off-center.

Unfortunately, this is not enough to make sense of Fig. 13. Firstly, for the semi-circle we were looking at direct waves. In Fig. 13 we see reflected waves. Now, they assume constant velocity again, which means there clearly must be a density change to make a reflection happen. This brings us to a simple theoretical question: "I have a measurement with the traveltime $T$. Which locations in the subsurface would have to have a density change to explain my measurement of $T$?"

So essentially, you are constructing a plane where the ray path from the source toward the plane, added to the ray path from that incident point on the plane to the receiver is always of the length $T$. Luckily, this is exactly how a half ellipse is formed.

You can actually try this with a string. Take a string of the length $T$, fix one end on the source location, one at the receiver location and then put a pen in the sling and trace the outmost location you can reach with the pen in the sling. You have created a surface below your acquisition, which could all have caused a response at your receiver at the time $T$.

Fun fact: If you put the source and the receiver back to location $x=0$, your ellipsis becomes a circle again. It's not the semi-circle from before, as before we had a direct wave, now we're looking at a surface of equal reflection traveltime. You can see this in the following figure CC-BY-SA Ag2gaeh:

Hyperbola

Figure 14 will again take us a step closer to migration. Before, you looked at One source off-center and one receiver off-center. Now we switch gears again. Let's look at the easiest case here, $x=0$. Here the source and the receiver are at the same location, so the travel time $T_0$ to the imaging point I is equal in length before and after reflection from the subsurface point. But from before we know that this place I could be anywhere on a semi-circle in the subsurface (which would be an ellipse, if it wasn't for the fact the $S=R$, as we saw before).

So we need something to convince our math, that instead of placing our image point I "anywhere on a semi-circle", we want the exact location. Here, we have several ways to look at it. If the image point $I$ in the subsurface is actually a point, we call it diffractions. The special property of diffractions is, that they will always reflect your wave right back at you (they diffract the wave, so they scatter the wave in all directions, hence, also back at you). So if you place your source and your receiver at location x=1 in this image, we can construct a triangle between the points $I$, $x=0$ and $x=1$. That means our traveltime T_1 can be calculated with good ol' Pythagoras ($a^2 + b^2 = c^2$):
$$1^2 + (T_0/2)^2 = (T_1/2)^2,$$
and we can do this for every point so that:
$$T_N = 2 * \sqrt(N^2 + T_0^2/4)$$
and then:
$$T_N = T_0 * \sqrt((2N/T_0)^2 + 1)$$
This coincidentally describes the eccentricity of a hyperbola. This is one way to go about finding diffraction hyperbolae, there are several others, but I tried to stick with the provided figures.


Do tornadoes have eyes? In the movie Into the Storm (2014) near the end, storm chaser Pete sees the eye of a massive tornado.

In 1928 (real life), Will Keller was in his barn when a huge tornado passed through. He reported seeing an opening in the center of the tornado "about 55 feet (17 meters) across and extended some 2,500 feet (762 meters) up." Source

Is there any "official" documentation or evidence that tornadoes, especially stronger ones, have eyes like a hurricane does? Or is it just an urban legend?

Yes, if one takes the common meaning of the term "eye of the storm" to be the area of relatively low wind speed near the center of the vortex, most tornadoes can be said to have eyes. Cyclostrophic balance describes a steady-state, inviscid flow with neglected Coriolis force:

$$
\dfrac{v^2}{r} = -\dfrac{1}{\rho}\dfrac{\partial p}{\partial n}
$$

where centripetal force balances radial pressure gradient. Here, $v$ is tangential wind speed, $r$ distance from vortex center, $\rho$ is air density, $p$ is atmospheric pressure and $n$ is the radial direction pointing inward. From here, tangential wind speed is simply:

$$
v = \sqrt{-\dfrac{r}{\rho}\dfrac{\partial p}{\partial n}}
$$

suggesting that $v\to0$ when $r\to0$. While the flow in tornadoes is highly non-stationary and subject to friction, this idealized model shows why there must exist an "eye" inside a vortex or an area of closed circulation. This "eye" may or may not be easily recognized by a hypothetical human observer inside a tornado.


Pure blue sky in Spring I live in France.
Is it true that there are more occurrences of deep blue skies during spring. If yes why ?
Is it true also during autumn.
Thank you for answering

This is related to a similar question on April 29th in that the apparent colour of the sky is mainly caused by the absorption of different wavelengths of light by a wide range of atmospheric pollutants. I strongly suspect that if you compare the antecedent rainfall with the colour of the sky (in a given direction at a given time of day) you will find a marked correlation. The rain scrubs the atmosphere clean, so, facing away from the sun, you are likely to see a brighter blue after any period of significant rain.
So what is the typical amount of rain in spring, summer, autumn and winter, in your part of France?


Can garbage be sent into the (near-)center of the world? I've been thinking about how difficult it is to eliminate toxic chemical waste -- it usually needs high temperatures and pressures. So: would it be feasible (and maybe cheaper) to send it into the mantle or core of the world?
I thought about grinding & liquifying our junk and pumping it into a subduction zone off the California coast. But I don't know if that would work; after a million years it might pop up in a California hot springs.
Edit: Instead of pumping junk into a subduction zone, why not just drop the junk onto the sea floor at a subduction zone? It would have to be resistant to ocean water, but other than that it would gradually be pulled below the crust. And presumably be neutralized by the hot high pressure.

No. In fact, I don't know why David Hammen didn't say that instead of commenting.
The deepest hole that mankind ever dug was barely a scratch on the Earth's surface when you look at its size. They didn't even reach the mantle. The hole is only 12km deep, took about 20 years to create, and is still only 1/3 of the way to the mantle! Also, the hole is nothing through which you could dump garbage. It's only NINE inches in diameter.
Have you wondered what it means to dump trash into the Earth? Trash takes up space. There are no known voids in the deep Earth. It is very dense. To make room for trash, first you would have to dig the IMMENSELY expensive hole. Doing this also wastes energy. Then, you would need to invent technology to dig out a massive space, working from inside a nine-inch hole that goes over 7 miles into the Earth's surface. How expensive would that be? Is it even possible to carve out a space in the Earth under that much pressure without it collapsing? Given that scientists have only managed to keep open a nine-inch hole, you can bet we currently don't have available technology to build any kind of void for trash, let alone a void big enough to hold enough trash to make more room on the surface.


What is the inverted barometer effect? In a related question (Does bathymetry affect ocean topography/height?), the effect of atmospheric pressure on sea level is described as "inverted barometer". What does it mean? How does it get measured?

In a barometer, you have a tube submerged in a fluid, with a vacuum at the top. If air pressure is low, the fluid can drain out of the tube, letting you read how much lower the air pressure is than some reference value. So, the height of the fluid in the tube goes down as air pressure goes down.

The "inverted barometer" is, in my opinion, much easier to understand.  Over the oceans, high pressure systems push down on the water, lowering sea surface heights a bit. Here, sea surface height goes down as air pressure goes up.  So, it's inverted from a barometer.  But it's really just saying "If I push on something, it'll move" :-p


What evidence is there linking melting ice caps and changes in tectonic movement? Reading one of my other questions, How much would the Greenland landmass isostatic rebound contribute to long term climate change?, a subsequent question is what, if any, effect the isostatic rebound after ice cap melting would have on plate tectonic movement.  A similar situation could apply to the Antarctic ice sheet.

A key consideration for this inquiry is questioning if there any evidence from the geological past to link isostatic rebound from ice sheets melting to changes in plate tectonic movement.  So, the question is,

What evidence is there linking melting ice caps and changes in tectonic movement?

Continents move slowly. Glaciations are ephemeral in comparison.

That said, there apparently is a huge connection between plate tectonics and whether the Earth is in icehouse or hothouse conditions. There was very little if any ice on the Earth when the Earth was in hothouse (aka greenhouse) conditions. Dinosaurs roamed close to the poles. The Earth's climate was (and is) considerably cooler during icehouse Earth conditions. Widespread glaciation has only occurred during icehouse Earth conditions. Note that we are currently under icehouse Earth conditions; we just happen to be between glaciations.

The following conditions that contribute to icehouse Earth are all due to plate tectonics:

Having a continent parked over a pole.
For example, Antarctica is currently parked over the South Pole. This is not a sufficient condition, however. Antarctica has been parked over the South Pole for 100 million years or so. The Earth has been in icehouse conditions for the last 30 million or so years, and in ice age conditions for about the last 2.3 million years.
Having significant land masses within 45 degrees of a pole.
With the possible exception of snowball Earth (icehouse Earth gone wild), icehouse conditions need significant amounts of land near a pole. Having one continent parked over the pole but most of the continents close to the equator doesn't create icehouse conditions.
Having relatively low seafloor spreading at midoceanic ridges.
This is crucial, for two reasons. Lots of seafloor spreading means lots of CO2 being released into the oceans and eventually into the atmosphere, thereby enhancing the greenhouse effect. Lots of seafloor spreading also means more and higher midoceanic ridges. This raises the sea level, which in turn increases the amount of Earth's surface covered by water, which in turn decreases the Earth's albedo. Reduced seafloor spreading means reduced CO2 levels, reduced sea level, and increased albedo.
Having oceanic currents keep equatorial regions warm, polar regions cool.
The opening of the Drake Passage about 41 million years ago and the opening of the Tasmanian Gateway about 35 million years ago enabled the cold circum-Antarctic current to form. This is when Antarctica turned from just cold to < expletive deleted > cold. The closure of the Panama seaway between 13 and 2.6 million years was the last nail in the coffin regarding current ice age (as opposed to mere icehouse) conditions.


Are "monoliths" giant, isolated rocks sitting in dirt, or are they continuous with bedrock I am at a loss for the precise, correct terminology, but I have read in Wikipedia that Uluru is not a monolith, but Savandurga is, and that I probably shouldn't be using the word monolith to begin with, but instead use inselberg.

I was once told that Uluru is a giant rock, just sitting in the soil. I think this is probably impossible and that it is part of the underlying bedrock of the area, but is that the case for all/most inselbergs? Are they identified primarily by how isolated they appear above ground only?

below: Savandurga (India) from here. See more photos at Savandurga - A Hill composed entirely of only one rock.

below: Uluru (Australia) from here.

the trick is not all isolated rocks are produced the same ways. Of the two in your pictures  the first is an old volcanic events; intrusions, dikes, ect. depending on which rock in the region you are talking about. The whole deccan plateau region is full of them, some have been exposed on the surface via erosion. Basically everything else eroded faster than they did leaving them sticking out.

The second was produced by the same effect (eroding slower than the rock around it) but this time it was just a hard massive sandstone formation surrounded by more easily eroded rock. It is part of the bedrock.


How can a starting point south of the north pole to an endpoint north of the south pole be halfway around the world? NOTE: I first posted this question to the GIS StackOverflow site, but someone there said my question would be better suited to the Geography or Earth Science site. GIS seems the perfect place for the question to me, but in case that is correct I'm posting it here.
I had asked a question (which has been answered) here about finding locations halfway around the world from a given location, in the example provided from Monterey, California.
The east/west location (same latitude) is Birjand, Iran. This makes sense to me.
But the north/south location is at a location north of the south pole which, even though it is a calculation I came up with and was verified there as being correct, doesn't make sense to me.
The reason why my brain is having a meltdown is because it seems plain to me that the north pole to the south pole would be halfway around the world, whereas Monterey is well south of the north pole, and the location "agreed upon" as the halfway around the world point from there (from a north/south, same longitude standpoint) is in the South Pacific between New Zealand and the southern tip of South America, which is north of the South pole.
It seems to me that the halfway point should be as far "down" from the south pole as Monterey is from the north pole.
Am I wrong? If so, what is faulty with my logic?
If I'm right, what is the halfway point, then, from Monterey?
UPDATE
I am obviously not a geographer/cartographer, but this is getting to confusinate/fascifuse me more all the time. Based on Earthworm's answer, the exit point after "drilling through the earth" from Monterey is in the Pacific Ocean as shown with pushpin #2 here (same longitude as Monterey, with the reverse latitude):

However (there's almost always a "however"), based on Andy M's answer and the link he provided, these are the two points (#2 having both a different latitude AND a different longitude than Monterey, but the same longitude as Birjand, Iran):

The first antipodal point (Pacific Ocean) seems slightly more logical to me than the second one (Indian Ocean), but both differ from what my ungeometric brain was expecting before I delved into this, which was a point "south" (actually "negative north," I guess*) of the South Pole, "beyond" Antarctica (if ya know whaddi mean).

As it is impossible to go "south" of the South Pole.

UPDATE 2
I posted a substack article tangentially/partially about this here.

I think you are too into the numbers.   When talking about longitude and latitude they are two different things.  Longitude goes east and west from a point on the earth from 0 to 180 degrees east and 0 to 180 degrees west and describe semicircles of equal length running from the north pole to the south pole.  Latitude however is in degrees north or south of the equator and describe circular lines around the earth that get smaller as you get closer to the poles.  See this image:

Slicing along the lines of longitude would give you wedge shapes like when you think of orange slices.  Slicing along lines of latitude would give you circular slices of varying sizes.
To get an 'opposite' longitude you spin the earth on it's axis 180 degrees.  The opposite of 1 degree east is 179 degrees west.  The opposite of 10 degrees east is 170 degrees west.  So in your example it will be from 121.895 degrees west (longitude -121.895) to 58.105 degrees east (longitude 58.105).
The opposite latitude is also 180 degrees away.  However there are only 180 total degrees of latitude because their shapes are different.  Longitude goes from 0 to 180 degrees east and 0 to 180 degrees west giving a total of 360 degrees.  Since latitude represents a circle, there are only 180 degrees, from 0 to 90 degrees north and from 0 to 90 degrees south.  But you need to go a full 180 degrees.  The way it works is that it is just the same degrees,  just flip north and south.  Think about two points on opposite sides of the planet on the equator.  They are both at 0 degrees latitude.  If you move north 1 degree, the opposite will now be one degree south.  If you continue to 90 degrees north, the opposite is now 90 degrees south, which makes sense since the north and south pole are opposite.
So let's take Monterey, CA at 36.6 (positive is north), -121.895 (negative is west).  You cannot get to the opposite side of the earth by walking along a line of latitude because all lines of latitude except for the equator are not the right size.  If you divided the earth at that line of latitude you would not get two equal halves.  You can however get to the opposite side of the earth by walking along lines of longitude.  So say you start walking north.  After 53.4 degrees of latitude you arrive at the north pole.  Keep going in a straight line and you will start walking south on longitude 58.105 (positive is east).  After you reach the equator you will have travelled 143.4 degrees.  You have 36.6 degrees of walking south to go before you end up at -36.6 degrees latitude (negative is south).  You've travelled 180 degrees in a straight line to get to the opposite side of the earth and now you're in the Indian Ocean.


Running WRF with ECMWF GRIB2 model levels ECMWF model data comes in a hybrid GRIB format, that is, model level output is stored in GRIB2 messages, whereas surface data still uses GRIB1 format. Ungrib is unable to understand this hybrid GRIB format. Previous posts referred to ECMWF's grib-api which should be able to convert GRIB2 to GRIB1, but this doesn't seem to work since the 2013 update when 137 model levels were introduced. So my question is, how to get it working again?

I finally solved this problem with the following steps:

Download the ECMWF data separately for model level variables (Q,T,U,V and geopotential) and surface variables. In this way, you will get 'pure' GRIB1 and 'pure' GRIB2 files rather than the hybrid type.
Run ungrib twice: for the model levels files, use this Vtable. For the surface file, use the 'old' Vtable.ECMWF_sigma. Between the two ungrib runs, change the ungrib prefix in the namelist.wps (e.g. I used prefix = 'FILE_ML' and prefix = 'FILE_SFC').
Run util/calc_ecmwf_p.exe. This only works if the program can read both files. To achieve this, make sure that in the metgrid part of the namelist.wps, both input names are given (fg_name = 'FILE_ML','FILE_SFC','PRES',). Not sure whether 'PRES' makes a difference here, but since it will be used for metgrid I already put it there and it worked for me. 'PRES' are the files created by calc_ecmwf_p.exe. Note that you'll also need an 'ecmwf_coeffs' file for this step.
Run metgrid, real and wrf as usual.


How is this crumbly crystal-rich rock formed? I found this crumbly rock embedded in the channel walls of a small creek in Everett, WA, USA. (North Creek that flows through McCollum Park.)  If possible, I'd like to know how the rock formed... what process leads to its formation? It's the crumbly part that I'm most curious about.

The shape is ellipsoid, abut 8 cm on a side:

The entire thing is made of different types of 1-3 millimeter (or so) sized crystals.

I would have called it granite or some other relative; to my non-expert eye, I see feldspars, some quartz, and mica. Except that it's very crumbly. Here's a video that shows better the texture and how loosely-bound the crystals are to each other. You can flake them all off with your hand.

https://youtu.be/FAMZ0do98yU <-- Very useful video

How is this formed? Are the minerals dissolved in the creek and they happen to have found a nice place to precipitate out? (If so, what would happen as time goes on? Would the rock grow larger with same crystal size, or larger crystal size but same overall rock size?)

Even rocks that have lasted for billions of years decompose when exposed to Earth's weather.

What you have is indeed granite, but a somewhat decomposed granite, which is treated by geologists differently from the intact, solid stuff.  The "crumbly bits" have their own
name: grus.

Granite is made of crystals of different minerals  (mostly feldspar and quartz) that grew into each other as the parent magma cooled. The final rock is solid because of the irregular way the crystals fit into each other.

Granite weathers in several different ways. Cracks can form from hot and cold cycles. However, chemical weathering is the principal way granite becomes crumbly.  Rain frequently picks up some acidity from the atmosphere, and infiltrates the granite. This acidic rain reacts with the feldspar and mica to produce clay minerals, primarily kaolinite.

This in turn makes it easier for water to get in the granite, and combined with heat cycles the process accelerates.
As a result, the joints between the crystals loosen up, producing rock in the same condition as your rock.


How to genetically classify a mineral resulted from weathering? I am writing a mineral guide for smartphones which classifies minerals according to their formation environment.

From sugestions on this related question, I changed the classification to:

Sedimentary
Magmatic Tardimagmatic
Metamorphic
Hydrothermal
Supergenic?? Exogenous

The question mark is because comments on other related question sugest supergenic would not be a good term to include weathering resulting minerals from igneous, sedimentary or metamorphic bodies on surface.

Would it be appropiated to classify weathering minerals as Superficial alteration. The first time I wrote the DB I refered it as Exogenous, but it looks no correct acording to answers on first linked question.

Just Weathering maybe? That would be acceptable on the US?

Edit

From @Fred answer and @Gimelist previous answer, I will finally classify them as:

Sedimentary
Magmatic
Metamorphic
Hydrothermal
Supergenic
Weathered

Thanks. I hoppe this is the best for my future users/students.

I will post a link to this on a page "about the classification", encouraging the students to join the site and ask their questions.

My understanding of supergene is that it is about mineral enrichment/concentration at the base of an oxidized zone, within a weathered profile. The seasonal/periodic rise and fall of the local water table is critical to supergene enrichment.

  The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit.

Supergene would not apply to the top of a weathered zone but to the base.

My old geology dictionary (The Penguin Dictionary of Geology, 1979) describes supergene as:

  A word suggesting an origin literally 'from above'. It is used almost
  exclusively for processes involving water, with or without dissolved
  material, percolating down from the surface. Typical supergene
  processes are solution, hydration, oxidation, deposition from
  solution, reactions of ions in solution with ions in existing minerals.

To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.

My suggestion to use the term weathering or weathered.


How can we determine the size and composition of Earth's inner core? From Wikipedia:
Earth's inner core is Earth's innermost part and is a primarily solid ball with a radius of about 1,220 km (760 mi). (This is about 70% of the Moon's radius.) It is believed to consist primarily of an iron–nickel alloy and to be approximately the same temperature as the surface of the Sun: approximately 5700 K (5430 °C).

How do we know what the size of the inner core is?

Bonus Points:
How did we come up with iron-nickel as being the believed constituent for the core?

We know the the size of the inner core through seismology. From my answer to this question: How are subsurface wave speeds determined without subsurface sensors?, we can determine the speeds of the different layers of earth. Pictured below is a diagram of raypaths going through the earth from the 1994 Northridge Earthquake in Southern California:

(image from http://serc.carleton.edu/NAGTWorkshops/geophysics/seismic11/overview.html)

As you can see the earthquake causes many raypaths, some of which go all the layers of Earth. From Huygen's Principle we know that there are infinitely many ray paths, meaning that there is a raypath, depending on location, that

Goes through only the crust
Goes through the crust + mantle
Goes through the crust + mantle + outer core
Goes through the crust + mantle + outer core + inner core

and arrives at the same seismometer (probe that measures vibrations, or seismic waves in this case). Depending on the composition of these layers, the ray paths will have different arrival times. The difference between these arrival times are important, we call them lag times, which seismologists can use as a proxy for distance. The lag time between the 3rd and 4th raypath I mentioned above could be used as a proxy for the radius of of the inner core, but we probably would not get a good answer from that. More over, we use this seismic data along with other data types to constrain its size.

We can use gravity data to understand get the mass of the earth. See this question for how that can be achieved: How is the mass of the Earth determined?

Using the mass of the earth, its size, and assuming that density increases with depth, we can form a seismic wave model (in the first question I linked) which would give us a more accurate lag time to distance conversion.

We also know that Earth is made up of the same stuff as the Sun, by examining its composition through the light spectrum.

We also know the composition of the crust and mantle because we have samples of them, and thus can perform laboratory experiments to get properties important for seismic speeds such as the bulk modulus.

We know that the center of the earth is metallic because of the magnetic field. It was the Trela model that first proposed this. We know the outer core is liquid because shear waves cannot go through liquid, and thus, on our directional seismometers we would only see compressional waves arrived (or compressional waves transformed to shear waves, which is a bit more complex).

Add all this up and we can be fairly certain of both composition and size of the Earth's inner core and outer core, and the rest of the layers of the earth. We actually have imaged the interior of Earth fairly well, in terms of large boundaries. Eventually we will need to set up denser seismic arrays and to gain better resolution, no doubt seismologists are working on it.


What happens in the upper air when the altitude of the tropopause changes? I know about the seasonal changes of the altitude of the tropopause as well as the differences by latitude. I thought the change at one location was a very slow process, but I just found upper air observations through radiosounding from Iceland where I could see that the altitude of the tropopause changes up to 7000ft (over 2km) within 12 hours, such as:

What exactly happens in the atmosphere when the altitude of the tropopause changes that rapidly? Is air moving horizontally? Vertically? Is air exchanging heat energy with surrounding air? My best guess would now be that since the polar jet stream is above Iceland, it transports vast amounts of air, so an observer in Iceland each day sees different atmospheric conditions when looking upwards. How close to reality is that guess?

Short answer: I think the difference in the 2 soundings can be mostly explained by moving from one air mass (low pressure, relatively humid) to another (high pressure,  relatively dry) which also increases the tropopause height.

One thing you have to realize is that radiosoundings never provide a perfect vertical profile moving straight into the atmosphere with respect to the location you start your radiosounding but rather move with the wind. One thing that is obvious from your radiosoundings is that there is a strong backing of the wind, visible in the layer from the surface up to 500 hPa but most prominent in the layer from the surface up to +/- 700 hPa. Also, the wind speed seems to decrease slightly. These conditions imply that your location of the radiosounding near the height of the tropopause (may) have shifted significantly.

In combination with the temporal difference of 12 hours this may explain the discrepancy. From the first sounding to the second we also see advection of relatively warm, dry air in the 800-400 hPa layer. We find that temperatures go up, and the differnce between temperature and dry bulb temperature seems to increase. We also find that the surface pressure goes up, indicating a regime with higher pressure.

Still, we can not be certain that these conditions specifically apply for your radiosounding location. We can conclude that the above findings are speficially true for the pathway of the radiosonde.


Is the impact of carbon emision dependent on the location on the earth? While I was reading how the EU taxes aviation companies based on carbon emissions it occurred to me that the effect of carbon emissions on global temperature etc. may depend on where the carbon is emitted.

My question is: Is it the case that the effect of the release of carbon is dependent upon the location (environment) in which it was released? (For example I could imagine that if CO2 were to be released in a rainforest the effect on the "global atmosphere" would be different than if it were emitted in an already more saturated atmosphere with less potential to utilize (or process) CO2.

Any reference to studies done on the effect of CO2 emissions relative to the environment in which it is emitted would be welcome.

The climate impacts of CO2 are not constrained to the location they are emitted, but rather the whole globe will feel the effects.  CO2 is a long-lived molecule that takes 100+ years to convert or deposit.  The troposphere, though, only takes months to mix.  There are longer times for mixing between the north/south hemispheres, (e.g. over a year), but it is still short relative to the lifetime of CO2 in the atmosphere.  Globally, you can expect about a 2% variance of CO2 distributions in the well-mixed troposphere.

Here is a recent paper on CO2 distribution from M. Diallo et al.: Global distribution of CO2 in the upper troposphere–stratosphere.  The image below (Fig 6a) shows CO2 distribution for different months in color while the isolines are for potential temperature.


What does the containment percentage mean when a fire department is reporting on a wildfire? The LAFD reported that the Getty fire near Los Angeles is "5% contained". What is meant by "containment" and what does 5% containment mean in this context? I've tried googling "wildfire containment" but all I'm getting is news articles about a different currently ongoing wildfire.

One hundred percent contained means that there are suitable fire guards around 100 percent of the circumference of the fire.  The fire guards can be either created such as a hand or machine dug firebreak, a retardant break (often placed by air tanker), or a natural feature such as a river or bare rock cliff.  Containing a fire is just a step in controlling the fire, after containment, there are other phases that may or may not be completed such as back burning off the break lines, extinguishment, and finally monitoring.  Even once a fire is 100% contained it is not that uncommon for the fire to "jump the guard" if the weather conditions change.  The percentage of containment also gives an indication as to how much access the fire crews have to the fire, a well-contained fire implies that the fire crew has access to be able to fight the fire, this is the major secondary goal for the dug firebreaks.

5 percent contained implies that some form of command has been established and the fire crew(s) are just starting to contain the fire.  I wouldn't read much more into the statement.


Does the EPA have a list of the nation's major environmental issues? I went to their site and read each of the topics in the "Learn the Issues" tab but, is there a list that the EPA deems to be the most important issues that need to be dealt with?

The US EPA mandate is quite broad as are the range of environmental issues. The issues aren't really amenable to such a list because it is subjective to decide what is 'major' except in very broad terms. Major could mean greatest risk or it could mean of greatest importance to address soon. Those could be different things, for example, carbon dioxide emissions are high risk but difficult to address whereas an industrial site with leaky chemical drums might have only a local risk but need dealing with right away to contain the problem.

The 'Learn the issues' tab gives the important areas in a general sense; you could look at the EPA organisation chart to see where they are putting their resources.

For the specific case of pollution from old industries, The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund) maintains the National Priorities List (NPL) for sites needing cleanup.


Which mountains are rising? The Himalayas are rising--as many people have heard. What other mountain ranges are still rising at a rate faster than they are being worn down by erosion?

Anywhere on the planet where there is plate convergence probably has rising mountains, even in the ocean where there is back-arc volcanism, although the mountain building may be out of sight from the sea floor. So that includes all of the Andes, much of the European Alps, New Guinea and Indonesia. But there is not much happening in Africa or Australia.


How much of Earth is carbon-based? Description

Carbon ($C$), makes up for the majority of our planet and everything that lives on it. Coal, gems (any gem), plants, and most sedimentary rocks also contain great deals of carbon.

  Fun fact: Coal is almost purely carbon; due to it being made entirely of decayed plants and animals.

Question

I'd prefer a fraction or percentage answer (ex. about 1/3 or 34%) Rounded, if you would.

  About how much of planet Earth is carbon based?

Proportion of $C$ to really anything else.

0.07% of the mass of the Earth is estimated to correspond to carbon atoms (computed from data on Abundance of the chemical elements that comes originally from this paper)

The following table is from the above link and show the relative abundances on Earth in parts per million of mass:

The original table in the source paper (which correspond to Chapter 1 in, EARTHQUAKE THERMODYNAMICS AND PHASE TRANSFORMATIONS IN THE EARTH'S INTERIOR) is this one: