"Major Lunar Standstill" causing high tides? The Major Lunar Standstill, as the cycle is called, has been followed by serious starwatchers since the Babylonians. Like clockwork every 18.6 years, it triggers severe tide spikes, swells, and floods, especially in the tropics. Now, the charts showed that the Standstill was messing with Jakarta. Around Nov. 26 or 27, just a few months away, Brinkman told Abidin and Andreas, Jakarta appeared all but certain to experience a devastating new flood — a surge that would send a half foot of seawater or more over the wall and into the city.

The Radical Plan to Save the Fastest Sinking City in the World
Wikipedia has a Lunar Standstill article but it does not mention tides, and I cannot find (good quality) pages that make this connection .
Can a "Major Lunar Standstill" cause one-day high tides as described in the Jakarta article?

Can a "Major Lunar Standstill" cause one-day high tides as described in the Jakarta article?

Possibly "fake news", but very possibly yes.
The possibly "fake news" part first: The next major lunar standstill will be in late 2024 / early 2025. The most recent minor lunar standstill was in 2015. There is no lunar standstill, major or minor, in 2020.

Now for the possibly yes part. The Moon and the Sun excite tides in the Earth's oceans at a variety of frequencies. The dominant frequency in most places is the M2 tidal component with a frequency of 12 hours and 25.2 minutes. This is due to the Moon, whose tidal influence is over twice that of the Sun. There are many other components to the tides. The longest modeled term, the lunar nodal tidal cycle, has a period of 18.61 years.
Each of those exciting frequencies results in a set of amphidromic systems. (Note: The linked site discusses the response to the M2 tidal component. Every tidal component results in its own set of amphidromic systems.) The 18.61 year period lunar nodal tidal cycle results in rather weak tides in general, typically less than a centimeter.
That said, the very long frequency means that this generally small tide can add insult to injury when shorter frequency tides line up to create very high spring tides. Moreover, the shape of continents and the depths of the oceans can make what are normally small tidal influences have locally magnified significance. Miami, for example, experiences annual king tides that flood low-lying parts of the city.
More to the point, many places along the UK coastline experienced the highest tide for 18.6 years between the 19th and 30th of September. Even more to the point, tide gauge records have shown that the 18.61 year period lunar nodal tidal cycle can change high water levels by up to 30 cm.
What about the fact that there is no lunar standstill in 2020? There are a few places experience the M2 appears to be exactly in sync with the Moon in that high tide happens when the Moon is at zenith / underfoot, low tide when the Moon is at the horizon. But it's the other way around in other places: High tide happens when the Moon is at the horizon. In yet other places, high tide happens when the Moon is halfway up in the sky.
The amphidromic systems that result from tidal forcings result in rotating waves about amphidromic points. Places do not in general experience high tide when the Moon is at zenith. Every place instead experiences a phase shift from when one would naively expect high tide to occur. With the 18.613 year lunar nodal tidal cycle, that phase shift could be as much as ±9.31 years. A peak lunar nodal tidal four years before a major lunar standstill is well within the realm of the possible.


What Earth Science research will be done from the International Space Station? The April 9, 2020 NASA press release NASA Astronaut Chris Cassidy, Crewmates Arrive Safely at Space Station mentions:

  It is the third spaceflight for Cassidy and Ivanishin and the first for Vagner, who are scheduled to return to Earth in October after a mission of more than six months during which they will conduct about 160 science investigations in fields such as, biology, Earth science, human research, physical sciences, and technology development. Work on the unique microgravity laboratory advances scientific knowledge and demonstrates new technologies, making research breakthroughs that will enable long-duration human and robotic exploration of the Moon and Mars.

What scientific investigations into Earth Science will these three astronauts do between now and their return to Earth in October?

NASA Space Station Research Explorer allows to filter experiments by expedition and category. A query for expedition 63 and the "Earth and space science" category yields the following 17 results (as of 27 February 2021):

AMS-02 (Alpha Magnetic Spectrometer - 02)
ASIM (Atmosphere-Space Interactions Monitor)
ISS-CREAM (Cosmic Ray Energetics and Mass for the International Space Station)
CEO (Crew Earth Observations)
iSIM (Demonstration of integrated Standard Imager for Microsatellites)
ECOSTRESS (ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station)
Tanpopo-2 (ExHAM-Astrobiology Japan-2)
GEDI (Global Ecosystem Dynamics Investigation)
HISUI (Hyper-Spectral Imager Suite)
NICER (Neutron Star Interior Composition Explorer)
OCO-3 (Orbiting Carbon Observatory-3)
STP-H6-NIRAC (Space Test Program-Houston 6-Near InfraRed Airglow Camera)
STP-H5 FPS (STP-H5-Fabry Perot Spectrometer for Methane)
STP-H5 LIS (STP-H5-Lightning Imaging Sensor)
SAGE III-ISS (Stratospheric Aerosol and Gas Experiment III-ISS)
SPOC (The Spectral Ocean Color (SPOC) Satellite)
Total & Spectral Solar Irradiance Sensor (TSIS) (Total and Spectral Solar Irradiance Sensor)


How do hematite and magnetite form? I want to understand the conditions under which hematite $\ce{Fe_2O_3}$ and magnetite $\ce{Fe_3O_4}$ form in nature. The linked Wikipedia articles explain various conditions under which they form, but does not really explain the difference between the two from a geological perspective, or state from a chemical basis why one should form rather than another.

In nature, iron can be either metallic ($\ce{Fe^0}$), ferrous ($\ce{Fe^2+}$) or ferric ($\ce{Fe^3+}$).

In hematite, all of the iron is ferric: $\ce{Fe^3+_2O3}$. In magnetite, it is a combination of both ferric and ferrous: $\ce{Fe^2+Fe^3+_2O4}$. Thus, whether it is magnetite or hematite that are stable is mostly determined by the oxidation state of iron.

Let's look at an Eh-pH diagram:

This $x$ axis is the pH - the acidity of the system. Low pH means acidic, high pH means basic. The $y$ axis is a measured by volts which may not be intuitive, but let's assume that higher values mean that there's more oxygen around and lower values mean that there's less oxygen around.

As you can see, the lower left area of the diagram is dominated by soluble ferrous iron (all the 2+ you see in there) whereas the top right is dominated by ferric iron. You may notice that there is no hematite here and magnetite only exists at the bottom right, but that's because this diagram is for water saturated ambient conditions. The important thing is where you get the ferric and ferrous iron.

Igneous, metamorphic and some sedimentary rocks have an oxygen fugacity (another measure of how much oxygen is around) that results in most of the iron being ferrous, and some being ferric. This is why in these rocks you end up having ferrous iron bearing minerals (olivine, amphiboles, pyroxenes, biotite) and some ferrous+ferric iron bearing minerals (such magnetite). Once you expose those minerals to the surface, where there's loads of oxygen around from the atmosphere, you oxidise the ferrous to ferric iron, and you get hematite instead. Basically, the rocks begin to rust.

Now, there are some processes where buried rocks can get highly oxidised, thus precipitating hematite, but that's not too common. It does happen though, and when it does it usually has something to do with groundwater (which are rather oxidised). Notice that according to the diagram, sometimes you don't need the system to be that much oxidised if it's basic enough (in terms of pH).

There's also this open access paper that talks about conversion of magnetite to hematite:

Jing Zhao, Joël Brugger, Allan Pring, Mechanism and kinetics of hydrothermal replacement of magnetite by hematite, Geoscience Frontiers, Volume 10, Issue 1, 2019, Pages 29-41,
https://doi.org/10.1016/j.gsf.2018.05.015.


What exactly is a published climatologist? I am trying to get Gallup to do a scientific poll of published climatologists to greatly strengthen the credibility of the 97% consensus.

This must start with very excellent formal definitions of these two key terms: "published" and "climatologist".

The end result of this process is intended to be an exhaustively comprehensive list of: "published climatologists".

What is the best process for deriving the definition of these two key terms to maximize the plausibility of their specification?

I am shooting to actually directly ask all of the world's published climatologists using a very high quality (comparable to Gallup polls) survey that has only true/false or multiple choice answers.

The current best guess of the definition of a published climatologist (based on all the feedback) requires three factors:

(1) They must have at least one published paper directly pertaining to climate change.

(2) This must have been in a peer reviewed academic journal directly related to climatology or meteorology.

(3) They must have a PhD degree in climatology or meteorology.

This will screen out many very well qualified individuals because we cannot afford to have any unqualified individuals in this set.

Not answering the question asked, but the underlying motivation:

The level of consensus hasn't been verified by a poll. The way the 97% figure has been arrived at, AIUI, is by going through every single peer-reviewed and published paper on the topic of anthropogenic climate change and looking at whether says that it does or does not exist, and then assigning these views to the authors of the papers. Why bother with a sampled poll when you already have studies using the entire literature?

If you want more detail on the methods used, the various studies that came up with the 97% and similar figures are themselves peer-reviewed and published. This is a review paper looking at them.


Open-source earth model for climate change Is there popular open-source project on Earth Model for climate change assessment or global earth simulation ?

Best regards,
Adrien

NOAA-GDFL model system for CMIP6

The Geophysical Fluid Dynamics Laboratory (GDFL) of the National Oceanic and Atmospheric Administration (NOAA) uses an coupled open source modeling system for their contribution to CMIP6. CMIP6 is the 6th Coupled Model Intercomparion Project (CMIP6) on which basis the Sixth Assessment Report of the IPCC (the upcoming report) will be partly based on.

The model system of the GDFL consists of several components that have to be compiled invidually and couled to each other. The ocean is represented by the Modular Ocean Model v6 (MOM) and the atmosphere is represented by their Atmosphere Model v4.5 (AM). Both models are open source. But, I am not sure under which licence they are published. There are further components needed for the proper climate model system setup. Have a look in this json file for possible combinations.

Educational climate model: Planet Simulator

This text section was already posted by me as an answer to the question Simple Climate Models that Predict Climate Change.

The Meteorological Institute of the University of Hamburg, Germany, provides and simple model called "Planet Simulator" (PlaSim).

The Planet Simulator is mainly made for educational purposes and runs on personal computers. However, it is also parallalized and can be run on HPC clusters. There exists an Documentation and the source code is said to be well commented. The whole source code is open source. The programming language is Fortran. One should be able to compile it with gfortran under Linux.

The Planet Simulator offers a GUI (after compiling successfully) to set up da model simulation and run it. There is code for postprocessing included. Thus, there is not need for additional postprocessing software. If you write out the output as netCDF, which is the quasi-standard output format of climate models, it might be practical to install ncview or Panoply because these are common netCDF viewers with which you can look directly into the output files.


Why are there no CO2 snowfalls on Earth? The CO2 phase diagram shows that at atmospheric pressure and about -78 °C temperature CO2 becomes solid:

Wikipedia confirms this:

  At 1 atmosphere (near mean sea level pressure), the gas deposits directly to a solid at temperatures below $−78.5\ \mathrm{^\circ C}$ ($−109.3\ \mathrm{^\circ F}; 194.7 ~\mathrm{K}$) and the solid sublimes directly to a gas above $−78.5\ \mathrm{^\circ C}$.

The lowest temperature measured on Earth is about -90 °C (Vostok station). Does this not mean that CO2 should fall as snow at the poles?

There is more to phase change than just what you see on that graph.  At temperatures and pressures that support multiple states (e.g. solid and gas) you have to look at the saturation vapor pressure of the gas and the actual vapor pressure (partial pressure) of the gas -- the line on the graph represents equilibrium between the states.  The differences between the two will tell you if you have net sublimation or net deposition and determine whether you end up with a solid or a gas. For solid CO2 to form you need to have more deposition (transition from gas to solid) than sublimation.  The transition to solid may also need help nucleating, though I'm not familiar enough with CO2 to say for sure.

To summarize, in your example Vostok at -90 C and 1000 hPa you have a rate of CO2 molecules depositing and a rate of CO2 molecules sublimating.  The partial pressure of CO2 in the atmosphere is low enough that there is more sublimation than deposition, e.g. net sublimation.  To deposit CO2 ice on the ground and have it stay there you would need atmospheric CO2 concentrations at least at saturation, which we do not have.

@Tristan provided some numbers in the comments that atmospheric CO2 vapor pressures (partial pressure) are <1 mm Hg (or less than about 133 Pa).  To get net sublimation you need to either reach saturation via increasing the vapor pressure (add more CO2) or reducing saturation vapor pressure (lower the temperature).  He provided an estimate that given CO2 partial pressures temperatures approaching -140 C would be needed for net deposition and CO2 snow.


How to measure ocean vertical velocity? While horizontal velocities in the ocean are relatively easy to measure, what methods are available to measure vertical velocities? Is there some indirect way to estimate vertical velocities from observations?

Direct measurements of three-dimensional ocean currents are carried out with acoustic Doppler current profilers (ADCPs). The ADCPs are usually moored and bottom mounted instead of being ship-based or attached to a floating mooring to minimize the vertical displacement associated with the vertical motions of the ocean surface caused by waves.

The ADCP does not measure horizontal or vertical velocities at a point but determines Doppler shifts along three to five acoustic beams that are typically slanted (most commonly 60°) from the horizontal plane and spaced around the horizontal compass. The most typical configuration (Janus) includes four orthogonal beans. The Doppler shifts measure slant velocities of suspended acoustic backscattering particles moving with the water relative to the instrument. Pairs of slant velocities are combined to produce vertical and horizontal velocities. The underlying assumption is that velocities are horizontally uniform over the beam separation. Other instruments (e.g., Teledyne Sentinel V ADCP) have an integrated fifth beam to provide a third vertical velocity measurement.

Indirect estimates of vertical velocities can be obtain in several ways. The most common approach is to take advantage of the principle of conservation of mass (continuity equation, as described in the answer by Neo).
$$
\dfrac{\partial w}{\partial z} = -\dfrac{\partial u}{\partial x}-\dfrac{\partial v}{\partial y}
$$
where $w$ is the vertical velocity. Assuming $w=0$ at the bottom, then measuring the horizontal velocities throughout the water column will give you an estimate of the vertical velocity. This method, while useful, tend to produce really noisy results as the vertical velocities in the ocean tend to be quite small and are masked by the noise in the horizontal measurements.

A completely different approach was recently introduced by Klein et al. (2009). It uses the surface Quasi-Geostrophic approximation to estimate low-frequency vertical velocities in scales between 20 km and 400 km from the surface down to 500 m. The needed data is some high-resolution Sea Surface Height (SSH, usually from satellites) and an approximation of the large-scale vertical stratification. Vertical velocities are estimated from the buoyancy equations at the surface and at depth in a modified version of the Omega equation (Hoskins et al., 1985).


How does MSLP change with elevation? trying to interpolate MSLP My understanding of MSLP is that it is a normalized value for pressure at some location as if that location altitude was zero.

"Thus, MSLP is not a function of elevation"

However, after inspecting few cases, I am beginning to question the previous statement.

Below is a screenshot from windy.tv for MSLP over the Himalayas from ECMWF with a high resolution of 9km:

http://imgur.com/a/IWXxz

Two main characteristics are obvious:

1- MSLP changes steeply between two adjacent points just due to the difference in elevation.

2- MSLP over mountains seems to be a strong function of temperature (since it varies a lot over night and morning)

1) Are these two previous statement correct?

2) Can I normalize MSLP in terms of elevation?

To get more insight at what I am trying to figure out: I am trying to interpolate observational MSLP data; however, since MSLP is very high on mountains I am getting wrong results around those points. In other words my algorithm would assume that a large area around the station that is on top of a mountain has an MSLP of 1020 while in fact, just as you move away few kilometers MSLP changes very quickly to 1010 because of the elevation drop, so how can I fix that?

Important note:

Theses "anomalies" in MSLP can only be seen with high resolution models for example they can be seen in ECMWF and not in GFS

http://imgur.com/a/vDkNh

So the Mean Sea level pressure is defined (simply) as the pressure of the station, corrected to sea level. However, methodological problems occur over terrain, such as assumptions that may not be true.

A common method used to correct the pressure is called the barometric equation. One assumption, for example, is that the mean temperature of the previous 12 hours is used to determine the average temperature of the imaginary atmosphere (where the terrain actually is). Of course this generates problems, such as the idea that the mean temperature used is not representative, the lack of lapse rate information, etc. These problems can yield to extraordinary MSLP gradients that may or may not actually exist in reality.


What is this stratefied limestone sphere? What is this stone from the alps of provence?
It's two spheres, one of them is made of at least 25 layers.

Your fossils look like Stromatolites to me.  Stromatolites start as a film of cyanobacteria on the substrate in marine and sometimes freshwater environments.  I am not sure if the bacteria capture sediment or weather the carbonates form on the bacteria themselves but overtime they develop layers of carbonate and other mineral deposits which later became fossilized.  There is a wealth of information about these on the internet.  Stromatolites are still found today, Living Stromatolites.  Wikipedia has a good description of stromatolites Stromatolites on Wikipedia.


Have cosmic ray muons or solar neutrinos been used to probe inside the Earth? By looking at the attenuation of cosmic ray muons passing through pyramids as a function of their direction, it seems it is possible to "look inside" by mapping their 3D density distributions.

Washington Post: Cosmic rays reveal mysterious void in Egypt’s Great Pyramid
Nature: Cosmic-ray particles reveal secret chamber in Egypt's Great Pyramid
arXiv: The secret chambers in the Chephren Pyramid
Digital Trends: Meet the tech that revealed a hidden chamber inside Egypt’s Great Pyramid

Question: Have cosmic ray muons or solar neutrinos been used to probe structures of the Earth, or to deduce or confirm any aspects of its structure in any way?

In November 2008 neutrino tomography was used to measure Earth's mass. A paper was published in journal Nature. The data was captured by the South Pole’s IceCube Neutrino Observatory.

In November 2013 IceCube announced it had discovered 28 neutrinos that likely originated outside the Solar System.

  The neutrinos that the IceCube detector had “caught” came from different angles because they probed different layers of Earth. By measuring how many neutrinos came from different angles, the scientific team was able to measure the densities of various Earth’s segments, and from that – the total mass of Earth.

  The neutrino tomography confirmed the traditional measurements on Earth’s mass, based on gravitational calculations and seismological data. That is especially interesting because neutrino tomography is a conceptually different and independent method – it doesn’t rely on gravity, but purely on weak interactions and the nucleon masses.

  While nothing new was discovered, the fact that a new technique has proven the old calculation right is exciting in its own terms.

Also, from the University of Barcelona.

In 2006 there was a proposal with Harvard University to establish a network of ten detectors to enable tomography of the Earth via antineutrinos.

Not related to the question, but interesting. CERN has a proposal to detect nuclear contraband using cosmic ray muon tomography.


Elevation of a point on Earth What purpose is served by taking sea level as the reference point for finding the height of any point on Earth when we all know that measuring the sea level is a very complex task and it differs from place to place and also keeps on changing? Why can't we just take Earth's centre as the reference point for finding the height of any location?

There are many reasons.

First, measuring from sea level is traditional. It started before we had an accurate way of measuring distance from the center of the Earth, and probably before most people knew it was (approximately) a sphere.  But anyone living by the shore could determine sea level to within a few feet.

Another reason is that measuring from sea level tells you useful things like pressure altitude, which are important if you're a pilot or mountain climber.  The polar and equatorial radii differ by about 14 miles (21 km), so depending on your location, a distance of say 6,365 km from the center could be deep underground or halfway to the stratosphere.


What affects the surface characteristics of cumulus clouds? I love looking at clouds. I love trying to describe them and compare what I see day to day.

I have dozens of questions about the things I’ve observed and I would really like to understand the physics of the world around me. Today I would like to focus on the surface dynamics of cumulus clouds.
Why do some cumulus clouds have distinct textured surface while others are softer and wispy at the edge?

I imagine it probably comes down to temperature and pressure. It may also be an effect of direct sunlight, I’m not sure. I notice the soggy cotton clouds are more common in the evening and the billowy ice cream clouds are more common mid-day.

Do clouds have surface tension like liquid water?

Does the flow of water either into or out of a cloud affect its surface characteristics?

No, clouds don't really have a 'surface' that could have tension like a body of water. The different looks in these two examples (left Cumulonimbus Calvus and right Cumulus Humilis) are greatly dependent on how they have formed and how are they evolving now.

The large Cumulonimbus is still growing in a relatively rapid speed. The cloud is reaching higher and higher upwards carrying moist air. The moist air due to turbulent flows and expanding of the rising air gets mixed with the cold air and instantly forms/extends cloud as it reaches saturation (saturation is reached with less water in colder air and air is colder in higher altitudes). If there wasn't the expansion then flows of dry air to the cloud would desaturate the cloud and more small scale variation could be seen as in the Cumulus Humilis. Also the Cumulonimbus being much larger and further away looks different just due to distance. The steady state like situation of the Cumulus Humilis where it isn't growing (perhaps a little on the top) and the fact that the lower atmosphere has stronger turbulent motions equals to the appearance where more cotton candy pieces 'drift' from the cloud.

Neither of these are ice droplet clouds (they look different just because they are made of ice and not water droplets), but all clouds that are in freezing temperatures have some very small percentage of ice in them too. The Cumulus Humilis might be below 0 Celsius and the Cumulonimbus definitely is at some height. A crude estimate is that temperature drops 6 Celsius every kilometer. The base of both clouds is probably somewhere between 1 and 2.5 kilometers and the Cumulonimbus might reach over 10 kilometers.


How much energy would be required to actively reduce the temperature of the oceans of Earth by 1℃? Is there a way to calculate the energy required to reduce the heat of oceans?

Am I wrong in thinking it is not as simple as reversing the calculation for specific heat of sea water?

The question is slightly confused, because reducing the temperature of the oceans, in a direct sense, doesn't require energy - it releases it. The amount that is released is simply related to the mass and specific heat capacity of seawater, as you suggest.

The missing question, though, is why the ocean is cooling. For it to happen naturally and simply release energy, it would need to be because its surroundings (e.g. the air) were cooler. If you want to actively cool the sea, then yes, that is going to consume energy. If the cooling has approximately the same level of performance as building-sized air conditioning, the power used by the cooling apparatus will be about 40% of the rate at which the energy is removed (and remember that this is not just the total energy divided by the time, because more heat will be leaking back in while you do it).

Leaving aside the, uh, engineering challenges of this scale of cooling, this leads to a question as to why one might want to do this. Remember that unless you devise some complex system to radiate this heat into space from above the atmosphere, you're going to be releasing the same heat into the same global climate system, plus the additional 40% that you've used to move it around.


Given only pressure and potential equivalent temperature, can I determine other variables? I am given a 3 box model of atmosphere where each layer is 300 mbar thick, and the potential equivalent temperature of each is given (from bottom to top - 350K, 325K, 375K).  Am I able to determine the specific humidity of each layer with just this information?  I am racking by brain, trying to make this work, but I feel I need more information.

I think you cannot, might be wrong on that though.

In a single-fluid atmosphere without condensibles, the pressure is essentially proportional to $P \sim \rho \, T$ and potential temperature is essentially $\theta \sim T
P^{1-1/\gamma}$, with the temperature $T$, and the adiabatic index of the gas $\gamma$.
So in this situation you could reconstruct density and temperature from $P$ and $\theta$, but if you add another fluid into the mix (which is your condensible), then I don't see how that should be possible.


How can the world's sea level rise and fall simultaneously? I have just been reading this article on Gizmodo (known for its hard science I know), that talks about sea level rising by up to 3 feet(!).

In the article and video, created from information from NASA it seems, it states that over the last 23 years sea level has risen in some areas and fallen in others.

Now, whilst I am aware that the level of water will vary with tides, how can the general sea level fall in some areas whilst it rises in others?

Surely if I add 9999 million gallons of water to the oceans, then the water level of the whole world should raise by the same amount everywhere?

How can the sea level rise in some places and fall in others?

There are lots of controls on sea level, not just the volume of water in the world ocean. These controls operate on different time and spatial scales, and interact in nonlinear ways. As a result, both global ('absolute') sea level and local ('relative') sea level can rise in some places and fall in others.

For example, absolute sea-level is currently rising, largely because polar ice is melting. But the rate of change is not the same everywhere, and indeed in some places sea-level is falling:

How can this be? Post-glacial isostatic rebound! Much of northern Canada was covered in a thick ice sheet in the last ice-age. This sheet was heavy enough to depress the lithosphere (the earth's crust)! Since the uppermost mantle ('asthenosphere') is plastic, it flowed out of the say, so to speak. The ice melted thousands of years ago, but the highly viscous asthenosphere is still flowing back, pushing the crust up as it does so. As the crust goes up, relative sea-level falls.

What about global sea-level?

Aside: Some people think changes in global sea-level, sometimes called eustasy, are synchronous and evenly distributed (see early literature on sequence stratigraphy). But, as I hope this tiny introduction will illustrate, it's more complicated than that...

There are lots of other mechanisms that affect sea-level, not just isostacy. Here's a list of Local and Global effects I made for my thesis (Hall, M, 1997, Sequence stratigraphy and early diagensis: the Sobrarbe Formation, Ainsa Basin, Spain, Manchester); I've also blogged about it:

Some effects, like changes in the shape of the geoid and hydro-isostacy, affect the deep ocean too — changing the amount of water that, say, the Pacific can hold. Like all the others, these vary in time and space, and have complex relationships to the other effects in that table... so it's quite hard to model all this!

Footnote: There's lots more on Earth Science Stack exchange about sea-level.


Would a gold-containing meteor cause it to "rain" gold? Not sure if here or physics is the best place for this question, but if there was a meteor that had gold in it, what happens to that metal during entry of the Earth's atmosphere?  Since gold melts at 1948° F (1046°C) and boils at 5378° F (2970°C), and Space.com says a meteor reaches about 3000° F (1650 °C) on average, even if that's just the surface temp, some gold would liquify (I think).  I'm guessing depending on the angle of entry, it could retain enough velocity to leave the atmosphere, but I think at least it some cases, it could rain down as either liquid or solid gold and would be gold meteorites.

As it melted, it would be broken up into a spray or even a mist by the airstream. The droplets would quickly slow down to their terminal velocity and solidify, so you would get a fine gold dust imperceptibly falling over a wide area.
I am basing this on my admittedly incomplete understanding of meteors that do not contain gold. When the one in Russia some years ago exploded, it didn't vaporize, but only so many pieces were found.


How can we predict if it's raining, drizzling or there is snow fall by using precipitation intensity (inches/hour)? I was analyzing a dataset in which precipitation intensity(inches/hr) and the type of precipitation was given. For example:

{precipIntensity:0.0029,pricpType:"Rain"}

I'm just curious how it can be predicted that it's raining in a particular area when the precipitation intensity is given ? Is there any formula or threshold by which we can predict the type of precipitation ?

TL;DR: When reporting precipitation types, we still have to manually look out the window.

TL;SR: You do not mention how the information is gathered, so I will go over the different ways.

The first and most obvious one is the air temperature.  If the air temperature is above freezing then you have rain, below you have snow.  Until recently reporting stations were all manned, and so someone would go out and look and determine what kind of precip is falling.  Reports such as if it was raining or snowing, cloudy or sunny, are based on the observation at that moment, not over the course of time.  With technology, a simple camera and light source can determine precip type.  Snow reflects light back to the camera whereas rain lets the light pass through the drop.

Radar is a little more complicated.  We now use what is known as Duel Polarization (Duel-Pol) radars.  Using signals polarized in different directions, we can measure the shape of the precipitation.

Wind resistance flattens out rain drops, making them wider than tall.  Hail tends to be round.  Snow may present itself on it's face appearing as hail, or side, appearing as rain.  The ratio of height to width gives the Spectral Differential Phase.  Snow has a lower value and rain has a higher value with some overlap.
Another important calculation is the Correlation Coefficient, which measures how similarly the two polarizations interact with the precip.  In the image below is a map of different precip types and their CC.  Note that snow has a much wider range of values than snow.  Snow type is determined by temperature, wet snow closer to freezing, drier snow as you get colder.

These and other calculations give on the fly estimations for precipitation type.

However, what you see on the radar on TV still uses the old way of mapping station reported temperatures onto the radar screen.  On this rain/snow radar loop You can make out the rain in green and yellow, the mix precip in pink, and snow in blue.  Note however the mix line (where the air is at 32°F/0°C, moves five times over the 10 frames, and it is not smooth.  This line is calculated by the measured temperatures from weather stations scattered over the area, drawing a line that marks the freezing point, much like drawing terrain contours.  While the radar updates every 10 minutes, weather stations are only sampled hourly or quarterly.

So without knowing the exact way your data was gathered, I would say someone stuck their head out the window and marked on the computer that it was rain.

Extra reading:
http://www.nssl.noaa.gov/tools/radar/dualpol/
https://www.weather.gov/media/lmk/soo/Dual_Pol_Overview.pdf
http://training.weather.gov/wdtd/courses/dualpol/documents/DualPolRadarPrinciples.pdf


How is it possible to use up the water in a region? The Dead Sea, rivers in California and the Aral Sea  are said to be shrinking due to water usage, e.g. for agriculture. Yet the water must go somewhere.

After the fields are irrigated,  the water either soaks into the ground or evaporates. In the first case, the groundwater is replenished. In the second case, the water ends up as rain, presumably within a few hundred kilometers  of the evaporation point. Either way, the water  gets back in circulation.

So what is happening here? How can water be "used up"?

This is a really complex problem and would require a really detailed explanation about atmospheric circulation, meteorology and hydrology.

The short answer to your question is that water is going somewhere else. If you look at the studies about moisture recycling, among the others van der Ent et al 2014 or 2010, you can see that the precipitation that generates from locally generated moisture is just a minor fraction, and usually is higher in very wet areas. So, your assumption of the "few hundreds kilometers" is generally wrong. Considering a very wet area like the Amazon forest, you can see that the moisture locally generated is the major source (about 70% in quantity) of the precipitations in South-Eastern Brazil. This is due to the atmospheric circulation and the topography of the continent.

Source van der Ent et al 2010.

To fully answer your question, both in case of precipitation and in the case of underground percolation, the water used locally in agriculture or other uses, would go to contribute to other drainage basins (both in the cases of surface water and underground aquifers).


What was the density and composition of Earth's atmosphere during the Cretaceous warmest period? There was time during the age of dinosaurs when the polar regions were ice free.  The earth was obviously much warmer but a run-away greenhouse effect did not occur.

This was most likely because the continents were so configured that ocean currents more adequately transfered heat around the globe.
And
The particulate dust from volcanic activity (more active back then) accumulated in the stratosphere, reflecting solar heat and light back into space.

One reason creatures of immense size such as dinosaurs were able to evolve is the oxygen requirements for the respiration and metabolism for such massive bodies were present in the atmosphere during this period.

Similarly, the fossil record indicates vegetation size was much greater during this period than today due to the higher amount of CO2.

This atmosphere would have to have greater percentage composition of oxygen (for dinosaurs) and CO2 (for greenhouse affect and greater plant biomass) or a much denser atmosphere or both.

What was the density of the atmosphere back then either in terms of air pressure at today's sea level and standard temperature
Or
In kg/square meter at STP (Standard Temperature and Pressure)?

What were the percentages of O2 and CO2?

Recent analysis of the contents of air bubbles preserved in prehistoric amber reveal the oxygen composition to be 32% back then compared to just under 21% today.  These tiny bubbles have remained trapped in these amber samples for about 80 million years, which dates them well into the Cretaceous era when dinosaurs and other huge creatures roamed the earth.

Said analysis also revealed that nitrogen made up the rest save 1% for Argon, CO2, and other trace gases. The percentage of CO2 was not specifically stated but mentioned as similar oxygen to CO2 ratio as today's atmosphere.  Whether the total air pressure air density of the atmosphere was greater back then is not mentioned, most likely because this would be difficult to ascertain from the samples.

An atmosphere 50% richer in oxygen but at the same atmospheric pressure and density at sea level as today would have allowed land animals to get by with a lower lungs to total body mass ratio and thus allowed the existence of extra massive creatures such as dinosaurs.

I assert that the asteroid that struck the Yucatan area 65 million years ago caused most of the forests and other terrestrial vegetation to ignite into flames.  The whole earth would have been on fire, at the end of which the oxygen levels were depleted to what they are today.  This is confirmed by analysis amber air bubbles from 40 million years ago, post asteroid impact, revealing an atmospheric composition and oxygen levels closer to today's.

Dinosaurs and other massive terrestrial animals could not then make a comeback since the lower oxygen content of the atmosphere would have restricted metabolism to maintain massive body sizes.


What would be the first thing which will render the Earth uninhabitable? There are quite a few things which can make an otherwise habitable planet uninhabitable, and some of these will eventually happen, sooner or later:

engulfed by its star when it becomes a red giant
destroyed by the nova or supernova of its star
loses its magnetosphere and the solar wind blows its atmosphere away
collides with a large enough object
gamma ray burst
maybe other astronomical phenomena?

some of these will inevitably happen to Earth in the future, but which one is to be expected to happen sooner? By uninhabitable I mean uninhabitable to currently known multicellular life.

For the sake of this question, assume that humans don't invent technology in the future which would stop this from happening, and also no extraterrestrial visitors, supernatural forces or similar effects intervene. Actually, let's assume that humans magically vanish today, just to not get distracted by the effects of human technology.

I'll try to put time scales on each of these events.

The Sun as a red giant - 5 to 6 billion years$^1$

The Sun is currently on the main sequence, which means that it's a "full grown" star - think of it as being middle-aged. It's been on the main sequence for around 4 to 5 billion years, and in 5 to 6 billion years, it will leave the main sequence.

Most yellow (i.e. spectral class G-ish) stars spend about 10 billion years on the main sequence. Then, they swell up as red giants. The Sun is just over halfway through the main sequence, so it has about 5 to 6 billion years left. After 5.4 billion years, it will grow. Here's an image showing how its radius (and other factors) will increase:

The Sun won't swallow the inner planets up right away - see how it takes a while for it to grow - but it will happen eventually. It will take another billion years to reach a radius 200 times that of its current size. It will enter the AGB phase, where it will finally grow enough to swallow the inner planets. It's uncertain as to whether or not Earth will be destroyed, but it will be heated up so much that liquid water will disappear and the planet will be uninhabitable.

NASA has an article on a Sun-like star swallowing up one of its inner planets, just as the Sun may do. The original paper can be found here.
Supernova/nova - Never

There are two types of supernovae: Type II and Type I. Type II supernovae are characterized by hydrogen; Type I supernovae have no hydrogen. You've probably heard of Type II supernovae when you learned about supernovae, and they're the more well-known. They're the result of the collapse of the core of a massive star. However, the progenitor, has t be much larger than the Sun - usually at least 8 solar masses.

Type I supernovae have no hydrogen. There are two main classes: Type Ia and Type Ib/c. The first category are the result of white dwarfs accreting mass from a companion star. The Sun has no binary companion, so even though it will become a white dwarf, it will never undergo this kind of supernova. Type Ib/c also result from core collapse, just like Type II. However, their progenitors are unstable, violent stars, typically Wolf-Rayet stars. Our Sun will fortunately never become one of those!

A nova is small compared to a supernova. It, like Type Ia supernovae, may be the result of a white dwarf accreting matter from a companion. Once again, though, the Sun has no companion star to accrete matter from.
Magnetosphere loss - Never

The Earth's magnetic field is very important, because it shields us from the solar wind. Without it, life on Earth probably couldn't exist! Its disappearance would not be good for us.

Fortunately, it doesn't appear that that will ever happen.

The Earth's magnetic field is believed to be caused by the movement of fluids in Earth's core. Wikipedia lists three conditions necessary for the existence of the magnetic field:

  An electrically conductive fluid medium
  Kinetic energy provided by planetary rotation
  An internal energy source to drive convective motions within the fluid.

The fluid in the Earth's core will never go away, and so long as the planet keeps rotating, that kinetic energy will always be there. So will the Coriolis effect, which also helps circulate the fluid and control the magnetic field. The source of the energy that keeps the material hot is due in part to tidal forces between the Earth and other bodies, such as the Moon and the Sun.
Collision - Not for a long time

The Earth has had one major collision throughout its life, and that spawned the moon. This idea is known as the giant impact hypothesis. When the solar system - and Earth - was young, the Sun had a disk of small pre-planetary bodies, known as protoplanets. There were more protoplanets than there are planets today, because many collided to form the planets.

The hypothesized protoplanet, named Theia, is generally described as Mars-like. It didn't hit the Earth head-on, but rather hit it an a 45 degree angle. The result was that Theia was destroyed and some of Earth was ejected. Much of this material came back to Earth, but some stayed and formed the Moon.

There aren't any more protoplanets, but there are still some large asteroids. The biggest is Ceres, which is tiny compared to Theia. Here's a picture of Earth, the Moon and Ceres (bottom left):

We're not likely to see another giant impact again. The other planets all have stable orbits, and the Moon's actually receding from Earth due to tidal forces. Sure, asteroid impacts are a possibility, but the possibility of a doomsday asteroid is tiny. Even a body like the one that killed the dinosaurs wouldn't extinguish all life. The Jet Propulsion Laboratory has information on the likelihood of such a catastrophic event (not a high one!).
Gamma-ray burst - Probably never

I wrote an answer on Astronomy about this a while ago. If I may, I'll quote from that answer:

  Okay, back to the topic at hand. Wikipedia, of course, has a short tidbit on the frequency of gamma-ray bursts effecting Earth:

    Estimating the exact rate at which GRBs occur is difficult, but for a galaxy of approximately the same size as the Milky Way, the expected rate (for long-duration GRBs) is about one burst every 100,000 to 1,000,000 years. Only a small percentage of these would be beamed towards Earth. Estimates of rate of occurrence of short-duration GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.

  'A small percentage' isn't too specific. The BBC article that is cited in this passage says the following:

    Observations of deep space suggest that gamma ray-bursts are rare. They are thought to happen at the most every 10,000 years per galaxy, and at the least every million years per galaxy.

  However, the 'small percentage' is never elaborated on.

$^1$An estimate

Earth will become uninhabitable long before the Sun swallows it up - if it is swallowed up - because its surface temperature will be so high life cannot exist. I wanted to see if I could figure out when that would be.

You can approximate the temperature of a planet by using the formula for effective temperature:
$$T=\left(\frac{L(1-a)}{16 \pi \sigma D^2} \right)^{\frac{1}{4}}$$
where $L$ is the star's luminosity, $a$ is the planet's albedo $\sigma$ is the Stefan-Boltzmann constant, and $D$ is the distance from the planet to the star.

The current mean temperature of Earth is about 15 degrees Celsius (288 K). However, this is the average surface temperature. Fortunately, the equation given for surface temperature is also of the form
$$T=C L^{\frac{1}{4}}$$
where $C$ is a constant. This means that
$$T^4 \propto L$$
The boiling point of water is 373 K, which is 1.295 times the current surface temperature. If we plug this in,
$$L= \propto (1.295)^{\frac{1}{4}} \approx. 2.81$$
So the luminosity of the Sun would have to be about 2.81 times the current luminosity of the Sun. This value isn't on the graph I gave at the top, though it appears to be about 7 billion years from now. Wikipedia gives this point as only 1 billion years from now, because of a greenhouse effect. So we've only got 1 billion years to live!


Approximation of ancient landmasses using current ocean floor data I am wondering how accurate such an approximation would be. I wish to take a current height map of the earth (including the ocean floor) and approximate the form of ancient landmasses by changing the sea level height.

I suppose this question could be answered by how much the ocean floor changes over time.

Timescales: Preferably over the last 200 000 - 300 000 years, but depending on the error of such an approximation, I am willing to settle for the last 10 000 - 15 000 years.

over that short a time there would be very little change in the land itself, all you really get is a sea level change due to changes in the ice sheets, continental movement is barely noticeable.
such measurements and maps already exist.
here is the earth 12,000 years ago.

Here is the same map with the changes highlighted.

sources for other maps
https://www.fieldmuseum.org/pleistocene-sea-level-maps
http://antiquity.ac.uk/projgall/sakellariou334/
Or you can even use this interactive map, which already does what you want to do, and compare it to past sea level.
As for why projecting backwards is easy, you may want to look up the term "continental shelf".


Please explain how this rock could be shaped like this i found this amongst some river rock. Please explain why or what happened to it.

These are fossil burrows... Looks like Thalassinoides or something similar. They are made by fishes, sea anemones, and crustaceans and can occur in different shapes... elongated, rounded, ending in t-sections, straight, spiral-shaped. A scalebar would be helpful for further classification.

Take a look at the Wikipedia page about it


How do upper-level cyclones and anticyclones affect surface level winds? Take something like the Bermuda High, for instance. I drew a crude illustration of it. It steers hot, humid air from the Gulf of Mexico towards the east coast of North America. But upper level winds are far away from the surface winds/mid-level winds, so how do they manage to influence them?
Same with a midlatitude cyclone. On the lower left quadrant (at least in the Northern Hemisphere), it will steer cold, dry northwesterlies at the surface. The end result can range from sunny, low-humidity conditions (such as after a tornado outbreak in the Mid-South) to bitter cold. How is this possible?

High pressures and low pressures at any height do not exist in isolation.  Had to remind myself a lot of this (so anyone feel free to correct), but the first thing worth highlighting is that the Bermuda High is a warm core high pressure and so extends a great depth through the atmosphere.
This image is a fairly typical cross section of the atmosphere at 35 North in June:

Source: NCEP/NCAR Reanalysis Monthly Means
The left of the two dashed lines is the center of the Bermuda High\Ridge.  Note how it it is very upright and strong through a large height... so the winds at low levels tend to be aligned to the winds at higher levels.  The high at each level has the same cause... being a favored area for the consistent sinking air caused by the Hadley Circulation [i.e. the necessity of poleward moving air to return to the Equator once it reaches certain velocities]
On the other hand the blue trough\low (the dashed line further to the right) is tilted.  This is the typical structure of midlatitude cyclones (i.e. cold core lows).  The starting upper level feature causes the surface low to develop ahead of it (downstream) because the air moving out of the upper trough sparks rising motion below it due to divergence\positive vorticity advection increasing with height.
The result (in the NH) is there will tend to be northwesterly winds at the ground locations near where the axis of the trough is passing over (and so southwest of the surface low\northeast of the surface high).  Such northwesterly winds will tend to bring cooler air and lower relative humidities in most places, but it just how cold or dry the air will be depends upon the source region of the airmass the northwest winds are blowing in (which itself relates in large part back to the strength and larger history of the trough itself).
Overall, fundamental cause of connections between motion\pressures at different atmospheric heights is the fact mass continuity must occur (if air rises, it must be replaced, and it must eventually sink somewhere else to maintain the weight-density to prevent continuing mass buildup/loss), and works out to clearer relationships such as thermal wind (the reality that different winds at different height levels is a direct consequence\identity of temperature advection in the layer between the levels) and the fact the two main terms that cause vertical motion in the quasigeostrophic approximation are differential vorticity advection with height (i.e. different spin changes at different levels causes vertical movement) and maxima of temperature advection below (plus two other terms on friction and external heat).
In a sense, the fact pressure at one elevation induces changes\motion in another elevation maybe shouldn't seem any less weird than the fact that a low-level low pressure system can affect the wind and weather hundreds of miles away from it horizontally.  This isn't spooky action at a distance, this is a continuous fluid where changes to one part of it causes impacts on another part.


What is Stock or Overflow Pit? Is it a terminology in geography? What is the correct word for it? I have an excel file that I have to make the join with another table that has a column listed of different kind of feature types. This was done by someone else who did GPS'ed and spell that word and handed it out to me to do the spatial join with a point layer.

What does Stock or Overflow Pit? Is it related to geography or geomorphology term? Is there another word that is similar to it? I tried to Google it but with no luck. I looked it up on the image on the google to find it and still have no luck. Would someone out there helped me what they are or what does it look like?

Edit: This was post in the GIS StackExchange and it's not approiate to post it since it is not related to GIS.
https://gis.stackexchange.com/questions/188827/what-is-stock-or-overflow-pit-is-it-a-terminology-in-geography?noredirect=1#comment284729_188827

Never mind I think I found what it is...

It is a tank that has a stock pit on the allotment. The tank usually about 30 feet radious and has a windmill.  It looks like this

http://www.panoramio.com/photo/9687839


Has Antarctica's coastline been completely mapped? (map discrepancies) Looking at different world maps, I noticed that there is considerable variety in how the coastline of Antarctica is depicted (even when taking the different map projections into consideration).
Are these discrepancies caused by the fact that the coastline of Antarctica has not been precisely mapped because the ice sheet obscures it in satellite and aerial photography? Do we have the technology to look through the ice sheet and locate the bedrock and has it been used on every part of Antarctica's coastline, or does map data still contain some guess work and interpolation?
Or are there perhaps competing ideas about how a coastline covered in ice should be outlined on a map? I noticed e.g. that Google Maps displays Berkner Island while Wikipedia claims that the island's bedrock is completely below sea-level.

Examples: Google Maps has a very different outline for the islands under the Filchner-Ronne ice shelf than other sources:

example 1: from Google Maps

example 2: from an example using the D3-Geo-Projection code library (not sure where the dataset is from)

example 3: from Wikipedia's Antarctica article (similar to example 2, but using a very different projection)

The key sentence here is

(not sure where the dataset is from)

Every cartographer has to decide what level of detail to use. Mathematicians discovered the Coastline paradox for themselves in the 1960's, but it has always been a fundamental part of cartography.
Different sources of data will come out of different methods of data collection, digitization, and storage.
Regardless of the method used, somewhere there has to be a cutoff. You can't represent a detail smaller than the pen you (or computers) draw it with. The cutoff may be a concsious decision of the cartographer based on the purpose of the map, or an effect of the software used. Or just carelessness.
But this means that different datasets and choices of representation will result in a radically different appearance of the map.


Can clouds be formed without a pollen particle's role? I read online that it is scientifically proven that pollen particles can trigger cloud formation
"is that true"?
if true ,does it mean that no clouds can be formed without pollen particles' role?
Is it scientifically proven that some clouds can be formed without a pollen particle's role?

Pollen is one of many types of cloud condensation nuclei (CCN). So can you make clouds without pollen? Yes, but you still need other sources of CC. Don’t fall into the false dilemma that pollen is a requirement for cloud formation. The more soluble the CCN is, the easier it is to form a cloud (see Koehler theory).
Can a cloud be formed without CCN? I saw it once calculated that it would take longer than the age of the universe for something like that to occur.


Methane from fracking? Methane has spiked sharply since 2014: BBC Methane surge needs 'urgent attention'.

This coincides with a large increase in  fracking. So I'm wondering if there could be a connection? I don't think the target formations could release significant methane because they are generally so deep and pressurized. On the other hand, since the seismic footprint of fracking is so large compared to conventional drilling, could overlying shallow formations be sufficiently disturbed by explosions to release methane from near-surface sources?

According to Howarth, et al. 2011, from 4 wells they sampled, flow back after hydraulic fracturing lead to a release of methane equal to 0.6-3.2% of lifetime production of the well. Fracking wells released methane equal to 3.6-7.9% of lifetime production from all sources, while non-fracking wells released 1.7-6.2% of lifetime production.

Petron, et al. 2014 come to similar conclusions, though they don't provide data for lifetime individual well production to allow comparisons. They measured from an aircraft and found 10ppb to 100ppb increases in methane concentration in the air above wells at the Denver-Julenberg fracking site. They note that their estimated methane release is 2-3 times higher than the EPA's estimates (i.e. the estimates under which the fracking company filed its environmental impact statement). I don't like this study as much due to lack of information about what stage of production the wells are at (if they fracked two years ago and are still pumping, then this is just due to leaky pipes, not due to the fracking process).

In any case, there is some significant evidence that fracking is releasing more methane than it is expected to. The first paper adds some discussion of prevention measures and such.

I will say this, it barely matters in the long run if the methane is leaking or being pumped into your furnace and burned. Methane isn't going to last too long in an oxygen atmosphere, and its all going to end up as CO$_2$ sooner or later.


How is climate change today different than the climate change that ended the ice age(s)? Someone I know posted a question about climate change that I do not know how to answer. While I do believe (for lack of better word) in climate change, I do not know how to answer this persons question. The tl;dr of the question is:

  If climate change is not a natural phenomenon, then how did the last
  ice age end?

The person is implying that warming/cooling reoccurs periodically on the Earth, and that the current climate change threat is overblown.

I have searched online for answers, but cannot find anything concise on this specific subject. According to this wikipedia article,

  There is evidence that greenhouse gas levels fell at the start of ice
  ages and rose during the retreat of the ice sheets, but it is
  difficult to establish cause and effect (see the notes above on the
  role of weathering). Greenhouse gas levels may also have been affected
  by other factors which have been proposed as causes of ice ages, such
  as the movement of continents and volcanism.

In short, how and why did the last ice ages end? I am assuming that the carbon dioxide concentration during these ice ages is much lower than the current estimate of ~410 ppm. Aside from the difference in carbon dioxide levels, what evidence suggests that the climate change of today is different than the climate change that ended the ice age(s)?

Difference #1: Speed. The warming at the end of the ice ages went much, much slower than what we are currently experiencing.
Estimates of the amount of warming since the beginning of the industrial revolution are in the order or 1 degree Celsius* - that's in 100-150 years time.
* Page 7

When the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years.

(NASA Source: How is Today’s Warming Different from the Past?)
The article Earth is warming 50x faster than when it comes out of an ice age sums it up nicely:

What humans are in the process of doing to the climate makes the transition out of the last ice age look like a casual stroll through the park. We’re already warming the Earth about 20 times faster than during the ice age transition, and over the next century that rate could increase to 50 times faster or more. We’re in the process of destabilizing the global climate far more quickly than happens even in some of the most severe natural climate change events.
That rapid climate destabilization is what has climate scientists worried. It’s faster than many species can adapt to, and could therefore cause widespread extinctions, among other dangerous climate change consequences. Coastal flooding in places like Florida has already become much more common than it was just 50 years ago, and sea level rise is expected to keep accelerating.

Difference #2: Civilization. At the end of the ice ages we did not have 3 billion people living within 200 km from a coast line
That is not an difference in the cause of the warming, but definitely in the effect.
One could argue that that same civilization will make us able to deal with the consequences, but looking at thing that already exists several centuries without change, surely raises doubts to our ability to deal with the current rate of climate change. Think (1) unequal global wealth distribution or (2) the psychology of our behavior (denial, politics).

BTW The question asked to you

If climate change is not a natural phenomenon, then how did the last ice age end?

is based on a false premise - it's a bit of a word game.
The current warming is still a natural phenomenon, but it's now primarily driven by our input, and not other 'natural' phenomena.


Why do those glaciers form on the lee side of the mountains? In the Scandinavian mountains, there is a strong effect of orographic precipitation.  The west receives far more precipitation than the east.  This difference can be a factor 5 or more in some places.

But when I observe the locations of glaciers, they seem to be mostly on the eastern side.  An example can be found by studying the Norwegian topographic map near Narvik.  Almost all the glaciers, on Rienatčohkka, Storsteinsfjellet, Ristačohkka, and others, are on the east side of the mountains, while the west side is mostly bare.  If the precipitation is orographic, shouldn't it fall on the west side?  Then why is the east side more glaciated?  Is this a typical effect, or is there a strange situation locally?

The key is with wind-drifting. The predominant westerlies cause snow to drift into protected places. We should perhaps recall that glaciers exist because they are essentially snow-catchers in a landscape that is sufficiently suitable for some of the snow to survive the summer melt period. The drifting and depositing of snow on the eastern side of mountains thus favours formation of glaciers in such locations. If you take a trip using Google Earth into the Swedish mountains to the East of the area you describe you will see that glaciers are also in north and south-trending valleys where of course they catch snow for the same reason. In this case it is the larger scale geomorphology that dictates the location and direction of glaciers. The latter implies that a glacier is not just formed in the lee direction of the predominant wind direction but also requires a suitable landscape geomorphology which affects the location of where the glacier forms.


What's the distance between the center of mass and geometrical center of Earth (CM-CF offset)? I asked the same question on Physics StackExchange site. I now know that there are several types of "center" and I can tell, I'm interested in the CM-CF offset (CM = geocenter, CF = center of figure).

Wu, Ray, and van Dam, "Geocenter motion and its geodetic and geophysical implications," Journal of Geodynamics 58 (2012): 44-61.

Based on Fig. 2 in the paper above, I calculated that the distance is 9 meters. However this 9 meters seems too small to me. In addition it's about geocenter motion, but on he vertical axis, it says "meters" and not "meters/year" or "meters / 1000 years" or something similar. On Fig. 5, it's clear that Δt = 1 month. But I don't understand what's Δt for Fig. 2. If there is at all...

I also found in this paper http://goo.gl/pPWD8l On page 174 it says that this offset is 0.8 km. However, it's 1995 data while the other article was published in 2012.

So I'm really confused now, I think I misunderstood something. I'm not a geophysicist, please help me out.

There is no inconsistency between the 2012 paper and the older reference(s).

Fig. 2 arbitrarily sets all the components (x,y,z) of all the displacement vectors of all the centers to zero at the beginning of the time period (about 123,000 years ago).

Furthermore the 2012 article states:

  The horizontal movement of
  topography associated with plate motion will then change the CF.
  Over time, these slow phenomena can create large offsets, up to
  hundreds of meters, between CM and CF. When the evolution of
  the internal load is reasonably inferred from other sources, then
  these processes may be able to explain a significant bulk of the current
  static offset between CM and CF.

Planetary Sciences, table 1.2, says the distance between CF and CM is 0.80 km, citing to Yoder 1995.

See also Evidence for convection in planetary interiors from first-order topography The Moon March 1973, Volume 7, pages 172-180

  It has been known for some time
  that a center of mass-center of figure offset exists for the Earth (e.g. Jeffreys, 1962).
  From a spherical harmonic analysis of the Earth's topography with the oceans replaced
  by an equivalent mass of rock, Balmino et al. (1972) find the center of mass
  displaced by 1.1 km from the center of figure in the direction 145°W long and 42 ° S lat.

And from the NASA memorandum Reports of planetary geology program - 1981:

  For Earth, with its combination of sialic ([denisty]~2.7) and simatic ([density] 3.0-3.3) crusts, the CF is displaced toward 41.6°N, 34.7°E, in the direction of the Eurasian shield, and close to the center of the continental province at 46°N and 27°E (Bills and Ferrari, 1978).

See also Geocenter - Degree 1 :

  The spherical harmonic coefficients of degree 1 represent the distance between the center of mass of the Earth and its 'center of figure', which in practice is the center of a set of tracking stations on the surface of the Earth. Because of their physical meaning, time changes in degree 1 coefficients can be expressed in several equivalent forms (1) as distances in mm along the Z (along the axis of rotation), X and Y axes; (2) as (fully normalized) coefficients of the geopotential; (3) as the changes in mass (per unit area) that would give rise to the geopotential coefficients, expressed either in kg/m^2 or cm of equivalent water thickness.  The relation between these forms can be found in Swenson et al (2008), equations 5 and 4...

And Planetary Surface Processes (2011):

  In fact, the Earth itself has a substantial center of mass – center of figure offset if the water filling the ocean basins is neglected. The floor of the Pacific Ocean is about 5 km below sea level, whereas the opposite hemisphere is dominated by the continental ... The waterless Earth's center of figure is thus offset from its center of mass by about 2.5 km at the present time.


Why is not snow melting in Ladakh at a rapid pace I am a novice and thus would like you not to mind too much if the answer to my question seems "obvious" to you.

I heard that in the cold desert of Ladakh, if you keep your face in sunlight and legs in shade then you can get a frost bite on your legs and a sunstroke on your face. If the sunlight is so much intense at the place (due to excessively thin layer since Ladakh's elevation ranges from 3000 m to 8000 m), then why doesn't snow melt rapidly during the sunshine.

One reason that I could think of is the very high albedo of the snow, but is there something else that's preventing the snow from melting very fast out there?

The albedo of the snow would be the primary reason the snow is not melting.  Using a simplified model there are two main sources of heat energy that the snow can absorb, the heat from the ground below, and the heat from the sun and atmosphere above.  The ground and the atmosphere are going to be colder at high elevation because of the lapse rate that gansub mentioned in his comment, which effectively leaves radiant heat from the sun to warm the snow.  Snow is a good reflector of near infrared to UV, the linked document on the top of page 206 shows the albedo for wavelengths from 400nm (blue/UV) to 900nm (near IR).  On the table you will find that the minimum albedo for snow (assuming fresh snow) is above 0.8 or 80% or better is reflected.

One aspect that might be confusing is that I don't believe you are getting a sunstroke, a body heat issue, but instead a sunburn.  Sunburns are damage to the skin from UV radiation.  At high elevations the UV from the sun is not filtered as much as it is at lower elevations, in addition what does make it through gets reflected back by the snow, effectively doubling the UV exposure when you are in a snow field.  See this site from the World Health Organization,


The age of tectonic plates There is information which says that East European Platform sticks out at the Baltic Sea and, therefore, we can see the ordovican layer in Estonia whereas crystalline Paleoproterosoic basement crops up in the Finland.

What does that mean? I see that other layers are cambrian and ordovican, which means that they were formed 500 and 400 mln years ago. Does it mean that East European Platform has formed 2 giga years ago when we had the Paleoproterozoic era? I ask because it is hard to believe that we could have the magma cristallization at that scale to solidify over the whole continents. I expect that these processes that shield formation has finihsed in the range 5-4 giga years ago and pretty solidified Earth existed for ~ca 2 bln years before Paloproterozoic ever begun. Why is that platform called Paleoproterozoic?

The process of forming continental crust is indeed thought to have started in the early Archean (i. e. between ca. 4 Ga and ca. 3.5 Ga). But it did continue later: Hawkesworth & Kemp showed in their 2006 review that while much of the continental crust had formed by 2 Ga, i. e. until the middle of the Paleoproterozoic, some of it still continued forming later.

As far as the Fennoscandian shield is concerned, it seems that though it started forming in the Meso-Archean, and that much of the eastern and northern part of it are Archean (see Slabunov et al. 2006), the southern and western part is indeed mostly Paleo- and Mesoproterozoic (see e. g. Lahtinen et al. 2008). In Figure 1 of Lahtinen et al. 2008, it seems that the southern part of Finland, just north of the Gulf of Finland (the Uusimaa Belt) is Paleoproterozoic.

Sources:
Hawkesworth & Kemp, 2006. Evolution of the continental crust. Nature, 443: 811-817.
Lahtinen et al., 2008. Paleoproterozoic evolution of Fennoscandia and
Greenland.Episodes, 31: 20-28.
Slabunov et al., 2006. The Archaean nucleus of the Fennoscandian (Baltic) Shield. In Gee & Stephenson (eds): European Lithosphere Dynamics, Geological Society of London, Memoirs, 32: 627-644.


Why do Earth and Venus have different atmospheres? Venus appears to be the closest to Earth in mass, density, size, etc. - though they clearly have different atmospheres.  Why do Earth and Venus have different atmospheres?

Note: This response is bereft of references. I'll try to add them later.

There is no definitive answer. There are a lot of conjectures, however.

Whatever the cause, the Earth is markedly void of carbon compared to Venus. The amount of CO2 in Venus atmosphere corresponds to a 0.88 km thick layer of carbonate. The Earth's geosphere (lithosphere plus oceans plus atmosphere) collectively contains about half that amount of carbon, almost all of it locked up in the lithosphere. The huge amount of carbon in Venus atmosphere versus the paucity of carbon in the Earth's atmosphere is the primary factor that distinguishes the two atmospheres.

Planet formation. The leading hypothesis regarding the late formation of the Earth is the giant impact hypothesis. Multiple simulations suggest that this collision had to be rather oblique. An oblique collision between a Mars-sized body and a not-quite Earth-sized body would have drastically changed the Earth's rotation rate prior to and after that collision. If the Earth was rotating very fast prior to the collision, that fast rotation combined with the collision could have resulted in the Earth losing a large chunk of its primordial atmosphere.

Venus does not have a large Moon. That suggests that it's formation was a bit less tumultuous than the formation of the Earth. With no big collision to eject that primordial atmosphere, Venus may well have been operating in runaway greenhouse mode from the very onset.

Water. Whether Venus first had free water on its surface or in its atmosphere has long been a subject of debate. Venus is now nearly devoid of water. If water was present in Venus early atmosphere, it would have served to even more strongly magnify the already huge greenhouse effect of a thick atmosphere that is opaque in the thermal infrared frequencies. If the very young Venus did have liquid water on its surface, it wouldn't have lasted very long.

Plate tectonics. One of the consequences of a very thick atmosphere and no liquid water is no plate tectonics. Venus has a very thick greenhouse atmosphere, which makes for a very hot surface. The high temperature of Venus's surface means the surface healed itself too rapidly. Plates couldn't form on Venus (Bercovici 2014). Water is an important lubricant for plate tectonics, particularly for subduction (Mian 1990). (But also see (Fei 2013) for an opposing view.)

With no plate tectonics, there was no mechanism to bury carbon inside of Venus. Plate tectonics developed fairly early on in Earth's history. By the time the Sun became hot enough (the early Sun was faint), the Earth had already started the process of sequestering away carbon into the lithosphere.

Life. Life loves carbon. It is one of the key agents by which atmospheric carbon is transferred to the lithosphere. Life apparently never had a chance on Venus.

References

Bercovici D. and Ricard Y., "Plate tectonics, damage and inheritance," Nature 508, 513-516 (2014)

Fei et al., "Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients," Nature 498, 213–215 (2013)

Mian Z. and Tozer D., "No water, no plate tectonics: convective heat transfer and the planetary surfaces of Venus and Earth," Terra Nova 2:5, 455-459 (1990)


Do warnings verify better nearer radars? As radar beams travel away from radars, they increase in elevation and widen.  Have any studies attempted to quantify the rate at which warning skill (such as in FAR and POD) deteriorates as a function of radar distance?  It would seem quite useful in objectively diagnosing where new radar sites may be most vital (and where to put them in countries that do not yet have radars), and could be useful in guiding warning decisions as well.  I'm particularly interested in tornado warnings in the US, though any related data/studies would be very interesting.

This may/may not actually answer your question "Do warnings verify better" because of the qualitative word "better" and other factors that play a role, such as terrain and forecasting office. Another factor to consider is the nature of the warning and size of the phenomenon. A radar, for example, may not be the best tool to show verification of a hurricane, but it may be better for verification of a tornado. I hope to answer your question by taking arguments to the extreme.

If warnings verify more and more accurately as the warnings get closer to the radar, they may end up in the "cone of silence," where the angle of the radar would not be able to capture the phenomenon.

The opposite of that statement would be that warnings are more accurate the farther away the phenomenon is from the radar. This is also absurd, not only is resolution of the radar cut, but the curvature of the earth also makes this idea absurd.

Conclusion: there is some middle ground. If you get to close, you may not only be endangering your radar (depending on the phenomenon) but you may miss data. It also matters what angle your scan is at. I would hypothesize that anything within the highest elevation angle of the radar would have the highest accuracy, but it would really matter what the phenomenon warned is and what size the phenomenon is.

Warning zones are issued by people, and people have flaws. I would hypothesize that your results may not be conclusive, since the habits of each WFO may vary. For example, a winter storm warning in Georgia is an inch of snow and ice, while Boston would need 6 inches of snow to issue a winter weather watch. Some areas see tornadoes more often than others, leading to some inherent biases, etc.


Cooling time of basalt flows? In places like the Giant's causeway in Ireland (Antrim basalts) there are columnar basalt flows of 100 metres or more. I'm aware that the cooling mechanism is complex, but is there any rough and ready equation for estimating the cooling time of such a basalt flow?

Of course there is, and in not that complex. Is called the heat equation, and is a type of diffusion equation that can be easily solved numerically or analytically in some simple geometries.

If you don't want to get involved in the math, you can use one of mane heat transfer simulation software, there are even online version that run in your browser like Energy2D, in which you can configure the geometry and thermal properties of your materials and let the simulation run.

The screenshot below is a problem with the geometry you suggest. But you would need to set the correct thermal properties of air and basalt.

If you are looking for a customized equation, you have to constrain the geometry of the problem. For instance: the cooling of a laterally infinite layer of material at 1000 °C of thickness X with a medium (air in your case) above it, at constant temperature of 10°C and a medium below it (bedrock) at initial temperature 5°C, you can look at engineering formulas handbooks, or post the question on the Engineering or Math Stack Exchange sites.


Is there a way to guess if its going to rain based on pressure temperature humidity and cloud cover I am using a API to get historical weather information, only it is missing the probably and intensity of rain.

I do have this data:

cloudCover
pressure
dewPoint
humidity
temperature

Is there a way to approximate the probability and or intensity of rain based on just the above.

If you live in a part of the world where the rainfall is dominated by frontal systems, and mainly by cold fronts, then there is a rough inverse correlation between pressure and rain. Otherwise, no. As Gerrit pointed out, rainfall is a whole lot more complicated than that. If you are looking for something to correlate with rain then I suggest you look into satellite-based cloud-top temperatures. The supercooled temperatures at the top of cumulus towers does correlate tolerably well with rainfall.


Does rain (temporarily) deplete the surrounding atmosphere of carbon dioxide? CO2 in the air dissolves into rain water, making them slightly acidic. Is that enough to deplete the surrounding air out of CO2? If yes, how fast does this occur? Is it only with the first drops of rain or do you need several hours?

How long does it take for the surrounding atmosphere to regain its original CO2 contents, assuming this actually happens?

Here is the mass-calculation. We will consider a column of the atmosphere with a footprint of 1m × 1m. This column weighs about 10,000 kg (per square metre). In these days of climate change we will assume the current average CO2 concentration is 400 ppm, yielding a total mass of CO2 in this column of 4 kg.
The rain doesn't wash out the entire thickness of atmosphere but only (in general) the lowermost troposphere. We will assume, generously, that some 2.5 kg of this 4 kg of CO2 is available to be scavenged by raindrops.
Now consider a cloudburst of raindrops, equivalent to some 100 mm  on the ground. So we have 0.1 cubic metres, or 100 kg, of fallen raindrops within our square metre column of air. The solubility of CO2 in air is strongly temperature dependent, up to 2.5 g per kg at 10 deg C. But at such a low temperature we couldn't achieve 100 mm of rainfall, so we will compromise at about 1.5 g per kg at 25 °C. So, assuming complete CO2 saturation within the raindrops (unlikely) our 100 kg of rain will contain 0.15 kg of CO2 , scavenged from about 2.5 kg of CO2 in the 'rained out' column of air, or about 6% of the low atmospheric CO2 .

Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.


What does the degree and order of Spherical Harmonics mean? I've been reading up about Gravitational Models and Spherical Harmonics.

Where I first read about them is in this scholarly article on Autonomous navigation with Gravity Gradients. It talks about Gravity Models being of order x and degree y.

What does order and degree mean in this circumstance? Is it something to do with the Lagrangian Polynomials used in the models?

Another example is found here which states that EGM2008 is complete to spherical harmonic degree and order 2159

It's Legendre polynomials, not Lagrangian.

The zonal harmonics (the $Y^0_l$ terms) depend only on latitude. These zonal harmonics are closely associated with the Legendre polynomials $P_l(x)$, where $x$ is the sine of the geocentric latitude.

The tesseral and sectoral harmonics (the $Y^m_l$ terms, where $m\ne 0$) are closely associated with the associated Legendre functions $P_{lm}(x)$.  (Note: These are sometimes called associated Legendre polynomials, but they aren't polynomials.)

Spherical harmonics are widely used in physics, so the presentations readily found on the internet generally reflect how physicists use spherical harmonics. There are some key differences between these easily found references on the internet and the forms used to represent gravitation. One is that physicists typically use colatitude, and hence use $P_l(\cos\theta)$ as opposed to $P_l(\sin\phi)$. Another is that physicists tend to use the complex form, while gravity models are expressed in terms of real sine and cosine forms. Finally, a set of gravity coefficients is inevitably going to be fully normalized coefficients, while physicists use a form with a different normalization.


What wind forecast datasets are available for forcing a wave forecast model? I am trying to set up a spectral wave model for waves forecasting in the Mediterranean. I need the meteorological forecast for this region. I am aware of the ECMWF datasets. But unfortunately, only the reanalyses datasets are freely available.

So, is there any free source for wind forecasting which covers the Mediterranean region?

Yes, the GFS model is a global model. The data is released in the public domain, so you can use it for free for any lawful purpose. See complete terms of use here. You can get the data here.


What is the Moon's distance from viewer at horizon? From a viewer's standpoint, when the moon starts to rise at the horizon, is the moon at the furthest distance from the viewer visually? The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to Earth's equatorial plane. Remember the moon orbits the earth not the viewer.

What is the Moon's distance from viewer at horizon?

As noted by others, the moon follows an elliptical orbit, which will lead to the greatest change in distance regardless of the observation angle.

However, we can place some upper and lower bounds on what the distance at the horizon would be by using the maximum and minimum orbital radii (the apogee and perigee respectively) along with Pythagoras's theorem.

In the image above, the larger circle represents the Earth, and the smaller is the Moon. $R$ is the radius of the Earth, $d$ is the orbital distance of the moon from the Earth's centre, and $x$ is the distance of the Moon from the observer when the Moon is on the horizon.

Pythagoras's theorem states that

$$d^2 = x^2 + R^2$$

Which we can rearrange to give $x$,

$$x = \sqrt{d^2 - R^2}$$

Now just substitue the numbers in. I used the following values from the Orbit of the Moon wiki:

Perigee: 362600 km, Apogee: 405400 km, average orbital distance: 385000km, radius of the Earth: 6371km

At Apogee, $x$ = 405349 km

At Perigee, $x$ = 362544 km

At average orbital distance, $x$ = 384947 km

  From a viewers standpoint When the moon starts to rise at the horizon, Is the moon at the furthest distance from the viewer visually?

As noted above, viewing angle is not the primary factor in the distance calculation. However, for a given point in its orbit, the Moon is at its furthest visible radius from the Earth at the Horizon. We can see this by comparing to the Moons distance when directly above the observer. This will be the Moon's orbital radius minus the radius of the Earth. For each orbital point this is:

At Perigee: 356229 km, at Apogee: 399029 km, at average orbital distance: 378629 km

Each of which is around 6300 km closer than when the same orbital configuration is viewed at the Horizon. The Moon may appear larger at the horizon, and hence closer, but this is an illusion.

  The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to Earth's equatorial plane

For the horizon distance, the position of the observer on the Earth makes no difference: when the Moon is at the Horizon the distance, for a given orbital configuration, will be the same (minus altitude differences on the Earth's surface). However, from some observational positions the Moon will never be directly above, so the second part is location dependent.

  I want one source from each of the following governments sites- ( U.K gov)(Russian gov)and (Chinese gov) and the sources HAVE to all state a ''similar'' distance.

I doubt that this data is available publicly on government websites. If it was, you could probably find it yourself.


Is there conclusive evidence to refute an earlier oxygenation of the Earth's atmosphere? The Great Oxygenation Event (sometimes called the Great Oxidation Event (GOE), as in the journal Nature) occurred around 2.2 to 2.45 billion years ago (Frei et al. 2009). However, in the article A Whiff of Oxygen Before the Great Oxidation Event? (Anbar et al. 2007) and in The rise of atmospheric oxygen (Kump, 2008) where it is hypothesised that through chemostratigraphy, there was a small amount of oxygen before the GOE.

This is disputed in the later article Hematite replacement of iron-bearing precursor sediments in the 3.46-b.y.-old Marble Bar Chert, Pilbara craton, Australia (Rasmussen et al. 2014), who state that the hematite found in banded chert of Marble Bar (and environs) are mistakenly interpreted as being evidence of a oxygenated ocean.

Is there conclusive evidence to refute the presence of an earlier oceanic/atmospheric oxygenation prior to the GOE?

Additional references

Frei et al. 2009, Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes

The earliest photosynthetic marine organisms (cyanobacteria) are known to have been established by 3.8 billion years ago from the isotopic composition of sedimentary rocks. The earliest microfossils of such organisms are dated at 3.5 billion years. Therefore these photosynthetic micro-organisms were pumping oxygen into the ocean and into the atmosphere at least 1.1 billion years before the Great Oxygenation Event and more likely 1.6 billion. In that almost unimaginably long span of time, these organisms must have created staggering amounts of oxygen. Much of it was soon dissolved and dispersed in the surrounding ocean, but some must have leaked into the CO2 and N2 atmosphere.

It is impossible to believe that after a thousand million years of oxygen production, not enough had leaked into the atmosphere to give it a measurable amount, notwithstanding the fact that there was no one around at the time to measure it. Some oxygen had been mopped up by iron and other elements from the earliest days, but not enough to show up clearly in the stratigraphic record until the so-called Great Oxygenation Event. It defies common sense to say that there was a sudden explosion of oxygen production 2.4 billion years ago and no significant amount had leaked into the atmosphere well before then.

So the answer to your question is no, there is not conclusive evidence to refute an earlier oxygenation of Earth's atmosphere. The question is, to what extent did it happen, rather than whether it happened. In other words, what was the percentage of O2 in the earth's atmosphere at, say, 250 million years before the GOE? We may be sure it was far less than in today's atmosphere, but nevertheless a significant amount and (at the time) an easily measurable amount.


Hypothetical: Can we rehabilitate arid/desert landscapes through the artificial precipitation from exhausts of hydrogen powered airplanes? Note: I know this question sounds fit for aviation stack exchange, but other aspects of this question like cloud formation, atmospheric behavior, precipitation and overall water cycle can be better answered here.
There are aviation manufacturers which are working towards bringing aircrafts fueled with Hydrogen that only/mostly release water vapor (as the major exhaust component). Now, if it proves to be true and safe enough, is it possible to facilitate artificial precipitation in the areas above which the airplanes fly over a period of months, thereby creating enough cloud paths that eventually cause rains.
Can we possibly make areas like Sahara Green using this methodology?

Rough calculations: A 747 burns about 10000 kg of fuel an hour. Assuming it burned hydrogen at the same rate it would produce about 100000 kg (or litres) of water an hour. Flying at 1000 km/hr that means it produces 100 litres of water per kilometre of flight, or 0.1 litre of water per metre.  Lets assume all of this water drops vertically below the plane in a path 100 metres wide. That means that we have 0.001 litres/m$^2$ of water, equivalent to 0.001 millimeter of rainfall. The plane could then turn around and repeat the pass, so in a 10 hour working day we could have 0.01 mm of rainfall
If we take a threshold of desert very conservatively at 200 mm rain per annum, and fly our plane backwards and forwards along a 1000 kilometre path for 10 hours a day, 5 days a week, it would only create 2 mm of rainfall a year. So to get 'non-desert' along our 100 metre wide strip of desert we would need to fly 100 planes every day!
Looked at another way. The Aswan dam in Egypt irrigates an area of 300,000 square kilometres. The dam releases about 50 cubic kms of water per year. 50 cubic kms  is 5 x 10$^{13}$ litres of water. Our plane produces 10$^5$ litres per hour, so we would need 10$^8$ , or 100 million, hours of flight to produce the same volume.  That would be 100,000 jumbo jets flying 24 hours a day, 365 days a year to irrigate an area equivalent to 3% of the area of the Sahara.


Why do rivers sometimes travel down the opposite side of the mountains from where the rain happens? My teacher explained that when wind coming from the ocean gets blocked by a mountain it makes rain on one side of the mountain, like in the image below. This rain leads to the creation of rivers.

(found on Google Images to be on numerous websites, difficult to determine original source)

My question is: Why is it that rivers sometimes run from the other side of the mountain inland instead of being on the same side of the mountain where the greater rain happens, traveling back to the sea?

One example of this is when monsoon winds coming from the Arabian Sea hit the Indian Western Ghats, it makes rivers which travel to the east instead of traveling to the west.

In that image you have displayed you are assuming a 2D flow i.e. in the x and z direction where is x is the direction along the mountain range  which is parallel to the ocean(or sea) and the z is the vertical direction. This is a very simplistic assumption of mountain topography as depending on the context one can have mountain gaps and then the moisture laden winds can assume a 3D flow i.e. in the x,y,z direction( y in this case would be across the mountain). In the specific case you mention namely the Western Ghats there is the famous Palakkad Gap which bring in moisture laden winds from the Arabian Sea into rain shadow area(at least from the perspective of the South West Monsoon) and can fill up the river headwater source on the rain shadow region and these rivers then flow from west to east.

Secondly the atmosphere is a continuously stratified fluid and in the orographic context one needs to consider what is called the Froude number. From a layman's perspective this is a ratio between the inertial forces and gravitational forces that determine the 3D state of the atmosphere.
From a perspective of the the atmospheric scientist the inertial forces in this case would be horizontal wind field(monsoonal wind) and the gravitational forces are represented by Brunt Vaisala frequency and is a angular frequency that tells you how air parcels oscillate vertically in a stratified environment.

So assuming the following
              $$ Fr_n < 1 $$
what this means the incoming wind from the ocean side is not strong enough the penetrate the mountain barrier and you can have what is called upstream blocking. Often during the monsoon the monsoon trough will spend most of it's time offshore and only give skeletal rainfall to the coastal areas.

In the other scenario where the following applies

$$ Fr_n > 1 $$
in this case the wind is strong enough to penetrate the mountain barrier and the capping inversion on the Lee side can be broken in many ways(diurnal sensible heating and latent heating and ample moisture) can cause dark cumulonimbus clouds to form on the Lee side and that would certain fill up the river source on the Lee side as well.

As a case study Tamil Nadu which is not often a beneficiary of the South West Monsoon and is a rain shadow zone has had a surplus rainfall for the past two  years thanks to the principle explained above. The Thamirabharani river feeds off the South West Monsoon as it originates from the Pothigai Hills on the eastern side of the Western Ghats.

This paper - Houze 2012 Orographic Precipitation  is comprehensive and the specific case of the OP will be covered in figure 3e/3f as well as Figure 30(unblocked flow).


Would a Biorock formed buiding be suitable for ocean floor research? Electrodeposition of dissolved minerals in seawater has been used to make coral reef repairs for quite some time. WOLF H. HILBERTZ patented the process and trademarked the name Biorock. I do not have access to IEEE, so I have only been able to read a small portion of this paper:
https://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=9015

https://doi.org/10.1109/OCEANS.2003.178283

The author of the article maintained that this process can build a seawall at a third of the cost of concrete, and it was suitable for building underwater constructions. I have only found references to using this process for repairing coral reefs, but none for construction purposes.

If the lower cost and material strength claims are valid, it would seem that this process would make it dramatically cheaper to build buildings at depth that could be used to make oceanic research facilities.

Is this a feasible approach to build ocean floor facilities for research or commercial purposes? Does the material formed have low enough porosity to be used as a building exterior wall?

I suspect the answer is no. The reason is that underwater constructions typically are supposed to be air- and water-tight, and to have strength enough to resist pressure differences. Biorock looks like it is naturally porous, so it would not be particularly good at holding water out. While the compression strength is like concrete, you really want to guarantee the solidity if you have humans in it.

Basically, risk and uncertainty is a cost too. It is often worth paying extra to know what a structure can handle. So hence it might just be easier to use underwater concrete, where there is likely far more standardised quality.

(Still, biorock is cool and will presumably in due time be well understood enough to compete with a lot of materials and methods.)