In general, does the presence of vegetation increase/decrease gross water loss (evapotranspiration) compared to barren land (evaporation only)? I am doing some literature review on desertification. However, I could not find any information related to my question. Based on my knowledge, barren land faced greater heating and wind than vegetated area but the presence of vegetation can lead to a huge increase in evaporation surface area. They seem to me opposing factors. Based on my intuitive guess, I would say barren land would suffer bigger water loss but has there been any reliable research done on this? Is there a method to calculate and compare the gross water loss of the two scenarios?

I think it is best to introduce some definitions. Often in such studies, two types of evapotranspiration (or evaporation, but I will stick to evapotranspiration during this answer for convenience) are defined: actual and potential evapotranspiration:

Source: presentation called Water resources and their management in Pakistan by Jannat Iftikhar

As you have already stated correctly: when vegetation is present, the surface (generally) holds more water, hence more water is lost to the atmosphere. While barren land experiences more heating and stronger winds, the barren land tends to hold less water to evaporate. Consequently, even though the conditions allow faster and more severe evapotranspiration, there is just no water to evapotranspirate.

The figure below shows an excellent example of this principle for two catchments in Saskatoon. Even though this figure isn't about an area facing desertification, it does exemplify the principle explained above.

Source: An Overview of Temporary Stream Hydrology in Canada (Buttle et al., 2012)

As you can see, the potential evapotranspiration is higher in summer for graph (a), whereas the actual evapotranspiration is higher in graph (b) due to its bigger stock of moisture.

To specify differences with respect to desertification, studies often compare catchments of similar size, meteorological conditions (radiation, precipitation, etc) but with different types of vegetation or different amounts/coverage of vegetation.

For catchments where we have a water surplus, we can check the discharge of that specific catchment and the average precipitation (which produces the discharge when multiplied by the area of the catchment). The difference between the two is the water lost to other processes of which evapotranspiration is the main one.

For the barren land situation, different methods are applied. One could try to calculate the energy balance of the surface based on measured or estimated meteorological and atmospheric parameters. Another option would be to place an evaporation pan, which is basically a flat surface with a layer of water. Subsequently, one can determine how much water is lost from it over a given period of time (taking into account the precipitation).

Sources:

Iftikhar, J.(2017). Evapotranspiration. Water Resources & their Management in Pakistan.

M Buttle, James & Boon, Sarah & Peters, Daniel & Spence, Christa & van Meerveld, Ilja & Whitfield, Paul. (2012). An Overview of Temporary Stream Hydrology in Canada. Canadian Water Resources Journal.


Utah rock pattern identification - looks like small craters This formation was found in the Capital Reef area of Southern Utah (38.2970546, -111.2979319).

There wasn't just one, but several of these small crater formations all over the area. All of them had the same basic structure: a ring of raised rock with fins, surrounding a depression that seems to be at about the same level as the surrounding rock. The rings were darker in color with lighter fins, and the depressions in the middle are lighter in color. All about 20-40 cm in diameter. The rock they are in is most likely a sandstone.

Does anybody know what this is and how it was formed?

The first image is a nearly straight down view, and the second image is an angled image to highlight the fins that ring the depression.

Keys for scale (there wasn't a banana available ;) )

Relief features made by microbial mats which were gelatinous. The ridges and fins are thought to be caused by small currents that flowed through the umbrella like bodies of these ancient bacteria.


What are the affirmations regarding the effects of climate change that have a high degree of consensus amongst climate scientists? I have seen ample consensus amongst reputable scientists that the earth is getting warmer, and this fact is due to human activity (e.g https://climate.nasa.gov/faq/17/do-scientists-agree-on-climate-change/)

The affirmation "97 percent of the scientists with the relevant expertise agree that climate change is real and caused by humans", in particular, gets a lot or airtime.

I have not yet, however, seen similar consensus for the effects of climate change.

Is there a large, documented consensus on any estimate of sea level raise or any other more "direct" effect on the human population?

Variation is not a problem, as long as a significant percentage of scientists/papers affirm at least X of variation of sea level, and X is enough to be a big problem

(Or the analogous affirmation for a different climate change effect)

To be more concrete, is there a survey of scientists or a meta analysis paper that mentions a significant effect, that would affect how humans live, and that shows 90% or more of agreement (of the relevant papers or the relevant scientists)?

Is there a large, documented consensus on any estimate of sea level
  raise or any other more "direct" effect on the human population?

As Will said in a comment, IPCC has some estimates on that matter, although they vary depending on which emission scenario you choose. From the technical summary of the IPCC Special Report on Ocean and Cryosphere in a Changing Climate, section "Projections":

  Future rise in GMSL [global mean sea level] caused by thermal expansion, melting of glaciers and ice sheets and land water storage changes, is strongly dependent on which Representative Concentration Pathway (RCP) emission scenario is followed. SLR [sea level rise] at the end of the century is projected to be faster under all scenarios, including those compatible with achieving the long-term temperature goal set out in the Paris Agreement. GMSL will rise between 0.43 m (0.29–0.59 m, likely range; RCP2.6) and 0.84 m (0.61–1.10 m, likely range; RCP8.5) by 2100 (medium confidence) relative to 1986–2005.

As for the meaning of this sea level rise on human population, it's better to look at the summary for policymakers of the same report:

  The increasing frequency of high water levels can have severe impacts
  in many locations depending on exposure (high confidence). [...] Extreme sea levels and
  coastal hazards will be exacerbated by projected increases in tropical
  cyclone intensity and precipitation (high confidence). Projected
  changes in waves and tides vary locally in whether they amplify or
  ameliorate these hazards (medium confidence).

On a more "philosophical" note, it is really difficult to predict the effect on humans because of the prophet's dilemma. If we know bad things are going to happen, we will (or at least we should...) take measures to prevent them. Then the predicted things will not happen, making the prediction seem wrong, even if it was right at the time it was made! So we can predict that the sea level will rise (it will, no question about that), but we cannot predict the effect this rise will have on humans, because they will likely adapt to it before the effect happens.


What is the difference between roughness length and zero plane displacement? Both roughness length $z_0$ and zero plane displacement $d$ seemed to be defined as the height above the ground at which wind speed theoretically becomes zero. But wind speed is also supposed to go to zero at $d+z_0$. What is the difference between the two, and how should they actually be defined?

First some definitions:

$z_0$: Roughness length is defined as the height at which the mean velocity is zero due to substrate roughness. Real walls/ground are not smooth and often have varying degrees of roughness, this parameter (which is determined empirically) accounts for that effect.

$d$: Zero Plane displacement is defined as the height at which the mean velocity is zero due to large obstacles such as buildings/canopy.

The two parameters are not the same because they describe the effects of two fundamentally different processes. $d$ can be anywhere from $6$ to $20$ times larger than $z_0$.

The basis for most turbulence modeling is the eddy viscosity model:

$$-\overline{u'w'} = \nu_t \frac{\partial U}{\partial z}$$

where $\nu_t$ is the eddy viscosity. Employing some scaling arguments with basis on the Prandtl mixing length model and integrating one arrives at the logarithmic law of the wall:

$${U} = \frac{u^*}{\kappa} \ln\, \frac{z}{z_0}$$

Your equation is

$${U} = \frac{u^*}{\kappa} \ln\, \frac{z-d}{z_0}$$
which is the law of the wall with $d = 0$ because it applies to flat plates. It is easy to see then, that by subtracting $d$ from $z$ the effect is to reduce $U$ at that height, which makes sense because large obstacles remove energy from the mean flow and slow it down.

Note that if there are no large obstacles then $d \approx 0$, but $z_0$ is still larger than zero.


What is the evidence it is feasible to reverse ocean acidification by adding large quantities of a base (bicarb soda)? A commenter made the following reflection:

  Ocean acidification is different than sea level rise and global warming, however. With ocean acidification, we're making an excursion unlike anything the planet has seen in 300 million years. There's simply no precedent that allows us to say "yeah, it's gonna hurt, but the world has already shown that it can cope with this kind of thing". It hasn't. As far as we know, this level of OA could produce a full trophic collapse -- and that isn't something that even I can't be cavalier about, as it would certainly be a civilisation-limiting (and possibly complex-life-limiting) event. Until we know for certain that the impacts of OA will be less severe than this, we should be doing everything we can to stop and reverse it.

I did High School chemistry. To me it seems that if you have something that is too acidic, then you change the pH by adding a basic (base) solution. (Albeit the reaction may cause some warmth).

But this feels like it is missing something that smarter people than me have spent time thinking through.

My question is: What is the evidence it is feasible to reverse ocean acidification by adding large quantities of a base (bicarb soda)?

Instead of using sodium bicarbonate why not use limestone instead? Limestone is already used on an industrial scale to neutralise acids and acidic solutions. Also, sodium bicarbonate needs to be manufactured, whereas limestone just needs to be dug up. The manufacturing of sodium bicarbonate would unnecessarily use energy and potentially create more carbon dioxide if it were to be used to neutralise the worlds oceans.

Danny Harvey of the University of Toronto has already looked into this. His solution is to deposit 4 Gt/a of limestone into the oceans. To put this in perspective, global coal production in 2013 was nearly double this at 7.823 Gt and it is more than global iron ore production in 2014 of 3.22 Gt.

The mining of so much limestone would be a massive and expensive undertaking. Then there are the added costs of grinding the limestone to $40 \mu m$, as specified by Danny Harvey. Added to this would be the cost of depositing the finely ground limestone to the oceans. Because the limestone could not be expected to be dumped at one coastal location and then disperse globally, this would require a fleet of ships to deposit the limestone all over the oceans.

The other things to consider include:

Are there sufficient quantities of easily obtainable limestone to do
this?
What would such a use of limestone do to the supply and cost of
cement, used for construction, etc.?
What impact would such a huge annual deposition of limestone have of
ocean life forms and biodiversity?

The other thing that Danny Harvey states in his document is that 4 Gt of limestone would need to be deposited in the oceans annually for at least 200 years for "a modest additional benefit".


Is water actually blue or is it transparent? This is my first post on StackExchange and I would like to ask a question:
Is water actually blue or is that just the reflection of the sky?

It is blue. But white light needs to cross a long distance through the water to actually get the blue tint.

This related question explains it for ice, but for water it is pretty much the same story.

This article, mentioned by @JeopardyTempest in the comments of the answer to the above question, tackles the case of the oceans. There it says:

  The ocean looks blue because red, orange and yellow (long wavelength
  light) are absorbed more strongly by water than is blue (short
  wavelength light). So when white light from the sun enters the ocean,
  it is mostly the blue that gets returned.


Mega-tsunami, what is the greatest possible height of a tsunami? The notion of a taller-than-skyscraper, so called "megatsunami" is not new - with the often-reported 524m (1720 feet) high Lituya Bay tsunami of 1958 is sometimes referred as such (despite the wave not reaching that high). In many movies (and some documentaries), there are massive tsunami depicted. Some of these movies depict tsunami taller than skyscrapers (such as in Deep Impact and Haeundae). There is also evidence of massive tsunami occurring in different places around the world in the past.

We have seen the reality of devastating tsunami in and around the Indian Ocean in 2004 and Japan in 2011 for example.  These, while not being 100's metres high, are still catastrophic.

How a tsunami forms and how it travels is well documented (thus is not the subject of this question), nor is this asking about the inland reach of such a disaster, they are answered in the related questions Is a mega tsunami that will destroy America inevitable?, Is Atlanta too far inland and too far above sea level to be affected by the comet in “Deep Impact”? and Why does every tsunami travel differently?. But rather, the maximum height possible for a tsunami from any cause.

Is there a theoretical upper limit for the maximum height of a tsunami?

Your question seems to lump at least three different phenomena together: tsunami waves(seismic sea waves), the effects of landslides near the coast, and the effects of asteroid impact into the ocean.  You might have also included rogue waves. Each of these are complex phenomena when you start considering 'realistic' boundary and initial conditions - so you should not expect a highly accurate answer from a simple model.

Seismic sea waves, or waves initiated by land slide, can travel great distances across the ocean. These waves have a long wavelength and therefore may be modeled as shallow water waves. Although the height of classical shallow water wave may be limited (in theory) by the wave steepness (1:7) where the wave 'breaks' and collapses, Computer models of tsunami are likely to be much more accurate.

If you are primarily interested in what happens near a coastline or in a bay, then the most accurate solution will likely be a computer model that also include realistic boundary conditions. See these computer models of a dam break and waves in an irregular water body.

The possible initial conditions for an asteroid impact could be so large that planetary material is ejected into orbit. The Martian meteorites found on Earth are believed to have originated from a impact on Mars. In a large impact, the height of the rim wall might not be an accurate estimate of the maximum altitude material was actually thrown.


Why would magma have high amounts of nickel and chromium? I am doing a research project on Mount Lamington and through my research I have found that its magma has unusually high amounts of chronium and nickel. What would cause this to happen? Is there science behind it, or is it unexplained?

The current thinking according to modelling and previous observations is that the high amounts of $\ce{MgO}$, $\ce{Cr}$ and $\ce{Ni}$ is due to the magma feeding the Mt. Lamington volcano being contaminated by the nearby Papuan Ultramafic Belt (Smith, 2014; Arculus et al. 1983).  The Papuan Ultramafic Belt is, according to Lus et al. (2001), a early Neogene (Tertiary) ophiolite.  The region itself is not associated with an active Wadati-Benioff Zone (Smith, 2004).

Smith describes that the composition of the magma that fed the Mt. Lamington eruption represents part of an unusual tectonic environment, as described in part in the answer to the earlier question What are the geological mechanisms for sea floor spreading in the Bismarck Sea?.  Smith describes that the magmatic geochemistry is influenced by the variables of crustal thickness, tectonic setting and the geochemistry of the lithosphere.

Finally, the relationship between the tectonics of the region and magmatism of the Papuan arc environment has been described as a 'delayed melting' as a partial melting of a source that was

  metasomatised in an earlier convergent event.

The complicated geology is shown in the image below:

Tectonic and geological map from Syracuse University Department of Earth Sciences, the ophiolite (PUB) outcrops are in purple.

References

Arculus et al. 1983, 'Ophiolote contaminated andesites, trachybasalts and cognate inclusions of Mt. Lamington, Papua New Guinea: anhydrite-amphibole bearing lavas and the 1951 cumulodome', Bulletin of Volcanology and Geothermal Research

Lus, W. et al. 2001, 'Papuan Ultramafic Belt (PUB) Ophiolite: Field Mapping, Petrology, Mineral chemistry, Geochemistry, Geochronology, And Experimental Studies Of The Metamorphic Sole', American Geophysical Union, Fall Meeting 2001, abstract #T52D-09

Smith, I. 'High magnesium andesites: the example of the Papuan Volcanic Arc' in Gomez-Tuena et al. (eds) 2014, 'Orogenic Andesites and Crustal Growth', Geological Society Special Publication 385 page 128


Where does molecular hydrogen in the atmosphere come from? This figure from Wikipedia's Atmosphere of Earth shows a hydrogen fraction of 0.000055 percent by volume.

Question: Where does molecular hydrogen in the atmosphere come from?

Does this come directly from biological production like much of the CO2 and CH4, or is this coming from geological sources or breakdown of methane by atmospheric chemistry for example, or someplace else?

Related: What are the sources of molecular hydrogen in human breath?

Gas proportions in the Earth's lower atmosphere; "The proportion of water vapor (H₂O) is variable so it is not represented in this chart, however it averages about 1% in the troposphere."

Besides man-made sources, hydrogen can be produced naturally through a process called serpentization.  Mafic and ultramafic rocks, which are rich in magnesium and iron silicates, react with water to produce a variety of breakdown products summarized in the Wikipedia article on serpentine

Serpentinization is a geological low-temperature metamorphic process involving heat and water in which low-silica mafic and ultramafic rocks are oxidized (anaerobic oxidation of Fe2+ by the protons of water leading to the formation of H2) and hydrolyzed with water into serpentinite. Peridotite, including dunite, at and near the seafloor and in mountain belts is converted to serpentine, brucite, magnetite, and other minerals — some rare, such as awaruite (Ni3Fe), and even native iron. In the process large amounts of water are absorbed into the rock increasing the volume, reducing the density and destroying the structure.[1]

The density changes from 3.3 to 2.7 g/cm3 with a concurrent volume increase on the order of 30-40%. The reaction is highly exothermic and rock temperatures can be raised by about 260 °C (500 °F),[1] providing an energy source for formation of non-volcanic hydrothermal vents. The magnetite-forming chemical reactions produce hydrogen gas under anaerobic conditions prevailing deep in the mantle, far from the Earth's atmosphere. Carbonates and sulfates are subsequently reduced by hydrogen and form methane and hydrogen sulfide. The hydrogen, methane, and hydrogen sulfide provide energy sources for deep sea chemotroph microorganisms.[1]

Roughly speaking, the magnesium-bearing component of the mafic/ultramafic rock is basic and undergoes acid-base reactions with water, generating no hydrogen (but possibly producing magnesium hydroxide, which indicates said basic conditions).  The iron-bearing components, by contrast, are reducing, especially under the basic conditions associated with the magnesium compounds, and they do generate hydrogen:

Serpentine is the product of the reaction between water and fayalite's ferrous (Fe2+) ions. The process is of interest because it generates hydrogen gas:[2][3]

$3 \text{Fe}_2\text{SiO}_4 + 2 \text{H}_2\text{O} → 2 \text{Fe}_3\text{O}_4 + 3 \text{SiO}_2 + 2 \text{H}_2$

The reaction can be viewed simplistically as follows:[4][5]

$6 \text{Fe(OH)}_2 → 2 \text{Fe}_3\text{O}_4 + 4 \text{H}_2\text{O} + 2 \text{H}_2$.

In addition, in the presence of carbonates and sulfates the reduction process can also produce methane and hydrogen sulfide.  The references cited in this passage explore these processes as sources of raw material and chemically stored energy for undersea life both in Earth and in subterranean ocean worlds elsewhere in the Solar System.
Cited references:
1.
"Serpentinization: The Heat Engine at Lost City and Sponge of the Oceanic Crust".  Link
2.
"Methane and hydrogen formation from rocks – Energy sources for life". Retrieved 6 November 2011.  Link
3.
Sleep, N.H.; A. Meibom, Th. Fridriksson, R.G. Coleman, D.K. Bird (2004). "H2-rich fluids from serpentinization: Geochemical and biotic implications". Proceedings of the National Academy of Sciences of the United States of America. 101 (35): 12818–12823. Bibcode:2004PNAS..10112818S. doi:10.1073/pnas.0405289101. PMC 516479. PMID 15326313.
4.
Russell, M. J.; Hall, A. J.; Martin, W. (2010). "Serpentinization as a source of energy at the origin of life". Geobiology. 8 (5): 355–371. doi:10.1111/j.1472-4669.2010.00249.x. PMID 20572872.
5.
Schrenk, M. O.; Brazelton, W. J.; Lang, S. Q. (2013). "Serpentinization, Carbon, and Deep Life". Reviews in Mineralogy and Geochemistry. 75 (1): 575–606. Bibcode:2013RvMG...75..575S. doi:10.2138/rmg.2013.75.18.


Are there minerals which are not been found on earth but which are still possible to exist? On Earth we find many kind of minerals, a lot of them are silicates. How much different kind of minerals would there be on Earth?
But are there Fe minerals found in meteorites which do no occur on Earth.

And how many combinations of metals/elements are possible to form minerals which doesn't exist on Earth. And what could be the reason that they don't exist on Earth?

To answer the first part, there are many minerals on earth which do not involve silicate bonded structures. For instance, non-silicates (minerals of carbonates, sulfides, sulfates, phosphates, and oxides are common non-silicate varieties). For a detailed list of mineral species, you should check out the Dana Classification here: Minerals Arranged by the New Dana Classification.

There are indeed Fe minerals which have no occurrence on Earth, outside originating from meteorite impacts. These minerals are various lattice polymorphs of Fe wit Ni. Kamacite and Taenite are examples of minerals which are found exclusively in meteorites, often distinguished by a Widmanstätten pattern.

The question as to how many possible mineral-producing elemental combinations are possible outside the bounds of our own planet, is outside my personal knowledge in a numerical sense, but the current known naturally occurring mineral species recognized by the IMA numbers around 5,141 valid species: The official IMA-CNMNC List of Mineral Names.

I may be outside the bounds of certain knowledge here, but restrictions on extraterrestrial mineral formation are likely akin to those on Earth: temperature, pressure, time, fluid composition (be it magma, or some aqueous solution), gravity, and atmospheric composition, just to name a few. Some minerals may be unable to exist on our planet because the formational/stability conditions of Earth do not offer much permanence. These prohibiting conditions could well be absent on certain other planets/stellar bodies.


LWC and Absolute Humidity What is the difference between "liquid water content" and "absolute humidity" in meteorology? Both have units of mass/volume.

According to the online chapter Water Vapor (University of British Columbia), the two variables you ask about are defined as:

Absolute humidity

$$\rho_{v}=\frac{m_{water\ vapour}}{volume}$$

Liquid water content

$$\rho_{LWC}=\frac{m_{liquid\ water}}{volume}$$

The main difference is that absolute humidity measures the mass of water vapour and the LWC measures the mass of suspended or falling liquid water content in a unit volume of air. A handy definition linking the two terms is (from the linked document):

  LWC is the liquid-water analogy to the absolute
  humidity for water vapor.


What is the distance between the tropics? What is the distance between the tropic of cancer and the tropic of capricorn here on Earth?

Now this would seem like I could simply google the answer to it and know the exact distance in miles (please provide imperial units) but I have been researching this and cant find an answer... I also don't know how to do the calculations myself so, yeah. Providing a number is definitely not what I am wanting, I would rather be told a bit more information that would allow me to fact-check your answers by doing some simple addition (like how big a degree is and how many degrees there are total (though I can probably find the size of degrees on google).

I am specifically talking about when you follow the curvature of the earth.

Let's start by the quick rule of thumb, I'll follow the way I do it mentally as I think the mnemonics I use could help you too.

First, the tropics are at 23.5° of latitude. And remembering that the original definition of meter is "A ten-millionth of an Earth's quadrant", it means the perimeter of Earth is 40,000 km, that consist on 360° of latitude, then:

$1^\circ = \frac{40,000 \, km}{360^\circ}= 111.11 \, km/^\circ$

Now, the distance between the tropics in a first approximation would be

$\text{Distance} = 2 \times 23.5^\circ \times 111.1 \, km/^\circ = 5221.7 \, km$

Now there are a few sources of error in this calculation. First, the actual latitude of the tropics is 23.43692° (or 23°26′12.9″). Second, the perimeter of Earth is not exactly 40,000 km (it is 40,075.017 km along the equator and 40,007.86 km along a meridian). And third, Earth is not a sphere, therefore not all the degrees of latitude cover the same distance. Taking all those factors into account the actual distance is 5,185.9 km (Calculated using a GIS software).

If you want more accuracy than a few hundred meters, you have to specify the date, because the actual latitude of the tropics oscillates between 22.1 and 24.5 degrees on a 41,000-year cycle. And it is currently changing at a rate of about 0.5 arc seconds of latitude per year, that translates in a displacement of about 14 meters every year.

NOTE: To make the answer more readable to everyone I decided to keep it in metric units (it also makes sense for the mnemonics I use to derive the length of a degree of latitude), so I leave the transformation to imperial units to you.


Is it possible to create an enclosed manmade weather system? There are plenty of experiments, usually geared toward kids, that involve "making a cloud in a bottle" or something similar.  These exercises are neat for what they are, but pale in comparison to the beauty of real clouds.  Really you're just making fog in a bottle.

Using currently available (preferably consumer grade) technology, is it possible to create real clouds?  Or even better, a real weather system?  Imagine you have an enclosed 10 ft wide cube.  If you build a landscape inside, complete with mountains and bodies of water, and you have complete control over the boundary conditions of the cube (temperature, airflow in/out, etc.), can you reproduce the beauty of a towering cumulus cloud inside the cube? One step further... can you create thunderstorms?

I have a very rudimentary understanding of how weather works, but the engineer in me says in theory this should be possible.  But in reality a lot of small details glare out at me as possible show stoppers.  Aerodynamics does not scale, because of the constant size of air molecules at all scales.  I suspect this limitation may affect my weather system puzzle as well.  Also with respect to thunderstorms, I suspect the 10 ft wide cube may not be able to mimic the role of planetary grounding, atmosphere, etc., in the creation of electric discharges.

Real clouds are beautiful because they are huge and you observe them from far away, thereby gaining the ability to see a distinct "boundary" and, therefore, shape. But if you ever travel through a cloud in a plane, thereby seeing one close up, you'll find that they really are "just fog". You'd struggle to recreate a scale cloud in a tiny environment; water molecules have a reasonably consistent size and you can't just downscale the entire system.

Similarly, you could probably create a thunderstorm but at that scale it would be over so fast you'd barely see it. An obvious example is the movement of water droplets as steam leaves your kettle and condenses. You just see a quick whoosh of vapour particles spiralling about and, well, that's about as close to a rainstorm as you'll get.

Some phenomena, such as air vortices, can manifest at smaller scales — I've seen more than a few mini-tornados forming in my garden dragging leaves around in a funnel fashion — but I'm not sure you'd ever be able to contain enough energy to see that happen for more than a fraction of a second in a small tube.


How reanalysis data influence our research/results? I am a student and I have a very simple and yet important question about reanalysis data. Recently, I attended a workshop where various other students discussing the use of ERA5 reanalysis data on their research and at some point, there was the question : "what does the use of reanalysis data means for your research and how this type of data can impact your results?" Nobody had a satisfying answer and now, I am trying to find papers discussing this issue.

For example, can someone use ERA5 parameters on a random forest model as explanatory variables and if so, what does it means for the results?

Apologies if it is a very basic question, I am new in this area.

Welcome to StackExchange SE!

I don't think I fully understand your question, but I'll try to answer it. Reanalysis data is the use of weather models and data assimilation to piece back the weather. It is a 4-dimensional dataset (Latitude, longitude, pressure levels, and time). You can do whatever you wish with that data (provided you follow the legal guidelines with using the ERA dataset), but know that it isn't perfect; it usually is at a coarse resolution, and doesn't always contain everything you may want. Often reanalysis data can be used as input into other meteorological models, such as the WRF model.

As far as a random forest model, it really depends on what your intentions and design are. Admittedly, I don't know much about random forest model or your experimental design. To answer the question of whether the data could be used as explanatory variables, sure if you have some data that isn't within the dataset. But be aware of the limitations. There are other highly used reanalysis datasets, such as the CFSR and MERRA-2 and a variety of other reanalysis datasets, but those have similar limitations too.


High albedo vs low albedo Albedo is a measure of the amount of light reflected back by an object that is incident on it.

So, high albedo means that a greater portion of light falling on something is reflected back. This also means a that greater amount of light goes back towards outer space which is then absorbed by the greenhouse gases present in the atmosphere. Thus high albedo contributes to global warming.

Now, if we consider low albedo, then that means a greater portion of light is absorbed thus raising the temperature or otherwise the heat content of the body. Less light is reflected back for greenhouse gases to capture. But then absorbed heat itself contributes towards global warming.

So as I understand, both low and high albedo contribute towards global warming. Is this understanding of mine correct?

When we do climate change engineering, what do we try to do in terms of albedo? Do we try to achieve high albedo or low albedo?

Additionally I want to know about the effect of 'concrete jungles' in urban areas on global warming?

tl,dr: low albedo = warming (more energy absorbed); high albedo = cooling (more energy reflected).

In principle, and grossly simplifying, energy from the sun warms the ground and less the air. The overlying air is then warmed by the ground, leading to convection, pressure differences, and all that.

So, a high albedo atmosphere would prevent sunlight from reaching the ground, having a cooling effect. Equally, a high albedo ground would reflect more sunlight, less warming the air. That's why glaciers or pole caps of ice have a feedback effect on cooling.

Furthermore, wavelengths reflected by clouds can help cooling an area by day, but also trap warmth radiating from the ground when they move over it. That depends on the situation.

A low albedo atmosphere would let more sunlight pass. In conjunction with a low albedo ground it has a warming effect. Again a potential feedback when ice starts to melt and exposes more ground, leading to more warming, etc.

An open sky will allow warming of the ground by day, but also partly cools back to space by night (continental or desert climate). Greenhouse gases are those that reflect this emitted radiation back instead of letting it escape into space.

Highly populated areas can have a "heat island effect", because of the low albedo of asphalt and concrete and the lack of plants and foliage to absorb sunlight for photosynthesis and evaporate ground water and thus cool.

That (highly controversial and IMO only driven by economic interest) geoengineering thing is about raising the albedo of the stratosphere in order to reflect more sunlight before it reaches the ground. Its adverse effects on ocean acidification and damage to marine life and terrestrial plants and animals ("acid rain") and unresolved side effects could outweigh the potential benefits. But that is a discussion on its own, IMO.

Hope that helps.


What? Northern lights are *not* simply caused by energetic charged particles from the sun? Reading the article Northern Lights: The traditional explanation for the aurora borealis is wrong, physicist says I was surprised to find out that the simple, standard explanation for the production of aurora that I have always read and cited (and is described well in this answer and it's linked sources) is at best incomplete.

The article cites this talk and this video. Briefly, the size and brightness of at least some Auroral displays are larger than can actually be explained by particles from the sun simply following field lines down to within a few hundred kilometers of the earth and exciting the atmosphere, especially on the night side.

Magnetic line reconnection can serve as an energy source to accelerate electrons to higher energies (and fluxes?) to produce the more powerful displays.

I'd like to know - is this reconnection phenomenon important with most displays, or only in highly unusual events? Can Aurora observed at midnight be excited by the energy of the particles as-is (from the sun) or is acceleration from reconnection necessary to insert them on lines that reach to the anti-sunward line on the earth?

The following NASA videos appear to be related:

https://www.youtube.com/watch?v=JZcSEdz54k0

https://www.youtube.com/watch?v=Wd2d3pNS7nM

https://www.youtube.com/watch?v=0vY4nDPrEKg

Solar wind particles directly entering the Earth's magnetosphere are not responsible for the majority of bright auroral displays. As you have found, it is magnetic reconnection that accelerates magnetospheric plasma that collides with the upper atmosphere to cause the visible aurora.

Polar rain

The Solar wind does enter the magnetosphere directly, and travels down the field lines that have their feet poleward of the main auroral oval. This is termed the polar rain¹. The particles in the polar rain are usually too low energy and low intensity to provide visible aurora, though they do produce X-rays as the particles accelerate in the atmosphere (for example, in this report of a Nasa study). On occasion, the polar rain can become energetic and intense enough to generate visible emissions, unsurprisingly termed 'polar rain aurora'².

Magnetic reconnection

Magnetic reconnection is responsible for the displays that people usually think of as the Northern Lights. The brightest aurorae typically occur on the auroral oval around midnight Magnetic Local Time (MLT). This can be seen in the results of the current OVATION model below.

The energetic electrons that cause the bright midnight aurora are generated by reconnection in the magnetotail, the portion of the Earth's magnetosphere that streams behind the Earth, dragged by the motion of the Solar wind (this is briefly mentioned in the NASA youtube videos linked in the question). We can tell this from the fact that the aurorae occur in a distinct oval around the pole.

The bright aurorae occur near the open-closed field line boundary³, toward the closed side of the boundary. Closed field lines are those that have one foot in the northern hemisphere, follow a continuous closed path through the magnetosphere and have a second (conjugate) foot in the southern hemisphere. This means that any charged particles on these field lines must originate from within the Earth's magnetosphere.

Conversely, the field lines accessible to charged particles from the Solar wind are the open field lines; it is along these field lines that polar rain occurs. These occur closer to the pole than the closed field lines, and form the dark area around the pole where the aurorae are not usually observed. The field lines are 'open' in the sense that they connect to the interplanetary magnetic field and are connected to the Earth at only one end, the other being open to the Solar wind.

An historical footnote

The idea that magnetic reconnection is the main cause of the aurorae is not a new one. I am not sure when magnetospheric sources of energetic particles, and reconnection specifically, became the dominant theory of the aurorae, but it was certainly before Dungey⁴ described the magnetospheric convection pattern in 1961.

So, why is this news in the 2010s? I would suggest that it is a case where an earlier, simpler explanation has become lodged in the public consciousness long after it has passed from being the state-of-the-art. Around the turn of the 20th century, the earliest investigations into the aurorae involved physical models of the magnetosphere and the Solar wind. These terrellas suggested that Solar wind directly caused the aurorae, but left investigators such as Kristian Birkeland unable to explain why the real aurorae did not occur over the pole itself, as the terrella model suggested they should.

Fairfield, D. H., and J. D. Scudder (1985), Polar rain: Solar coronal electrons in the Earth's magnetosphere, J. Geophys. Res., 90(A5), 4055–4068, doi:10.1029/JA090iA05p04055.
Zhang, Y., L. J. Paxton, and A. T. Y. Lui (2007), Polar rain aurora, Geophys. Res. Lett., 34, L20114, doi:10.1029/2007GL031602.
J. A. Wild et al. (2004), The location of the open-closed magnetic field line boundary in the dawn sector auroral ionosphere, Ann. Geo., 22: 3625–3639, doi:10.5194/angeo-22-3625-2004
J. W. Dungey (1961), Interplanetary Magnetic Field and the Auroral Zones, Phys. Rev. Lett. 6, 47-48, doi:10.1103/PhysRevLett.6.47


What is the shortest path between two points on Earth's surface? I am a Math student and don't know about longitude and latitude. This question was asked in CSIR-NET Mathematics. Please help me to solve it.

Two points $A$ and $B$ on the surface of the Earth have the following latitude and longitude co-ordinates:

A: $30^\circ $ N , $ 45^\circ$ E

B: $30^\circ $ N , $ 135^\circ$ W

If $R$ is the radius of the Earth, what is the length of the shortest path from $A$ and $B$?

If you don't want to do the calculation yourself, you can use an online calculator like the one provided by NOAA.

Alternatively, if you do want to do the calculation yourself you can use the haversine formula.

  This uses the ‘haversine’ formula to calculate the great-circle distance between two points – that is, the shortest distance over the earth’s surface – giving an ‘as-the-crow-flies’ distance between the points (ignoring any hills they fly over, of course!).

  $$a = \sin^2\left(\frac{\Delta\phi}{2}\right) + \cos \phi_1 ⋅ \cos \phi_2 ⋅ \sin^2\left(\frac{\Delta\lambda}{2}\right)$$

  $$c = 2 ⋅ \text{atan2}( \sqrt a, \sqrt {1−a} )$$

  $$d = R ⋅ c$$

  where $\phi$ is latitude, $\lambda$ is longitude, $R$ is earth’s radius (mean radius = 6,371km)


Do high pressure systems draw air towards them? I refer to the this very recent article, which quotes Andrew Watkins (Manager of Climate Prediction Services at the Australian Bureau of Meteorology).

My understanding has always been that air flows away from high pressure towards lower pressure, so the following quote from the referenced article confuses me. Can anyone explain it for me?

  "There's been a big high pressure system drawing air in off the ocean,
  keeping it a bit cooler for Sydney," Dr Watkins said.

It would be nice to have a synoptic chart relevant for the comment. My guess is that the high pressure cell was not drawing air towards itself. Instead, the location of the high pressure cell was such that it caused cooler air from the ocean to be moved towards Sydney. Fort this to happen, the high pressure cell would have been south of Sydney


How could an earthquake be stopped once triggered? A fault that ruptures causing an earthquake, can cause a chain reaction of dynamically triggered earthquakes in nearby faults, thus causing a much larger seismic event.

What could be some unlikely but still plausible, or creative ways to stop this chain reaction of earthquakes, so that e.g. a major city can be saved?

This is a very big stretch of the imagination and the technology to do so does not exist and most likely never will. But, adapting noise cancelling technology to cancelling the waves produced by earthquakes could be considered.

A system to do so would require an earthquake monitoring system coupled with a wave & strength analysis system that would then produce an out of phase wave pattern to cancel out the earthquake waves.

Some of the problems with this would be the response times required & how to generate a out of phase wave system of equal magnitude to the earthquake waves. Extreme care would be needed so that the out of phase wave generator did not cause a similar amount of damage, or more, than the earthquake waves.

Also, the out of phase wave generator would need to be able to produce wave patterns at extreme short notice, repeatedly & possible continuously to ensure immediate responses.

The wave generator would also have to produce waves of extreme complexity in three dimensions from pulse waves to shearing type waves.

To ensure fast analysis times of complex wave patterns, quantum computers (which currently do not exist) would need to be used.

Such a system would be complex and expensive.


Yellowstone Eruption Possibility? What is the probability of the Yellowstone supervolcano erupting during any given year? I had heard that it erupts once every 100,000 years. Does that mean there is a .001% chance of it erupting during any given year?

1 in 100,000 is an estimate of frequency based on past eruptions which should not be confused with possbility or probability.  It is an oversimplification to state the probability of an eruption as 0.001% chance per year.


Rate of underground formation of carbon-14 by neutron capture Carbon-14 constantly forms in the atmosphere due to neutron capture by nitrogen-14 and subsequent emission of a proton. Other less frequent mechanisms involving neutron capture by carbon-13 or oxygen isotopes also exist, as well as radium decay, as the link explains.

My question is: given an old (compared to the half-life of $\ce{^{14}C}$, more than 100 million years old let's say), sample of coal with for example 2% nitrogen and 80% carbon, how much carbon-14 would be present due to the neutron flux underground?

Obviously this is going to be at least 1000 times less than in modern plant materials. But what order of magnitude would be expected?

In case it helps, I'll add these references:

Background neutron flux determination at a depth of 3200 mwe underground Nuclear Instruments and Methods in Physics Research A 357 (1995), p 524-534.
For shallower data: Variation of Environmental Neutron Flux with the Depth of Water and Soil Journal of Nuclear and Radiochemical Sciences 9, p 45-47.

I do not have access to the article you cite for the deep subsurface neutron flux but I question whether either article will be particularly useful. The shallow water and soil article is concerned with neutrons in the atmosphere and these attenuate so won't be significant at depth.

The major neutron source at depth are spontaneous fission of U-238 and α-n reactions from U and Th series alpha decay. So your flux will be highly dependent on the amount of uranium and thorium and the presence of light elements that will undergo the α-n reaction. This means that the flux will likely be very different from the Broken Hill ore deposit. You may want to look at the literature on subsurface Cl-36 production for flux estimates, but I'm unaware of any dealing with coal deposits.

In coal the C-14 production will be dominated by neutron capture on C-13. Nitrogen n-p should be insignificant because of it's low abundance. I think the n-p reaction depends on higher energy neutrons produced in the atmosphere (but check that).

Assuming you know or can bound the neutron flux then you can estimate the C-14 from the neutron capture cross section of C-13 - 1.4 mb (Chart of the nuclides 16th ed) and the half life of C-14 - 5715 years, assuming steady-state.


The apparent path of the sun An American College Test sample question asks:

  Based on the shadow directions in these experiments, which of the following best describes the difference between the apparent path of the Sun as seen from the observation points in the Northern and Southern Hemispheres?

A. The Sun travels a more southerly path in the Southern Hemisphere than in the Northern Hemisphere.

B. The Sun travels a more northerly path in the Southern Hemisphere than in the Northern Hemisphere.

C. The Sun rises in the East and sets in the West in the Northern Hemisphere, but the opposite is true in the Southern Hemisphere.

D. The Sun rises in the West and sets in the East in the Northern Hemisphere, but the opposite is true in the Southern Hemisphere.

I've read the explanation for B several times. I don't understand the meaning of "traveling a more northerly path" in the southern hemisphere. Does the alignment of the compass and the shadow show the reverse direction in which the sun is traveling? (In this case, since 9 of the 15 directions recorded pointed South, the compass directions were aligned to point North.)

When taking these standardized tests, the first thing to do is to try to solve the problem. If the problem is weirdly stated, as standardized test writers are wont to do, the next thing to do is to eliminate obvious non-answers. (I didn't know that when I took those tests 40+ years ago.)

Choices C and D are obviously wrong. The data shows that regardless of hemisphere shadows point more or less to the west at sunrise, east at sunset. Since the shadows point opposite the Sun, this means the Sun rises in the east, sets in the west. This leaves choices A and B as the only viable options.

Try to match columns (days) from tables one and two based on shadow length against choices A and B. Day 1 in table 1 is an exact match against day 2 in table 2. This column doesn't help with answering the question. The other two columns do help. Day 2 in table 1 is most similar to day 1 in table 2, and day 3 in table 1 is most similar to day 3 in table 2.

Day 2 in table 1 and day 1 in table 2 are most illustrative. Every shadow in day 2, table 1 has some northward component while every shadow in day 1, table 2 has some southward component. Since the shadows point opposite the Sun, this suggests (B) is the correct answer. This is consistent with the other results.

As a sanity check, what about option (A)? This is not consistent with the tabulated results from day 2 in table 1 versus day 1 in table 2, or from day 3 in table 1 versus day 3 in table 2. Option (B) is the only possible answer.


What separates the Karakoram Range, the Hindu Kush, and the Himalayan Range? In Google Maps, I don't see any boundary between the Karakoram (a.k.a. Karakorum) Range, the Hindu Kush, and the Himalayan Range. What separates these ranges?

The River Indus in Jammu and Kashmir of India and Gilgit-Baltistan under Pakistan control is usually taken as the dividing line between Himalayas and Karakoram.

The River Gilgit, a tributary of the Indus flowing from the North-west has its confluence with the Indus from the North-East near the town of Juglot or Jaglot about 45 km south east of Gilgit on the Karakoram Highway in Gilgit District and then the Indus flows south from here.

The confluence between these rivers is known as "Tri Junction Point" or "Junction Point of Three Mountain Ranges". It is located at the junction of the 3 lofty mountain ranges, the Karakoram, Himalayas and Hindukush.

To the North of this confluence or to the north of both Indus and Gilgit rivers is Karakoram.
To the south  of the Indus before merger and to the East after merger are the Himalayas
To the south of Gilgit river and West of the merged Indus is Hindukush.

In the Ladakh district of India, there is an east west range called the Ladakh range to the north of Indus, and sometimes this is taken as an extension of Karakorams. Beyond or to the north of Ladakh Range is the Shyok River, a tributary of Indus that flows westwards and joins the Indus near Skardu, and more commonly the mountains to the north of Shyok are called Karakoram range.


At what point are water droplets too small to make a rainbow? This question asks How to tell if fog is made out of water droplets or ice crystals?

I know that ice fog makes a rainbow where fog does not.

Ice crystals aside: How does the water droplet size determine the characteristics of a rainbow? When is a water droplet too small to make a rainbow?

Some time ago I posted this answer about how rainbows are formed, and the Wikipedia link Trond Hansen posted mentions droplet size relative to the wavelength of light.

For a rainbow to form, the droplet size has to be large enough, relative to the color with the longest wavelength of visible light, for it to be refracted before reflecting off the backside of the droplet. Refraction occurs because, as the wavefront encounters the change in density between air and water, it slows down. This implies that a droplet would have to be greater than half the wavelength of red light, which is about 740 nm, or about 370 nm.1 Also, the light responsible for producing the rainbow enters the droplet off-center and reflects off of the backside of the droplet off-center, so the droplet's diameter would need to be a bit larger than 740 nm.

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


What's the difference between topography and orography? Both seem to be a study of a planet's surface. Topography seems to have more to do with the graphical depiction of surface features, but there seems to be a lot of overlap...

Topography, in the eyes of Earth Scientists, is the study of the surface features of the Earth (or other planet), and includes all features of that surface, natural or artificial.

From the Oxford Dictionary:

1.The arrangement of the natural and artificial physical features of an area

Topography comes from the Greek topos, meaning 'place'. It is a study of all the features of any specific area, not necessarily just elevation, as depicted in topographical maps.

Orography is a specific study of the features and 'topography' of mountains:

The branch of physical geography dealing with the formation and features of mountains

Comes from the Greek óros meaning 'hill'. Orography can also be known as orology, oreography or oreology... It is concerned with the formation and development of mountains, hills and ranges, for example the formation of a mountain range or ranges is know as an 'Orogeny'. Earth Scientists can refer to groups of mountains or ranges as 'Orogens'.

Orography falls more broadly under the study of Geomorphology, which is not necessarily just constrained to surface features, as in the case of topography.


Sink holes in drainage area I live in Florida (aka the land of sink holes).  Due to the flat nature of my area, it is common place for housing developments (and any developments really) to dig large drainage areas to give water a place to go other than the newly constructed buildings.  In the case of my neighborhood that means that a large depression was dug to drain water from the land where all the surrounding houses were built.  The drainage area is roughly square, probably 50 meters by 50 meters in size, and about 4-5 feet deep (I'm pretty sure this is a common practice, even in less-flat areas).  In our case houses are built surrounding it in a big "block", and my house backs up to it.

It's covered in grass and well maintained, so I take my kids back there to run around semi-regularly.  We bought our house about 6 months ago, and about 3 months ago a large sink hole opened up in this drainage area.  Large in this case means that it is probably 2 meters deep at the deepest point and has an overall diameter of about 5 meters.  It's on the other side of the drainage area so it isn't right next to my house, but it's certainly not far.  We also recently found a second (and much smaller) hole - approximately 20 centimeters in diameter and 20 centimeters deep.  This small one is much closer to my back yard.

Of course I'm definitely interested in this sink hole as it pertains to my house (aka does this imply that this area may be prone to sink holes), but I'm also curious about these things generally.  To keep it to a simple question, I'm wondering if this is a sink hole that opened up like all other sink holes in Florida - aka a collapsed underground hole/cave that just happened to miss all the surrounding houses?  Or is it possible that this is a local affect, aka something about these drainage areas can lead to sink hole formation, implying no immediate concern to the surrounding houses?  I realize this is probably not an answerable question for my specific sink hole, but I thought people here might have some insight into whether or not drainage areas might cause their own sink holes.

In case it isn't clear, this drainage area has no drain point itself.  During heavy rain, water flows into the drainage area and then slowly evaporates or percolates into the ground.  In case it matters, when it does rain, water typically collects on the opposite side of the drainage area than the side which contains the sink hole. I.e. the sinkhole is on the "high" side of the drainage area (although the elevation difference probably isn't more than a dozen centimeters).

Having had some time to do some digging (hahaha), I have as close to an answer as I believe is possible.

Small update just because: one of the smaller sinkholes has dangerously grown, in a way that I wouldn't believe if I didn't see it.  It has widened slightly to about 45-60 cm, but grew substantially deeper.  With a tape measure I clocked it in at 3.3m.  No joke.  It's pretty much a death trap to small animals or children.  I do not take my children back there anymore nor does anyone else seem to play there, fortunately.

Onto answering my question.  This is Florida, the land of sinkholes, and it seems that the assumption made by all parties involved is that this is an actual sink hole, and not some obscure side effect of the drainage area.  After querying my HOA I learned that the area is owned/managed by the local county government.  It doesn't sound like they bother doing geological studies (because sink holes are so common around here), but instead just fill sink holes in as they appear to avoid liability.  They are actually aware of the larger hole and put it on an "official" sink hole map (which will probably have a minor effect on my insurance rates).  They will also fill it in.  However, they are being quite slow about actually fixing it (which is a surprise because of the potential liability issues).

From what I have read on various government sites, sink holes around here are assumed to be fairly independent, i.e. a sink hole within 50 feet of your home doesn't imply that your house is any more likely to experience damage from a sink hole than any other house in the general area.  However, since the organization responsible for filling the hole is not going to be performing a geological survey, nor are they likely to bother consulting professionals, a best guess is the best I'm going to get.


Why do we consider hydrostatic pressure and lithostatic pressure separately? In petroleum geology, why do we consider hydrostatic pressure and lithostatic pressure separately?
Surely the pressure at any point, whether fluid or rock, at depth is simply equal the weight of all the fluid and rock overlying it? Hence why isn't pressure for fluids and solids equal at a particular depth?

I think (but I'm not an expert on the topic) that your assumption is wrong! The pore fluid pressure and effective pressure exerted on the rock are not identical. And during log measurements, it is only the pore fluid pressure that is measured, $\sigma_\text{pore}=\rho_\text{water}gz$. As long as the water is connected through pores to the earth's surface and it is assumed to be hydrostatic (not-flowing), the measured pressure in the pores will create a pressure to push up the overlying water only -- the rocks will take care of carrying the overlying rocks themselves! If you'd drill a borehole, the water-filled column would be filled with water exactly to the earth's surface. The effective pressure on the whole system is then $\sigma_\text{effective}=\sigma_\text{lithostatic}-\sigma_\text{pore}$.

However, once a seal is formed (e.g., a shale formation overlies a formation), the pore water suddenly has to also carry the overlying rock formation! The pressure will then increase significantly, and the pore water pressure that you measure becomes more similar to the effective pressure.

The pore water pressure thus increased below a seal because it is stuck. Once you drill a hole from the surface to this formation, you allow water to flow freely to the surface, and it is clear that it is under overpressure with respect to the lithostatic pressure, because it will blow out!

See also this comprehensive set of slides: http://ocw.utm.my/pluginfile.php/1509/mod_resource/content/0/To_upload_OCW_Formation_pressures.pdf .


Active rifting in Antarctica? The West Antarctic Rift exists between the Trans-Antarctic Mountains and Marie Byrd Land (see map below for reference)

Image source: NASA

The rift system is believed to be like the East African Rift, consisting of several interconnected rifts, many are believed to be inactive.

However, the Wikipedia article vaguely mentions:

  it is now known that West Antarctica is moving away from the East Antarctic Craton in a north/northeasterly direction (approximately in the direction of the South Georgia Islands) at a rate of about 2 mm per year or 500,000 years per kilometre.

What evidence is there for active rifting in West Antarctica?

Unlike the East African Rift system, it is not possible to view the rifting crust of the West Antarctic Rift directly due to the extensive ice cover over the region (1). However, scientists can and have inferred the nature of the rifting from other methods, including seismic, radar sounding, geodetic methods and by examining the petrology of exposed rocks in surrounding areas. Also, of significance, are observations made of glacial activity, particularly of the prominent Thwaites Glacier (2).

There seems to still be some uncertainty as to the nature of the current tectonic status of the West Antarctic Rift.

On one hand, observations of radar sounding and subglacial water routing at the base of the Thwaites Glacier show some melting that Schroeder et al. (2014) (2) suggest that the melting is due to a geothermal flux that is consistent with magma migration and magmatism, they record a minimum average geothermal flux of ~114 mW/m2, with some areas peaking at >200 mW/m2.  Petrologic observations by Martin et al. (2014 (3) based on samples of of Cenozoic outcrops of surrounding exposed areas on the shoulder of the West Antarctic rift system suggest active rifting with mantle 'refertilisation'.

On the other hand, seismic observations from authors such as Lough et al. (2013) (4), match geodetic data from the POLENET (5) program suggest that much of the rift is not presently active.  Although several earthquakes have been recorded in West Antarctica, very few occur in the rift itself, and these tend to be much smaller magnitude.  Lough et al. (2013) suggest that some of the shallower quakes occur due to glacial activity.

The seismicity further reinforces the conclusions made by Winberry and Anandakrishnan (2003) (6) that the earthquake pattern suggest that the West Antarctic Rift is a dormant rift system, with a possible hotspot origin for volcanic activity occurring in the nearby Marie Byrd Land (1).

The evidence suggests that the West Antarctic Rift system is either dormant, or a very slow moving one.

References

(1) Winberry and Anandakrishnan, 2004, Crustal structure of the West Antarctic rift system and Marie Byrd Land hotspot Geology

(2) Schroeder et al. 2014, Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet, PNAS

(3) Martin et al. 2014, Increased mantle heat flow with on-going rifting of the West Antarctic rift system inferred from characterisation of plagioclase peridotite in the shallow Antarctic mantle Lithos

(4) Lough et al. 2013, Subglacial volcanic seismicity in Marie Byrd Land detected by the POLENET/ANET seismic deployment American Geophysical Union, Fall Meeting 2012

(5) POLENET

(6) Winberry and Anandakrishnan, 2003, Seismicity and neotectonics of West Antarctica Geophysical Research Letters


Are there more earthquakes near the equator or poles? When comparing the average distance of the all known earthquake epicenters to the nearest pole, is the longitudinal distance to the equator or the poles the smallest of the two?  Please note that any period for which earthquakes were able to be tracked must have taken place globally and allowed the location of the epicenters to be be estimated in a meaningful way as it relates to the question; meaning if the location is off by 3% that's likely okay, being off by 50% would not be okay.

The Global Historical Earthquake Archive (1000-1903)

Global earthquake epicenters, 1963–1998

Most earthquakes happen at the edges of the Earth's tectonic plates. Look at a better sample of earthquake epicenters collected using modern seismological techniques and compare to this List of tectonic plates

Earthquake epicenters are concentrated at the edges, and more sparse in plate interiors, but there are regions of high seismicity at high and low latitudes.

If you really want to know whether the concentration of earthquake epicenters is greater near the equator than near the poles, then you should try the following:

1) Divide the surface of the globe into ~30 regions of equal area.

2) Make a table with a row for each region. Give the table two columns: the region's latitude (L), and the number of epicenters in the region (E).

3) Compute the arithmetic average of E for all 30 regions, call this G. Take the square-root of G and call this D.

4) Now look at your table.  How many regions have a concentration E>5*G? How many of these are located at 'polar' latitudes and how many are located at 'equatorial' latitudes?

5) If you find that 80% or more of the E>5*G regions are in 'equatorial' regions, then that is probably evidence that significantly more earthquakes are measured in 'equatorial' regions. If you don't find this much, the effect is small.


Which universities are best for studying Oceanography as an undergrad? I am a high school senior studying in a local school in Bangladesh. My passion is to study oceans & marine life. The drive of getting higher education in Oceanography has turned into ardent compassion for me. I am, therefore, seeking insightful & important pieces of information regarding which universities would be best for higher education in Oceanography.
Your guidance & help is much wanted & would be highly appreciated.
<3

I noticed that there is a push to close the question, and I get why. But I do think that guidance towards a university is still important, even if it does not fit the Earth Science SE guidelines. So here is my answer (as someone who does not study oceanography, rather as a meteorologist): It depends.
What I have found is that the question you should ask is not 'what is the best,' rather 'what is the best for me?' You may want to learn from the best, but you might end up miserable. What can you afford? How far are you willing to travel for your degree? What aspects of oceanography are you interested in -- chemistry, climatology, biology, geology, etc.? Presumably, different universities will emphasize different specialties. Look at what the faculty research, and you will find what
Knowledge is knowledge. With solid reading skill and good resources, you can probably teach yourself enough without needing a degree. If it is just a passion, I would recommend that route. If it is what you want as a career, go to university and get the degree.


Transfer precipitation forecast in mm to expected snowfall in cm What conversion functions exist to transfer precipitation forecast in mm to expected snowfall in cm? Simple rules of thumbs as well as more advanced methods would be of interest.

The snow density, which is the "conversion function" you are looking for, of fresh fallen snow varies with atmospheric conditions, vapour saturation and temperature since these parameters determine the snow grain morphology (See this figure from SnowCrystals.com; I leave it as a link for copyright reasons). Densities can vary from as low as < 100 kg m-3 for cold conditions to maybe > 400 kg m-3 for wet snow. This essentially cover the spectrum for a normal snow pack. If you, by your question, are thinking about weather services reporting how much snow will come from a snow fall it is by no means a an easy thing to predict since you may "know" the amount of precipitation from a model, but you will have more difficulties knowing the density of the fallen snow unless you device a classification based on the atmospheric conditions during snow fall (based on snow crystal structure as in the figure). Hence for most purposes, the snow pack thickness is of little value and most will want the water equivalent of that snow, i.e. how much liquid precipitation it corresponds to.

If snow is falling during drifting conditions, the density may become higher than the falling snow itself would have resulted in. This is because with wind drifting, snow crystals are reduced in size by crushing and can hence be more densely packed.

With time the snow pack will densify due to metamorphic processes. This will cause the snow to decrease in thickness with time. But that is perhaps a different question since yours were about fresh snow.


How can I plot a Skew-T log-P diagram? For displaying atmospheric soundings the use of Skew-T Log-P diagrams is very common. The manual THE USE OF SKEW T, LOG P DIAGRAM IN ANALYSIS AND FORECASTING from the Air Weather Service explains what this diagram is and how it can be used. What tools are available to create Skew-T Log-P diagrams and how do they differ?

Skew-T Log-P diagrams can be plotted in most mathmatics software.  I have seen examples in Matlab (and by proxy Octave), GrADS, NCL, IDL and I have my own code in Python that generates Skew-T plots.  There are also some programs such as NSHARP and BUFKIT that are more full featured.  You can also find websites that plot forecast soundings such as twisterdata and real data soundings.

The major variances arise from the specific use case of whoever wrote the code you are using.  The most basic code will generally be able to tell you the lifting condensation level (LCL), level of free convection (LFC), equilibrium level (EL) and perhaps the 500 mb lifted index, all for a surface parcel.

The more advanced code will generally be able to calculate the above quantities not just for surface parcels, but also for the mixed layer and be able to find the most unstable parcel.  Convection oriented code will give you CAPE, storm tops and other severe weather parameters and will also tend to be able to analyze the hodograph.  BUFKIT can do analysis to identify snow growth levels and some other winter weather related quantities.

One of the subtle differences in skew-T plotting software is how they handle the moist adiabats.  This can be modeled as a fully reversible process or a pseudo reversible process and this produces subtle temperature differences aloft on the adiabat.  There can also be differences in whether the moist adiabat only considers liquid water and vapor, or if ice process are included in the latent heat release.

Here is an example of what my Python code produces:

Var          SFC            ML              MU
CAPE  J/kg   1877           1877            2415
CIN   J/kg   46.9           46.9            0.4
LI_max       -9.5           -9.5            -11.3
LI_500       -7.3           -7.3            -8.4
LI_30        -4.8           -4.8            -6.4
TOPS  m      14800          14800           15400
LCL   mb (m) 892 (1000)     892 (1000)      862 (1292)
LFC   mb (m) 831 (1604)     831 (1604)      857 (1343)
PRS   mb     1000           1000            871


Why is Earth's inner core made of an iron-nickel alloy? This question has puzzled me for a while. I know that earth's mantle is made of different minerals, metals and rocks etc. and that has always made complete sense to me.  But why is the inner core made of an iron-nickel alloy?  The only reasons that I could come up with (they are kind of crazy) is that:

A. The iron-nickel alloy that composes the inner core is heavier than other elements in the mantle and outer core, causing it to sink to the center of earth.

B. Since both iron and nickel and attracted to magnets earth's magnetic field drew the to metals into the inner core mixing them into the alloy.

C. Earth started as a giant asteroid composed of an iron-nickel alloy (which many are), and other materials from space built upon it causing earth to have an iron-nickel core (I told you they were crazy!).

But these explanations don't really make much sense to me.

The first thing you should think about is how the accretionary disk cooled and the cosmochemical constraints this put on Earth (But I am not going into details here). From studying meteorites it is apparent that the oldest meteorites don't show signs of chemical differentiation (e.g. melting, ...) and are thought to represent the solids that formed from the accretionary disk. Because of their characteristic round structures, chondrules, they are called Chondrites. The most chemically primitive Chondrites (e.g. https://en.wikipedia.org/wiki/Allende_meteorite) roughly have the same composition as Earth. This is why it is thought that Earth formed by accretion of these smaller chondritic objects.

There are also other meteorites called "achondrites", meaning "no chondrules". They show signs of chemical differentiation (we can find stony-, stony-iron-, and iron-achondrites). For this chemical differentiation to happen it is necessary to think of the meteorite as having a parent body, on which this differentiation took place. These parent bodies differentiated similar to earth into an iron-nickel core (iron-achondrites), an olivine-rich mantle (stony and stony-irons) and a silicate crust (stony-achondrites). Because differentiation takes time, it is somewhat unlikely that a parent body formed, was destroyed and the iron-core was recycled to nucleate Earth (Earth has roughly the same radiometric age as many meteorites). So your suggestion C would take quite some explaining. Also suggestion B is not temporally possible, because the magnetic field needs a liquid iron core to work and therefore only came into existence after the iron migrated to the core.

A few words about iron-nickel. This has something to do with the abundance of elements in the accretionary disk (http://upload.wikimedia.org/wikipedia/commons/e/e6/SolarSystemAbundances.png). Iron and Nickel are very common elements. They are also siderophile, which means, that when a chondrite melts, the iron will try to separate from the sulfide- and silicate-melt. Because of the larger density of this melt, it will try to move towards the core of a planet. But it is very likely that other elements form a certain percentage of the core's chemical composition and it can be reckoned that this will be similar to some of the compositions of iron-meteorites.

If you get more interested in this I can fully recommend "McSween, Harry Y. (1999). Meteorites and their parent planets (2. ed. ed.). Cambridge [u.a.]: Cambridge University Press. ISBN 978-0521583039." which is very enjoyable to read and because of its descriptive approach not outdated. The newer book is also very good "Huss, Harry Y. McSween, Jr., Gary R. (2010). Cosmochemistry. Cambridge: Cambridge University Press. ISBN 978-0521878623.".


Why does air seem to affect local surface temperatures so much? Last winter, several areas in the US and Canada were hit by a "polar vortex." I happen to live in one of those areas and was amazed how much the temperature seemed to change so suddenly just because a bunch of "air" had changed locations.

Why can air temperature influence surface temperatures so radically?

The surface temperature is the temperature of the air at the surface (rather than the temperature of the ground itself).  This temperature is typically taken between 1 and 2 m off the ground, and this is the temperature we feel when we are outside.  Simply put, the reason air affects this temperature, sometimes radically, is because temperature is a property of the air (it is related to the mean kinetic energy of the molecules comprising the air).

If we are curious about the change in temperature we experience, we might write $\frac{DT}{Dt}$, where $\frac{D}{Dt}$ is a material derivative and $T$ is temperature.  This change in temperature is Lagrangian, or in other words it is the temperature of a parcel of air as it moves around.  We can expand this as $$\frac{DT}{Dt} = \frac{\partial T}{\partial t} + \mathbf{u}\cdot\nabla T$$ What this equation says to us is this that the change in temperature can be related to two effects:

The change in temperature of air at a fixed location in space (e.g. outside your house), and
The transport of different temperature air to your location by the wind.

The first bullet point is going to be modified by energy transfer between the ground and the air (conduction) and radiative losses (radiation emission).  These changes are on the scale of how temperature changes between morning and afternoon -- nothing too radical.

The second bullet point is where the radical changes can take place.  Temperature is a property of the air, so if new air moves in to your location with a different temperature, that will strongly determine the local surface temperature.

You mention the polar vortex, which is a often misused term which has recently come into popular vocabulary.  The polar vortex is primarily a mid-upper atmospheric circulation above the poles.  When you hear it on TV you are most likely hearing it misused and the generally just mean a really strong cold front with a (perhaps unseasonably) cold arctic continental airmass behind it.  A front, in simple terms, is an enhanced surface temperature gradient that separates airmasses with different properties.  The key feature is a strong temperature gradient -- a relatively large change in surface temperature over a relatively small distance.

This goes back to the earlier discussion on the primary contribution to radical changes in temperature being the wind bringing in air with a different temperature.  When a cold front arrives, it is being driven by the wind and this is an example of the transport of temperature by the wind (cold air advection).

In summary, air affects local surface temperatues so strongly because temperature is a property of the air.  If the air currently around your town is replaced by new air, that air will have its own temperature and so you will experience a change in temperature -- if the new air is radically colder, you will experience a radical temperature change.


What would the precursors to a repeated Lake Toba super eruption? Lake Toba, Indonesia is a supervolcano which was the site of

  a massive supervolcanic eruption estimated at VEI 8 that occurred 69,000 to 77,000 years ago, representing a climate-changing event. It is the largest known explosive eruption on Earth in the last 25 million years.

It is believed by some scientist to have caused the Toba Catastrophe Theory, resulting in a 'bottleneck' in early human populations.

The region is most definitely still very active with continuing seismic and volcanic activity.

What would be the precursors to a repeat of a Lake Toba super-eruption?

Massive, caldera-forming eruptions like the one at Toba usually happen at large silicic systems. At such systems, we expect a surface uplift as the pressure builds in the magma reservoir. This can be measured by radar interferometry (InSAR). It is the case at Laguna del Maule volcano (Chile), were uplit up to 28 cm per year has been measured by InSAR (Feigl et al. 2014). A similar pattern would be observed at Toba if a magma reservoir was being replenish. However:

We don't know the timescale needed for overpressure, thus eruption, of the reservoir. It depends on many parameters, such as reservoir size and depth, strength of host rock, rate of fresh magma supply...
We don't even know if such uplift will lead to an eruption. The magma could very well be intruded into the crust (in the form of dikes and sills), releasing the pressure in the reservoir. The uplift would then cease without an eruptive crisis.


How accurate is a tipping-bucket rain gauge? My question is simple - how accurate is a tipping-bucket rain gauge?

I have read about what causes the errors (wind, bucket mechanics for extreme events, ...) and I know the accuracy is strictly related to the rain rate, in the sense that, e.g., TB gauges tend to highly underestimate in extreme conditions.

However, I'd like to have a number, say, errors around +-25%. I know the number itself won't be accurate, it's just to have the order of magnitude. References appreciated, since I myself looked around with no success :-)

The following simulation results shows that the Tipping Bucket estimates suffer from significant errors if based on time scales less than ten to fifteen minutes.

Comparison of Tipping-Bucket Error Statistics:

(Source of above diagrams)

  In this study we attempted to characterize the errors associated
  with tipping-bucket rain gauges when used to provide rainfall
  intensity estimates at small temporal scales. The main source of the
  TB gauge sampling error is its sampling mechanism and its inability
  to capture the small temporal features of the rainfall time series. We
  found significant error levels in the 1-min estimates especially at
  low rain rates, but we also found that as the time scale of the
  computed rain rates increased, the error decreased substantially. With
  time scales longer than 15 min, the error becomes negligible. The
  gauge’s performance and its associated errors are sensitive to the
  applied sampling interval and the bucket volume. Therefore, we
  recommend sampling intervals on the order of 5–10 s, along with a
  bucket size no larger than 0.254 mm (0.01).  Our analysis wasbased on
  rainfall observations that were mostly dominated by convective storms
  with few stratiform events. Similar analysis may be needed to
  investigate the scope of applicability of the developed formulas under
  different climatological regimes. However, the formulas serve as a
  first-order approximation that can be used in practical applications. (Source)


Equinoxes and solstices: start of the season or mid-season? In the United States, the upcoming autumnal equinox is marked on most calendars as the "first day of autumn." Similarly the solstices are commonly called the "first day of summer" and "first day of winter." However in most other languages -- and even in older discussions in English -- the solstices have names like "Midsummer's Day" and "Midwinter's Day."

Is there some sound reason (e.g. typical temperatures, asymmetrical sunrise/sunset times, thermal inertia, etc.) to consider a solstice as the first day of a new season, rather than the middle?

Also (perhaps less on-topic) is there any record of when the change in nomenclature took place in the U.S.? Are there similar discrepancies in other English-speaking countries or in other cultures?

There are three main ways to reckon seasons:

Solar. The 3 months with the greatest insolation are designated summer, so the solstices and equinoxes fall in the middle of the season. In the Celtic calendar, summer started on 1 May; in the traditional Chinese calendar it is 5-7 May. The cultural 'Midsummer' and 'Midwinter' festivals reflect this.
Astronomical. The solstices and equinoxes are the starts of the seasons, with summer starting on about 21 June (it varies). Its use dates back at least to the Romans, and it's used in most western cultures today (apparently not in Russia, Australia, or New Zealand).
Meteorological. This is what professional meteorologists use (e.g. UK Met Office), and is based on the prevailing weather on land at mid-latitudes. Seasons are 3 months long and summer starts on 1 June.

I've tried to illustrate the relationships with insolation and temperature here:

There are some other ways too:

Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.

Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:

The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.


Is there any rule of thumb to decide the indentation hardness test? How to decide whether Brinell Hardness test, Rockwell test or Vicker's test is to be applied as far as grain-size is concerned? Is there any rule of thumb to decide the type of indentation hardness test?

No. Grain size is not a factor . Test method depends on the size and shape of the test piece and why the test is being done. Vickers can use different loads so can be used for very small areas and the microscope can be used to select certain locations such as a carburized layer. Rockwell can test larger specific locations such as the components of a weld HAZ. Brinell hits a fairly large area ,it also requires significant thickness like 1/2 ". Vickers and Brinell results are based on the area of the impression , while Rockwell measures the depth of penetration. These comments apply to standard bench testers , portable testers is a different game.


What are the causes of the supercontinent cycle? Throughout geologic history, Earth's continents have broken apart and come together to form supercontinents multiple times, in a somewhat regular period, known as the supercontinent cycle. The length of a cycle is estimated to be 450 million years, with the most recent supercontinent Pangaea forming about 300 mya.

What processes cause this cycle and length? That is, why hasn't continental drift stabilized to some equilibrium (one supercontinent, or separate continents), or why can we observe regular periods? Is the cycle due to change in the future, and why?

Please take into consideration that I am not a specialist of plate tectonics, just a paleontologist.

Although this cycle is often nicknamed the Wilson cycle (probably because of Wilson, 1966), the idea that supercontinent formed cyclically every 440Ma was advanced by Worsley et al. 1984 (see review on the subject by Nance & Murphy 2013).
The mechanism they hypothesize for the breakup of the supercontinent is the mantle heat flow accumulating below the supercontinent while the formation of the supercontinents are bound by the cooling effect on the density of the oceanic lithosphere (see also Nance et al. 1988): so basically, heat accumulate below the insulating supercontinent until it causes it to break up, thus creating rifts and a new oceanic lithosphere, which, with age, cool down and thus become more dense making it more prone to be subducted by the continents (if I understood correctly).
As to "why ca. 450 Ma?" this has probably to do with the cooling speed of the oceanic lithosphere, I would assume.
Another important point: although there are evidences for the existence of a supercontinent breaking-up at 300 Ma (Pangaea), at 750 Ma (Rodinia), at 1.6 Ga (Nuna or Columbia), etc., there are also evidences for an absence of supercontinent at 1.2 Ga (see Pisarevsky et al. 2014), hinting that this cycle is maybe not that regular.

References:
Nance & Murphy, 2013. Origins of the Supercontinent Cycle. Geoscience Frontiers, 4(4): 439-448.
Nance, Worsley & Moody, 1988. The Supercontinent Cycle. Scientific American, 259: 72-79.
Pisarevsky, Wingate, Li, Wang, Tohver & Kirkland, 2014. Age and paleomagnetism of the 1210 Ma Gnowangerup–Fraser dyke swarm, Western Australia, and implications for late Mesoproterozoic paleogeography. Precambrian Research, 246: 1-15.
Wilson, 1966. Did the Atlantic close and then re-open?. Nature, 211: 676-681.
Worsley, Nance & Moody, 1984. Global Tectonics and Eustasy for the past 2 billion years. Marine Geology, 58: 373-400.


How can isostatic compensation of the crust be reconciled with a relatively strong upper mantle? As I understand it, the outer portion of the Earth can be divided into the crust and mantle on chemical grounds (separated by the Moho), or into the lithosphere and asthenosphere based on mechanical properties. The lithosphere is relatively strong and includes the crust and the upper area of the mantle. The asthenosphere below is relatively weak and deforms by diffusion creep due to the high temperatures, though the lithosphere/asthenosphere boundary is gradual (since it is temperature dependent).

However, isostatic compensation for mountain ranges on continents etc. requires the mantle directly below the crust to flow. However, this is part of the lithosphere and is relatively strong - I would expect that isostatic compensation occurs for the lithosphere with respect to the asthenosphere. Is it the case that although relatively strong, this area of the lithosphere (the mantle just below the crust) is still sufficiently plastic to allow isostatic compensation of the crust?

Because it is not the strong portion that gets displaced. The mantle just below the crust bends, just like the crust above it, together they make up the lithosphere,  It is not the thing being displaced it is the thing doing the displacing. The asthenosphere is being displaced.

Your image is missing  something important.

Images courtesy of http://www.physicalgeography.net/fundamentals/10h.html


Identification of rock formation along Wales coast I hope that you can help me, my wife and I visited National Trust - Stackpole, Pembrokeshire last week where I took a couple of hundred photos.
I've attached a photo of the coloured cliffs there.  For me to enter this into one of our club competitions I need to know the correct terminology for the rock formation.

.

I hope that there is a someone who could let me know

This is Marloes Sand Beach, a classical fossil site. The nicely colored rocks are sandstones of the Silurian age (around 425 million years old). The different dipping angles of the sandstone layers are a result of tectonic processes, which were folding the rocks.

Further information about Marloes Sand can be found here


Find planetary temperature I’ve asked this on Worldbuilding, but can anyone find/make me a formula that can be used to predict the mean temperature of a planet, while factoring in greenhouse effect?

What you are looking for is called a zero-dimensional climate model. The equation without the Greenhouse effect is simple, though with a lot of simplifications, one with a very crude, linearized, Greenhouse effect is possible.


converting segd data to SU format using seismic unix I tried to convert segd format to su format using seismic unix by below command:

segdread tape=1.segd > 1.su

but I have an error:

segdread: Error with length of first record
    ... first record = 270320 bytes differs from ((1 + n_gh + n_str * (n_cs + n_sk) + n_ec + n_ex) * 32)
        with n_gh=2, n_str=1, n_cs=16, n_sk=0, n_ec=32, n_ex=32

I would be grateful if you could help me to fix it.

SEG-D is an uncommon format. From my experience, here is how you need to approach this problem. You can't easily jump straight from SEG-D to SU. I've had extensive experience with SU and the best methodology is to first take your current seismic data type (SEG-D) and convert to SEG-Y. Only after converting to SEG-Y format can you then jump to SU.

So, here is an outline and workflow of a solution:

  1.) Download and use this tool for SEG-D to SEG-Y format: http://users.chariot.net.au/~witek/segd2segy.htm

  2.) Now that you have all your SEG-D data converted to SEG-Y data, use the following BASH  script to convert a single SEG-Y file to SU:

#!/bin/bash
echo Provide Input File: ;
read sdata;
segyread tape=${sdata} verbose=1 endian=0 segyclean > ${sdata}.su
echo "New File: ${sdata}.su";
rm -rf binary header;
echo Done.;

***Keep in mind that - based on the type of machine you have - endian may need to be set to 1.


How good were climate models of the 1990s at predicting the global temperature trends of the 2000s/2010s? Was there a significant bias between the ensemble of climate models and the long-term temperature trends?

What about spatial patterns?

You might take a look at the Technical Summary of the most recent IPCC Assessment Report (5).
Thematic Focus Element #3 is "Comparing Projections from Previous IPCC Assessments with Observations"
It says:

Global Mean Temperature Anomaly
Relative to the 1961–1990 mean, the GMST anomaly has been positive and
larger than 0.25°C since 2001. Observations are generally well within
the range of the extent of the earlier IPCC projections (TFE.3,
Figure1, middle left) This is also true for the Coupled Model
Intercomparison Project Phase 5 (CMIP5) results (TFE.3, Figure 1;
middle right) in the sense that the observed record lies within the
range of the model projections, but on the lower end of the plume. Mt
Pinatubo erupted in 1991 (see FAQ 11.2 for discussion of how volcanoes
impact the climate system), leading to a brief period of relative
global mean cooling during the early 1990s. The IPCC First, Second and
Third Assessment Reports (FAR, SAR and TAR) did not include the
effects of volcanic eruptions and thus failed to include the cooling
associated with the Pinatubo eruption. AR4 and AR5, however, did
include the effects from volcanoes and did simulate successfully the
associated cooling. During 1995–2000 the global mean temperature
anomaly was quite variable—a significant fraction of this variability
was due to the large El Niño in 1997–1998 and the strong back-to-back
La Niñas in 1999–2001. The projections associated with these
assessment reports do not attempt to capture the actual evolution of
these El Niño and La Niña events, but include them as a source of
uncertainty due to natural variability as encompassed by, for example,
the range given by the individual CMIP3 and CMIP5 simulations and
projection (TFE.3, Figure 1). The grey wedge in TFE.3, Figure 1
(middle right) corresponds to the indicative likely range for annual
temperatures, which is determined from the Representative
Concentration Pathways (RCPs) assessed value for the 20-year mean
2016–2035 (see discussion of Figure TS.14 and Section 11.3.6 for
details). From 1998 to 2012 the observational estimates have largely
been on the low end of the range given by the scenarios alone in
previous assessment reports and CMIP3 and CMIP5 projections. {2.4; Box
9.2}

I've attached an image as well from that summary:

Estimated changes in the
observed globally and annually averaged surface temperature anomaly
relative to 1961–1990 (in °C) since 1950 compared with the range of
projections from the previous IPCC assessments. Values are harmonized
to start from the same value at 1990. Observed global annual
temperature anomaly, relative to 1961–1990, from three data sets is
shown as squares and smoothed time series as solid lines from the
Hadley Centre/Climatic Research Unit gridded surface temperature data
set 4 (HadCRUT4; bright green), Merged Land–Ocean Surface Temperature
Analysis (MLOST; warm mustard) and Goddard Institute for Space Studies
Surface Temperature Analysis (GISTEMP; dark blue) data sets. The
coloured shading shows the projected range of global annual mean near
surface temperature change from 1990 to 2035 for models used in FAR
(Figure 6.11), SAR (Figure 19 in the TS of IPCC 1996), TAR (full range
of TAR, Figure 9.13(b)). TAR results are based on the simple climate
model analyses presented in this assessment and not on the individual
full three-dimensional climate model simulations. For the AR4 results
are presented as single model runs of the CMIP3 ensemble for the
historical period from 1950 to 2000 (light grey lines) and for three
SRES scenarios (A2, A1B and B1) from 2001 to 2035. For the three SRES
scenarios the bars show the CMIP3 ensemble mean and the likely range
given by –40 % to +60% of the mean as assessed in Chapter 10 of AR4.