Seismometer records ground displacement or acceleration I believe Seismometers record ground displacement. However, I have also read in certain articles that this can be ground displacement or acceleration depending on the frequency of the seismometer. Could someone kindly elaborate on how a seismometer works.

A geophone (type of seismometer) contains a coil of wire, wrapped on a mass, surrounded by a magnet. As the Earth moves we assume the mass stays still due to inertia and this changing magnetic field will produce a current in the coil of wire. This current is measured as a voltage and relates to the rate of change of displacement of the Earth with respect to time or:

$$
v \propto \frac{dx}{dt}
$$

Where v is voltage, and $\frac{dx}{dt}$ is the velocity of ground motion. Correct me if I'm wrong but the difference in seismometers eg. MEMS accelerometers (acceleration) vs geophone (velocity) is their frequency response.

https://www.crewes.org/ResearchLinks/GraduateTheses/2008/Hons-MSc-2008.pdf


Is the atmosphere becoming thicker? Is the atmosphere getting more dense with various gases, car pollution (200 million cars just in North America), factory pollution, more water vapor and denser cloud cover? If so could a "thicker" atmosphere act like a lens and magnify the Sun's rays to an intensity a higher than what it should be?

No, the atmosphere is not becoming thicker.

If anything at all, the atmosphere is getting thinner, but only on very long time scales.  Planet Earth very slowly loses parts of it atmosphere due to atmospheric escape, either to space or to the solid Earth.  Historical atmospheric pressure is hard to determine, but billions of years ago, it might have been much thicker than it is now, in particular with a lot more greenhouse gases.  One clue is the faint young sun paradox; we know there was liquid water at a time the solar output was 20% less, which would require so much greenhouse effect that the total atmospheric pressure must have been much higher.  But the jury is still out on that one.

The atmosphere is not becoming significantly denser, either.

The concentration of gases that we are adding to the atmosphere is typically measured in parts per million (ppm) or parts per billion (ppb).  The effect of adding to this is small compared to the natural variability in atmospheric surface pressure / density due to weather and other effects.

The atmosphere does not act like a lens.


solar irradiance/radiation difference I currently read a few papers and one of them stated to forecast solar irradiance using measures of solar radiation.
I hope this question is not trivial as I'm actually from germany, but if there is a specific difference between these two terms I would be glad if someone could explain it.

Solar irradiation is a measure of the energy delivered by the sun per unit area, watts or joules per square metre for example.. It is often recorded over a specific time period, so it is very much to do with solar radiation, but not exactly the same thing.


Does clearing snow contribute to climate change? I've been reflecting on climate change and pondering how much of it is truly man-made. Anyone who's shoveled a walkway know that the snow melts faster beside the walkway than it does in the middle of your yard. This is because you've exposed the ground which can absorb the sun's heat. Whereas the snow in the yard reflects it.

The same is true of glaciers: They melt away from rock faces (ie, terminal morrains, bergschrunds, etc.), and as more of the Earth's surface is exposed, the more heat the surface of the Earth can absorb, and the faster the rest of the Earth's ice can melt.

Consider the combined surface area of all the roads and parking lots that are cleared of snow each winter (as well as the increased number of roads and parking lots which capture a lot of heat each year). Snow clearing to the scale as is seen in recent decades far exceeds what has been accomplished in the past. Even as recently as the early 20th century people still made their way around on top of the snow in sleighs.

How much of a contributor to climate change can be attributed simply to roads and the relatively modern practice of snow removal?

Urban areas, where most snow clearing is done, are heat islands already, so it would be tough to disentangle the effect of clearing snow off roads.  Whitewashing black asphalt is one of the strategies being tried to reduce the heat effect in the summer, though, and black asphalt is seen as a big factor in heat islands, so it seems reasonable that exposing black pavement in winter would also have some impact, but detailed studies so far have mostly focussed on deadly summer heat, not winter effects.


Great Lakes - cookie cutter clouds On 2014-07-10, in the afternoon, the GOES East satellite image in the visible showed a mass of cloud in central North America. However, in the middle, the Great Lakes stood out in a most extraordinary way, since they were almost completely free of cloud. It was like a cookie-cutter. The cloud followed the outline of the lakes precisely. Why is that?

Here is a second view, from MODIS data: MODIS image of the Great Lakes

There are a couple reasons for this.  First, Lake Michigan is still cold this time of year, relative to the land that surrounds it.  Warm air flowing over the lake will exchange heat and cool, reducing its buoyancy, which will alter the heights at which clouds will form and inhibit lift for surface parcels to achieve that height.

That helps explain the cloudlessness over the lake, but this extends a bit inland as well.  I'd have to do a little digging to verify this, but just from that image it looks like that demarcation of cloud/no cloud around the lake is a sea breeze front (or in this case, a lake breeze).  The daytime lake breeze flows inland from the water, rises over land and then flows back to the lake where it descends.  This will promote clouds where the circulation rises and inhibit them where the circulation falls.

There may also be an orographic effect on along the northern portion of western MI shore, as there are large sand dunes and hills in that area.  The upslope flow could be the reason the clouds hug that shore a bit closer than other regions around the lake.

In summary, that looks like a really well defined lake breeze circulation, which explains the shape and location of the clouds.


Is there a name for this weather phenomenon? I was wondering if there was a name for the effect I’ve noticed over a lake in really cold weather.  You can see white wisps over it, which I think is mist from the lake rising into the air and condensing in the cold, sort of like breathing out in cold weather.

It is called frost smoke or steam fog (or a half dozen other names), sea smoke is the same effect just over the ocean.

It is caused by  high moisture saturation and strong temperature differences between the water and the air. http://glossary.ametsoc.org/wiki/Steam_fog


Will a nuclear bomb stop an earthquake from happening? I was recently watching the San Andreas trailer and a thought occurred to me as to how best to prevent earthquakes. I figured, why not nuke it? My professor said that it's possible for nukes to stop hurricanes so it got me thinking as to what else nukes could stop (besides humanity). The friction that develops is because of two plates moving against each other, right? So if you used enough nuclear bombs to completely obliterate a plate, the other plate wouldn't have anything to rub against, correct?

A nuclear explosion in the subsurface will result in ground motion which in theory can trigger an earthquake (due to passage of dynamic waves) if a locked fault has already accumulated sufficient strain over the last few decades/centuries due to slow motion of plates.

Having said that all the nuclear stockpile in the world is not enough to obliterate even a small part of the plate boundary. The 1960 Chilean earthquake released accumulated strain energy of the order of 3 Gigatons of TNT or 200 Gigatons of TNT equiv or 12 million Hiroshima type bombs (Numbers are based on calculations by JC Lahr and are available at http://www.jclahr.com/alaska/aeic/magnitude/energy_calc.html)

So yes, an explosion in the subsurface can probably act as a trigger for an impending earthquake but it cannot stop if from reoccurring again after few decades/centuries.


Why RBF is gridless and kriging is not? I read about it somewhere in a paper.  Why is kriging not gridless if I can krig points in space? Whats is the big difference from RBF?

Kriging IS gridless. In fact Kriging and RBF are formally equivalent. The reason kriging tends to used on grids is more historical in the oil industry than anything else. The original papers in geostats made no mention of grids. They became popular in the oil industry because a) Flow simulation is generally done on a grid  b) upscaling is non linear (so the linear kriging change of support that was developed for mining was not applicable)..and modelling on a fine grid with flow based upscaling became the norm. c) People were more interested in simulations than estimations...and upscaling becomes even more important in this case


What are the most similar Earth analogues to Mars' seasonally recurring slope linea? Recurring Slope Lineae (RSL) on Mars are suggested to be water that seasonally melts from underground ice and sublimates through the sand and dust to darken the surface. Slowly flowing downhill to form the lines.

I'm not sure it has been determined that it is water and not CO2. But assuming that it is water (brine), what are the nearest analogues on Earth to a Martian RSL environment? Are there any RSL's on Earth? What kind of life thrives in them?

Here is a brief video of how they change seasonally.

Analogues to Mars Recurring Slope Linea (RSL) is a current study topic in  Antarctica (Dry Valleys). On Earth, analogues are known as water tracks, which are linear zones of higher moisture along slopes in polar regions where water transit during snowmelt. This figure from Ward Hunt Island (NU, Canada) show well developed and typical water tracks.

Source:  Water tracks in the High Arctic: a hydrological network dominated by rapid subsurface flow through patterned ground Michel Paquette et al. Arctic Science, 2017, 3:334-353, https://doi.org/10.1139/as-2016-0014

On Earth, as shown on this picture from Ward Hunt Island, water tracks are from snowmelt and thus not from brine, unlike in Antarctica where brine water as runoff is common.

  Water tracks share many morphological and seasonal characteristics with RSL, including downslope propagation of linear or branching patterns of surface darkening, growth during spring/summer seasons, and fading during winter

and

  Saline fluids associated with water track flow are sourced by snowmelt, shallow ground ice melt, and the direct conversion of atmospheric water vapor into brines through high-elevation salt deliquescence

from Joseph Levy, Hydrological characteristics of recurrent slope lineae on Mars: Evidence for liquid flow through regolith and comparisons with Antarctic terrestrial analogs, Icarus, Volume 219, Issue 1, 2012, Pages 1-4

This mean that this Antarctica analogue to Mars RSL have several sources of water (meltwater, shallow ground ice and atmospheric water vapor deliquescence).

Comparatively, on Mars, source for the RSL have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow groundwater. And more recently, from deep aquifers  through fractures (impact, tectonic) such as shown in this study at Palikir Crater inside Newton Crater Basin and Triolet Crater.

Nevertheless, there is entire sessions at the Lunar and Planetary Science Conference dedicated at Martian Brines (MARTIAN BRINES:  OLD SALTS AND NEW VIEWS) and RSL or actual slope processes (THING FALL DOWN GO BOOM:  MARS DOWNSLOPE MOTION). While models are getting better and more elaborated, there is still opposing views and this dynamic field of study is moving very rapidly.

Finally, life found in brine on earth are halophiles, a type of extremophiles - but this is a whole topic in itself.


At what rate are the polar ice caps shrinking? At what rate is loss of polar ice caps occurring? Do we have enough data to distinguish a meaningful trend? If we look at the trend since we have satellite measurements (40 years or so), is that enough?

It's important to identify which ice.   Polar bears are arctic, and they hunt in large part on sea ice.   Arctic sea ice is decreasing and the most common point used for the disappearing arctic ice is the arctic sea ice minimum, meaning, the yearly low point, usually late September, so by that definition, we'd have an ice free arctic, you know, for a few days, but ice will form again as winter kicks in.

That loss of arctic sea ice probably won't kill "all" the polar bears but it would likely kill a fair share of them, making their hunting more difficult.   This has already started and will probably continue to get worse.

Also, arctic sea ice has virtually nothing to do with flooding cities.    Flooding of cities has to do with melting of glaciers on land - essentially water that isn't currently in the oceans but as it melts it adds to the oceans.   Also, warming oceans expand, so warmer water increases flooding too.

As far as the timing of the ice free arctic minimum, it's very hard to predict due to natural variability year to year, but 40 years doesn't seem far off - at least, looking at the trend, but there's also no guarantee the trend will be consistent.

It's gone from the 8 million square miles plus range into the early 70s into the 4s and 5s millions recently, dipping below 4 million in 2012 but rising back above that 2013-2014.  2015 we haven't hit the minimum yet so it only goes up to 2014 for yearly minimum.

If there's a mechanism that helps retain ice, such as cold water currents near the pole or a weakening of the warm Atlantic gulf stream, that could extend the ice quite a bit longer.   It could also happen quite a bit sooner than 40 years if we have a few more years like 2012 or 2007, each year showed a significant and unexpected reduction in minimum ice cover compared to previous years.

A rather famous sea ice prediction was done by Professor Wieslaw Maslowski who in 2007 predicted we could see an ice free arctic by 2016 plus/minus 3 years - which Al Gore later quoted and said "there is a study that says we "could see" an ice free arctic by 2013 and the deniers have loved referencing and misquoting that quote ever since.   I think Maslowski's predictions moved later a few years shortly after, but nobody remembers that.  Everybody remembers 2013, though he actually said 2016 plus/minus 3 years.    Ironically, we could still see a big sea ice drop by 2019 and in that case, Maslowski wouldn't be far from wrong, but his is still one of the most made fun of predictions in all of science.

Maslowski's estimate was more aggressive than anyone else, but that doesn't mean he did bad work.   I've never looked into the specifics, but there's a ton of articles, some less friendly than others, on his 2016 plus/minus 3 years (which some people simply refer to as a failed 2013 prediction)  Here's one

Also an ice free arctic in late summer means sea ice will still form in fall and stay through the winter and spring, so Polar bears will still likely have some sea ice to hunt from long after the "ice free arctic" happens, but the warming in general makes their survival more difficult and that's likely to continue and get worse.

As far as flooding cities, sea ice doesn't raise sea level, so that's a different subject.   That has more to do with the melting of glacial ice on land, primarily Greenland and Antarctica.    The melting of entire glaciers is on a whole different timescale and the melting of all of Antarctica might never happen, even in worst case global warming models, at least, it might not happen until Antarctic drifts off the south pole into warmer waters, but that's several million years away.    Parts of the Antarctic glacier could melt and parts have already melted, but only a teeny tiny percentage so far.

The IPCC forecasts for sea level rise includes both melting glaciers and warming and expanding oceans and they predict maybe 2-3 feet by 2100 (or 1-3 feet, depending on who you ask).   Compared to that, if all the glaciers melted, we could expect a sea level rise of about 230 feet, so clearly, nobody is predicting glaciers will melt completely anytime soon - not for many hundreds if not thousands of years, but those predictions are even more difficult.

But like sea ice predictions, glacier melting predictions are hard to estimate by trend cause the ice can give way more quickly or more slowly depending on a variety of factors.   Precise predictions are enormously difficult and not guaranteed to follow trends from the past.

There's no shortage of articles to be found on sea level rise as well.

This is, of-course, one of the problems that a good climate scientist faces.   "When will that happen?" - The honest answer is, we don't know, we can predict about when it's likely to happen, so the skeptic says "so you don't know."- which misses the point entirely.    There's no question bad things will happen as a result of climate change.   It's just hard to predict exactly what will happen or exactly when.


Why are tropical cyclones forming earlier in the North Atlantic basin? This tweet from Brian McNoldy includes a graph suggesting that tropical cyclones are typically getting named earlier in the year in the Atlantic:

What are the causes for this?

The shift appears to match up to a large change in the number of cyclones that peak as tropical storms in the early part of the TC season (here defined as March-July), shown by the blue (tropical storms) versus purple (hurricanes) in this graph (made using the HURDAT2 dataset from NHC):

It appears that a large part of the increase in tropical storms lines up with a coincident decrease in tropical depressions (shown in green).
It's notable that tropical depressions only start appearing in the dataset starting in 1963.  I don't know it for a fact, but because the timing lines up with the advent of satellite weather data it suggests TDs may have been added once satellite offered a better picture to find and analyze weaker systems.
Therefore, it would seem one possible theory might be that there was an initial predilection to hold less organized systems at tropical depression status, but as data has increased from hurricane hunters, satellite resolution upgrades, and additional/more rapid data reports, more of these systems were progressively graded as tropical storms.

Looking into the data at full resolution, it appears the trend may be greatest in weak and moderate tropical storms (focus on the lesser change in dark blue colors, and in most of the pink bands):

Does this pattern also match the rest of the year?

I'd suggest yes and no.  Here's the corresponding graph for the late parts of the season:

So it looks like:

Tropical storms are still on the upswing in the late season, just not nearly as much (the trend line for early season goes from 0.5 to 2.5, for late season it goes from 1 to 2).
Cyclones maxing as tropical depressions have also sharply dropped away in the late season, closely matching the early season pattern (indeed, late season TDs were less to start with, in parallel with the smaller TS increase).
Also note that the number of hurricanes themselves have increased in the late season by over 50% (while remaining fairly constant in the early season).

You can look into the trends in each storm type in the following set of graphs:

TD/TS/HUR 50 years: early, mid, late, total
TS/HUR 100 years: early, mid, late, total
By strength full history: early, mid, late, total
(Note these analyses don't include 19 unnamed TCs in 1967-69 where no intensity is given in HURDAT)

Many certainly do propose climate change as a possible mechanism to shift the intensity and numbers of TCs.  Quite a few warming modeling studies have suggested there would be an increase in tropical storms.  It appears that this paper (Kunkel et al 2009) has some interesting discussion into the topic in the hurricanes and typhoons section.  The conclusion of:

  In summary, robust detection of trends in Atlantic and western North
  Pacific TC activity is significantly constrained by data heterogeneity
  and deficient quantification of internal variability. Attribution of
  past TC changes is further challenged by a lack of consensus on the
  physical linkages between climate forcing and TC activity. As a
  result, attribution of any observed trends in TC activity in these
  basins to anthropogenic forcing remains controversial.

seems to offer a fair reflection of the overall situation as of now in tropical cyclones and possible connections to climate change.  There's certainly plenty of debate over how significantly climate change is influencing the shifts seen; some will draw more conclusions than others.

Regardless of whether it's due to changes in identification practices or other causes like human climate change, it's clear there are more named systems in the early season, and that would certainly often result in an earlier first name.

On the other hand, is it due particularly to sufficient ocean temperatures existing earlier in the season over wider areas?  It would seem odd that such a change would mostly impact only the number of tropical storms, and not change the number of hurricanes.  But further analysis should certainly be done and the other MPI factors.

I do offer one final small postulate, based both upon these graphs and upon my own perceptions... perhaps at least a small part of the upswing in tropical storms might be due to an increase in the buzz at the start of each new year.  It seems there is more and more talk and "excitement" and interviews as each year get started.  And I wonder if that may prime forecasters to make earlier designations sometimes.


How much water will flow into the Caspian Sea if it is connected to the World Ocean? I wonder how much benefit would a hydroelectrical project built on this inflow bring.

There are projects to fill up the Erie, Salton, Qattara and the Dead Sea. But for the Caspian, there is only a proposal for a Panama-like canal with locks - https://en.wikipedia.org/wiki/Eurasia_Canal.

This picture gives the scale, but not the numbers.

https://www.floodmap.net/?ll=43.334232,43.460796&z=5&e=0

I think the Soviets might have done some calculations.

Welcome to earth science stack exchange !

People living along the banks and flat hinterlands in the flooding areas will not be amused of such an enterprise. I would also say that sacrificing all that potentially fertile land might trigger protests. And as the Caspian water table reaches global sea level, power production will go down.

The mentioned canal would need locks to keep the water from flowing from the Black Sea to the Caspian because the Black Sea only has a ~50m layer of fresh water over a huge basin of anoxic salty waters that contain gases from the decay of organisms. The "interface layer" is unstable, raising it via an outflow of fresh water could eventually cause a release of gasses like hydogen sulfide in a larger scale. Also, the anoxic water below the boundary layer is highly corrosive to machinery.

Power generation with water in such a large scale is cheaper and more sustainable along fresh water currents or in tidal power stations.

Now that was not a real answer, that would have had some math like flooded area  * height difference(28m) * fudge factor for topography and a division by the cross section of the inflow to get a feeling for the time it would take to fill the pan, but it has some background on the setting we're talking about.

Hope that helps, if not, let me know :-)

Edit: i just realized that much of my answer is somewhat nonsensical because there is a water divide between the two water bodies from where it goes downhill to both sides. While a closed pipe could be imagined for a constant flow and to drive turbines, it doesn not seem very practical. But that's engineering, not my strength ...


Where can I find a list of active mining claims in my area (Northern Nevada)? I live in the Reno/Sparks area and have started rockhounding.  One aspect I am quickly realizing is that many sites are actively being mined.  In order to avoid running afoul of local laws, I would like to get a map of active mining claims and potentially a map of expired claims.  Expired claims would be helpful for finding interesting sites.

You may want to check this out ESRI open data http://opendata.arcgis.com/ if this is what you were looking for.

One another thing is that you might want to contact BLM's Nevada State Office.

http://www.blm.gov/nv/st/en/prog/minerals/mining.html

They may have the data if they are on the Public lands. I am not sure about the private lands for that.


How can I tell the difference between granite and syenite? (I'm not a geologist, just helping my kids collect rocks).

It is confusing - both rocks are commonly pink overall. But, granite has abundant quartz, syenite has no quartz to very little. Quartz will be the grey translucent mineral that looks just like a blob with no distinct shape.

You can use this website: https://www.virtualmicroscope.org to see examples of syenite and granite (use the search box).


What are the conditions for an ionosphere to form? I already asked this on Astronomy SE but did not receive any answer so far:

What are the prerequisites for an ionosphere to form?
For example, can a planet without any atmosphere have an ionosphere?
What about a planet that is very far from its sun, is there a point where the solar wind is too weak to create an ionosphere?

In one sentence, what are the conditions for an ionosphere to form on a given planet?

Most of the visible matter in the universe consists of ionized matter (I'm citing thise from the publicly available lectures from R. Fitzpatrick and the monograph from J.A. Bittencourt - Introduction to plasma physics). This is true independent whether you measure it by mass or by number of atoms and molecules.

Why is this important?
As I see it the ionosphere is the part of the atmosphere that connects the electrically neutral atmosphere at high pressures and the low-pressure ionized regions of the universe.
Thus, any planet will have firstly an ionisphere and secondly maybe an electrically neutral region that we call "atmosphere". There is a caveat here, as the ionosphere doesn't have to be fully ionized, just have enough electrons and ions floating around to act as a plasma.

Why is gas ionized at low pressures?
The amount of ions that fly around in a certain volume is not only a function of the amount of freed electrons, but also of the amount of electrons that recombine.
The strength of ionization will be a function of the process under consideration. However recombination will be independent of this and be governed by a $\sim n^2$-dependency on the density $n$.
This will generally result in a disproportionally weak recombination as pressure / density decreases high up in the atmosphere. Or in other terms: At low pressures, you can get ionized thermally, by UV-photons, [...] but you don't find a partner anymore to recombine.

Concluding
I've presented a case why every planet must have an ionosphere. Details like the solar wind, distance from the star, it's class and atmospheric variables then control the shape of the entailing magnetosphere and exact height-profiles of ionized species.


Does gravity differ from place to place on Earth Does a particular object have the same weight on every part of Earth or does it vary?

There is an entire field of Geophysics called gravimetry dedicated to measuring the magnitude of the gravitational field.

First, we should distinguish between weight (a force) and gravity (an acceleration). Gravity is the acceleration that Earth gives to objects near its surface due to the gravitational force.

The acceleration of an object near the surface of Earth is due to the combined effects of gravity and the centrifugal acceleration from the rotation of Earth. The resulting acceleration is weakest at the equator and maximum at the poles, with a difference in magnitude of about 0.5%, because the outward centrifugal force produced by rotation is larger at the equator than at the poles.

The standard gravity, $ɡ_n$ or $ɡ_0$, (the expected or mid-range value of the gravitational acceleration of an object near the surface of Earth) is 9.80665 $m/s^2$.

Gravimetry measures and studies gravitational anomalies: local variations in topography (e.g., mountains) and geology (rock density) that cause changes in the gravitational field. These gravitational anomalies are measured with instruments called gravimeters. Rocks with lower density, such as sedimentary rocks, result in negative anomalies.

Another effect affecting gravity is altitude, as an increase in altitude will result in a change in gravity of about 0.03% per kilometer. The maximum difference in gravity is about 2 Gal (0.02 $m/s^2$) from sea level to the top of Mount Everest.

The gravity field of Earth has been measured recently with a variety of satellites (GRACE, CHAMP, GOCE). The resulting data can be used to generate global geoids such as EGM96 (geoid calculator). Gravitational anomalies can be extracted by calculating differences with respect to the geoid. The range of variations is of order ±300 $mGal$ (±0.003 $m/s^2$).

Other factors have a small effect on gravity, such as the gravitational force from the Moon and the Sun that causes the tides. The fluctuations associated with these effects are of order 0.2 $mGal$ (2 $µm/s^2$).


Weight vs. Mass of Clouds I came across a statement online that said that an average cloud has a weight of 1 million pounds. My main question is, does a cloud actually have weight on Earth or was the term "weight" a colloquial expression meaning "mass"?

From my understanding, weight is a force defined as W = mass × gravity, or essentially F = ma. Because the cloud is not falling, its acceleration is 0 -- that is, the acceleration of -9.8m/s2 exerted by Earth's gravity must be counteracted by another equal and opposite force in order for the cloud to be stationary in mid-air, hence the "a" portion of F=ma is 0, so F, and therefore weight, must be 0. Is this thinking correct?

However, when the state changes from gas to liquid -- that is, when it starts raining - the water molecules in the liquid state obviously have weight. So my secondary question is, does a molecule's state change affect its weight? For gases which are "lighter than air", is their weight negative? (I suspect yes because of the force equation).

There are different senses of weight used within branches of physics and engineering. In the strictest physical sense "weight", is given by W = mg. i.e. weight is the force on an object due to gravity alone.  Clouds are not "weightless" in that sense, since they are not far enough away from the Earth to escape its gravitational pull.

The reason that clouds stay up in the sky is, as you say, because they are acted on by an equal and opposite force, namely the surrounding buoyancy of the air. Rain drops are formed by water molecules condensing around some sort of nucleus (a speck of dust, for example). This is triggered by the cooling of the cloud, or lifting to lower pressures, which reduces the moisture-carrying capacity of that particular "parcel" of air.

While the arrangement of water molecules in the cloud make it light enough to be buoyant in the air, the arrangement of those same molecules in rain drops are not – so they begin to fall.

By analogy, I would think of the fact that a ship is buoyant, despite its huge mass, but if you 'condensed' the ship into a lump of steel with the same mass, it would obviously sink. It's weight remains the same however, no mass has been removed, and the value of g has not changed. So to answer your second question, no, phase changes do not affect weight. (Although strictly speaking, in quantum physics it can do – but the amount is negligible here)

Gases which are "lighter than air" will eventually settle in a portion of the atmosphere where the surrounding gases are the same density. They are not weightless, nor do they have a negative weight. The molecules are still experiencing a force due to the Earth's gravity.


How did the Rhine originally look like? (before human intervention) For personal reasons I decided to examine the shape and formation of the Rhine.

Unfortunately though, the Rhine has long been diverted from its original course by human intervention, so I tried to find how it originally looked like prior to this, but without much success.

Does anyone have a source s/he could share with me, or perhaps even describe how and in which way it was diverted from its course?

Thank you very much!

It would help if you'd ask a more clear question -- it's a dynamic river system so it is literally changing its shape every second! The story over long time-scales can be found on Wikipedia: https://en.wikipedia.org/wiki/Rhine#Geologic_history . You can find some more detailed information with some overview maps (esp. Fig 3) here https://www.sedimentologie.uni-freiburg.de/staff/Preusser2008NJG.pdf .

In broad terms, the Rhine in its current state is due to two processes. First of all, the North Sea Basin, i.e., North-West Europe is sinking constantly, providing a great place for rivers to deposit sediments. This is why the Rhine ends up in the Netherlands, because the Rhine can deposit large amounts of sediment without silting up and blocking its own course. Second of all, the formation of the Alps caused a huge potential for sediment transport (realizing that all that rivers really do is transport water and sediment from high points to low points), and the Alpine orogeny furthermore caused the creation of the Rhine Graben. The Rhine thus found the perfect source (high Alpine mountains), channel (Rhine Graben) and deposition space (North Sea Basin).

The story over smaller time-scales also plays over smaller distances. The Rhine changed its course during glaciations for example, because the advancing ice caps pushed sand out in front of them (moraines), in the Netherlands this literally pushed the rivers into a more southern course. The story about these details goes on and on and on! If you have any specific questions, you may want to contact the Geological Survey of the Netherlands or Geological Survey of Germany, they have people who dedicate their lives to studying the past and the present Rhine!


Significance of crystal classes in crystallography I am studying crystals and I learned that there are 32 crystal classes with well-described data regarding symmetries. I have visited a few sites and am having difficulty determining the significance of these classifications. For example, how can any crystal be categorized under these 32 classes? I understand that the information exists somewhere within the symmetry data, but it's difficult to tell what it says; I'm trying to learn a lot of foreign concepts at once (space groups, lattices, symmetry concepts, etc.).

I suppose I'm asking two questions: how can I determine the class a mineral falls under and how were the 32 classes determined?

The references you and @farrenthrope cited (or a good introductory mineralogy text) should have answers.

In brief:

The crystallographic class is significant to mineralogy because it is direct result of the mineral's crystalline lattice (its most fundamental property.) Each mineral can belong to only one crystallographic class.

How can I determine the [crystallographic] class an [unidentified] mineral [specimen] falls under?

You'll need to inspect your specimen and try to recognize the symmetry operations (like rotations and reflections) present in some physical properties of your specimen, commonly the symmetry of euhedral crystal habit, the symmetry of optical properties, or the symmetry of an x-ray diffraction pattern etc. Each crystallographic class is defined by a unique set of symmetry operations.

How were the 32 classes determined?

A combination of observation and mathematics. The law of rational indices was deduced by Haüy (1784, 1801) from the observation of the stacking laws required to build the natural faces of crystals by piling up elementary blocks, for instance cubes to construct the faces of the rhomb-dodecahedron observed in garnets or the pentagon-dodecahedron observed in pyrite, or rhombohedrons to construct a scalenohedron of calcite. Hessel (1830) proved that, as a consequence of the law of rational intercepts, morphological forms can combine to give exactly 32 kinds of crystal symmetry in Euclidean space, since only two-, three-, four-, and six-fold rotation axes can occur.


Do clouds float on anything? Clouds of the same type have such a consistent altitude, it appears as if they're floating on an invisible layer.  Is this true?

Put another way, is there a significant change in air composition at the point  where clouds float/form, or is that altitude determined primarily by air pressure?

Clouds are made up of very tiny liquid water droplets that have small fall speeds.  This means that with just a little bit of upward velocity in the wind, the cloud water can remain aloft and appear to float.  Clouds are not always static blobs -- if you watch some clouds you will see that air can flow through them, condensing into new cloud where it goes in and evaporating into clear air on its way out (easily visible in mountain wave clouds).

The reason clouds tend to have a consistent base altitude is due to how temperature and water vapor behave in the boundary layer.  On sunny, windy days the boundary layer is well mixed and potential temperature and water vapor mixing ratio are constant with height.  With a constant potential temperature the actual temperature will decrease at about 10$^\circ$C per kilometer of height.  With constant specific humidity and decreasing temperature as we go upward this means the relative humidity is increasing.  At some height the relative humidity becomes 100% and we call this height the lifted condensation level (LCL), which will also be the height of the cloud bases.  If surface characteristics are similar across an area, so will be the LCL and this will make all the clouds in the area have similar bases.  You were on the right track with the significant change in air composition, but it is a thermodynamic change with pressure playing a significant role.


Convert air vapor pressure to relative humidity Is it possible to convert Air vapor pressure ($N/m^2$) to relative humidity (%) given a known air temperature?

For example, I know that relative humidity can be estimated as:

$$ RH = 100* \frac{e_{a}}{e_{s}}$$

where $e_{a}$ is the air vapor pressure and $e_{s}$ saturated vapor pressure at air temperature, both with units of mb. Specifically, $e_{s}$ can be estimated by:

$$e_{s} = 6.11*\exp\left(\frac{17.27T_{a}}{237.3+T_{a}}\right)$$

where $T_{a}$ is the air temperature in $^{o}C$.

However, in my case the air vapor pressure has units of $N/m^2$?

How can I use this conversion with these values/units? Is it simply the case of converting $e_{a}$ to mb via:

$$e_{a} (mb) = e_{a} (N/m^{2})*0.01$$

and then using the equation?

$$1\:\mathrm{N/m^2} = 1 \:\mathrm{Pa}$$
$$100 \:\mathrm{Pa} = 1 \:\mathrm{hPa} = 1 \:\mathrm{mb}$$

So yes, you do have valid units of pressure.  And can easily convert it.

The calculation $ RH = 100* \frac{e_{a}}{e_{s}}$ will work as long as the pressures are in equal units, whether Pa, mb, Gbar, etc, since it's just a ratio.  They just need to be the same.  So, you can convert your given $e_a$ into mb by multiplying by 100, convert your $e_s$ into Pa by dividing by 100, or just apply the change in the $e_s$ equation to get $e_s$ in $\:\mathrm{N/m^2}$.

We often use your $e_s=6.11∗exp(17.27T_a/(237.3+T_a))$ in meteorology since we work with pressures in mb (or equivalently hPa).  But indeed the same equation simply works with the constant adjusted to the proper units as:

$$e_{s} = 0.0611*\exp\left(\frac{17.27T_{a}}{237.3+T_{a}}\right)$$

giving answers in Pascals ( = $\:\mathrm{N/m^2}$).

So long story short: yes, all of your equations and reasoning are good, your units are all pressures, they just don't match form.  But you can indeed adjust at any step to account for that.  Simplest is multiplying your $e_a$ (in $\mathrm{N/m^2}$) by 100 or dividing your $e_s$ (in $\mathrm{ mbar}$) by 100 to make them match.

Also of note, the first equation you gave is exactly valid.  The second equation, as you indicate, is an estimation.  The longer version described in this paper would give exact values if you wish, but it looks like you're unlikely to be off by more than 0.1%, so what you're doing is likely fine unless you're need very exacting precision.


Is a billion years of Earth's history missing? Appears that a 4.4 billion-year-old crystal is oldest piece of Earth, and the crystal's chemistry -- specifically, the ratio of oxygen isotopes within it -- suggests that the temperatures on Earth 4.4 billion years ago would have supported liquid water, and therefore perhaps life; Earth is 4.54 billion years old.

According to this xkcd comic, "all the crust older than 3.5 billion years has been recycled into the mantle by subduction."

Is it true that it is possible there is a roughly one billion years of Earth's history with water present that's unaccounted for, and if so, do we have any reason to believe we'll better understand this time in Earth's history?

There was an article in that year's Scientific American, which I've read in the Polish edition. I don't have that paper now, but I think this was that one: http://www.scientificamerican.com/article/the-oldest-rocks-on-earth/

The discovery is described in short here: http://news.nationalgeographic.com/news/2014/02/140224-oldest-crust-australia-zircon-science/. It's about Zircon crystals, that are to be 4.4 billion years old. However, as the article states, the found is not (yet?) widely researched. But it's accepted, there are rocks that are 3.8 billion years old.

The problem is, only a special kind of crystals could survive the conditions on the young Earth, and zircons are one of them. They preserve only some part of the information about the geological history of the Earth. So it's not like that, that nothing has survived the first billion years, it's only a special minerals and rock did. It's not enough to answer many questions that are of top importance, like the origins of the life (but probably no geological sources would ever do, because of the fragility of the speculated pre-cellular life forms). However, we do get a lot of valuable information that will allow us to learn many facts about the Earth's history we didn't know before.


Why should there not be water deep (e.g. below 6 kms) in the Earth's crust? In 1970, the USSR began drilling at the Kola Super-deep Borehole. The target depth was 15,000 meters;

The stated areas of study were the deep structure of the Baltic Shield, seismic discontinuities and the thermal regime in the Earth's crust, the physical and chemical composition of the deep crust and the transition from upper to lower crust, lithospheric geophysics, and to create and develop technologies for deep geophysical study,

according to its Wikipedia entry.
Data obtained from previous seismic experiments had been interpreted to indicate a transition, which was supposed to be from granite above to basalt below about 7,000 meters. However, one of the surprising findings of the experiment was that there was no such change of kind of rock; the difference was metamorphic, now said to be a result of the changing pressure. Also,

...the rock at that depth had been thoroughly fractured and was saturated with water, which was surprising. This water, unlike surface water, must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock.

The source for this entry is Allen Bellows at damninteresting.com (which coincidentally places the supposed granite-basalt transition at "3-6 km"):

Because free water should not be found at those depths, scientists theorize that the water is comprised of hydrogen and oxygen atoms which were squeezed out of the surrounding rocks due to the incredible pressure.

So, why should water not be found at those depths? Based on what assumptions were people surprised to find water there? Or was it only journalists who were surprised?
I'm sorry I don't have more initial research; the truth is I don't know where to start looking. Online searches only give me results like this article at Science Magazine, which is related only because in its case, too, water is supposed to be "squeezed out" of rock, synthesized, as it were from its chemical components. (I asked this question at Codidact.physics, but it seems to need the broader context of geology)
Related: What do continents "lay" on?

There are two reasons for this surprising finding:

Compaction. Once you have high pressures at depth, the less dense material goes up. Take a bucket of water, put sand in it, and squeeze the sand really hard. Water goes up. Then, you'd expect no water at depth of several kilometres.
Even if you somehow had free water at these depths, the expectation is that they would form hydrous but solid minerals. For example, adding water to diopside, enstatite, and quartz leads to the formation of hydrous, but solid, tremolite:
$$\ce{2CaMgSi2O6 + 3MgSiO3 + SiO2 + H2O = Ca2Mg5Si8O22(OH)2}$$
or, adding water to quartz and corundum leads to the formation of kaolinite:
$$\ce{Al2O3 + 2SiO2 + 2H2O = Al2Si2O5(OH)4}$$
Increasing pressure leads to the equilibrium in these reactions shifting to the products, i.e. the solid hydrous phases without any free water.

As to why the water was actually found there, there's still some debate in the scientific community. One of the explanations ("...must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock") is definitely reasonable. The other ("scientists theorize that the water is comprised of hydrogen and oxygen atoms which were squeezed out of the surrounding rocks due to the incredible pressure.") is probably incorrect.
This (paywalled) paper provides an overview in a very accessible language: https://doi.org/10.2138/gselements.16.6.381


Can you measure BOD/COD real time using any sensor? There is a requirement to measure BOD/COD in a wastewater treatment plant in real time. Is it possible? And if so are there any sensors available in the market for it?

COD: Chemical Oxygen Demand
BOD: Biochemical Oxygen Demand

Realtech.com has a runtime monitoring senser solution for BOD/COD Sensor.
My understanding is that COD is straight-ward to measure in real-time but BOD monitoring cannot be done in real-time.   The sensor listed uses a BOD equivalent monitoring technique.

The governing environmental regulatory agencies for a specific waste water facility should have public statement of acceptable BOD monitoring methods.


I found this strange spherical stone in Gillette Wyoming. I have no idea what it is. Please help. These are recent pictures of it. It’s heavy, I see small minerals that catch the light in it, very bumpy, spherical, doesn’t seem to be magnetic, I was falling down a deep trench and kicked it up at the bottom. Area was sand, sage, and small cacti. (https://i.stack.imgur.com/p2Bbz.jpg)

This is a so called Moqui Marble. A spherical concretion formed by sand and iron based minerals like limonite.

Further information can be found here


If lava flows back into the ground, would it be called magma? If lava flows back into the ground, would it be called magma again? Is there a difference if it flowed into a new hole vs the flow it came from?

Lava is per definition the molten material on the surface or a hardened rock thereof. Lava is expelled from a volcano or fissure. There is a rich vocabulary to describe the composition, formation and processes of lava.

Magma is a melt within the earth. Magma is formed when material reach a temperature for melting or partial melting, e.g. in a magma chamber. Complex high temperature chemistry is used to describe how solid material melts to magma and how it recrystallizes into igneous rocks as a response to temperature, pressure and changed composition.

Magma can originate from any kind of material. The definitions doesn't refer to the composition or origin of the material, but the manifestation. Magma can be melted or partially melted crust, also old volcanic crust, so if old lava somehow re-enters a magma chamber it will be magma. When magma is erupted, it is lava.

There is often some confusion, even among professional geologists, about many of the terms we are using. Some terms describes a process and other describes an object. Sometimes we say Upper Jurassic, sometimes Late Jurassic depending on the context. Some terms are historical and some are modern... There are often overlaps.

As for any language, it's good to use a broad vocabulary and adopt to the jargon, but most important is to communicate the ideas and observations as clear as possible.


What is it called for the part of a hill where it discontinuously gets steeper? What is it called for the part of a hill where it discontinuously gets steeper? If you climbing an easy slope and encounter a new steeper slope (such as formed by a rocky hill and accompanying soil slopes leading up to it), is this change called anything?

As far as I am aware there is no single term to describe the sudden change in the gradient of a slope. Personally I would describe it simply as a sudden increase in slope. However there are many words to describe the landforms that occur when gradient sharply increase.

Terms such as cliff, escarpment and mountainside all describe the steep landform as whole. Whereas terms such as flank or face describe the side of the hill only with a steep gradient.

You might find this link particularly helpful:
https://www.macmillandictionary.com/thesaurus-category/british/parts-and-features-of-mountains-hills-and-cliffs


How does humidity vary with height in the Earth's atmosphere? I am busy with the development of an "environment" model that can be used for flight simulation of all kinds of flight vehicles — ranging from quad-copters, unmanned aerial vehicles, manned aircraft, up to rocket launchers for satellites.  The model consists of sub-models for terrestrial gravity; the earth's size, shape, and motions; the geomagnetic field; the atmosphere; and so on.

Currently I am using the COSPAR International Reference Atmosphere (CIRA-86) to calculate air pressure and temperature for heights up to 120 km. But, to be able to calculate air density, I also need to model the effects of humidity.  I know that water vapour is only present in varying quantities in the troposhere, and that high humidity is therefore more likely at lower altitudes.

Does anybody have models of the probability of experiencing some value of relative humidity as a function of height above sea level?

Edit. As an example of what I really need, the MIL-F-8785C model for wind speed and turbulence, for example, gives the mean wind speed at a height of 6.1 m above the ground, given the logarithm of the probability of exceeding the wind speed. So, a model of the humidity as a probability of exceeding the the mean humidity as a function of height is what I really need.  Do you know of any models that provide this?

Humidity strongly varies as a function of time and space, which is why standard atmospheres like CIRA may choose to omit it at all.  It simply doesn't make sense to include an “average” humidity profile, because such an average is not meaningful.

However, there are other sources for relative humidity profiles.  You can obtain them from reanalysis data.  If you want probabilities, you could calculate them from reanalysis.  I have not used probabilities, but I have used profiles from Anderson et al. (1986) in the past:

Anderson, G. P., S. A. Clough, F. X. Kneizys, J. H. Chetwynd, and E. P. Shettle (1986), AFGL atmospheric constituent profiles (0–120 km), AFGL, TR-86-0110.

Anderson transcribes them in his paper, which is in PDF and not ideal to read.  The same data are distributed along with the Atmospheric Radiative Transfer Simulator (see also Wikipedia article).  This radiative transfer model comes with a set of XML files, that includes profiles from both CIRA and from Anderson et al.  Those are not probabilities but “typical” H₂O profiles for five scenarios: tropical, mid-latitude summer, mid-latitude winter, sub-arctic summer, and sub-arctic winter.  For example, a mid-latitude summer H₂O profile can be found at this link.  The data are in XML so should be easy to read, but they also provide reading routines for Matlab and Python.  The unit is volume mixing ratio, which may actually be more suitable than relative humidity if you are interested in calculating air density.


What are the tallest hydrothermal vents in the world? Hydrothermal vents are commonly found near active volcanic areas and provide for a rich and complex environment for many biological organisms (archaea, bacteria, tube worms...). Many new hydrothermal vent systems are being discovered and many more are likely to be discovered in the future. My questions are which hydrothermal vent system is currently considered to be the tallest? What contribute to make that system larger? How old is the vent system? Are there any peculiar organisms associated with the system that haven't been found anywhere else?

The tallest hydrothermal vent is the 60 m (180 ft) tall carbonate Poseidon vent, among the Lost City hydrothermal vent system on top of the ~4km high Atlantis Massif, located 20 km west of the Mid-Atlantic Ridge at 30°N.  The vents emit pH 9-11 metal-poor fluids at about 90°C.

The composition of the hydrothermal vents are aragonite, calcite (both polymorphs of calcium carbonate, $\ce{CaCO3}$), and brucite ($\ce{Mg(OH)2}$) giving the white colour of the vents, the pinnacle of the Poseidon vent is shown below:

NOAA Ocean Explorer

The Lost City hydrothermal vents are discussed in detail in the University of Washington's Lost City Research and NOAA's Formation of Carbonate Chimneys at the Lost City Hydrothermal Field page, from the websites, in answer to your questions:

Age: presumed to be over 30,000 years old.

What contributes to its height: Asides from the age of the vents, which allows the vents to build up. The vents are formed on a base of thick fossiliferous pelagic limestone, which form an impervious lid trapping the hydrothermal fluids and geothermal heat.

This limestone overlies a sedimentary breccia, which overlies fractured and faulted basement of highly deformed serpentites and exposed Mg-rich mantle rocks (peridotites).

Biomass: It is believed that 58% of the fauna are endemic to the Lost City environment, including the Lost City Methanosarcinales inhabiting the anoxic interior zones of the vent, which are an example of Methane- and Sulfur-Metabolizing Microbial Communities Dominate the Lost City Hydrothermal Field Ecosystem (Brazelton et al. 2006).  Observations suggest that $\ce{CH4}$ and $\ce{S}$ cycling dominate the ecological processes in the Lost City vent environment.


Natural spiral pattern of grass - what could cause this? During a nature walk inside an old abandoned quarry I stumbled upon strange spirals that appear to be naturally formed.

What could cause this spiral formation? Is it a known phenomena?

To clarify , the images are from the same place , but made with difference of couple of days. I took the photos during Winter time in Israel.
The Quarry was abandoned decades ago, so i don't think that this is a result of the working equipment.

Also i have been looking at photos of crop circles but it looks like the two are not related.

I came across this photo from Mount Calavera, San Diego County, California.  It is described as rock art and is also found in the floor of a quarry.  The spiral pattern, including the vegetation, is very similar to your photo.  In your photo it looks like the rocks have just been removed.

Rocks appear to affect the soil moisture available for vegetation by shading. From a study in Southwest China investigating the influence of bare rocks on soil moisture:

•We found that bare rocks influenced the surrounding soil moisture by shading.

•The effect degree of rocks to surrounding soil moisture correlated with its shape.

•Soil moisture on the north side of the rocks was significantly higher than others.

•The location at 15 cm north of the rocks was ideal site for plantation restoration.

Source: http://www.sciencedirect.com/science/article/pii/S0341816213003123

Is it possible that rocks used to be placed in a spiral pattern in your photo that allowed the vegetation to take hold?


Would a Yellowstone eruption destroy global agriculture? Someone recently claimed in my hearing that if the Yellowstone caldera were to erupt, the resulting ash cloud would end all agriculture for a year or two. (The speaker is not a scientist, and neither am I.)

Is that accurate?
Are there reasonable scenarios (i.e., not this) worked out for the effects of a supervolcano eruption?

I did see this question, where one of the commenters points out that such an event would be unprecedented, so our ability to predict is limited, but I'm still curious about whatever we do know at this stage.

An eruption of the Yellowstone super volcano would cause agricultural disaster over a very large area. Its global effect would be significant, but not totally devastating.

The resulting climate cooling could last up to a decade. The temporary climate shift could alter rainfall patterns, and, along with severe frosts, cause widespread crop losses and famine.
But a Yellowstone megablast would not wipe out life on Earth. There were no extinctions after its last three enormous eruptions, nor have other supereruptions triggered extinctions in the last few million years.

Eruption of super volcanoes is rare which makes it difficult to ascertain what exactly would happen when the Yellowstone super volcano eventually erupts - which won't be any time soon.
Yellowstone last erupted 174 000 years ago, which was a minor eruption. Lava from Yellowstone won't be the problem, but the ash and gases will be.
The last major eruption, 630 000 years ago, covered much of western and central United States with ash. The maximum thickness of the ash from that eruption is 660 ft. The eruption was a double eruption, 170 years apart. The amount of ash thrown into the atmosphere with each eruption caused the ocean to cool by 3 degrees Celsius with each eruption.


Can Volcanic Eruptions Help Combat Global Warming in the Long Run? I've been reading about volcanic eruptions on wikipedia, and I've found that very big eruptions cause the earth's temperature to drop by a small fraction of a degrees Celsius due to the ash it releases which blocks the sunlight from heating the earth (particularly the 1991 Pinatubo eruption that caused global cooling by 0.5 Celsius).

Does this mean if we trigger massive eruptions around the globe, will we be able to combat global warming?

The subject you are looking for is called climate engineering. In general, changing atmospheric composition in order to achieve a cooling effect that counteracts climate change is conceivable.

Whether triggering volcanic eruptions is the most feasible approach (or possible at all) is of course a completely different issue. From my understanding of volcanoes, you would really need massive eruptions with large plume-heights to achieve long-term impact.

Also note that we would need to sustain the resulting atmospheric change over a long time. And the side effects of releasing large amounts of pollutants into the atmosphere need to be considered too.

For some more aspects read this answer to a related question.


Does a geomagnetic storm visibly deflect a compass? Reading Solar Storms Could Confuse Whales and Cause Mass Strandings and the linked open access paper in Current Biology Gray whales strand more often on days with increased levels of atmospheric radio-frequency noise I see that there is a significant correlation between the strandings and certain kinds of electromagnetic disturbances, but not a significant correlation with perturbations of the Earth's "DC" or static geomagnetic field alone.
That led me to wonder if the direction of the magnetic field that I would see on a compass or some instrument that averages over seconds or longer would show any significant deflection during a Geomagnetic storm.
Can there be deflections of say 1 degree or more? Or would I have to use a microscope or put a small mirror on the needle and bounce a laser pointer off of it and on to a wall to see the deflection?

You can definitely see a large geomagnetic storm with a compass, if you have the timing to catch one and the patience to sit and stare for a few minutes.

If you look at these minutely measurements from Lerwick observatory for one of the more recent large storms (the 2003 Halloween storm), you can see a roughly 4.5 degree swing in declination (labelled "D", the horizontal magnetic field angle to geographic North) over about 15 minutes at about 07:00. "I" is inclination, vertical field angle to the horizontal plane, "F" is total intensity of the field.

  Lerwick (LER) based on 1-minute definitive data 2003-10-29 shows plots for D and I in degrees and F in nT. D shows a dip to -2 degrees in the hour before 07:00 UT and then a sudden rise to about +1.5  degrees at about 07:00 with spikes to +2 degrees.

It will depend on where you are as to how big this change in the magnetic field is, and how big the storm is. For this storm, the UK geomagnetic observatory network gives a good idea of how the effect seen depends on where you are.

  Compass angles (positive West, negative East) measured at BGS Lerwick, Eskdalemuir and Hartland observatories during 2003-10-29 and 2003-10-30. The the biggest change is seen at Lerwick, a smaller change is seen at Eskdalemuir further to the south (further away from the auroral zone where the field changes are occurring), and a smaller change still at Hartland.


What would happen if the inner core bulged and moved a tiny bit? The inner core is solid only because of the very high pressure of the outer core and mantle . Say, if the inner core moved a teeny tiny bit would some of it liquify and melt? Or does it stay solid?
Also if the Inner core bulged would a bump about 1/8 of the size of the mantle occur on the inner core because of space taken up?

The following paragraphs are reproduced from https://www.nationalgeographic.org/encyclopedia/core/
"Growth in the Inner Core
As the entire Earth slowly cools, the inner core grows by about a millimeter every year. The inner core grows as bits of the liquid outer core solidify or crystallize. Another word for this is “freezing,” although it’s important to remember that iron’s freezing point more than 1,000° Celsius (1,832° Fahrenheit).
The growth of the inner core is not uniform. It occurs in lumps and bunches, and is influenced by activity in the mantle.
Growth is more concentrated around subduction zones—regions where tectonic plates are slipping from the lithosphere into the mantle, thousands of kilometers above the core. Subducted plates draw heat from the core and cool the surrounding area, causing increased instances of solidification.
Growth is less concentrated around “superplumes” or LLSVPs. These ballooning masses of superheated mantle rock likely influence “hot spot” volcanism in the lithosphere, and contribute to a more liquid outer core.
The core will never “freeze over.” The crystallization process is very slow, and the constant radioactive decay of Earth’s interior slows it even further. Scientists estimate it would take about 91 billion years for the core to completely solidify—but the sun will burn out in a fraction of that time (about 5 billion years)."


Does the Great Pacific Garbage Patch increase sedimentation rates over the patch? As in, does the debris in the patch area eventually sink?

And if so, could sedimentation measurements over these regions provide a more fine-scaled measure of environmental conditions than sedimentation measurements over other regions?

This is somewhat a partial answer, as there is still a considerable amount of research being performed on the effects of the Garbage Patch.  The focus of this nswer will concentrate on what the US EPA (3) identifies as being the pollutant that contributes 96% of the Garbage Patches in the north Pacific - 'microplastics', pellets less than 5 mm in size.

According to Rios et al. 2010 (1), the plastic in the North Pacific Gyre are found to function as "a solid-phase extraction media" causing adsorption and concentration of pollutants out of the water column, similar to what has been found for marine sediments.

However, microplastics are found to be what Rios et al. (1) describe as being "inverse sediments" in that they do the opposite of natural marine sediments and remain floating on or near the ocean surface. Zarfi et al. 2011 (2) observed that microplastics can be incorporated into the natural sediments, and potentially wash up on beaches (e.g. if caught in a coastal current as seen n the diagram below) etc - whether or not, being incorporated into these natural sedimentation processes provides a 'sink' for the microplastics is still unclear (2).

References

(1) Rios et al. 2010, Quantitation of persistent organic pollutants adsorbed on plastic debris
from the Northern Pacific Gyre’s ‘‘eastern garbage patch’’, Journal of
Environmental
Monitoring

(2) Zarfi et al. 2011, Microplastics in oceans, Marine Pollution Bulletin

(3) US EPA, 2011, Marine Debris in the North Pacific, U.S. Environmental Protection Agency


How would our weather change in the event of a magnetic pole shift? Every two hundred thousand years or so the magnetic poles flip. Obviously it is not life ending but how would our weather change? How long does the transition take? Is there a map or model to show where the warmer areas would be effected from the loss of the mesosphere during transition?

https://www.nasa.gov/topics/earth/features/2012-poleReversal.html

Magnetic reversals are very random and unpredictable,but average about one every 260,000 years. We could have the next at any time,but as I say, they are unpredictable. So faras is known,they don't affect the weather,but they are very useful to geologists because they make tiny magnetic crystals in solidifying volcanic rock line up with the Earth's magnetic field. Thus,millions of years later, geologists can tell how the rock was lined up with the field when it was formed and can see for themselves how the alignment has changed in the intervening timespan. That gives them an insight into continental drift and other crustal movements. It is particularly useful in the study of sea floor spreading.


Why does wind blow offshore in the morning? I live in San Diego, CA, and surfers capitalize on dawn hours because the offshore (seaward) winds help "hold up" the waves, i.e. prevent them from crashing before the surfer gets to ride it a while.

I'm only a beginner, but when I went to Korea, I met surfers from Santa Cruz, CA and Tianjin, China, who said it's the same everywhere.

Why does this happen?

The phenomenon you describe is denoted as a land breeze. It is caused by a difference between the sea surface temperature and the land surface temperature.

Surface Temperature

During day time the surface temperature at land rises faster than the sea surface temperature, whereas during night time the land surface cools faster than the sea surfaces. As a result, the sea surface temperature is higher than the land surface temperature in the morning.

Formation of the Breeze

The sea surface heats the air above the sea stronger than the land surface does with the air above land. The warmer air masses above the sea rise to higher altitudes yielding a low pressure region. As a result, the colder air masses from above the land 'travel' to the low pressure region above the sea. This 'traveling' of air masses is wind: wind, which blows from the land to the sea.

Here is a nice Figure from Wikimedia Commons describing the sea breeze (A, evening/afternoon) and the land breeze (B, morning). The Figure was provided by Jesús Gómez Fernández.

Shower Curtain Example

If you shower in a shower with a shower curtain, you might experience that the lower end of the curtain moves towards your legs. The physical processes are similar: The warm shower water heats the air within the shower. The warm air rises which causes a low pressure region at the bottom of the shower. The air is colder at the bottom of the room outside the shower which leads to a high pressure system. The air from the high pressure system (bottom outside the shower) 'tries' to flow towards the low pressure system (bottom inside the shower) which moves the bottom end of the curtain towards you.

This example works only if the room temperature in the bathroom outside the shower is not too warm/hot.


What would a rock thin section look like without any polarizers? I'm interested in knowing what features can still be discerned.

I've been struggling find any image of a thin section of a rock under a regular light microscope, or a petrographic microscope with the polarizer and analyzer removed.

It would look almost identical to the image obtained using plane-polarised light.

Some minerals would look darker, especially those with strong pleochroism such as biotites and amphiboles, because all light is now transmitted or blocked regardless of orientation.
Minerals with large relief differences such as carbonates (e.g. calcite) would cease to have the differences and would just have high relief.

From a static image it could actually be hard to tell that there is no polariser. A careful and experienced observer might deduce it from small hints, given some prior knowledge on what the rock contains.


When does a stream become a river? Does a stream require a certain width or volume before it can be classified as a river, and if so, what is it?

There's no official distinction between a river and a creek, both of which are categories of streams. As an example, consider Pine Creek in Pennsylvania and Po River in Spotsylvania County, Virginia. Pine Creek is 87.2 miles long and has a flow rate that ranges between 40 to 30000 cubic feet per second. Po River on the other hand is 1.9 miles long and has a row rate that ranges between less than 2 to 4000 cubic feet per second. The longer and larger one is called a creek while the shorter and smaller one is called a river.


Is every space group realized by some mineral? Every mineral has it's own internal building scheme, a lattice on which it's atoms lie. Mathematically, this can be described by the space group of the mineral. From mathematical considerations it's known that there are exactly 230 symmetry groups which can occur as the space group of a mineral. Now my question is: Is each of the 230 space groups realized as the symmetry group of a mineral?

Now all of the 230 space groups are realized by a natural occurring mineral.
I found this blog: crystalsymmetry.wordpress.com where space groups are listed with at least one chemical compound is listed for each space group. Minerals are listed for all of the space groups.
For example, Benitoite has fairly unusual crystal symmetry. I think it was first mineral found for P-6c2 space group.
188 P-6c2 Example – Benitoite, BaTi(Si3O9)
From Crystal Structure of Benitoite.
From a crystallographical point of view this compound (Benitoite)
is especially interesting, being the only known member of the ditrigonalbipyramidal
symmetry class.


What is sub-tropical wet climate, semi-arid climate and semi-tropical continental climate? What is sub-tropical wet climate, semi-arid climate and semi-tropical continental climate?

I encountered this while reading climate of my state Haryana.
(I have no background in environmental science)

The sub-tropics are climatically very variable. Most of this zone is arid or semi-arid, but there are some wet areas. The wet areas also vary considerably. Some of them have quite cold winters where the temperature just manages to keep a few degrees above zero, others keep comfortably above zero.

Sub-tropical wet climates can be found at the northern extremity of the South China Sea in places like Hongkong and Hainan Island, both in southern China. Here you can find classical rainforest not much different from that which exists over most of S.E. Asia, so that would be sub-tropical wet climate.. The climate in elevated areas of tropical Africa and New Guinea also falls into some definitions of sub-tropical (definitions vary a little) and have a similar climate to S.W.China. Further away from the tropics you can still find wet areas, but as I say, the sub-tropics tend to be mostly arid or semi-arid.

Continental subtropics tend to be more arid and have colder winters, while small islands in subtropical areas have a marine climate and tend to be damper and have milder winters. The Canaries are an example. North Island, New Zealand, is subtropical and has a climate similar to the better areas of the Mediterranean. The Sahara desert is mostly subtropical and very arid, but the Atlas mountains in the north are damper. Mountains tend to attract rainfall.


Effect of organic matter on salinity Organic manure is used in agriculture around the globe.
I am interested in how does organic matter affect the salinity of soil? Does it increases, increases or remains unaffected? and is there a study to support the argument?

Organic matter affects the pH and makes the soil more acidic. The best example of this is in peat bogs, where only acid tolerant plants can live and the peat is so acidic that micro-organisms don't flourish, thus preventing decay. There is the famous Tollund Man, found in a peat bog in Denmark if I remember rightly. The body is in an almost perfect state of preservation, yet is about 3,000 years old! Tollund Man was apparently executed by hanging in ancient times and his body thrown into the bog. The principle is the same as the jars of eggs, onions, gherkins and so on which are pickled in vinegar.


What is a temperature inversion and can it trap smog/pollution? Just as the title says, I heard about this term but am not sure how it works.

Normally, temperature broadly decreases with altitude, and convection is effective: locally warmer air will rise, and cooler air will fall. A temperature inversion is where the air temperature rises with altitude. This means that convection is less effective because the air above is already warmer, and so there is less mixing of air between altitudes.

Since pollution is generally produced at ground level, temperature inversions can trap the pollution (e.g. smog) at ground level.


What is "focus point" in WRF-plots grid box? (python code) has anyone used the python code from here (written by Geir Arne Waagbo) to plot skewT plot from WRF output?

I've got a question regarding some of the functions used in the code found in pywrfplotUtils.py - which is the getXY(lon,lat) function that gets called in getDimensions(nc) function.

Below are the codes:

def getDimensions(nc):
 Nx = nc.getncattr('WEST-EAST_GRID_DIMENSION')-1
 Ny = nc.getncattr('SOUTH-NORTH_GRID_DIMENTION')-1
 Nz = nc.getncattr('BOTTOM-TOP_GRID_DIMENSION')-1
 dx = nc.getncattr('DX')
 dy = nc.getncattr('DY')
 lons = nc.variables['XLAT'][0]
 lats = nc.variables['XLONG'][0]
 # find coordinates for focus point
 x,y = getXY(lons[Ny/2,:],lats[:,Nx/2])
 return Nx,Ny,Nz,lons,lats,dx,dy,x,y

def getXY(lon,lat):
 x_nr = 0
 y_nr = 0
 while (lon[x_nr] < lon_focuspoint):
  x_nr += 1
 while (lat[y_nr] < lat_focuspoint):
  y_nr += 1

 print "x_nr:" str(x_nr),"Lon:",str(lon[x_nr])
 print "y_nr:" str(y_nr),"Lat:",str(lon[x_nr])
 return x_nr,y_nr

The focus point is a variable set in the pywrfplotParams.py:

#This defines the grid box for which skewT-plots etc are based
lat_focuspoint = 60.2
lon_focuspoint = 11.08

Unfortunately, I don't know what focus point is referring to, so when I use the values set by the author, obviously I get an error, and that error is - IndexError: index out of bounds.

I have found this link useful in providing the definition for the attributes asked in that question, but I'm not entirely sure if I should also get the cell indices from latitude and longitude in the WRF model grids.

Your thoughts are very much appreciated!

A Skew-T/Log-p plot is a vertical profile from a point, and it appears in that code that the point you are plotting the skew-T for is 60.2 latitude, 11.08 longitude.  The snippet of code:

def getXY(lon,lat):
 x_nr = 0
 y_nr = 0
 while (lon[x_nr] < lon_focuspoint):
  x_nr += 1
 while (lat[y_nr] < lat_focuspoint):
  y_nr += 1

finds the closest grid point west and south of your focus point by setting the x and y gridpoints to 0 and incrementing the index as long as the latitude/longitude values at that grid point are less than the focus point.  This is what the focus point is for -- the lat/lon location you want the skew-t/log-p plot at.

The exception IndexError: index out of bounds. means that the above code tried to access a value lon[x_nr] or lat[y_nr] that was out of bounds.  This means that the latitude/longitude coordinate of your focus point is not within your domain.

To run the code successfully, edit the focus point to be a point within your model domain, specifically the value of latitude and longitude that you want the skew-t profile for.


Which Earth minerals would Moon colonists miss the most? In my science-based novel, Moon colonists need to return to Earth to collect some rare or absent mineral(s) Ideally, something they could derive from seawater. Which minerals might they be...?

The composition of Moon rocks is pretty much the same as that of Earth. However, none of the processes that concentrate specific minerals in one location (i.e. into a mineral deposit useful for mining) exist on the Moon.  This is due to the lack of tectonic activity. Therefore in the Moon you would expect the rocks to be much more homogeneous than on Earth. Only maybe meteorites, their impact craters, and ancient volcanic activity (as pointed by @userLTK) might have provided a way to concentrate some minerals in various places. So, due to this homogeneity, to get one gram of let's say copper, you would have to process hundreds of times more rock than would be needed in an Earth-based copper mine.
Also as Fred mentioned, there would be many challenges for mining in the Moon, but in the context of your plot those might have been solved. Having enough energy, you can probably get pretty much any mineral from the Moon (for example a mass spectrometer would be an effective but highly inefficient way to mine all the elements from within a piece of rock).

If your plot doesn't require that it be a mineral, I think what they might need the most is some sort of organic compound. Even with current technology there are many chemical compounds that can't be synthesized, and we rely on plants or animals to obtain them. A famous example is Maitotoxin, a small molecule that chemists have tried to synthesize for 22 years without success.

So perhaps there could be a particular organic compound that has been recycled and reused over time in the bodies of the plants and animals on the lunar colony, but over time that compound degrades (by cosmic rays, UV light, or whatever), so animals and/or plants start developing problems due to the lack of this compound that none of the organisms placeable in the colony are capable of synthesizing. Therefore, they need to go back to Earth to get it from some ocean-dwelling creature.

Perhaps it would be something like a vitamin required by plants.  Or maybe a compound that could be needed to cure a disease.


gamma-ray spectrum vs energy decay I am going through An Introduction to Applied and Environmental Geophysics, a book by John Reynolds (2011), to better understand radiometrics and gamma-ray spectrometry. The author provides some tables about decaying as well as a plot of airborne gamma-ray spectrometry data.

Table 15.2A shows the Uranium decay series, while Table 15.2C shows the Thorium decay series. The plot shows the survey result of an airborne gamma-ray spectrometry.

As one can see in the plot, the author relates

the Potassium series with peak at 1,46 MeV with corresponding element 40K
the Uranium series (shown in Table 15.2A) with peak at 1,76 MeV with corresponding element 214Bi
the Thorium series (shown in Table 15.2C) with peak at 2,82 MeV with corresponding element 208Tl

The problem is: for both Uranium and Thorium decay series shown, the decay values presented at the tables differ from the peaks at the plot. I would expect to see the Uranium series peak with a value of 3.272 MeV (214Bi decay value in Table 15.2A) instead of 1,76 MeV shown in the plot.

The same for Thorium series: if the corresponding decay energy of 208Tl is 5.001 MeV accordingly to Table 15.2C, why does the plot show a corresponding value of 2.82 MeV?

I will first focus on the 214Bi decay. The 3.272 MeV is the total amount available for the β- decay, i.e. the difference between the ground states of 214Bi and 214Po. If you have a beta decay into the ground state of of 214Po, which happens in 19.9 % of cases (all data are from Firestone, R. B. et al., “Table of Isotopes”, 8th ed., 1998, p. 9211, in short “ToI”), there will be no gamma emission from 214Po, the 3.272 MeV are distributed between the electron and the electron antineutrino. However, in 16.9 % of cases, the decay leads to an excited state of 214Po with an energy of 1764.499 keV which can then deexcite among other possibilities by emission of a 1764.494 keV gamma photon (15.36 % of beta decays). The decay can produce a large number of gamma ray lines, but most happen with low probability. You can have a look at page 23 of this 214Bi table of radionuclides extract to get an impression.

In summary, the 3.272 MeV get distributed in varying proportion to the electron and the electron antineutrino from the beta decay, zero or more gamma-ray photons, and some small amount to nuclear recoil, etc.

In the case of 40K decaying via electron capture to 40Ar (10.72 % of cases), the total decay energy (Q-value) is 1504.9 keV. Most of the time (10.67 %), this goes to an excited state (1460.859 keV), which in turn gives rise to the 1460.830 keV gamma-ray line. The rest of the energy goes to the electron neutrino.

Similarly, for 208Tl, the 5000.9 keV is the Q-value of the β--decay. Most of the time (48.7 %), the decay proceeds via an excited state (3197.743 keV) of 208Pb, which deexcites via another excited state (2614.551 keV) where 99 % of decays also lead. This state the deexcites via the emission of a 2614.533 keV gamma ray photon. I believe the 2.82 MeV from Fig. 15.1 is a typo, since the reference in Reynolds’ book points to the article “Airborne Gamma-Ray Spectrometry Surveys”. There Fig. 4.4-1 is the same as Fig. 15.1 from the book, but in rather low resolution and with hard-to-read numbers. The text, however discusses the 2.62 MeV gamma ray line, which is very likely a rounded value of the 2614.533 keV from the “Table of Isotopes”.

The sum of the probabilities of different gamma ray lines from the same decay can be larger than 100 % if the deexcitation happens via a gamma-ray cascade, i.e. if the nucleus first transitions into an intermediate excited state and then again to the ground state or further intermediate states. This means that a single beta decay results in multiple gamma-ray emissions. This is illustrated in the Wikipedia article on Gamma rays using the example of the 60Co decay which results in two photons emitted in > 99.9 % of cases.


References for moving and nested grids in models Would anyone know of references that give detailed explanations on concepts such as moving grids and nested grids in models?

Book:

Shyy W, Udaykumar HS, Rao MM, Smith RW. Computational Fluid Dynamics with Moving Boundaries. Taylor& Francis: London, 1996.

Some relevant papers:

Jin C, Xu K. A unified moving grid gas-kinetic method in Eulerian space for viscous flow comnputation. Journal of Computational Physics 2007; 222:155–175.

Hirt CW, Amsden AA, Cook JL. An arbitrary Lagrangian–Eulerian computing method for all flow speeds. Journal of Computational Physics 1997; 135:203–216.

Piggott M, Pain C, Gorman G, Power P, Goddard A. h, r, and hr adaptivity with applications in numerical ocean modeling. Ocean Modelling 2005; 10:95–113

HuangWZ, Ren Y, Russell RD.Moving mesh methods based on moving mesh partial differential equations. Journal of Computational Physics 1994; 113:279–290.

Miller K, Miller RN. Moving finite element. SIAM Journal of Numerical Analysis 1981; 18:1019–1032.

Dorfi EA, Drury LO. Simple adaptive grids for 1-D initial value problems. Journal of Computational Physics 1987; 69:175–195.

Tang T. Moving mesh methods for computational fluid dynamics. Contemporary Mathematics 2005; 383:141–174.

Tang H, Tang T. Adaptive mesh methods for one- and two-dimensional hyperbolic conservation laws. SIAM Journal of Numerical Analysis 2003; 41(2):487–515.

Tang H, Tang T. Multi-dimensional moving mesh method for shock computations. Contemporary Mathematics 2003; 330:169–183.

Adaptive grid concepts have been applied to the Princeton Ocean Model (POM).

Original Paper for POM:

Blumberg, A. F. and G. L. Mellor, A description of a three-dimensional coastal ocean circulation model. Three-Dimensional Coastal ocean Models, edited by N. Heaps, 208 pp., American Geophysical Union., 1987

With adaptive mesh:

Hofmeister, Richard, Hans Burchard, and Jean-Marie Beckers. "Non-uniform adaptive vertical grids for 3D numerical ocean models." Ocean Modelling 33.1 (2010): 70-86.


Complete missing outcrop problem Given A is upper limit of sand stone, B is the lower limit of the planes that are equal in distance and dip. Dip angle is 29 degrees.
Complete the outcrop of this map.
—————————————————————————-
Now I know that strike lines should go in height 400
But there are 3 points so how could that even be possible.
2 of these points are on strike line but what about the third?
I really don’t know how to approach this question
Also from dip angle I can easily find the distance from each strike line but that is for later

First step - draw a strike line where line A intersects the 400 m line.
Second step - you know that the sandstone layer is of equal thickness and dip, so you can draw a parallel line at the place with line B intersects the 400 m line. This will give you the thickness, as expressed on a horizontal surface. You know what the dip angle is, so getting the real thickness is simple trigonometry.
This should get you started.


Can Ozone (O$_3$) form in a vacuum and if so can it deflect solar radiation I am working on a geoengineering/space infrastructure project and part of that includes the possibility of using oxygen mined from the moon (specifically lunar regolith) to cause ballistic objects to spin spreading particles in a loose shield to reflect sunlight. The material would all be collected back on the moon which would intercept the orbit of the material. However, as ozone is just 3 oxygen atoms that connect together in the presence of sunlight, would releasing clouds of oxygen in a way that pushes the clouds together allow the formation of O$_3$, even temporarily?

If this would work, would O$_3$ free-floating in very loose clouds in space help deflect solar radiation at all?

This is part of a larger project to create targeted shading effects to produce a limited risk effect on the earth like regrowing ice sheets. There are a lot of reasons for people to find this project silly but all the research I have done continues to support it in new and interesting ways and any concerns people have raised so far have theoretical solutions. So please don't take time to simply criticize without providing meaningful feedback.

If this would work, would $O_3$ free-floating in very loose clouds in space help deflect solar radiation at all?

No, for many reasons:

Your cloud will disperse. That's what gases do in vacuum.
And then the dispersed cloud will get swept away by radiation pressure and the solar wind.
So you'll have to be constantly replenishing your loose cloud.
There are 3 billion metric tons of ozone in the Earth's atmosphere.
Compare that huge quantity with the 380.95 kilograms of lunar rock brought back by the six Apollo missions that landed on the Moon, or the 0.401 kilograms retrieved by Russia's unmanned Luna missions.

The engineering feat you are proposing is more than six orders of magnitude larger than anything humankind has done with regard to space. The Apollo program peak cost was a bit less than 5% of the total US federal budget. A factor of ten (one order of magnitude) larger scope would be far beyond the capabilities of the US government. Even with the entire world pitching in, a two order of magnitude increase would be nearly impossible. A six order of magnitude increase is economically impossible.

The worst part: Even if successful, your cloud won't do much. Oxygen in all its forms (atomic oxygen, molecular oxygen, and ozone) is nicely transparent in the frequency range where sunlight is at its peak. Evidence: You can see the stars on a clear night.


Are there ways stormwater attenuation can be quantified for comparison between different systems or conditions? Various sources agree land cover changes impact the attenuation of stormwater. E.g. forest areas generally slow the rainfall-runoff response and moderate it, reducing peaks in hydrographs, as compared to urban areas.

Is there a way stormwater attenuation can be quantified, by field measurements (eg. observed streamflow) or model outputs? If so, what are some examples of how this can be done? The reason to quantify attenuation would be to compare differences in attenuation between different basins or between different conditions within a basin.

A typical ratio calculated to quantify this type of response, especially at larger scales (such as for land use changes) is the runoff ratio:

$$R = Q/ P$$

where $R$ is the runoff ratio [mm/mm or dimensionless], $Q$ is the annual flow volume [mm], and $P$ is the annual precipitation [mm]. The runoff ratio is usually calculated for a given data period (multiple years of data) or on an annual basis. It is tricky to calculate for individual events since the antecedent conditions play a large role, but on an annual basis this would be a decent metric to compare different basins or the same basin in time. This is assuming you have a number of years of data to calculate the ratio from.


Which method is used to calculate tonnes carbon from tonnes CO$_2$ equivalents of GHGs? It appears that all GHGs are first translated into Carbon Dioxide Equivalents (CDEs) and that calculation is fairly straight forward.

Many report in tonnes of Carbon instead of tonnes CDE. I am unsure how this is calculated:

Actually count the carbon atoms in each species
Pretend that they really Carbon Dioxide, and simply apply 12/44 to tonnes of CDE to get a CDE carbon content. For example, nitric oxide has a CDE value but no actual carbon, but you can come up with a carbon mass using this approach.
Some other method

Is there a prescribed approach or standard basis?

OK it depends a lot on what exactly you mean. There is a known problem with people talking about "carbon" / "atmospheric carbon" / "Carbon Dioxide" and using the terms imprecisely - so there is often a confusion about which exact chemical species is being discussed.

Tonnes of C to CO2 is (as you correctly stated) a conversion based on molecular mass, but this doesn't really help us if we're talking about something like methane which contains carbon, but has a dramatically different effect in terms of global warming. It is even more complicated when you take into account the change in lifespan of these different species (methane degrades in the atmosphere much more quickly than CO2 for example)

The usual method to deal with this is to calculate Global Warming Potential (GWP). This compares the actual radiative forcing over time (the change in the earth's energy balance) to a fixed time horizon (usually 100 years) when compared with CO2. We can therefore compare the actual equivalent effects of releasing a number of different gasses in units of CO2 equivalent.

The details of how it's calculated and why the time horizons are where they are is in the IPCC AR5 WG1 CH8 technical supplement (8.SM.11.1 Equations for the Global Warming Potential)

Hope this helps


Methane in Martian Soil Measurements taken by the Curiosity rover have detected minute amounts of methane in the Martian atmosphere.

I was wondering, is it possible that greater amounts of methane are present beneath the surface, i.e. several meters below the Martian soil?

I ask as I wonder if the discovery of large amounts of methane in the Martian soil may provide evidence of past/present life.

Studies shows there is Methane on Earth's Crust. The chemical form how it is stored is called Methane Clathrate,

"a solid clathrate compound (more specifically, a clathrate hydrate)
in which a large amount of methane is trapped within a crystal
structure of water, forming a solid similar to
ice."
(source:wikipedia).

There are two main origins for this structures on Earth's Crust, mainly developed at the Oceanic Crust and stored some centimeters or meters below the water interface, after the sulfate reduction zone:

Microbial reduction of CO2.

Thermal decomposition of organic matter.

Both sources imply organic activity so possibly your question encloses that much-contested question about whether there was or not life on Mars in the past.
Regardless there were or there were no life, Lefèvre et al.(2009), clarify the occurrence and possible sources for methane on Mars from what we know with our current observation possibilities:

"The detection of methane on Mars has revived the possibility of past
or extinct life on this planet, despite the fact that an abiogenic
origin is thought to be equally plausible"

They continue...

"An intriguing aspect of the recent observations of methane on Mars is
that methane concentrations appear to be locally enhanced and change
with the seasons."

And finally:

"We find that photochemistry as currently understood does not produce
measurable variations in methane concentrations, even in the case of a
current, local and episodic methane release. In contrast, we find that
the condensation–sublimation cycle of Mars’ carbon dioxide atmosphere
can generate large-scale methane variations differing from those
observed."

This is still on debate and maybe someone can contribute quoting more recent articles, but the occurrence of Methane on Mars soil is measured, but this do not provide a proof that there was life on the planet.
That condensation-sublimation cycle may lead to CH4 storage on soil around the poles, and form a kind of "Methane permafrost", but formed for physical-chemical processes with no life interaction.
Also asking for "large amounts of Methane on soil", the answer possibly is no too, because either Mars had life, Earth's organic activity has developed big Methane Clathrate deposits on Oceanic Crust because of the listed organic associated process.
To recognize an organic origin of CH4, isotopes of C of the samples should show low concentrations of heavy C14, as life prefers to use lightweight ones: C13/C12
.
That hypothetical biologic Methane would be found on the big depression that was supposed to have a water ocean. The latest formed on soil would have been liberated to the atmosphere at the death of the ocean (because of pressure decrease), but rests of organic CH4 could maybe be found drilling the zone.
The new of past life occurrence has not yet been published, and could come from other chemical compounds.
I usually cross my fingers when I think about it.
Lefèvre, F. Forget, F. "Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics."Nature (2009)


Prevailing winds between 30 to 60 degrees latitude Prevailing winds are generated by Coriolis effects.

I think I understand why NE winds are the prevailing winds in 0 to 30 degrees and 60 to 90 degrees latitude in the northern hemisphere (e.g., according to the picture below). But I don't understand why westeries are the prevailing winds in 30 to 60 degrees. If one throws a ball from a point at the equator to the north pole, shouldn't it deflected to the opposite direction by the direction of the rotation of the earth (i.e., creates SE winds)?

Although not 100% sure, after some additional searches, I think the answer is the law of inertia. If one throws a ball from at the equator to the north pole, the ball also moves to the right even if one did not intend to do so. The same effect we see when one throws a ball from a moving car (example).

The speed is faster near the equator. Therefore, even through Coriolis effect is working, the law of inertia overrules the effect. That is, the movement (to right) of the ball is faster than the rotation of the earth.

Regardless of from north to south, or south to north, Coriolis effect and the law of inertia work in opposite directions. Stronger one determines the direction.


How did natural processes as we know them develop around effects of winter? Everything on earth evolved around changing seasons and the different versions of resources they bring with them, so I'm curious, how did natural processes take advantage of winter qualities to shape earth as we know it? It seems like the advantages captured from other seasons are more obvious, specifically to plant life (spring- showers, summer- direct sunlight) so what's the unique aspect of winter that helps continue the process?

I don't know if one answer can list all the positives, but one I can think of is this: In many (not all) places of the world winter produces the most violent storms. Because deciduous trees lose their leaves during winter, they thus have less wind resistance, which in turn lessens--but does not eliminate--their vulnerability to being toppled over by severe winds.And of course, hibernating species take advantage of winter by sleeping through it and pretty much staying awake for the rest of the year. (I sometimes wish we humans could do the same.)