A parcel of air in an isothermal layer I'm having a bit of trouble figuring out a solution to this problem:

There is an isothermal layer of air which has a temperature of 0 °C extending from the surface to 1 km height. A parcel is 0.5 °C is released at the surface in the isothermal layer. How high does the parcel rise before it descends back?

I know what an isothermal layer is and I know that the parcel will rise until it reaches the surrounding air temperature. I am just not sure how or which formula I would use to solve the problem.

Isothermal, as you are likely aware means constant temperature. Your problem has the givens:

The 0 - 1 km layer has a constant temperature of 0 C
A surface parcel initially has a temperature of 0.5 C

We can likely assume the parcel is not saturated and you are aware that that a parcel with a positive relative temperature perturbation is buoyant and will rise.

To question you need to look at next is: what happens to a parcel of air as it rises?  Your 0 - 1 km layer has a constant temperature but not a constant pressure so the parcel will expand as it rises.  If the parcel expands then its temperature will decrease.

At what rate does the temperature of an unsaturated parcel of air decrease as it rises?  This number will allow you to calculate the height that the parcels temperature decreases by 0.5 C and neutral buoyancy is attained.


What is an isolated land area of one type of rock surrounded by land of a differing rock type called? For example, if there were a large land area with exposed basalt, in the middle of which is a smaller isolated patch of Granite, what is that isolated patch called?

I came across the single-word geological term for this some months ago, and now it eludes me.

Something tells me it had a similar ring to Moraine (as in glacial debris), but I may well be misremembering that connection.

You might want to look at these topics, depends on the size of features that you want to look at:

Batholith -- s a large mass of intrusive igneous rock (also called plutonic rock), larger than 100 square kilometres (40 sq mi) in area,[1] that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such as granite, quartz monzonite, or diorite -- https://en.wikipedia.org/wiki/Batholith
Stock (geology) ==  is an igneous intrusion that has a surface exposure of less than 100 square kilometres (40 sq mi),[differing from batholiths only in being smaller. A stock has a discordant relationship with the rocks that it intrudes. The term stock usually refers to individual, relatively small plutons, less than 20 km (12 mi) diameter, usually in relative isolation.Many stocks are cupolas of hidden batholiths. Circular or elliptical stocks may have been vents feeding former volcanoes -- https://en.wikipedia.org/wiki/Stock_(geology)
Dike (geology) --  is a sheet of rock that is formed in a fracture in a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing cracks -- https://en.wikipedia.org/wiki/Dike_(geology)


Newton's & Kepler's age of the earth calculations - References? "Everybody knows" that Newton and Kepler calculated the age of the earth. My problem is that, whilst "everybody knows" this, no-one gives a reference that I can read for myself.

If, for example, I want to read what Thomas Burnett believed, I download a copy of Telluris Theoria Sacra and I can read for myself that he accepted the reality of Noah's flood. The same is true of St Augustine's beliefs as there are several online translations of City of God Against the Pagans.

But Newton and Kepler?

Zilch. Sweet F.A. Absolutely nothing.

Even when a website  references a text, either I can't find the text, or there is no age-of-the-earth calculation in the text that I can find.

So, did either Newton or Kepler calculate the age of the earth, or is this just an urban myth? If it's true, does anyone have references that I can look at for myself. These will have to be secondary references (English translations) as I expect the actual primary reference to be in Latin, and sadly, I only read English.

Your question may be better suited to either SE History or SE History of Science and Mathematics. The date of the so called creation of the Earth has nothing to do with Earth Science.

For Kepler I found he wrote the book KANONES PUERILES, in it he calculates the creation date to be 27 April 4997 BC.

The published works of Newton reveal little. Some authors on Newton mention an unpublished document he wrote in either 1704 or 1705. Any calculations he may have done regarding the so called date of creation may be in his unpublished writings.

You may need to review the bibliographies of authors who wrote biographies on Newton, such the 1855 book by Sir David Brewster, Memoirs of the Life, Writings, and discoveries of Sir Isaac Newton, volume 2.


Is the color of the sky the same everywhere on earth? Is the color of the sky at noon (local time) in, say, NY, Buenos Aires, London, Nairobi, Sydney, New Delhi and Tokyo the same? I choose the specific time of noon to exclude the twilight colors of the sky and I choose cities that aren't above the northern or southern pole to make it easier.

Also can the color of the sky be the same or not depending of the season? For instance, the color of the sky of Buenos Aires on January 1st would be the color of the sky in NY on June 1st.

Also, is the color of the sky of one region on earth the same all year round and all day long, once again, without taking in account twilight?

Absolutely not. While the answers by casey and farrenthorpe correctly state that the blue color is due to Rayleigh scattering, the composition of the atmosphere varies considerably from place to place - and with different composition come different degrees of scattering, and different color / intensity. Typically regions of greater industrial activity will carry larger densities of particles which, in the presence of moisture in the air, will become scatterers. The wavelength dependence is a function of the size of the particles - so as the size changes, so will the color.

See my answer to the question Why is the sun brighter in Australia compared to parts of Asia. The same mechanism that makes the sun "brighter" also makes the sky "darker" (namely, less scatter).

This is true even on a nominally "clear" day - because there is always some particulate matter in the atmosphere. And the concentration of particulates really does vary with location on earth - see this image  as an example (from NASA).

The other point worth keeping in mind is altitude: the sky looks darker when you are at the top of a mountain, even if the composition of the atmosphere is the same. That is because there is "less atmosphere" to scatter. And of course, some places on Earth are (always) at a different altitude...


How can I calculate the sensitivity of a seismometer? I would like to know if a specific seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but I'm not a seismologist and am trying to figure out how to relate the specs to one another.

I have:

Velocity output band: 30s (0.03Hz) to 100 Hz
Output Sensitivity: 2400 V/m/s
Peak/Full scale output: Differential: +- 20V
Sensor dynamic range: 137 dB @ 5 Hz

Thanks in advance!

create a bench test using an acceleramentor and a transducer since their values are known then equate the results to your sesimo


Meaning of the C in the unit "mg C L-1" Could somebody tell me what the "C" signifies in the unit mg C L-1? I was wondering if it stood for concentration but it seems redundant as litres are mentioned. Thanks.

The paper which uses the unit is "Dissolved Organic Carbon Thresholds Affect Mercury Bioaccumulation in Arctic Lakes" by French et al. 2014.

Given the subject matter of the paper, I'd assume that it stands for carbon, and the whole expression refers to milligrams of carbon (or organic carbon) per litre of lake water.


Could one say that granites are metamorphic rocks, or not at all? In my old textbooks, granites used to be part of the metamorphic rocks.
Is this still true or not ? If not fully true, to which extent ?
Could someone point me towards clear examples or definitions showing they are considered not metamorphic rocks any more ?

If not metamorphic, please which part of the rock classification do they belong to exactly ?

Thanks,   Gilbert.

This is the key:

  used to be part

It is important to look at this from a historical point of view. Up until the 1950s and early 1960s, there was no agreement to how granites form. This became the granite controversy.

On the one hand, experimental work showed that granites crystallise from magma, but this magma had to be derived from basalt-like magmas. This led to two problems:

Where is all the basalt from which the granite was supposed to form?
What happened to all the rock that was there before the granite (aka the "room problem")?

This led people to think that granites formed by metasomatic replacement of other rocks. Essentially, you have other things than were not granite and then they were transformed to granite through various geological process, without ever crystallising from magmas. This is what people say when they talk about granites as metamorphic rocks.

But, this is not the case and later research demonstrated that granites from by crystallisation of magma and the process of metamorphic formation of granites (by metasomatism, or "granitisation") does not actually exists. There were (and still are) many questions left unanswered on exactly how this happens, but we know that this does happen and granites are indeed igneous rocks. In fact, there's a great paper published just this week in the journal Nature, showing modelling of how some of these things can form.

Nevertheless, granite formed can be sometimes related to metamorphism. Extreme cases of hot metamorphic can cause melting of (previously sedimentary and then metamorphic) rocks to form magma that eventually crystallises as granites. This is known as migmatisation, and is commonly used to explain the widespread occurrence of "leucogranites" in the Himalayas for example.

Additionally, some high-grade metamorphic rocks contain quartz, feldspars, micas, and amphiboles. The metamorphic texture (foliation and lineation) is not always obvious, making it easy to mistake metamorphic gneisses as igneous granites.


Strangely bright morning twilight over Switzerland Yesterday morning (04.11.2014) I woke up at 6:40 as usual and noticed that it was relatively bright out. I had a better look around 7 and concluded that it was definitely quite a bit brighter than it was the day before at that time. There was also a strange, yellow tint to the light.

I looked up when the sun comes up in Basel (where I live) and found out it's at 7:18. Later I did some googling to see if anyone else had noticed this and came across this article about something similar happening in 2008. It mentions polar stratospheric clouds as a likely cause. The following evening however, I didn't notice anything remarkable. And as I write this the next morning, The sun has now been up for an hour but due to clouds it looks darker than it did an hour and a half earlier in the morning yesterday.

So I'm wondering, what is the cause of this unusually bright morning twilight? And can I expect to see it again in the coming days/weeks/months?

Something that might relate to this is the siberian winter that seems to await Europe.

PS: I also wouldn't be averse to other people around Europe confirming that they also noticed this.

If these were polar stratospheric clouds, that could explain a brighter than normal sky either before sunrise or after sunset.  The higher the clouds are, the more lead/lag time you will have to observe the phenomena before the sun comes into view.  The reason for this is simply that the clouds are in direct line-of-sight with both you and the sun, but you and the sun are not in line-of-sight.  The sun illuminates these clouds and being cold icy clouds they reflect much of this light to your eyes.  100% of the light you see is scattered giving the light a diffuse glow.

Unfortunately, I'm not aware of any stratospheric forecast products for these clouds.  The closest thing is an analysis of the 450 K $\theta$-surface showing area within the polar vortex with temperature at or below -78 C.  These depict the area within the polar vortex that are favorable for polar stratospheric clouds.  However, these do not show where the favorable area is, nor give an indication if these clouds will actually form.  You can view the northern hemisphere plots here.  The other stratospheric products deal with the size of the polar vortex, UV-B penetration and ozone analysis which do not aid in the forecast of these clouds.


How are wind speeds typically distributed? What probability distribution do wind speed measurements typically follow?

I have seen a Weibull distribution used, but the page was a bit lacking on background information so I would appreciate confirmation and a reference, if possible.

If it is a Weibull, are there typical parameters that are used, or can these vary?

Thanks.

Yes, the most commonly used distribution for wind speed is the Weibull - at least when it comes to predicting wind speeds at prospective wind farm locations.

Yes, the parameters vary.

See, for example, the book "Wind Energy - The Facts", the output of an EU research programme (ISBN 9781844077106, also freely available online).

Or Seguro & Lambert's paper Modern estimation of the parameters of the Weibull wind speed distribution for wind energy analysis

As a starting point for estimation, it's usual to take $k=2$; this is equivalent to the Rayleigh distribution. However, the Weibull is more generalised, and often provides a better fit (i.e. $k$ isn't exactly 2).


Which places on Earth would be affected the least by severe climate change? If I had the choice to move to an arbitrary region on the planet, which regions should I favour and which should I avoid in terms of habitability in face of the possibility of an extreme climate change?

The places on Earth that have historically had the most stable climates are typically within the tropics and close to sea level/coastlines.  The tropics are not influenced as much by the rest of the Earth's weather patterns since it is more of a source of weather (e.g. the strong convective atmospheric motion that moves air away from the tropics due to the dominant solar heating).  Staying close to coastlines ensures that any rising global temperatures are moderated by the abundance of water.  Staying close to sea level ensures that you are not influenced much by changes in glacier activity nor snow-melt elevation changes.

There is literature that states that tropical ecosystems are most sensitive to climate change, and that tropical areas will see climate change sooner.  However, my point is that the climate itself will be the least extreme in the tropical regions near the ocean. Furthermore, I would like to point out that climate change per se will not make most of the planet uninhabitable as the question insinuates.  As the climate changes, there will certainly be very large changes to the land-surface and ecosystems... including desertification of some areas.  However, any regions with sustainable ecosystems will be habitable, given that there is a source of fresh water large enough for the human population (which the Tropics often have, due to frequent rain... though areas dependent on snow-melt feeding rivers will suffer).


What is the "pressure gradient" within the richards equation I'm trying to understand the Richards equation that can be used to compute the flow of water in soil. In a textbook I found the following:

Unfortunately, the textbook doesn't really explain what the pressure gradient actually is. Is it the matrix potential? Are the soil pores actually pulling water from the surface into the soil?

Or is it maybe the groundwater? The large the difference between surface and groundwatertable the higher the "pressure gradient"?

The pressure as measured at a point z+dz (dz infinitesimally small) and z.

At the surface, pressure is the atmospheric pressure. Just below the surface, let's say at 1 cm depth, pressure is atmospheric pressure + whatever weight of the water column (taking into account saturation and so on).

If the pressure gradient is in equilibrium with the gravity, you will have no flow (water in a glass do not mix, although at the top of the glass the pressure is lower than at the bottom, the water at the bottom feels a little push upwards equal and contrary to the push downward it receives from the weight of the water just above)

Think about this: you are at the bottom of a water reservoir (bottom not sealed). Pressure is the atmospheric pressure + depth of the reservoir. This is enough to induce a flow of water outwards from the reservoir, seeping below/through the dam.

Figure is not my own work, it is from a publication of Olsen and Stephens (2016) that can be found at this URL https://www.researchgate.net/publication/319206472_RELEARNING_HOW_TO_LOOK_AT_PIEZOMETRIC_DATA_FOR_SEEPAGE_EVALUATION


Was this reef protected? I came across this satellite animation the other day. It shows a reef being entirely destroyed to build an industrial complex (airport, harbor, various facilities...). The animated GIF is showcased on the website of a company called Digital Globe (here is the web page cached by the Internet Archive in case they take it down).

I find this quite shocking given how long it takes for reefs to form (I read "100,000 and 30 million years for a fully mature reef to form"). My understanding is that lots of those reefs are actually protected.
My question (I know it's a tough one):
Is there a way to find out which reef this was and whether or not it was protected?

The caption under the image on the Digital Globe website identifies the location as Fiery Cross Reef.

Multiple sites identify what's going on as the Chinese government building an airstrip and related facilities on the site to solidify its claim to the South China Sea.

According to this 2015 BBC story:

  China claims almost the whole of the South China Sea, resulting in
  overlapping claims with several other Asian nations including Vietnam
  and the Philippines.

That story is based on a Jane's 360 analysis of satellite images:

  The 23 March images show a paved section of runway 503 m by 53 m on
  the northeastern side of Fiery Cross Reef, which China began to turn
  into an island in late 2014. Paving and ground preparation of other
  sections of the runway has also begun further along the island. In
  addition, workers have paved about 400 m by 20 m of apron.

According to the Permanent Court of Arbitration on the wider South China Sea territorial dispute between China and the Philippines: (PDF)

  ...China had caused severe harm to the coral reef environment and
  violated its obligation to preserve and protect fragile ecosystems and
  the habitat of depleted, threatened, or endangered species.

But it didn't seem that the reef in question was explicitly protected by any governmental action, especially given the dispute over which country governed the territory. China does not recognize the jurisdiction of the court.


Does anyone know of a comprehensive listing of geostationary weather satellites? Periods of operation at longitude--current as well as historical. The historical list on Wikipedia is incomplete. Is there a single site with status of operational satellites (real-time) or do you have to go to every operator you can think of?

The WMO OSCAR database is a list of all Earth observation satellites¹.  The resulting table can be sorted by orbit type, status (inactive/operation/planned), agency, and other aspects.  From their own description:

  This table shows all known past, current and future satellites for meteorological and earth observation purposes.It can be sorted by clicking on the column headers. The filter on the right allows to display only specific satellites.

A screenshot showing three GOES satellites and the scroll-bar on the right is shown below:

Note that OSCAR has a lot more capabilities than this.  For anything Earth-observation-from-space related, it is a superb resource.

¹Except classified (spy) satellites...


Could an icy/extremely-cold asteroid/comet ever strike and cool the Earth? This is obviously an imaginary question, but it seems like something computable (which I don't have the mathematical ability to do so unfortunately). P.S. I do not have in-depth knowledge about comet/asteroid/meteoroid/even any space object at all, so please correct me if I made any mistakes. Also, please answer the question considering the current state of the Earth, not a super-heated Earth.
Some propositions:

The asteroid/comet is sizable, cold to the core, and is made up of materials with high heat capacity
The asteroid/comet "strikes" the Earth at low speed
The asteroid/comet strikes the Ocean

Related: How gently could a comet/asteroid/meteorite “hit” Earth?

Could an icy/extremely-cold asteroid/comet ever strike and cool the Earth?

No.
The smallest possible velocity is about 11 km/s velocity, and that would require a near miracle. For that to happen, the object would have to enter the vicinity of the Earth through a very small keyhole near the Sun-Earth L1 or L2 point with a very small velocity (a comet will not have that very small velocity), then be nearly ballistically captured by the Moon, and then fall to Earth. A comet would be more likely to hit the Earth at 40 km/s, or larger.
And that means that it does not matter how cold or how hot the object was prior to impact. The kinetic energy of the impact will dwarf whatever thermal energy the object had prior to the impact.


What is the significance of the "super historic" rainfall for July 2015 in southern California? On July 19, 2015 there was record rainfall over the Los Angeles and San Diego areas.  This is amidst a historic drought and the rain is needed.

This article:
http://www.weather.com/storms/hurricane/news/southwest-flood-threat-july-2015-tropical-storm-hurricane-dolores

states that

  Widespread showers and thunderstorms across the Desert Southwest are being fueled by moisture from former Hurricane Dolores.

and

  Los Angeles and San Diego set all-time rainfall records for the month of July on Saturday.

and

  National Weather Service meteorologist called [it] "super historic."

What is the significance of the "super historic" rainfall for July in California (July 19, 2015) in terms of climate change and water reservoirs used for municipalities?  In other words, what is the likelihood that climate change could bring more of these types of rain events in the future?  Related, what is the relative impact on water reservoirs and how much relief from the drought does such an event provide?  Does California have a long-term plan to capture more of this type of flash-flood rainfall in the future?

This event is "super historic" only because of its proximity to the coast.  It is fairly common to get flash flooding in the mountains and deserts of Socal at least a few times each summer, due to the Southwest Monsoon.  This event was different in that a dying tropical system moving north off of the coast of Mexico interacted with a trough off of the Northern California coast.  The combination of these two essentially funneled tropical moisture north directly into the coastal regions of Southern California.

Linking single events to long term global change is virtually impossible to do reliably, so I won't speculate. However one could argue that rising sea surface temperatures could allow tropical systems to stay more organized near Southern California, and increase the probability of events like this. But again, it is never a good idea to try and link a localized extreme event with a global phenomenon.

In terms of drought relief and reservoir storage these rains have virtually zero impact.  They impacted the southern third of California, while the majority of water storage is in the central and northern part of the state along the Sierras. The rain came down pretty quick and didn't soak in to any of the soils, so vegetation will still be just as dry as before the rain. California needs heavy snows in the Sierras for any serious drought relief. Although these rains have given many people a false sense of security.


How do current pollution levels in Los Angeles compare to the 1970s? As I understand it there are two key kinds of air pollution: ozone and fine particles.

Are there any long-term data series that chart average ozone levels and/or fine particulates over time going back to 1970?

The air quality in Los Angeles does not meet federal air quality standards.  That being said, the air quality has improved immensely since the 1970s.

From the California Air Resource Board, in 1965 the maximum one-hour ozone concentration was 0.58 ppm.  Since then, that number has come down to about 0.12 ppm.  You can obtain the latest ozone data from EPA.  See a  30 year ozone trend image below from the South Coast Air Quality Management District:

Particulate matter is a bit tougher to quantify.  PM10 (coarse and fine particles together) has been tracked since the late 80s, but PM2.5 (fine particles) has only been tracked since 1999.  You can read a bit about it here.

The reduction in particulate matter has not been as dramatic as ozone.  This makes sense, though, since ozone is a secondary pollutant whose precursors (NOx and VOCs) largely come from vehicle tailpipes.  NOx and VOC emissions from vehicles has decreased significantly in recent years, especially with fleet turnover.  In contrast, coarse and fine particulate matter come from many different sources, e.g. road dust, agriculture, cooking, etc. which is difficult to control since rain is the major control method.


What is the formula used for atmospheric visibility? I am working on NCEP GFS data to plot various maps. One such plot I would like to have is visibility. I have seen some of the sites showing visibility charts and the source of the data was shown as NCEP GFS.

I could not find any variable related to visibility in the GFS file.

Is there any specific formula available for calculating visibility?

I calculate surface visibility from WRF output using a calculation that I adapted from DTC's Unified Post Processor, specifically from their Fortran routine found in UPPV2.2/src/unipost/CALVIS.f. The calculation is based on hydrometeor mixing ratios, and air temperature and pressure, all from the lowest model layer. If your GFS output has hydrometeor mixing ratios, you can use this formula to calculate visibility. The documentation in the original code reads:

This routine computes horizontal visibility at the
surface or lowest model layer, from qc, qr, qi, and qs.
qv--water vapor mixing ratio (kg/kg)
qc--cloud water mixing ratio (kg/kg)
qr--rain water mixing ratio  (kg/kg)
qi--cloud ice mixing ratio   (kg/kg)
qs--snow mixing ratio        (kg/kg)
tt--temperature              (k)
pp--pressure                 (Pa)

If iice=0:
   qprc=qr     qrain=qr and qclw=qc if T>0C
   qcld=qc          =0          =0  if T<0C
               qsnow=qs and qclice=qc  if T<0C
                    =0            =0   if T>0C
If iice=1:
   qprc=qr+qs   qrain=qr and qclw=qc
   qcld=qc+qi   qsnow=qs and qclice=qc

Independent of the above definitions, the scheme can use different
assumptions of the state of hydrometeors:
     meth='d': qprc is all frozen if T<0, liquid if T>0
     meth='b': Bocchieri scheme used to determine whether qprc
        is rain or snow. A temperature assumption is used to
        determine whether qcld is liquid or frozen.
     meth='r': Uses the four mixing ratios qrain, qsnow, qclw,
        and qclice

The routine uses the following
expressions for extinction coefficient, beta (in km**-1),
with C being the mass concentration (in g/m**3):

   cloud water:  beta = 144.7 * C ** (0.8800)
   rain water:   beta =  2.24 * C ** (0.7500)
   cloud ice:    beta = 327.8 * C ** (1.0000)
   snow:         beta = 10.36 * C ** (0.7776)

These expressions were obtained from the following sources:

   for cloud water: from Kunkel (1984)
   for rainwater: from M-P dist'n, with No=8e6 m**-4 and
      rho_w=1000 kg/m**3
   for cloud ice: assume randomly oriented plates which follow
      mass-diameter relationship from Rutledge and Hobbs (1983)
   for snow: from Stallabrass (1985), assuming beta = -ln(.02)/vis

The extinction coefficient for each water species present is
calculated, and then all applicable betas are summed to yield
a single beta. Then the following relationship is used to
determine visibility (in km), where epsilon is the threshhold
of contrast, usually taken to be .02:

   vis = -ln(epsilon)/beta      [found in Kunkel (1984)]

I have adapted the code from this routine to a Python function below, which you can use for your purposes:

def calculate_visibility(qv,qc,qr,qi,qs,T,p):
    """
    Calculates visibility based on the UPP algorithm.

    See documentation in UPPV2.2/src/unipost/CALVIS.f for the description of
    input arguments and references.
    """
    Rd = 287.
    COEFLC = 144.7
    COEFLP = 2.24
    COEFFC = 327.8
    COEFFP = 10.36
    EXPLC  = 0.88
    EXPLP  = 0.75
    EXPFC  = 1.
    EXPFP  = 0.7776

    Tv   = T * (1+0.61*qv) # Virtual temperature

    rhoa = p/(Rd*Tv) # Air density [kg m^-3]
    rhow = 1e3       # Water density [kg m^-3]
    rhoi = 0.917e3   # Ice density [kg m^-3]

    vovmd = (1+qv)/rhoa + (qc+qr)/rhow + (qi+qs)/rhoi

    conc_lc = 1e3*qc/vovmd
    conc_lp = 1e3*qr/vovmd
    conc_fc = 1e3*qi/vovmd
    conc_fp = 1e3*qs/vovmd

    # Make sure all concentrations are positive
    conc_lc[conc_lc < 0] = 0
    conc_lp[conc_lp < 0] = 0
    conc_fc[conc_fc < 0] = 0
    conc_fp[conc_fp < 0] = 0

    betav = COEFFC*conc_fc**EXPFC\
          + COEFFP*conc_fp**EXPFP\
          + COEFLC*conc_lc**EXPLC\
          + COEFLP*conc_lp**EXPLP+1E-10

    vis = -np.log(0.02)/betav # Visibility [km]
    vis[vis > 24.135] = 24.135

    return vis


Is there any animation to demonstrate if the sea level rise up? I found a very cool video here:

Draining Earth's oceans, revealing the two-thirds of Earth's surface we don't get to see

https://www.youtube.com/watch?v=-uOwv_Krqk8&feature=emb_logo

However, I am looking for a video that demonstrates the sea-level goes up. I think there'd be many of them because it's a result of the Global warming. But I can't find any. Can someone post one?

There is this NASA animation showing 12-13 years between 2002 and 2015. It is interesting for showing the counter-intuitive lowering of sea levels nearest to land based ice mass losses, especially around Greenland and Pacific Alaska. This is due to local gravitational effects, ie less ice mass reduces the pull on ocean water near where the ice melts, so water levels actually fall in such places, whilst places furthest from them experience the greatest sea level rise.

(Any tips for embedding this video?)

https://youtu.be/VY_SeZiBcM4


Will increased precipitation in Antarctica prevent sea level rise? It has been suggested that global warming will lead to increased precipitation in parts of Antarctica. This would sequester water in the ice sheet, preventing sea level rise.

However, the slope (and thus the height and volume) of continental ice sheets is limited by ice properties. What if the ice sheet is already at its maximum slope/height/volume (is this known)? Wouldn't adding more ice just cause more flow to the sea?

According to "Ice Sheet Modeling"

  ice behaves as a deformable plastic material, which means that there
  is a critical shear stress, below which no strain (deformation or
  flow) will occur ... If the slope is too low, the basal shear stress
  will not match the critical shear stress, ... but as snow piles up,
  ... flow will begin. ... The result of this is that a glacier has an
  equilibrium profile

I am presuming that the ice sheets are already slightly above their equilibrium profile (since they are flowing). Since the profile depends on the area and shape of the base (which is shrinking due to melting around the edges), they are already holding as much ice as possible, and adding more snow to any region will just accelerate the flow. I don't know on what timescale this occurs. (I have not tried the computer models described in the paper.)

There is some scope for continuing debate because quantifying the various components of the ice/snow/water balance are fraught with difficulty, and many of the estimates have error bounds which approach the magnitude that is being measured. However, a good best estimate, subject to continuing research, is given in:Is Antarctica losing or gaining ice?
This cites the following two graphs:

Clearly there are important regional differences, with East Antarctica gaining slightly, but not enough to compensate for the ice loss in west Antarctica.

It is true that the amount of fresh snow in the Antarctic is increasing, but it still doesn't amount to much. Antarctica is still the driest continent, by far, and much more so than Australia. The controlling factor is not the amount of snow on the land, but the fate of the sea ice around the perimeter. Notwithstanding climate deniers, there is abundant evidence that the oceans' sea surface temperatures are warming, including the Southern Ocean. This reduces the seasonal extent and thickness of sea ice, which lowers the oceanic albedo, and increases near-surface heat absorbtion. It is a well-documented feedback process. Overall the warmer ocean around Antarctic destabilizes the shelf ice, thereby unlocking the glacial ice which would have been held back. So we have two opposing non-linear processes, mobilization of coastal land ice (mass loss), vs increased snowfall (mass gain). At present, and for the forseable future, the mass-loss is winning. I'm guessing this will continue to be the case because the negative feedback is very powerfull. I don't think there are any reliable forward projections about how precipitation in the Antarctic will evolve.

(Later) In view of the comments, maybe it would be helpful to visualize the daily precipitable moisture around the world. This is available at El Dorado Weather.


Hydrocarbon potential in Ganges Brahmaputra delta According to Curray (1991):

  Total sediment thickness beneath the [Ganges–Brahmaputra delta] southeast
  of the hingezone exceeds 16 km...

Considering a normal geothermal gradient and data for oil and gas formation, this suggests that at such the at some point we must have oil and gas reservoirs.

What could be a possible explanation why no such discoveries have been made so far in the region?

Reference: Curray, JR (1991). Geological history of the Bengal geosyncline. J. Assoc. Explor. Geophys. 12, 209–219.

There have been a few discoveries in the Bay of Bengal.

Santos made a gas discovery in 2012, and depending on what you'd call part of the delta complex (all of the Bengal Fan?), there are others. One field, Sangu, saw several years of production, but seems to be shut-in today. Another, Kutubdia, is awaiting development.

It's true though that there have not been many at all, if you compare with some other big deltas, like Niger or the Gulf of Mexico. Blakely (2010) suggested there are border disputes, which definitely slows exploration. I'm just guessing, but there may be other factors, such as regulatory issues, slow government licensing, or political pressures. Reading around, it does seem fair to say that the region has not been fully explored, and clearly there is a working hydrocarbon system.

References

Blakeley, I (2010). Bay of Bengal. GEO Expro 7 (6). Available online


Discrete Slant Stack on seismic data In the formula for slant stacking (tau-p transform) a substitution t=tau+d/v is made.

If we consider the substitution as a vector equation then how can vector d/v have the same length as vector t given that in most surveys the number of data points for offset(d) is less than for time (t) .

The $\tau$–$p$ time domain $t$ is a function of offset $d$, so the result is an array of size $n_t \times n_d$, where $n$ is the number of samples.

The inputs are a vector $\tau$ of travel time at zero offset, or $t(0)$, an array $p$ of ray parameter, which is in turn a function of velocity $V$ and angle, and a vector $d$ (usually called $x$) of offset.

Here's an example of some visualizations of the $\tau$–$p$ domain from a paper by Sergey Fomel; they might help explain what I mean by an 'array' — you can think of them as images:

The resulting travel-time $t(d)$ is an array of size $n_t \times n_d$, where $n$ is the number of samples. For a given offset at a given time sample, the result is a scalar — a single value of $t$.

By the way, stevej's answer is a great explanation of how exactly to calculate the ray parameter term, given limited information. Do follow that link to Yilmaz, and maybe also read the Radon transform article.


Dino-birds or "Pigeon-o-saurus" It seems to be an accepted fact that Theropod dinosaurs evolved into present-day birds, but I am still leery of this theory. Can biologists and paleontologists really compare these distinct animals and conclusively show that they are "one-in-the-same" creature, based upon certain morphological similarities?  Is this idea "set in stone?"

First, let me link a variety of popular science articles which can give you some background explanation. Here are Scientific American, Smithsonian, and Audubon magazines.

The 'smoking gun' evidence linking birds and dinosaurs is the evolution of feathers. Feathers are a feature that set the birds apart morphologically from the rest of the tetrapods, and indeed from the rest of all animals. All birds have feathers and nothing that isn't a bird has feathers. So a logical place to start looking for the origin of birds is the origin of feathers.

Since the dawn of modern paleontology, there had always suspected links between dinosaurs and birds due to the fossils of Archaeopteryx found in the 1860s. Thomas Huxley claimed the two groups were related as early as 1863. But it wasn't until recent decades that the fossil record started being filled in with definitive links between Archaeopteryx and therapod dinosaurs, such as more species intermediate between birds and therapods and fossil impressions indicating that some therapods had feathers.

The rest is just filled in by logical deduction, or Occam's Razor. There is clear evidence that all birds have feathers, and no other animals alive today have feathers. There is now clear evidence that therapods had very similar skeletons to birds with feathers about 150 million years ago. There is also evidence that many therapods had feathers, a trait otherwise confined to birds.

Let our null hypothesis be that the origin of birds is unknown, and our alternative hypothesis be that birds evolved from dinosaurs. Given the similarities noted above (and, keep in mind, the evidence is much stronger for scientists who specialize in this area), do you think there is enough evidence to reject the null hypothesis and conclude that birds evolved from dinosaurs? If not, are there any plausible alternative hypotheses?

The great thing about science is that you never have to take someone else's word for it. Everyone has the right to be a skeptic, just keep an open mind and look at the evidence and you can draw your own conclusions.


Why do forecast areas on weather.gov appear as twisted squares? I get my weather forecasts from good ol' NOAA's weather.gov site. On the detailed site weather pages, there's a map that shows the forecast area as a green square (for Boston at least, the square is about 1.5 miles on a side). You can click on nearby areas to change the presented forecast to that new location.

Here's the question: why is the square shown as the forecast area not oriented north/south/east/west? For some reason, near the US East Coast it's twisted clockwise, and on the West Coast it's twisted counter-clockwise. I assume it's something about the easy representation of weather information in a GIS system, but that's only a guess.

Here are some examples, from East to West. First, Boston:

Second Indianapolis:

Third, Denver:

Fourth, San Francisco:

Note that, if you go even further west to Hawaii, the pattern breaks, and the square is perfectly north/south/east/west:

So, any ideas?

The equal-area projection used to create the continental U.S. grid for weather forecasting does not represent lines of latitude and longitude as straight lines.  Instead, they are curved (note the Canada-USA border curvature below, which is actually along the 49th latitude parallel).

An equal-area projection is often used in regional weather modeling because it is important for each cell to represent the same amount of physical space during computation.  The map images posted in the question are using the Mercator (or Mercator for web) projection, where lines of latitude are horizontal and lines of longitude are vertical, but area is distorted.

The grid-cells from the regional model are also designed in a way that maximizes cost-benefit of computational power.  You want to minimize the number of grid cells modeled while maximizing the number of grid-cells in your domain that are relevant to your study area.  This ensures that you aren't wasting computational power and is often achieved by changing the orientation of the domain a little.  So, the grid cells do not align nicely on the mercator map used on web-app maps like google, bing, etc.  However, the grid-cells line up perfectly if visualized using the native projection for the image frame (e.g. below).

The reason that Hawaii does not follow the pattern is that the data for Hawaii is obtained from a model simulation for a different grid.  The nesting of grids can be seen in the image below.

I suggest you read Grids in Numerical Weather and Climate Models
 for a nice look at the factors involved when choosing a grid definition.
You could also look here for more info about NOAA prediction.

North American Mesoscale (NSM) forecast model domains used by NOAA.


What causes dye to bleed from an agate stone? I came across this review on Amazon. The cold drink was placed on top of the agate stone and the dye bled and left a permanent mark on the table.
Why does this happen? Is it because of the condensation as mentioned by the customer? Can regular warm water also cause the same effect?
I just want to know why dyes work, and what makes them bleed.

Dyeing agate is a common practice- the stone is real, but it's been cosmetically altered. The stone gets soaked in a chemical solution, which is absorbed into the microscopic pores in the stone.  Whatever dye the person who made these coasters used must have been water-soluble.  So, yes, cold water would also cause the pigments to bleed.


Is there the right term for time points in hourly weather forecast? Each hourly weather forecast has two columns with date and time. The first column: forecast creation date and time (the column (1) in a table below). The second column: forecast hour (the column (2) in the table below).

Is there an established term for the second column? Points? Slices?

The Weather Company uses 'Time' name for this column.
NOAA uses 'Output Timestep' name for this column in the GFS forecast model.

And also, is there the right term for the first column?

Table with example of hourly weather forecast
+--------------------+---------------+----------------+
| Forecast Creation  | Forecast Hour | Temperature, K |
| Date and Time (1)  |       (2)     |      (3)       |
+--------------------+---------------+----------------+
| 2019-03-28, 00-00  | +0            | 303            |
| 2019-03-28, 00-00  | +3            | 305            |
| 2019-03-28, 00-00  | +6            | 307            |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| 2019-03-28, 06-00  | +0            | 307            |
| 2019-03-28, 06-00  | +3            | 308            |
| 2019-03-28, 06-00  | +6            | 309            |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I spotted that a scientific paper [1] uses the "lead time" term, and then its definition [2] was found from the Glossary of Meteorology by the American Meteorological Society.

forecast lead time
The length of time between the issuance of a forecast and the
occurrence of the phenomena that were predicted.

[1] https://link.springer.com/article/10.3103/S106837391405001X
[2] http://glossary.ametsoc.org/wiki/Forecast_lead_time


Plate boundary lon/lat data I'm working on a map in GMT and am having trouble finding lon/lat data for the minor plate boundaries (specifically the adriatic). Is there a database I can refer to?

I did a little poking around and came across a few projects that might be interesting.

Based on the work of Peter Bird (2003) there's a github project (fraxen/tectonicplates) that hosts georeferenced data of most major plate boundaries.

Seeing as you're interested more in minor plate dynamics, there's another project called GPlates that is an multi-OS open source visualizer for plate boundary dynamic reconstructions. While I haven't looked at the potential outputs available, I imagine you would be able to export data from this platform into a more traditional GIS data format (.shp, .gml) that could be read in GMT.


Why are the latest additions to the Hawaiian-Emperor seamount chain the highest? The Hawaiian-Emperor seamount chain stretches from Russia to the Hawaiian islands.  When I look at them on a map, it seems that the oldest seamounts by Russia are shorter and smaller than the newer seamounts/islands, and even in the most recent additions (the Hawaiian islands) there seems to be a gradient in size, with the older islands being the smallest and the newest island by far the largest and with the tallest volcanoes.

Is this gradient in size due to erosion?  Were the seamounts at one point islands?  Or is there something related to the volcanic activity and plate motion itself that is producing larger volcanoes more recently?

As it was explained to me at university there are two factors; buoyancy and erosion.

Rock buoyancy is a major factor, fresh Basalt is hot and dry and has a much lower density than older oceanic crust. This is why the mid-Atlantic ridge rises above the surrounding seabed.

The effect is even more pronounced with seamounts because they're composed of even hotter rock that takes much longer to cool and wet. As seamounts age they cool, making them denser. As they cool, they absorb water, making them still denser. Where that water interacts with the still cooling rock, secondary mineralisation occurs, which fills gas pockets and other voids, making the rock denser again.

All of this results in the seamount sinking farther into the crust which reduces it's height above sea-level over, relatively short, geological time.

At the same time the mounts are sinking they're also being weathered from above. This shortens them, and also disguises the depression in the seabed from the sinking mountain with debris from above, since erosion generally slows as the mounts sink deeper. Also, as they move north out of tropical waters and coral growth stops, they stop growing at all.

The newer mounts are taller only because they're younger, hotter, and drier, they'll sink and shrink as they age.


Are there any sulphides, sulphates, carbonates that cannot be dissolved by aqua regia? I was looking into these specific minerals: arsenopyrite, pyrite, chalcopyrite, barite, calcite, dolomite. I investigate issues with tellurides not showing expected gold concentrations.
There is gold predicted at the site where these samples are. We tryed to prove the presence of gold through aqua regia tests, but the resulting gold concentrations are low. My suspicion is that the majority of the gold resides as an inclusion in these minerals, and the aqua regia test won't be able to show that because of its inability to dissolve the host.

This was also asked in Chemistry Stack Exchange, where it was noted that barium sulfate is insoluble in water and generally insoluble in acids.  A quick check reveals that indeed the otherm minerals can be dissolved in nitric acid and so should yield to aqua regia.  Thus barite is the troublemaker.
Barite can be dissolved in hot alkaline chelating solutions, as described here[1].  This, of course, is not compatible with the acidic solvent you intend to use to dissolve and measure the gold.  It is not clear from the reference whether a pretreatment with such a chelating agent to remove the barite before placing in aqua regia would work when the barite is intermixed with the alkali-insoluble sulfides listed in the question.
Reference
1.
Bader Salem Ba Geri, Mohamed A. Mahmoud, Reyad A. Shawabkeh,  Abdulazeez Abdulraheem, "Evaluation of Barium Sulfate (Barite) Solubility Using Different Chelating Agents at a High Temperature", Journal of Petroleum Science and Technology 7(2017), 1, 42-56.


How to calculate relative humidity from temperature, dew point, and pressure? Is there a formula given the temperature, dew point, and pressure to find relative humidity?

I have seen several calculators like this one, but I would like to know how to calculate this myself.

I am aware that there are several formulas that can calculate this with just the temperature and dew point, but since I'm writing a program, I would like to be able to use the pressure data that I have for greater accuracy.

You can refer to this question for more detail on the origin of this formula (based on the Magnus approximation), but if you do some algebra to the expression there for dew point ($TD$) as function of temperature ($T$) and relative humidity ($RH$), you get
$RH=100 \, e^{\Large \left(\frac{c\, b (TD-T)}{(c+T) (c+TD)}\right)}$
With $b=17.625$ and $c=243.04$.
In this case, where $TD$ is one of your input variables, there is no need to consider the pressure, pressure have no effect in $RH$, or more accurately, the pressure dependence is already considered through $TD$.
The pressure would come into play if you are computing $TD$ from water vapour pressure, because water vapour pressure is what have a small dependence in atmospheric pressure.
The Magnus approximation above is considered valid for:
$0^oC < T < 60^oC$
$1\% < RH < 100\%$
$0^oC < TD < 50^oC$
There are also other equivalent formulas that extends their validity range by changing the constants, like this one
$RH=100\cdot10^{\Large m\left( \frac{TD}{TD+T_n}-\frac{T}{T+T_n}\right)}$
Where values for the constants $m$ and $T_n$ depend on temperature and are tabulated:

See this document for more details.
There are also very simple approximations to these formulas, like
$RH \approx 100 - 5 (T-TD)$
You can find a discussion on the accuracy of this approximation here.


What were the geometric coordinates of the Chicxulub impactor 66 million years ago? At the moment around mexico we can find the leftovers of the Chicxulub impactor which could have extincted most dinosaurs. But 66 million years ago was after the breakdown of Gondwana. So back to those days where did exactly (probably approximately) hit the meteorite. Was it far from Yucatan?

Sixty six million years ago the Chicxulub meteorite struck the Yucatan peninsular in the same place as the crater is today. The peninsular hasn't moved very far since then, though some of the continents have, India for example. South America was already well adrift from Africa. At the time, most of Yucatan was probably under a shallow sea, too shallow to slow the impact to any great extent. Struck at that speed (about 55 km per sec), water is as solid as stone, but 50 feet of stone would have done little to slow the speed of such a large bolide. The water and much of the rock beneath it was vaporised.


What is the total Earth's interior energy budget? What is the total Earth's interior energy budget?

What is the heat flux per m2 that warms the Earth surface because of the Earthy's internal heat.
How much of that heat is replenished from the radioactive decay?
How much of that heat is replenished from Moon's tidal forces?

If you see wikipedia here:
en.wikipedia.org/wiki/Earth's_internal_heat_budget

They have a nice summary of the answer I think you are looking for:

  The flow of heat from Earth's interior to the surface is estimated at 47 terawatts and comes from two main sources, the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust and the primordial heat left over from the formation of the Earth. Earth's internal heat powers most geological processes and drives plate tectonics. Despite its geological significance, this heat energy coming from Earth's interior is actually only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation.

You can divide by the surface area of the Earth to get your rate per square meter.


Rayleigh scattering from the moon light If the moon reflects exactly the sun spectrum, then the blue photons part of the spectrum should scatter in the atmosphere during the night (assuming a perfect dark night sky). Why don't we see a bluish light during the night, the equivalent of a blue sky during the day ?

Answer to this question is very well given at Physics forum pointed out by @gerrit. In short, Light should be strong enough in order to notice its colour by human eyes. Even on full moon night, light from the moon is 10 times less luminous than the dark limit of civil twilight hence we don't perceive sky color or even moon colour like we do during the day.


Are these the net radiation at surface, and the complete energy balance at surface? Could not find these in my book but I found something I think might them online (is this correct):

Net radiation balance:
R_NET = SW↓ - SW↑ + LW↓ - LW↑

Complete energy balance:
R_NET  - G = H  + LE

Were H and LE are sensible and latent heat fluxes, and G is the ground heat flux.

Are these right?

Please help

Thank you

Yes, these are the correct terms.  The first equation is generally termed the 'surface radiation budget' and the second the 'surface energy budget'.

As @Deditos pointed out, additional terms for biological storage and flux can be added and are in fact important sources when considering a microclimate, and these would generally be placed into the surface energy budget.

Another form of the first equation is

Rn = ϵLW↓ − σϵT_s^4 + (1−α)SW↓

Where ϵ is the longwave emissivity of the surface, σ is the Stephan-Boltzman constant, T_s is the surface temperature, and α is the albedo (see Huber et al., section 3.2).

In certain circumstances, it is useful to set them equal to each other by solving for Rn, so you may also see

ϵLW↓ − σϵT_s^4 + (1−α)SW↓ = G + H + LE + (S + B)

Where B is the biological flux.


Why has the average low for the hottest months in Clearwater Florida about 5 degrees higher than the historical average? Look up Clearwater Florida on Wikipedia and it gives you the average low for the Months of July and August as being 74.2F. About 3-4 years ago I picked up running as a main hobby and the temperature is the biggest factor determining my speed every day. Since then Ive been following the temperature and I am sure that for the last 2-3 years at least the daily low has been 78F to 82F for a mean of about 80F.

Why is the recent average lows for July and August so much warmer than the historical average?

Is this just a recent trend due to El Nino or some other weather pattern?

What you are observing is called anecdotal weather observations.  I will address it in a number of points, none of which many people will agree with, but so be it.

2-3 years is weather, not climate.  Climate is measured in millennia, not days.  Historical averages are measured, well historically, which for most locations in the US is 50-300 years.  During those years, methods of measurement have changed, so historical numbers may also have glitches in them, such as the the highest US temperature ever recorded is still in dispute because of how it was measured.  But historical averages are calculated from all of those years, ones with droughts, unseasonable cold fronts, and so on.  Warming patterns which are the basis for global warming studies are based on looking at all this data, plus many years of indirect data from ice cores, tree rings, sediment deposits, and many other sources, not from 2 years of personal study.

It is routine to have years that are outside of the average, that is what averages are.  It is also human nature to amplify the variation and see extremes.  I did not go that far back, and I used only one source, but I looked at a little recent recorded data for Clearwater.  I took daily numbers and went with variations to the daily average temp for that date.  For Aug 2017, there are 8 days available thus, and the daily lows have been recorded as +17 degrees to average, or +2.15 degrees.  For 2016 back to 2013 you get +27, -2, +24 and +7 for Aug, or as an average daily difference about +0.87, -0.06, +0.77 and +0.23 with a average for the 4+ years of +0.38 to average.  Only the partial month for 2017 exceeds 1 degree variance to average.

July numbers are, starting with 2017, 41, 37, -29, 13, -31 or in daily variations +1.32, +1.19, -0.94, +0.42, -1.00 for a 5 year average of +0.20.  Although the last two July's have exceeded the plus one degree variance, two of the prior three were almost the opposite.  That is weather and normal variation.  To get to climate numbers requires looking at those patterns over centuries, not over a couple years.

Trust me, I am not refuting global warming.  I am however refuting using such anecdotal observations as a bases for the claims.  Weather patterns work in cycles, and before climate change claims can be made the cycles must be accounted for.  When a location has an especially hot day, or month and references are made to global warming, it make that side of the argument look silly.  When a blizzard occurs, there is a record low, or an seemingly especially cold day, and the deniers point and chant global warming and laugh, they may also feel they scored points, but under statistical analysis they look silly as well.

I do not claim the above to be a statistical analysis.  I also did not cherry pick data, I simply only had time or willingness to do a quick 5 years.  That was more than enough to see yearly variations and demonstrate that a perceived variation of 4-5 degrees is actually 1, and 1 degree is still within typical yearly variation.  To make a real claim requires a pattern of trending real variation in a continuing upward direction and that require rigorous and systematic data collection and analysis.


What do physical oceanography grad schools look for? I'm a junior studying math at a Canadian university and I'm planning on applying to oceanography grad schools. However, I haven't taken much physics or geology courses, and am just starting to swap out some of my math courses for courses like remote sensing and environmental modelling.

What are some good grad schools for physical oceanography and what do they typically look for in an applicant? Will decent math and physics grades and high grades in geology courses look good, along with a decent GRE score? I'm thinking of applying to Canadian and US institutions. If you have any suggestions on where I can apply, I'd appreciate that too!

I'm interested in marine acoustics, ocean engineering, and physical oceanography in general. My top choices right now are Scripps, and the program at the University of New Hampshire.

Most of the physical oceanography students I know studied mechanical engineering, physics or mathematics in undergrad. Strong physics and mathematical skills are very important. Programming is also a plus. Having a few earth sciences courses is good, but the physics and math is much more important, so I think you will be in good shape.

However, beyond the basic background, clear ability to do research is very important in PhD admissions. Even if the applicant doesn't have any research experience, there are ways he/she can show that potential. A clear statement of purpose that outlines and contextualizes the problems the student wants to address in graduate school will catch the eye of any professor looking for students. There many students who have posters at AGU, GSA ect, however, the truth of the matter is that most undergraduates with research experience entering graduate school aren't ready to hit the ground running anyway. Professors know that, as they have had students before.

For courses, I would say skip the environmental modeling course unless it is directly related to what you want to research. Take the remote sensing, and instead of environmental modeling, take a full on numerical modeling course. A rigorous undergraduate level (or if you can stomach it, graduate level) will give you a very strong foundation for whatever simulations you may or may not to run during your career as scientist, even if you start out as a purely observational scientist. Fluid Mechanics is also a no brainer if you still have time.

Finally, the oceanography researchers at LDEO (columbia university) are top notch. So are the ones at University of Washington, Hawaii, and Rhode Island.

Good luck on your applications, you have a lot of time to decide what you want to do (since your junior year just started I'm assuming).

The best advice I can give you is look at what researchers are doing on their websites and try and read a few of their papers. If you know any professors with these same interests, ask them what you don't understand.  Earth Sciences is much different than math (I came from pure physics), spend some time trying understand what an oceanographer does. If you can figure that out, you will be more than prepared to reflect that in your statement of purpose and you will be a stellar candidate for graduate school.


Is there an instance where the sun sets or rises partly, then return back? I am reading Longest Sunset from XKCD. At first, I've thought that he mentions these phenomena just for fun, but it turns out to me that it might happens, based on the level of somewhat seriousness that I perceive from his writing. He doesn't talk about that in detail.
For the sunset:

Sunset starts the instant the Sun touches the horizon, and ends when it disappears completely. If the Sun touches the horizon and then lifts back up, the sunset is disqualified.

I'm not sure if the sunset is disqualified is because it happens, but we don't count it, or because he's just making fun. But I can't prove that this cannot happen. The more we head to the poles, the shorter the night is. Ultimately there will be a point that the sun still sets, but not completely, right?
For the sunrise:

For the purposes of our question, this is not a sunset:

The phrase for our purposes strengthen my doubt that he is being serious. The logic is the same above.
But these two illustrations are in the series of other apparently amusing ones, which are the sun as the cell in division, or as the egg in hatching (if you read the book, you will see this effect stronger).
So, is there an instance where the sun sets or rises partly, then return back?

Yes, such sunrises happens every year at the beginning and end of the polar nights at high latitudes. One can have a few days with a glimpse of the sun but disqualified sunsets and sunrises.

Sunsets occur at the end of the midnight sun period by the end of the summer, the first sunset is not complete.

Sun at it's highest elevation at midday. (To be honest, the picture might be taken the day after the first sunrise, as some mountains are hiding the horizon.)

Here is e.g. an article from Svalbardsposten, the northernmost newspaper in the world, reporting of the first rays of sunlight after the polar night and some pictures from the last sunrise/sunset before the polar night in northern Sweden.

The same occurs at the southern polar circle and south thereof, unless it's cloudy...

Update: here is a great time laps from Davis Station in the Vestfold Hills showing exactly what you asked about: Mid winter


How much methane clathrates are buried in continental deposits? Methane clathrates are

  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.

They mostly are on the bottom of the world's oceans; however, the overly brief wikipedia section for continental deposits suggests that it also occurs in Siberia, northern Canada and Alaska.

How much methane clathrates are believed to be buried in these continental deposits?

According to Role of methane clathrates in past and future climates,

  Methane occurrences and the organic carbon content of sediments are
  the bases used to estimate the amount of carbon currently stored as
  clathrates. The estimate of about 11,000 Gt of carbon for ocean
  sediments, and about 400 Gt for sediments under permafrost
  regions...

So 400 billion tons.


Weather forecast based on pressure, temperature and humidity only (for implementation in Arduino) I have a project for my school to make, and I'd like to have some materials of research/graphs of dependencies about how the weather is predicted (i.e. cloudy, sunny, rainy). I've been searching the internet for the past few days but couldn't find something rather helping.

I can use an Arduino UNO and a bunch of sensors (i.e. atmospheric pressure, temperature, humidity, etc.), but my main problem is how to accurately interpret the parameters measured.

Such simple algorithms are empirical and for the same reason very local, so depending on your location they can have very bad performance. In the other hand, some people argue that properly calibrated they can be over 90% accurate.

Most of them are based in the Zambretti algorithm or some variant of it. This algorithm was originally implemented in a forecaster device produced by the firm Negretti and Zambra in the early XX century.

It considers the absolute value of the pressure, the trend of the pressure, the season and the wind direction (although wind direction and season have a small impact in the output). The algorithm is well described and translated to formulas in this article, but in summary it works calculating a tabulated forecast number $Z$ as follows:

From your measured pressure $P$, temperature in Celsius $T$ and the altitude in meters $h$ compute the atmospheric pressure reduced to sea level $P_0$. There are many formulas for this, a common one is:

$P_0=P\left(1-\frac{0.0065 h}{T + 0.0065 h+ 273.15}\right)^{-5.257}$

Compute the pressure trend and

If the pressure is falling compute the forecast number as $Z = 130-\frac{P_0}{81}$
If the pressure is steady compute the forecast number as $Z = 147 -\frac{5 P_0}{376}$
If the pressure is rising compute the forecast number as $Z = 179-\frac{2 P_0}{129}$

Adjust $Z$ for wind direction:

For Northerly winds adjust $Z=Z+1$
For Southerly winds adjust $Z=Z-2$

Adjust $Z$ for the season:

If Winter adjust $Z=Z-1$
If Summer adjust $Z=Z+1$

Look up for the forecast from the following table:

This was made for the UK, and many people have developed modified version to work in other areas. You will find many implementations online with downloadable code, as this one in javascript, or this one in C for Arduino UNO, an explanation of this Arduino UNO implementation can be found here.


Why is Europe warmer than North America at similar latitudes? Traditionally it has thought to be the Gulf Stream. But other researchers, like Richard Seager and Tapio Schneider, propose different arguments as to why.

How much of a role does the Gulf Stream really play? Who is right? (or are they all at least partially right?)

It is true that the Gulf Stream plays a role on the different climates of each region; I would not call it an 'urban legend' as Richard Seager and other scientists put it, however it seems that how much it actually changes the climate is currently under debate.
From Wallace Broeker:

One of the major elements of today's ocean system is a conveyor-like circulation that delivers an enormous amount of tropical heat to the northern Atlantic. During winter, this heat is released to the overlying eastward air masses, thereby greatly ameliorating winter temperatures in northern Europe.

Thermohaline circulation—often dubbed "the ocean conveyor belt"—carries warm surface waters (pink) from the tropics to the North Atlantic, with the return flow at depth (purple). But contrary to many accounts (summarized by diagrams such as this), this heat conveyor plays only a minor role in keeping European countries warm during winter months.

It seems that although, as you stated, the Gulf Stream traditionally was thought to play a major role in the climate difference, new studies emerging shows that only contributes a small amount to the temperature difference.

The cooling effect could account for 30 to 50 percent of the temperature difference across oceans, the study suggests.  It also explains why the cold region is just as big for both North America and Asia, despite the continents' differences in topography and size.
The cooling depends on heating air over warm ocean water. Since the warm currents along western ocean boundaries in both the Pacific and Atlantic are similar, the resulting cold region to their west would be similar as well.  The new study adds to other recent research that found that ocean currents such as the Gulf Stream aren't capable of transporting that much heat to northern Europe, instead contributing only up to 10 percent of their warming.

There are also studies suggesting that the conveyor belt model itself was extremely oversimplified, and its role in ocean overturning cycles is being re-evaluated:

As the study of the modern ocean’s role in climate continues apace, the conveyor belt model no longer serves the community well — not because it is a gross oversimplification but because it ignores crucial structure and mechanics of the ocean’s intricate global overturning.

Based on the evidence at hand, I believe that the Gulf Stream does play a role in making Europe warmer than North America at similar latitudes; however how large a role it plays perhaps has been overestimated, and with the new ongoing studies perhaps different climate elements, such as the atmospheric elementsrather than the oceanic currents, can be modeled and brought to light in the scientific community, much as Richard Seager is doing now.

The oceans do still play an important role in keeping Europe’s winters mild, but it is nothing to do with the Gulf Stream. The winds that blow northeast onto Europe from the Atlantic carry with them air that is relatively warm even in the winter; the large heat capacity of water means that the sea cools off more slowly in the winter, and this also moderates the temperature of the air above the sea surface. This contrasts with the eastern US, where the prevailing southeast winds are cold, having lost their heat to the thousands of kilometres of land surface they’ve already passed over.
So the oceans are still involved, but it is the atmosphere that is the true key to explaining Europe’s mild winters; and in a pleasing geological twist, it is apparently the presence of the Rocky Mountains that causes the large scale waviness of atmospheric circulation that magnifies the temperature contrasts on either side of The Pond (Richard Seager explains this in more detail in this more comprehensive piece at the American Scientist).


Websites providing visual weather data What websites are there providing visual weather data? The question actually contains the past and future weather. The purpose is for this question is to provide a list of easy-to-access websites that give a weather enthusiast/researcher overview of the weather at a given time. Please list what models the website uses and other describing information.

Ps. I think this should be a community wiki question and answer so that the list can be updated. So feel free to edit this question too.

weather.us

If somebody is looking for free global ECMWF forecasts the above site provides a fairly complete set of links that provide information 10 days into the future. You can track the control member(which I believe is a deterministic forecast) and also the ensemble output.  In addition you can look at worldwide lightning detection sites as well as radar images of US and other selected countries. For followers of tropical meteorology  hurricane tracks of ECMWF are also available - ECMWF  cyclone tracks.
The availability of free ECMWF forecasts comes via the courtesy of Jörg Kachelmann who owns the site.


Water on Mars and Earth If water on Earth came from meteorites, why doesn't Mars have substantial water? What made it more highly probable on Earth than on Mars?

If water on Earth came from meteorites, why doesn't Mars have substantial water?

First off, that's a conjecture regarding the origin of the Earth's water rather than a known fact. A few times a year or so, a new journal article will appear that argues that the Earth's water is primordial, then another arguing that it came from comets, then yet another arguing that it came from asteroids.

If the Earth's water is mostly primordial, most of it is over 4.5 billion years old. If it came from asteroids or comets that collided with the Earth after the Earth had formed, it's still very, very old. Regardless of the source, almost all of the Earth's water has been here for at least 3.8 billion years old, since the end of the late heavy bombardment.

The same would apply to Mars. It has had almost four billion years to lose its water. So has the Earth; some argue that the Earth, too, has lost a lot of water to space in those four billion years.

The key causes of the disparity is that the Earth is significantly more massive and has a magnetic field. Mars's essentially non-existent magnetic field means that water molecules in the atmosphere are more readily split into hydrogen and oxygen than are water molecules in the Earth's atmosphere. Mars's smaller gravitational field means the hydrogen produced by these events has a much greater chance of escaping before it re-forms water than on the Earth.

A very recent conjecture poses another possibility, which is that Mar's mantle is slightly different in composition than the Earth's, and this different composition enabled Mars's mantle rocks to absorb significantly more water than did the Earth's.


Abiogenesis: Formation of Lipids from Montmorillonite I have been really interested in scientific hypotheses regarding abiogenesis, particularly the lipid-world hypothesis. However, I could not find information on the chemical pathway that leads to the synthesis of amphiphilic molecules such as fatty-acids. All I've been able to find is that it involves the mineral montmorillonite which allows the step-wise formation of fatty acids using carbon monoxide (CO) and hydrogen (H). However, I want to know the exact chemical process. Thanks! Here's a link to a video explaining Abiogenesis.  Note: I simplified the Montmorillonite structure and only included the parts that were involved (mainly the very negative oxygen atoms)

My hypothesis is the following: If alkanes were present in the earth's oceans, polymerization of fatty acids could have occurred via chain radical addition. However I'm not sure where the initial radical would come from on the montmorillonite clay particle. Just an idea.

Good question! One that's stuck with me since reading about clay's purported role in providing scaffolding to early organic molecules in a Scientific American article from the late '80s. Many years later I ran into a bonafide clay scientist who said "Of course!" when I asked her about clay's role in establishing early life.

Anyway...

I suspect that molecular attraction and ordering is more of a driver than a specific chemical process (but I'll claim ignorance here). What I have found is a slide from a talk entitled "Chemical Evolution Theory of Life’s Origins" given at the State University of Stony Brook's Astronomy department in which the author highlights an underappreciated chemical property of clay sheets, namely that of mirror symmetry on opposing crystal faces. Recall that these sheets are actually molecular-thin crystals attached to each other by very weak bonds, the implication being that the crystal surfaces themselves are mildly charged providing a surface for monomers to automatically align:

Every physical separation between these crystals provides identical faces on opposing sides of the void. Do these faces act as holding jigs for water-borne monomers to line up into lipids? The authors lab results confirm this. However he provides no details for how, specifically, that catalysis happens.

It's worth noting that this (clay-based) process sounds almost exactly the reverse  of chemical cracking of long-chain crude petroleum compounds in which naturally occurring molecular sieves are used to break bonds (and allow re-ordering of resultant fragments). From Wikipedia:

  The catalytic cracking process involves the presence of acid catalysts (usually solid acids such as silica-alumina and zeolites) which promote a heterolytic (asymmetric) breakage of bonds yielding pairs of ions of opposite charges, usually a carbocation and the very unstable hydride anion. Carbon-localized free radicals and cations are both highly unstable and undergo processes of chain rearrangement, C-C scission in position beta as in cracking, and intra- and intermolecular hydrogen transfer. In both types of processes, the corresponding reactive intermediates (radicals, ions) are permanently regenerated, and thus they proceed by a self-propagating chain mechanism. The chain of reactions is eventually terminated by radical or ion recombination

Here's another important paper that I wish I had more time to read: Origins of life: From the mineral to the biochemical world, in which, among many other important things, the author writes,

  One of these involves enantioselective adsorption on crystal faces.
  Hazen et al. [13] have investigated the adsorption of the two forms of
  an amino acid (aspartic acid) on well-defined faces of calcite
  crystals. These faces themselves already possess the property of
  chirality, i.e. the arrangement of atoms exposed on the surface is not
  superimposable to its mirror image...

This paper is a pretty good resource. This "brief guided tour through “mineral-based” prebiotic scenarios" is clear and the references likely complete, and it also highlights the role of clays in storing molecular information, as well as the role of metal sulfides in establishing (maybe) early metabolic reactions:

Let us know what you dig up!


What is El Niño Modoki? What are the characteristics that distinguishes a El Niño Modoki from a "normal" El Niño?

What are the effects of El Niño Modoki on atmospheric and oceanic processes? How does it affect weather systems?

What are the mechanisms that determine whether an El Niño event is a normal event or a Modoki event?

Here is a nice picture from Ashok & Yamagata (2009):

It seems like the Kelvin wave is held back for some reason that I am not familiar with. From the figure below it looks analogous to a standing wave vs a freely propagating wave.  Interestingly, some authors argue that the frequency of these events has increased in recent years for anthropogenic reasons. i.e. climate change.

  a, An El Niño event is produced when the easterly winds weaken; sometimes, in the west, westerlies prevail. This condition is
  categorized by warmer than normal sea surface temperatures (SSTs) in
  the east of the ocean, and is associated with alterations in the
  thermocline and in the atmospheric circulation that make the east
  wetter and the west drier. b, An El Niño Modoki event is an
  anomalous condition of a distinctly different kind. The warmest SSTs
  occur in the central Pacific, flanked by colder waters to the east and
  west, and are associated with distinct patterns of atmospheric
  convection. c, d, The opposite (La Niña) phases of the El Niño
  and El Niño Modoki respectively. Yeh et al.3 argue that the increasing
  frequency of the Modoki condition is due to anthropogenic warming, and
  that these events in the central Pacific will occur more frequently if
  global warming increases.

The most concise definition i found is:

  The peak warming of the sea surface temperature anomaly (SSTA) is confined to the  central equatorial Pacific until boreal winter instead of propagating to the east.

You may already be familiar with this paper, but I found this passage interesting:

  Because of the obvious distinction from the traditional El Niño
  [Rasmusson and Carpenter, 1982] and even from that defined by NOAA in
  2003, we refer to the SSTA pattern observed in 2004, namely, warming
  in the central Pacific (∼NINO4 region) flanked by colder SSTA to the
  west and east, as an El Niño Modoki (pseudo-El Niño) event; this term
  is now popular in Japan and east Asia. (The word Modoki was introduced
  by T. Yamagata during 2004 while explaining a probable cause behind
  the abnormal summer climatic conditions over Japan. It has been often
  used since then by various Japanese Mass Media. “Modoki” is a
  classical Japanese word which means “similar but different.” A news
  article also appeared in The Japan Times on 24 July 2004 under the
  heading “'Mock El Niño' culprit behind heat wave, floods: Professor,”
  which follows: “The heat wave and floods in various parts of Japan are
  being caused by an El Niño-like phenomenon in the central Pacific
  Ocean, a Japanese researcher said Friday. Toshio Yamagata, a professor
  at the University of Tokyo specializing in climate dynamics, said an
  increase in the sea surface temperature has activated convection
  currents and promoted a high-pressure ridge in the Pacific, bringing a
  hot summer to Japan …”

(Ashok et al. 2007)


Sea Surface Height Data Is there a good dataset on global ocean sea surface height? I found this, http://climate.nasa.gov/interactives/sea_level_viewer, but there is no data I can download and it's hard to see the latitude and longitude coordinates.

The easiest global sea surface height database is from Aviso: http://www.aviso.oceanobs.com/en/data/products/sea-surface-height-products/global.html
Aviso has been distributing Topex/Poseidon and ERS altimetric data worldwide since 1992.


Temperature change in Earth atmosphere models? NASA's page about Earth atmosphere models gives a weird equation about temperature change in different atmospheric layers. One of the formulas looks like this:

Can someone explain to me what this means?

There's some kind of explanation about the units under the picture. The formula is based off the average temperature in degrees Celsius (measured over the entire year, and the entire Earth), which is 15.04 at sea level, and the temperature decreases by 0.00649 degrees every meter above sea level (the average lapse rate). The formula is 'valid' until 11 kilometers, where the troposphere ends.
It's just a model of the average temperature; of course, at the poles it will be colder and at the equator it will be warmer. The lapse rate also varies, while the average of 6.5 °C per kilometer is quite well-known, it can vary between 9.8 °C when it's dry and about 5 °C when it's moist; see Wikipedia for the derivation of these rates.


What visual wave behaviour help to tell if a tide is going in or out? I have always wondered how someone could tell, by a brief observation (a few minutes at most), whether a tide is receding or advancing on a rainy day.  Assuming there is no access to tide times and the ground is completely wet due to the weather.

The reason why I am emphasising a rainy day, is due to the wet sand on the ground, on a dry day, wet sand would indicate whether the tide is going in or out. On a rainy day, everything is wet, no way of telling.

Are there immediate waveforms or wave behaviour that could determine the direction of the tide?

As SimonW points out strong tidal currents will modify the wave shape and significant height.  The Wolf & Prandle (1999) study provides a neat summary description of the effects of currents (of any kind) on waves:

  (i) Wave generation by wind—the effective wind is that relative to the surface current, and the wave age (cp/U*) and effective surface roughness may be important, e.g., Janssen (1989). Here cp is the wave phase speed and U* is the friction velocity of the wind. The effective fetch also changes in the presence of a current.

  (ii) Wave propagation—the effects of depth refraction are easy to spot, turning the mean wave direction towards shore-normal. Current refraction has a more subtle effect, dependent on the spatial variation of currents, whether decreasing or increasing towards the coast. Generally shoaling depths will increase the tidal amplitude towards the coast until friction reverses this trend. The waves will tend to turn towards the direction of the current axis.

  (iii) Doppler shift—the effect of a steady current on intrinsic (relative) wave frequency. Waves of the same apparent (absolute) period will have a longer intrinsic period in a favourable (following) current and a shorter intrinsic period in an opposing current.

  (iv) Steepening of waves on an opposing current (related to (iii)), due to shorter wavelength and increased wave height from wave action conservation.

  (v) Modulation of absolute frequency by unsteady currents and modulation of intrinsic frequency by propagation over spatial gradients of current. If the current is steady the absolute frequency should be constant, if the current is homogeneous the intrinsic frequency should be constant. If both intrinsic and absolute period show a tidal modulation, the currents must be effectively inhomogeneous and unsteady.

  (vi) Wave–current bottom stress. Various empirical theories for wave–current interaction in the bottom boundary layer suggest that the friction coefficient experienced by waves in a current regime will be larger than in no current. This also applies to the effective current friction factor in the presence of waves.

  (vii) Effect of vertical current shear on wave breaking. Wind-driven surge currents would be relevant to this, the tidal currents have no surface shear.

I think the most "observable" of this effects from a "brief rainy day observation" will be their #4 effect. The steepening of waves as they oppose the current can be observed relatively easily. Care must be taken though when interpreting item #4: In steady (constant in time) and homogeneous (constant in space) current, the wavenumber remains unchanged, only the apparent (absolute) frequency and phase speed change:

$$
\omega = \sigma + \mathbf{k}\cdot\mathbf{U}\\
$$

$$
C_p = C_{p0} + U
$$

where $\omega$ and $\sigma$ are the apparent and intrinsic frequencies, respectively, $k$ is the directional wavenumber vector and $U$ is the current vector. $C_{p}$ and $C_{p0}$ are apparent and intrinsic phase speeds, respectively. Due to the conservation of wave crests that says:

$$
\dfrac{\partial k}{\partial t} + \dfrac{\partial\omega}{\partial x} = 0
$$

wavenumber, and thus the steepness of the wave can change only in unsteady or non-homogeneous current field, in absence of other effects.

However, visually, steepness is not the only property of the waves that can reveal strong underlying current. For example, in absence of swell and in presence of strong Eulerian currents and light intermittent wind, small wind-generated ripples can be observed to form on the surface. These waves are almost capillary, very short and low, and propagating slowly. The direction of their propagation can be identified visually because the front face of the wave is steeper than the rear. In presence of strong Eulerian flow against the direction of wind, the whole patch of these short waves can be observed to move backward, rather than forward, thus revealing the direction of the underlying current.

In a similar but different effect, underlying Eulerian flow can be identified in a situation where the current increases to the point where it equals the opposing group velocity of the waves. Since the wave energy is advected with group velocity, they cannot propagate beyond this point, and usually a line the divides the two regimes can be seen: one side with smooth surface without waves, and the other where waves are present, propagating toward the line but steepening and whitecapping when reaching the line. This physical process is known as wave blocking.

Another classic example is the mouth of the Columbia River, where the waves during ebb tide become so steep they often break along the Columbia River Bar. During strong ebb tides, large ocean waves, especially swells, become larger, steeper, and also they come closer together. The resulting dangerous conditions change rapidly as the tide turns to flood with waves being smaller and less steep.

.

One study that looked at the effect on wave height is Gemmrich & Garrett (2012). The attached figure from their paper 2 shows how the significant wave height is affected (modulated) by the normalized tidal speed. Larger waves occur during times of larger tidal currents. . The theoretical considerations can be found in Tolman (1990) where a thorough explanation of the changes in surface wave amplitude, direction, and frequency caused by currents. Other studies looking at wave height modulation include Thornton & Kim (2012) and Wolf & Prandle (1999).


Magnetic "magnetic hills"? I have found on Wikipedia that the term "magnetic hill" is used for an optical illusion. However, I have heard that there are true magnetic hills, i.e., locations where you can't use compass simply because the nearby hill generates its own magnetic field, which drives your compass crazy.

Is there a list of such places, so that one can visit any of them? (I'm especially interested in places in Europe.)

Certainly there are such places. They are simply spots where the nearby rocks have a high concentration of magnetic minerals with a strong remanent magnetization. They're not necessarily literal hills: any kind of topography can be magnetized in this way. I'm not sure what exactly you mean by "drives your compass crazy" -- its direction will be affected, but it won't spin around madly since there's still a field for it to align to.

These phenomena are called magnetic anomalies, and their effect on a compass is called magnetic deviation. You can get an idea of anomalies at a large scale by looking at the World Digital Magnetic Anomaly Map -- however, this map shows anomalies as measured or inferred at 5km above sea level, so small-scale surface features won't show up well. You'll see that, in Europe, there are a lot of anomalies in north-eastern regions (corresponding to iron ore deposits, I suspect) and in Iceland (corresponding to lava flows). At the surface level, there is a fairly recent magnetic declination chart of Europe, but the spatial resolution is too low for the small, intense features which you seem to be interested in.

I think these small-scale magnetic anomalies are mainly of interest to navigators (marine ones might be marked on nautical charts -- I'm not sure) and possibly to exploration geophysicists (who might use them to infer the presence of ore bodies). Unfortunately, data collected for mineral exploration purposes tends to be kept private for commercial reasons. However, geological maps can give you some clues: volcanic rocks tend to be relatively magnetic so if they're near the surface they're good candidates. I found this paper about magnetic anomalies on Mount Etna which shows magnetic declination varying by about five degrees across different sites on the volcano.


Effects of CERN on earth's magnetic field? CERN is a scientific site developed to create anti matter. Does this have any negative impact on the environment?

CERN is a scientific site developed to create anti matter

The scientific activity at CERN involves many things, anti matter being just one of them. For more information you can read their anti matter page.

  Does this have any negative impact on the environment?

No. The amount of anti matter is negligible. Any anti matter produced in CERN is also annihilated at CERN as well and does not "escape" outside into the environment. The CERN experiments require lots of power, so there are power plants that have their own environmental impact. There are also people driving and flying to CERN, but those are indirect environmental effects that are not directly due to the experiments.

  Effects of CERN on earth's magnetic field?

CERN has large magnets that are used in their experiments. Their magnetic field is 100,000 times the Earth's magnetic field! But, the magnetic field is constrained to CERN itself and has no effect outside of CERN, and it definitely has no effect on Earth's magnetic field itself.


Help determining virtual geomagnetic pole Magnetic measurements have been made on some lavas found at 60ºN and 90ºW. The inclination angle is 37º. If the horizontal direction of magnetism of these lavas is due west, calculate the position of earth's magnetic pole when these lavas errupted.

I found the magnetic latitude using $\arctan(\frac{1}{2}\tan(37^{\circ})) = 20.6^{\circ}$, but I'm not sure how to get the pole location since we are not given declination angle. I think you use this formula:

$\cos\theta_p = \cos\theta_s \cos\theta_m + \sin\theta_s \sin\theta_m \cos D$

but not sure how without declination angle D.

You say you're "not given the declination angle", but you also say "the horizontal direction of magnetism of these lavas is due west". That's your declination angle, right there! Since I assume (from the very round-numbered location) that this is a homework exercise or similar, I won't work through the rest of the calculation here. However, if you need more guidance on VGP calculation, I can recommend Chapter 7 of Robert F. Butler's freely available book.


What tectonic structures exist on the Eurasian - North American plate boundary in eastern Siberia? It is reasonably well known that the North American tectonic plate includes a portion of eastern Siberia.  What is often typical in plate tectonic maps is that the actual plate boundary is often drawn with a degree of uncertainty, for example, the map below from the NASA Earth Observatory website is very scant on details of this particular boundary, at times, the plat boundary is referred to as 'diffuse'.

What tectonic structures exist on the Eurasian - North American plate boundary in eastern Siberia?

This plate boundary is one of the least understood in the world, primarily due to the remoteness of the location meaning that there has not been long term observations of seismicity etc.  However, it is not a forgotten boundary and has come under recent scrutiny.

One of the most comprehensive studies of the area was Stanford University's Plate Tectonic Evolution of Northeast Russia, 2004 that produced the following tectonic map:

The workshop participants describe the plate boundary as transitioning from the ultraslow spreading of the Gakkel Ridge in the Arctic Ocean, across the diffuse extensional zone in the Laptev Sea in the north, into the diffuse transpressional 'Moma Rift'.

They describe the uniqueness of the plate boundary as the Euler pole of rotation occurring on or near the plate boundary itself (labelled as NA-EU Pole in the diagram above), which results in the general extensional in the north and compressional complexes in the south.

Further research presented in the conference paper Recent geodynamics and evolution of the Moma rift, Northeast Asia (Imaev et al. 2009), suggest that the "Moma Rift" was once an extension of the Gakkel Ridge and was a extensional rift, but as the Pole of rotation moved, it has become transpressional - with an uplift of up to about 4mm/year, representing a convergent section of the boundary.


Seeking details for the "historical rate" of arable land loss In doing research on the issue of desertification (aka land degradation) I keep running across the same basic sentence but no source or detail to support or clarify it:

  "Arable land loss is estimated to be at 30 to 35 times the
  historical rate."

Can anyone help me find a source that specifies this "historical rate"? Over what length of time is history being measured? What is the geographic scope of this data?

Failing a specific source for this quote, can anyone provide a reliable source for the data subject the quote refers to (i.e. a long term track record of desertification)?

No context is given, but at face value this is a meaningless quotation. Globally there is a net increase in arable land from close to zero about 8000 years ago, to the current maximum of just over 40% of the gross biological productivity of the planet. 'Arable land loss' can refer to the land lost to urbanization, salinization or desertification. One might also make a distinction about agricultural land lost to hydrologic intervention, as in the decreasing flows of the Amu Darya, and Sur Darya in Central Asia. In addition, over the coming decades we will begin to see agricultural land lost to climate change impacts. No single assessment of the 'historical rate' of arable land loss is meaningful. One has to evaluate the various processes separately, and then aggregate them at regional level.


What are the best maps, if any, we have of the convection cells in the Earth's mantle? As the title states, what maps, if any, do we have of convection currents inside the Earth's mantle, and which would you suggest to be the most detailed and accurate?

If you're looking for a cool, well detailed map of convection cells that looks like a modern weather map....forget it. What you're looking for has been notoriously difficult to produce, if not impossible. Even the most advanced seismic tomography techniques using seismic wavespeeds can only resolve mantle "features" thousands of kilometers in scale, but really, only in the X-Y plane. These techniques do a poor job of resolving anything in the Z plane.

Even the locations of convection cell boundaries appears harder to find than theory suggests. Currently, the influence of convection boundaries has been mapped from the surface elevations of oceanic plates, but those maps look like odd "heat maps" indicating where oceanic crust has domed up beneath upward mantle flow. No vertical flow lines boundaries are even remotely suggested with these two-dimensional maps. You can read the actual paper published in Nature, 2016 here: Global dynamic topography observations reveal limited influence of large-scale mantle flow