Rivers flowing into Pakistan Why do Rivers flowing into Pakistan come from either Afghanistan or India and not from inland mountains?

Is it possible for Pakistan to source fresh water from its northern mountains avoiding India or Afghanistan so that the water can feed the entire nation?

I'm a bit confused why you say the water particularly comes from Afghanistan and India.
Perhaps the colors on that graphic end up being a bit confusing...

As your own graphic does indicate, the Indus basin basically runs the spline of Pakistan.  One could argue many many other countries aren't nearly as lucky, with rivers quickly cutting across their country, and so are under much more dependence on countries upstream (and owe more responsibility to countries downstream) (a random example).

Almost all of the water from the northern Pakistani mountains does flow down into central and southern Pakistan and to the Indian Ocean.

Perhaps this fact will be more apparent if the outlines of all the major waterways flowing eventually down into the Indus are shown (from RiversNetwork.org):

All that area of blue waterways is flowing into the Indus, and down through the country.  These rivers include large gatherings into the Chenab, Sutlej, Zaskar, Nubra, and Shyok, all of which spill into the Indus.  Yes it does include some parts of northern India/Kashmir and eastern Afghanistan.  But note how it also covers almost all of the land in northern Pakistan.

For good measure, this second image, put together from the wealth of tools at worldmap.harvard.edu, hints that most water in SE Pakistan also flows into the Indus (the red outline is all areas from which water will flow into the Indus) (Why a discrepancy?  Only guess is maybe SE Pakistan isn't shown on the other map because there's not major waterways in that area?!?!?):

Then when you add in the other independent rivers basins in Pakistan like the Dasht, Nal, and Hub:

(Source: Rivers of Pakistan on Wikipedia)

you can see most of the rivers/water out west also stay within the country rather than leaving it.

So in the end, almost every drop of rain that falls on Pakistan, from the northern mountains, to the deserts, to the heartland, to the Iranian border, all of it already flows further on into Pakistan for use.  In the end, there's only a few tiny slivers of land in the country where water falling on the country is lost by flow to other countries (such as places like near Chaman).

What may be confusing about the image you gave is the gray colors up in the north, nearer the Basha [as well as in southwestern Pakistan].  But those colors aren't showing that water there isn't coming into Pakistan, but only that that area isn't irrigated land.  Basically all the water in those gray areas, like the Pakistani portions of the Hindu-Kush/Himalayas/Karakoam Mountains, flows down into the Indus and through Pakistan.  Plus even more additional water from neighboring countries.  So in other words Pakistan gets more water than what falls on it.  Other countries definitely aren't so lucky.  And that water is already coming down into the rest of the country.

In terms of feeding the country, irrigation could maybe be expanded a bit... but I believe the problem isn't just the lack of water... but that a lot of the rest of the soil is fairly poor for growing.  The book Pakistan's Soil Resources (available online) classifies more than 1/4 of the country's soil potential as "Agriculturally unproductive or non-agricultural land" due to wind erosion, salinity, extremely low, etc.
(Some additional land might be made arable by leeching down salt levels, but I believe it would take long periods of time and great amounts of water.  Soil Quality and Agricultural Sustainability, by Rattan Lal, (Google Books preview) looks to include some interesting description of the greater complexities and some longterm potentials of many areas of the world, including Pakistan.)

On the other hand, it sounds like the more urgent concern maybe isn't eating but drinking? (disappointingly, I think you'll find that most other parts of the world probably aren't very aware of your problem... I certainly wasn't).
 Unfortunately this problem trend is showing up in many other places, such as well-publicized recent issues in southwestern South Africa.

In the end, the primary problem for much of Pakistan's population likely doesn't stem from the complete lack of water... but instead from the lack of needed infrastructure, pollution issues, and mismanagement, as this article alludes to.  These are issues that the entire world does struggle with (such as the troubles in Flint in the USA).  There are already some parts of the world there are literally growing concerns of not enough water existing in entire regions to sustain it whatsoever (such as in the SW US/impacting NW Mexico)  But if the Indus is flowing steadily down to the ocean through your country (please do indicate if its not, the problem may be more serious then!!), it's not a matter of no water, it's the challenge of detouring enough to areas to meet needs, and keeping it clean.

Karachi does look a bit of a challenge area on a map.  The good news is it's only 60 miles from the Indus.  Quite a few places source their water from such a distance - some places even do get it from hundreds of miles away, even from the far side of mountain ranges as you kind of suggested.  But the unique challenge is likely how flat the land is in the south nearer Karachi.  Places like California and Rome can take advantage of elevation to better feed the distant water via gravity.  Karachi on the other hand may require much more pumping to get the water from the Indus, and that might well not be cheap/easy over even distances like 50 miles?

(As noted, It looks like most of the N Pakistani mountains are south of the continental divide, so almost all their water flows your way already. The few miles of snowpack flowing into Tajikistan and such a) may well be needed by their people and b) could be diverted into the Indus with some effort... but that won't solve problems if the Indus is already steadily flowing. The Suleiman Range might offer some options to divert a little more water west of the Indus using tunnels like in the LA Aqueduct... but that would depend a great deal on the specifics of the topography and precipitation levels in those mountains for feasibility.)

So, indeed, all that water from your mountains is indeed flowing right through the heart of Pakistan, "right by your window" almost (plus the gift of extra input from areas of far northern India).  It's just getting it from the Indus to where it's needed.  And it just needs to be taken care of carefully.

In the end, Pakistan actually has it a lot better water-wise than much of the Arab world.  Find the green:

(image from NASA MODIS satellite)
That spline is the blessing that led to the growth of your country... and its the great challenge of the country today.


Why isn't Iberia a tectonic plate? I usually read that Iberia is a subplate, while India is a plate.

But it was a plate at the beginning of the Alpine Orogeny:

  Source: wikimedia.org

  Description: Tectonic map of southern Europe, North Africa and
  the Middle East, showing tectonic structures of the western Alpide
  mountain belt. Only Alpine (tertiary) structures are shown.

Both were plates that collided with the Eurasian Plate, forming respectively Himalaya and Pyrenees chains.

What makes Iberia a subplate and not a plate like that of India?

The Iberian plate may have been a sub-plate once-upon-a-time, but in modern maps it is usually shown as part of the Eurasian plate, and the next plate to it is the African plate. The same thing applies to the so-called Indian plate. Prior to 43 million years ago it was indeed a separate plate, but then it fused with the Australian plate and there is no longer a plate boundary between India and Australia. The resulting plate is therefore usually referred to as the Indo-Australian plate.

A lot can happen in tens of millions of years, and one of the things that can happen is a change in plate boundaries. There is no longer a plate boundary between what was the Iberian plate and the Eurasian plate. If you are referring to events which happened tens of millions of years ago, it might make sense to refer to them a separate plates, which is why the article you quote refers to an Iberian sub-plate.


How to simulate wind's trend from his windrose distribution? I need to simulate a realtime wind's trend from his windrose distribution (made from statistical data).

How winds change direction and speed in function of time? I cannot pick a random value from that distribution because I'll simulate some unrealistic situation (Example: at minute 1, wind blows from N at 3 kn, on minute 2 wind blows from SE at 10 kn)

Edit n.1

Actually i'm taking data from these datasets: https://catalog.data.gov/organization/735d0118-b2a7-4246-a0e3-608b0fa8d1ec?res_format=CSV&tags=wind-speed

You can't. A windrose aggregates over time, so you lose all the information about patterns over time. You're trying to do a time-based simulation, but your data source discards all time-specific information.

You need a different set of data, to base your simulation on. One that contains the dimension of time.

The changes in direction and speed over time vary hugely depending on the local climate and topology.


Global scale seismology experiments / observations disproving flat earth conspiracy? Recently I've taken an exceptionally unwise interest in the beliefs on conspiracy theorists, in particular flat earthers.  Flat earthism has been trending heavily lately and indeed is undergoing some sort of revival.  Of course, such beliefs run afoul of all scientific disciplines, including geology and geography.

This made me remember of the use of seismic waves to map the core of the earth and also the detection of earthquakes from remote parts of the globe.  These, or course, rely on the true globular nature of the Earth.

Question:  Are there particularly accessible or convincing accounts of such large scale detectable geologic phenomenon that implicitly rely on the globular geometry of the Earth?

Google would probably suffice but I'm not sure I have the correct terminology.  [My background is in mathematics, in case that would be helpful.]

Edit:  Let me clarify my request by asking for resources on global seismology which could be effectively presented to someone at college freshman level of education.

As you rightly say, seismicity is one geological proof of an almost spherical planet, but surely it is far easier to prove your case by satellite data, such as scenes from http://weather.msfc.nasa.gov/GOES/ Irrespective of the position of the satellite, the Earth always appears as a disc, never 'edge on'. For that matter, if the Earth wasn't approximately spherical there wouldn't be any stable satellite orbits - so no satellite pictures in the first place. You could use your mathematical skills to demonstrate that the only stable orbital configuration is around a sphere. Also the consistency of gravity, at any known point on the planet's surface, points to a spherical Earth. Then there are commercial and military flights which have, over time, flown arcs along almost every conceivable great circle, without ever coming to an edge. Turning to astronomy, every stellar or planetary object large enough to form under gravity appears as a disc - never edge on - surely no coincidence..... etc. etc.

But I'm curious - why bother?! You are never going to convince the likes of creationists, climate-change deniers, 'flat earthers', and the like. They have already made up their mind, and don't want to be confused by the facts. No matter how much evidence you supply, it is like water off a duck's back to the closed mind. They are comfortable with their own warped model of reality in their head - no matter how erroneous. Paradoxically, they view the discomfort of having to adjust their world view as a form of 'cognitive dissonance'. So trying to convince flat earthers is like the proverbial 'flogging a dead horse'.


Does the Sun and Moon basically appear to "move on the sky" identically regardless of location and date? For a long time, I've been trying to use Stellarium (simulation) and many visualizations and animations in order to get a good idea of how the Sun and Moon move across the sky, as seen by a human from the surface of Earth.
It's surprisingly difficult to grasp this, at least for me.
It seems to me that the Sun always "rises" in the "East", goes slowly up to "above our heads", and then sets to the "West" in the same manner, making a kind of half-circular path. After that, after some unknown time, the Moon kind of "follows" the Sun in this (more or less) exact path, also coming up from the East and "setting" in the West.
The fact that the Moon is orbiting around Earth, and Earth orbits around the Sun, and yet they move like this, makes no sense to my brain. It seems like the described path would only be true for the Sun, or the Moon, but not both.
And is it always (roughly) the same? Or does this vary depending on where you stand on Earth, and what date/year it is? It was very difficult for me to make my own experiments in Stellarium. It seemed like it would vary a bit, but not too much.
The reason I'm trying to figure this out is both because of general curiosity, and wanting to accurately describe the Sun and Moon in my story. In The Lord of the Rings, Tolkien frequently talks about the movement and look of these objects, which appear to follow the same rules as in our world. It's clear that he had very deep knowledge of how these things appear to move on the sky over the day, and I like such "details" to be accurate.
Basically all the animations and illustrations I find of the movement of the Moon and Earth around the Sun are focused on a "space overview" rather than how it looks from Earth.

Like Fred said, this probably belongs on Astronomy SE, but I'll give my best answer anyways.
No, the sun and moon do not take the same path each day. The key to understanding this is knowing that the earth is tilted 23.5$^\circ$.

Let's take an example- the arctic circle. On the summer solstice, the sun doesn't set- It goes around and around (called the midnight sun). In the winter solstice, the sun doesn't rise in the Arctic circle.
I think a careful observation of mine might be useful for you. The word Mediterranean means "middle earth." Tolkien is likely referring to the specific geography- specifically the area around the Mediterranean Sea. In fact, Tolkien does state that the Mediterranean is the place he envisioned, but he does use a flat earth, so the cosmology doesn't really match up with reality. This is also another nail in the coffin for flat earthers.


Why do some places have rain frequently? There are some places on Earth which holds the record of being "The wettest place on Earth". On what factors these places differ from other normal places?

An example of wettest place on Earth is Cherrapunji

PS: Normal places doesn't include deserts.

The factors contributing to such differences between any given 2 locations are simply too numerous to be specific. From the top of my head : Hadley cell, local topography, source of humidity upstream (oceans, lakes, ...), etc...

In the case you are referring (i.e. Cherrapunji), this is mostly due to a combination of Himalaya (topography forcing), Indian Ocean (source of humidity), Walker circulation and the strong tropical evaporation at those latitudes (among other things).


How long does one touch on a stalagmite/stalactite lasts? There is a discussion about whether touching a stalagmite or a stalactite would stop it from growing or not: https://answers.yahoo.com/question/index?qid=20090629155053AAYFhCM .
The results are that the oil on human body does prevent a stalagmite or a stalactite from growing, a short while though.

My question is, how long does it takes for the oil to completely vanish and allow the stalagmite or stalactite to resume growing.

The duration cannot be estimated as it is dependent upon many other factors, such as the diameter of stalagmite/stalactite, its age etc.

Normally these are formed in limestone caves and sometime in salt mines as well.


Could the magnetic field influence tectonic forces Paleomagnetism can be measured as the magnetic field at the time of rock forming is preserved in some minerals.

Could the paleomagnetism and the present magnetic field somehow influence the movements of tectonic plates?

The electromagnetic force and related field is a strong force at very small distances (governs the way the proton and electron are held to an atom) but is relatively weak over large distances.  I don't see how that small force could act on processes involved in the convection of the mantle.  If memory serves, the iron in magmas preserves the force of the electromagnetic field on earth at the time the magma cools to form rock. It leaves its imprint but has no affect on the process or origin of magmatism much less the convection that drives plate tectonics


What statistical methods are best for analyzing long-term rainfall data? What statistical tools are best analysing rainfall data (overall trends, decadal trends, intensity distribution, extremes, etc.)?

It depends on your data, if the rainfall data is in a grid with temporal and spatial dimension, you can use a NetCDF format to analyse the data via R, matlab, IDL or Python. NetCDF is Network Common Data Form, which is a very common format of grided and temporal data. In Python, you can simply do several 10-year average map to see the long term decadal trend. Or you could plot a transient period of a smaller region with average rainfall to see monthly or seasonally change. To find out the intensity of distribution you could plot a map with a logarithmic scale of colour. Use a threshold to identify extreme rainfall event that is above the threshold. I use a Python package called iris which can easily plot graphs using NetCDF data. You can look at some examples here http://scitools.org.uk/iris/docs/latest/gallery.html

For getting the rainfall data, you can download the rainfall data from the CRU-NCEP database https://crudata.uea.ac.uk/cru/data/hrg/ CRU stand for Climate Research Unit and it has the most accurate historical data available to the public. They are reanalyzed data from meteorological stations and ships. The highest resolution available is 0.5 latitude * 0.5 longitude degree grid. And for temporal resolution they have 6-hourly and daily. The data is in NetCDF format which is a format most map processing data use. If you don't know how to handle ncdf you could use Google Earth as well https://crudata.uea.ac.uk/cru/data/hrg/cru_ts_3.23/ge/ .

To know more how the data is derived you can read this paper. Hope it helps. http://onlinelibrary.wiley.com/doi/10.1002/joc.3711/abstract


How will the rising ocean affect aquatic life? On one hand it creates more habitat for oceanic life, on the other hand, it warms up the oceans and mixes the salt and fresh waters.

Biological communities (ecosystems) commonly change along topographic (bathymetric) slope - because conditions change along the slope. For example, there will be a temperature gradient with elevation along the side of a mountain, and gradients of temperature and the amount of incident sunlight reaching the sea floor just offshore. When climate changes, this can shift conditions up or down the slope.

The organisms of an ecosystem must be able to colonize any "new habit" that may be created by climate change in order to take advantage of it.  If conditions shift too quickly for the species to adapt by migration along slope, species may become extinct before they can become established in another area. For example, consider coral reefs, which are dependent upon depth, if sea-level rises too quickly, the population of surviving corals may become too small to successfully colonize reefs in new areas.

The answer to your question is complex. If you search the web for the term velocity of climate change you will find that your question is being actively researched by scientists.


When is the next glaciation due? Let's say we invented a whizzy technology that took CO2 back to pre-industrial levels, say 280ppm, how long would it take for glaciation to resume ?

(I'm not angling for a denialist perspective here, I know warming is a problem)

This answer assumes 280 PPM CO2, at least until the ice age and oceans begin to draw CO2 from the atmosphere.

If we look at the Pleistocene and we measure how long glacial periods last and how long inter-glacial periods are, You could say, observing the Earth for the last 2.5 million years that being in an ice age is Earth's natural state, with only brief periods between ice ages.

Ice ages have also followed pretty regular patterns that makes them, in theory, somewhat predictable.   Ice ages mostly followed a 40,000 year cycle, between about 2.5 million years ago to about 1 million years ago, then switched to roughly a 100,000 year cycle over the last million years.

It's not precisely known why the cycle switched from 40,000 to 100,000 years.  That's known as the 100,000 year problem.  But if we use the current 100,000 year cycle as a ballpark measuring stick or if we measure the length of interglacial periods (which are generally pretty short, 10,000 - 30,000 years), then the next ice age can be estimated at not too far off.  Maybe 10,000 years.

But if we look closer at what actually triggers ice ages, which is (simplified version), colder summers in the Northern Hemisphere, driven by orbital variations.    We can get a better estimate when ice ages should come by looking for when the Northern Hemisphere summers will get colder.

Milankovich cycles don't always neatly line up and the right conditions for the next ice age, based on orbital changes is a bit unclear.  When the red line in this chart below is low ice ages are more likely to happen, and we're in a dip now, but coming out of a warmer summer period and relativly soon entering another one.   There's a slightly bigger dip that peaks in about 60,000 years from now, another one 100,000 years from now and a bigger one, about 130,000 years from now.

Using this chart as a guideline, the next glaciation is more tricky to predict.   Perhaps in 60,000 years.   These predictions are hard to make though because ice ages are self sustaining.

So, short answer, perhaps the best answer.   Nobody knows.   The Milankovich cycles aren't lining up in the right way to make this prediction easy.  We may be set for an unusually long inter-glacial period.

As for how catastrophic would it be.   Well, for one, we'd see it coming and stopping an ice age would probably be easier than stopping ice from melting.  Releasing CO2 and CH4 into the air for example.  For a longer answer, how catastrophic would it be is a world-building question.


Are there any DIY conductivity sensors that will hold calibration for long periods? {multiple months} We've just published our DIY underwater loggers: http://www.mdpi.com/1424-8220/18/2/530
and the #1 thing we would like to add to the platform is conductivity. The loggers themselves will easily run longer than a year, but unfortunately we can't find any other projects that get much more than a couple of weeks out of traditional contact probes [like the Atlas series] before they drift quite badly. Does anyone know of other projects building conductivity probes which hold calibration for months to a year?

I've built DIY conductivity probes for subglacial measurements. Unfortunately my sensors remain under ~100m of ice so I haven't be able to recover them to check the calibration, but for the same reason, I've taken multiple measurements to reduce calibration drift, as I'm unable to re-calibrate them. So far, they have produced sensible data for 2+ years, but I haven't check the calibration. However I can share the results of my tests and research in order to produce a stable sensor.

There are two main types of conductivity measurements: The first one is the potentiometric method. This is the most common one, and measures conductivity by creating an electric current between two or more electrodes embedded in the medium to measure. The second type is the inductive method, in which is a magnetic field what goes trough the medium, and you measure conductivity through variations in the induction effect that that magnetic field have in a coil.

(picture  taken from Knight)

Inductive probes are contactless, therefore, the most stable ones. However, they are more complex to build and don't work well with very low conductivity (< 100 uS/cm). Glacier water is often in that very low conductivity range, something that, in addition to the higher complexity made me choose the potentiometric method (you can see a bit of my attempts to put together an induction sensor in this forum).

For potentiometric probes, oxidation, deposition of salts or others chemicals can change the calibration parameters. This would be enhanced when direct current is used, as that will create acids in the water that will quickly corrode the probe. To reduce that problem, probes of inert materials are used, like platinum, gold or graphite (more common in DIY projects due to its lower cost). But to reduce deposition of chemical compounds in the probes you still need to avoid direct currents and use high-frequency alternating currents with zero mean, otherwise if there is a net current towards one electrode, you will accumulate acids or ions there that can degrade or coat the electrode and change its properties (i.e. change the calibration).

The picture above shows an example of an electric signal that can be generated using a false ground and the PWM output of an Arduino board. The setup could be as follows:

Where R1 and R2 have in general to be equal to ensure a signal with zero mean, and the value have to be chosen depending of the range of conductivity values you want to measure and the resolution. If you want to cover  a wide range (pure cave water to marine water), you will have very low resolution (un less you use a AD converter with more resolution than the 10-bits provided by Arduino boards). Alternatively you can have multiple sensors each one optimized for a different range.

For probes meant to be deployed outside of lab conditions, concentric electrodes are recommended, otherwise natural currents going trough the ground/water can affect the measurements. The setup I used is this one:

Where a central graphite electrode is surrounded by a ring of graphite electrodes. As  you can't solder to graphite, I used conductive epoxy to glue it to a piece of plumbing copper tube modified with legs so it can be solder to a PCB. It looks like this:

To avoid gluing, some people choose aluminium or stainless steel electrodes, that are affordable and do not suffer much of chemical corrosion.

Some of the data that was produced by this probes were used for this publication.

Many comercial setups use three or four electrodes. I don't understand all the advantages of those sensors. In some cases they are just multiple sensors each one calibrated  for a specific range.
I've also seen three concentric electrodes. I haven't do the math, but my suspicion is that they measure the current in two independent electrodes with different surface area. Then, you can model and calculate the resistivity of the layer of deposits/corrosion that covers the electrodes and compensate your reading accordingly, reducing the calibration drift issues.


How much role does radioactivity play in making Earth geologically active A hot molten core is important for making the Earth geologically active. I believe most of the heat is from the time of the planet formation, and the high pressures due to everything pushing down to the core. How much of this can be attributed to radioactivity? How can we know it for sure, considering the pressure and temperature make it in accessible? Research show that radioactive potassium plays a role in it, but if it is true the how can a light element such as potassium sink to the core where it can generate heat by radioactive decay?

The idea that the heat of the earth is from the time of its formation dates back to the late 1800s before radioactivity was known.  Unfortunately for that theory it was shown that an initial blob of molten rock would cool to a solid chunk, radiating its heat into space, in a few tens of millions of years.
When radioactivity was discovered it was seen as a way out of the problem but the known radioactive elements were sufficiently rare in the earth's makeup that they couldn't provide enough heat.  Finally in the fifties the bulk composition  of the earth and the occurrence of radioactive isotopes were well enough known that it was shown that there is enough radioactive potassium, with a long enough half life, to provide the observed heat flux from the earth's interior.  Most of the heat is generated in the mantle, not the core since, as you point out, that is where the potassium is.  The mantle is also the layer that has convection currents in it to release that heat and drive plate tectonics.
The outer core is liquid because, at the pressure it is under,  being a liquid is the thermodynamically stable state of the heavy core minerals.  The ice under a skater's blade turns into a thin layer of water under the passing skater's pressure, lubricating the passage of the skate.  The water does not warm up much, it is still below freezing, but it is not stable as a solid under the pressure of the skate. As soon as the pressure is released the water returns to ice which is the stable state of H2O at atmospheric pressure and sub-freezing temperatures.  Similarly the outer core is liquid because that is its stable state given the pressure and temperature at that depth.
Increase the pressure more, as happens as you go deeper, and the stable state of the core material is a solid.  This explains the reason the inner core is solid.


Specific humidity range in tropical lowlands? I am running a land biosphere model that uses meteorological data as drivers. The model has a threshold of 32g/kg for specific humidity. The data I am using taken from a reanalysis performed by J. Sheffield at Princeton has some values of S. Hum. higher than 32g/kg. Given that such data is of resolution of 1 degree and 3 hourly interpolated from 6-hour data, what is a typical range for S. Hum. in lowland tropical areas. I need to know this to deem if these data is close enough to the real world or if it includes unrealistic values I will consult the author and point out that data might be inaccurate for these regions. It is difficult to find online any direct measurements, I only find these big data sets such as NCAR-NCEP.

edit: looking at a region of the Amazon, I see frequent values around the 30g/kg range, for example here http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NCEP-NCAR/.CDAS-1/.DAILY/.Intrinsic/.PressureLevel/P/1000/VALUE/ds:/qa/temp//celsius/unitconvert/u/a:/v/:a/mag/:ds/%28qa%29//var/parameter/interp/nip/DATA/AUTO/AUTO/RANGE/P/1000/VALUE/T/0.0/dekadalAverage/X/-180/0.5/180/GRID/X/360.0/makeperiodic/Y/-90/0.5/90/GRID/X/Y/fig-/colors/grey/verythin/mews_prov/black/thin/countries_gaz/-fig//T/last/plotvalue//antialias/true/psdef/index.html?layers=countries_gaz&layers=qa&T=21-30%20Jun%202013&bbox=bb%3A289.775%3A-10.432%3A308.296%3A0.734%3Abb#instructions

Referring to a research article "The Role of Temperature and Humidity on Seasonal Influenza in Tropical Areas: Guatemala, El Salvador and Panama, 2008–2013" by Soebiyanto et al, 2014 DOI: 10.1371/journal.pone.0100659, the authors investigate a few regions in tropical wet and dry (savanna) climates in Central America, some of which are lowland. The authors state that Panama and El Salvador study locations have less varied topography and are at lower elevations than Guatemala. They give the following Specific Humidity values and standard deviation i g/kg:

Lowland Panama province in Panama: 17.66 +/- 1.04 g/kg
Chiriqui province in Panama: 15.38 +/- 1.47 g/kg
West-central departments in El Salvador: 14.29 +/- 2.14 g/kg
San Miguel, El Salvador: 14.84 +/- 2.32 g/kg

So, a specific humidity in the 10-20 g/kg seems like a reasonable range for seasonally dry and humid lowland tropical regions in Central America.


Do tectonic plates "float" over the mantle and "collide" like icebergs? I'm always hearing about tectonic plates as large chunks of crust floating on the mantle just like boats. In timescales of millions of years they move and even collide.

But I'm starting to think this is just a pop-science model, or a methaphor, for a much more complex situation. I didn't made the calculation but I feel that the mass of the Indian plate is not as large to account for the uplifting of the Himalayas just by kinetic energy transfer. At those speeds (puny, even if large compared to other plate movements) wouldn't the material stress of the Eurasian plate had absorbed all the momentum by now? I get that the inertia of India is huge, but is it really as much as to keep pushing even today? Does it has so much inertia that it is still slowing down as it pushes Eurasia? I feel like there is a constant force been applied tangentially to the surface of the plate that could account for this instead of just a freely moving plate smashing another like two icebergs in the artic sea.

Does the idea of plates floating like boats and the idea of them interacting by mechanical collisions is really somehting more than a suggestive way of viewing a process that takes enourmous amounts of time, energy and mass so that we, insignificant and ephimeral creatures, can have a toy model in our minds? Is India been pushed by a force or is it really just moving like a billiard ball until it collides with another and changes its momentum?

EDIT:
Ok, so I've actually done the calculation now:

According to the USGS, the Indian plate had a speed of $v =9 \; m/century = 2.85\cdot 10 ^{-9}\; m/s$.

The surface area of the plate is $A = 1.19\cdot 10^{7}\; km^2$. If we suppose the thickness of the crust here to be of $h = 50\; km$ (which is thicker than it probably is) then the volume of the plate is $V = A\cdot h= 5.95\cdot 10^{8}\; km^3 = 5.95\cdot 10^{17}\; m^3$. We can estimate the mass of the plate by assuming a density of $\rho = 3\; g/cm^3 = 3\cdot 10^3\; kg/m^3$ (this density is higher than the average we should expect for the crust so we are not been very conservative at all). Thus the mass of the Indian plate is around $m = \rho V = 1.79\cdot 10^{21}\; kg$ in the best case scenario.

Then the kinetic energy of the Indian plate had to be lower than $E_k = \frac{1}{2}mv^2 = 7269\; J = 1.7 \; cal$, which is even less than what @Keith McClary has suggested since this is less than a $1/300 \; th$ of the energy of a candy bar.

Now, we can use Newton's Second Law of Motion in the form $\Delta t = mv/F$, where $m$ is the mass of the Indian plate and $v$ is its velocity, to get the time needed to stop the plate, $\Delta t$, when we apply a constant force, $F$, against its motion. Even if the kinetic energy is insignificant it is not easily absorbed during a collision due to the huge inertia of the plate. But still if we suppose $1$ million people, each person pushing with $3000 \; N$ of force then those people could have stopped the continent in less than $\Delta t = 30\; minutes$. A single weight-lifter would have been able to stop the entire Indian continental plate if he pushed with $F = 8000\; N$ for about $\Delta t = 20.2\; years$.

I think that the mechanical stress of the entire eurasian continent creates larger forces that a single human and this "collision" has been going on for millions of years (not 20 years) and is still going on. So this is where it looks absurd to me to talk about a "collision" of plates for the formation of the Himalayas. The driving mechanism has to be a huge force pressing the Indian plate against Eurasia.

you are missing a big factor, the plates are not moving due to the momentum of an initial impulse. They are being actively moved by the push and pull of mantle convection. Much like how icebergs are pulled along by ocean currents. the iceberg analog however breaks down because icebergs melt before they can do much complex interaction, where as continental plate material is more or less permanent. also icebergs are subjected to far lower forces than continents, a closer analogy would be ice in glacier.

The amount of energy the mantle is supplying is massive, far far more proportionally than an iceberg is subjected to, more than enough to drive continental plate together and build mountains.  if you are interested in the detailed mathematics you can start here.

The continents float on the mantle becasue they are less dense, but they are moved by mantle movement transferring energy.


where are the poles of rotation of the tectonic plates located? Euler's "fixed point" theorem ... can be stated as:

  The most general displacement of a rigid body over the surface of a
  sphere can be regarded as a rotation about a suitable axis which
  passes through the centre of that sphere.

Thus all plate motions can be described by a rotation axis, which passes through the centre of the Earth and cuts the surface at two points, called the poles of rotation. The relative motion of two plates then needs a pole of rotation and an angular velocity to be defined.

So where are those poles located?  Is there any map or resource indicating where those are 'poles' are?

Up to now, we constrained the (relative) plate movements mostly with seismic slip measurments.

Since 10-20 years, with the diffusion of GPS measurments, it has been possible to have a more granular distribution of movements and a more precise estimation of the rotation pole for a given plate.

Roughly speaking, then, you should look for the work of authors like these:
https://meetingorganizer.copernicus.org/EGU2017/EGU2017-14816-1.pdf (just a random "scientific" google result for the search)

The end product (an accurate determination of rotation poles) should help in estabilishing the seismic hazard, by observing gaps and differential displacements, possibly representing loading of the fault, in a very primitive Reid (1910) way of thinking:

https://earthquake.usgs.gov/earthquakes/events/1906calif/18april/images/ElasticRebound.gif

I have no right on the image, it comes from the USGS site.


Are there websites where I can get "lightning frequency maps" in near-real time (worldwide)? I have an NASA Inspire VLF-3 radio receiver kit that I'm going to put together. It amplifies VLF electromagnetic signals that are already in the audio frequency range and makes them audible. One of the interesting things that it may make audible are VLF whistlers, signals that are triggered by lightning strikes and produced by the response of charged particles in the ionosphere orbiting around lines of the Earth's magnetic field.

I know that there are both spacecraft and ground stations that detect and report lightning activity, but are there websites where I can get "lightning frequency maps" in near-real time (worldwide)?  I live in Asia near 25 N latitude.

I've asked separately What are the optimal times and conditions to listen for whistlers?

Click for full size.

Absolutely: The Blitzortung project has near real-time data for most if not all of the world.

I've also never taken the time to research how lightning detectors exactly work, but it's likely similar... and you can read about the Blitzortung instrument here.

Windy.com also appears to now have lightning data over at least the largest part of the globe (perhaps using the Blitzortung source).  And though it's not for your region, GOES new satellites also have a lightning detector on them, which you can view at some data from on any of the GLM links on this page.


Have these optical satellite ground station locations been chosen for clear skies? Having lived in southern California, I know that some areas on the planet can be absurdly sunny and clear throughout the year, and having lived several other places, I know some areas can be chronically overcast.

The article Laser Light to leverage free-space optics in space for Optical Satellite as a Service describes a proposed group satellites in medium Earth orbit (MEO) that would maintain high speed optical data links with a large number of Earth stations. I did some further reading, and found the map shown below. I assume this is still conceptual and the final ground station locations may be different.

But I am wondering, besides that one station in southern California, do these appear to be in meteorologically favorable locations for continuous optical data links to satellites? Are these particularly sunny/clear sky locations?

Does a map of clear-sky hours per year - independent of day or night - exist?

As pointed out in this comment and this article the network can work by reconfiguring depending on atmospheric conditions. But do these appear to be chosen by access to clear skies, or access to fiber networks?

above: Graphic from The Speed of Light: Laser Light and Optus Explain Optical Communications Partnership to Via Satellite Magazine

Yes, mean cloud cover is routinely measured from satellites.  Like all satellite data (and in fact all measurements), it does have an uncertainty, but for the purpose of this question the satellite product of mean cloud coverage is good enough.  Personally, I would hesitate to trust the data at very high latitudes with frequent cover of snow or ice, because those are hard to distinguish from clouds with any form of passive down-looking remote sensing.

The figure below is released by ESA and derived from the MERIS and AATSR instruments on the former ENVISAT satellite.  Although the caption does not specify, I suspect that it uses visible channels and that it therefore only relates to daytime cloudiness. It would be interesting to see how it compares to 24-hour cloud cover!

Full image caption and credit:

  Global annual mean cloud cover derived from three years (2007–09) of Envisat data. The map shows areas with little to no cloud coverage (blue) as well as areas that are almost always cloudy (red). Clear skies are immediately visible over deserts (such as the Sahara, Namib and over the Atacama). Regions with constant high-pressure systems are detectable, such as the Pacific. On the other hand, the North Atlantic Ocean in the mid-latitudes is mostly covered with clouds, where storms develop. The UK is often cloudy, whereas the Mediterranean shows sunny skies.
  Data from both the MERIS and AATSR instruments on Envisat were used.

  Credits: ESA/Cloud–CCI

(On behalf of ESA and the Cloud-CCI I would like to apoligise for the poor choice of colourmap, but this figure predates the time at which many of us were educated on its poor suitability)


Is Atlanta too far inland and too far above sea level to be affected by the comet in "Deep Impact"? In "Deep Impact", the president says that "New York City, Boston, Atlanta, Philadelphia, all will be destroyed". New York and Boston are on the water and would be in danger from a tsunami of any size, Philadelphia is 39 feet above sea level and 50 miles inland. Atlanta is over 200 miles inland and between 750 and 1100 feet above sea level. Would an impact event of the size imagined in the movie actually send a wave that far inland and that far up? Would the natural topography of the region (lots of small hills) affect the wave?

Tsunamis form as a series of moderate amplitude, long interval waves that travel away from the initial impact.  The first of these waves has the highest amplitude of the initial waves, and becomes the 'big one' later. Subsequent waves are caused by water rushing into the void created by the initial impact, bouncing off of each other, and starting the next wave out.

As the radius of the impact waves increases, the power in each wave gets spread out over a larger and larger circumference, at a rate of $2πr$.  This is a steady geometric decrease in the power any given portion of the wave has.

As these waves start to reach shallow water, the waves in front begin to slow down.  This causes the waves behind them to become part of the tsunami.  This build up continues until you reach land.  Once at land, no more power is being introduced into the wave, no more water is being pulled in.  What you see is what you've got at this point.  None of the follow up waves will go anywhere near as far inland as this initial wave.

To elaborate, following landfall, the tsunami would encounter:

The barrier islands to Georgia's east protect it from most severe storms.  Their arrangement would also introduce an interference pattern into the wave that would incline the big tsunami to spread out more.
Beyond that, there is a large, flat area of low elevation where the wave would travel easily, but it would lose a large percentage of its power crossing this area.  Once again, the wave is losing power as it spreads.
Next, you get to the continental shelf that separates North Georgia from South Georgia.  In a rather sharp increase, land goes from a few hundred feet above sea level to, as you mentioned, 750+ feet.  That is one steep hill to climb for an old, tired tsunami.

Without subjecting this to a full simulation I can't be certain, but I think that any impact capable of creating a tsunami that could reach Atlanta would be completely unsurvivable.  Some of the simplest forms of life might make it, but everything else would be gone.

That does not mean that Atlanta wouldn't suffer substantial damage from other factors, such as all of the water launched into the air by the impact of a red hot flaming rock and any chunks of that comet that might break off from the friction of passing through the atmosphere, but right now Atlanta is pretty safe from tsunamis.


How to interpret correctly this chart about nitrogen oxide? I found the below chart in a test for university access in Sweden, with the following question:

How large was the total emission of nitrogen oxides caused by Swedish consumption under the period 2004-2008?

I have the correct solution, but it does not match my answer. I reasoned like this:

Both 2004 and 2008 should be included, so we have 5 years.
The emissions abroad are about 112 thousand tons on average, so 112*5 = 560
The emissions in Sweden are about 225 thousand tons on average, so 225*5 = 1100.
So the total should be about 160+1100 = 1660.

However, apparently the correct answer is 1100.

I am quite sure I am missing something obvious, but I cannot figure it out.

Translation of the most important terms:

Utsläpp i Sverige: emission in Sweden
Utsläpp utomlands: emission abroad (caused by imports).

The original question in Swedish:

  Hur stort var det sammanlagda utsläppet av kväveoxider orsakat av svensk konsumtion under perioden 2004-2008?

A person answered to me on a dedicated Facebook group. He suggests that the labels are about areas, not lines, so the grey area (emissions in Sweden), is only the visible area, it does not continue below the dark area (emissions abroad). I find this representation very confusing.

As an example, the emissions in Sweden in 2008 are 225 - 100 = 125, the difference between the total and the dark area, and not 100 as I thought.

This way, the correct answer is 1100, because the upper line already represents the total emissions, and between 2004 and 2008 we have an average of 225 for 5 years.


High Discharge Value in SWAT modelling At first run I’ve encountered the problem since the values of modeled and observed discharge are significantly different.
The correlation between them is nearly 0,2 as the modeled discharge gives much higher values.
I have already checked the precipitation file (it has some missing values which I substituted with zeros) and also did the correlation between the discharge and precipitation which showed the result nearly 0,35; while the cross correlation with three-day lag is 0,6.
In addition, the model predicts the precipitation values very accurately, though the discharge is very high.
How can I identify what is the conceptual logic behind the algorithm of inflow-outflow calculations in SWAT (or maybe refer me to the literature on the matter) so I could go through the output again and identify the potential problem?

SWAT model has a pretty good technical and theoretical documentation on their website : http://swat.tamu.edu/documentation/

Regarding the conceptual logic, SWAT is based on sub-watershed discretization. Inside these, it defines Hydrological Response Units (similar slope, land use and soil). Then, you simplify it on the basis of the HRU heterogeneity, you may chose between assigning to the sub-watersheds the response of the dominant HRU or define a multiple responses. At this step, SWAT knows which parameters to use in the hydrological processes you have selected and can run the simulation.

I would suggest that you read the introduction of the theoretical documentation and, assuming that surface runoff is a major contributor to your discharge, maybe the chapter 2.1 on surface runoff.  You need to understand the Curve Number Method wich is used to compute runoff volumes. If you want to decrease runoff speed, you may increase the manning coefficient (friction to flow) for both overland flow or channel flow. As it seems that you have a time of concentration greater than one day, you should also check the surface runoff lag parameter [SURLAG].

But as SWAT is a sophisticated model with a lot of parameters and sensitive to scale, discretization methods and input resolution, it is hard to know what's wrong with your simulation. It is quite normal that a uncalibrated model, even physically based, provides results far from the observed discharge. To calibrate a model, you must first identify the most sensitive parameters by running a sensitivity analysis. Then, as you know what parameters will have significant impact on the simulated discharge, you can run a calibration by varying them in a physically acceptable range.

Hope this help,

D.D.


Is it true that a butterfly flapping its wings can result in a tornado in a distant location? I have heard that extreme storm events can be caused simply by a butterfly flapping its wings somewhere in a distant location.  Is it true that such a small disturbance in the air in one location can result in such a large catastrophic event in another separate location?  If so how can we know this is possible, and how is this even possible?

The butterfly is a colourful illustration of Chaos Theory, and the word butterfly came from the diagram of the state space (see below).

A system that is chaotic is extremely sensitive on its initial value.  In principle, if you know exactly how the state of the universe is now, you could calculate how it develops (but due to other reasons, it is theoretically impossible to know the state exactly — but that's not the main point here).  The issue with a chaotic system is that a very small change in the initial state can cause a completely different outcome in the system (given enough time).

So, suppose that we take the entire atmosphere and calculate the weather happening for the next 20 days; suppose for the moment that we actually do know every bit.  Now, we repeat the calculation, but with one tiny tiny bit that is different; such as a butterfly flapping its wings.  As the nature of a chaotic system is such that a very small change in the initial value can cause a very large change in the final state, the difference between these two initial systems may be that one gets a tornado, and the other doesn't.

Is this to say that the butterfly flapping its wings results in a tornado?  No, not really.  It's just a matter of saying, but not really accurate.

Many systems are chaotic:

Try to drop a leave from a tree; it will never fall the same way twice.
Hang a pendulum below another pendulum and track its motion:

(Figure from Wikipedia)

Or try to help your boyfriend in what must be one of the loveliest illustrations of Chaos Theory ever.  Suppose you are running to catch the bus.  You keep sight of a butterfly, which delays you by a split second.  This split second causes you to miss the bus, which later crashes into a ravine, killing everyone on board.  Later in life, you go on to be a major political dictator starting World War III (Note: this is not the plot of the linked movie, but my own morbid reinterpretation).

Tell me, did this butterfly cause World War III?

Not really.

(Figure from Wikipedia)


Making sense of the math of climate change Let me state upfront, I'm not arguing the existence of climate change, just trying to clarify my own understanding of something that doesn't make sense to me yet. With apologies for the layman's question...

I've seen similar numbers frequently, but let's use this xkcd
as a reference. It states that a 4.5 C change in the global climate is the difference between Boston under a half mile of ice, and the temperate zone it is today. Boston's current annual average temp is 10.75 (~15 average high, ~7 average low). Looking for an analog for a city that's about 4.5 C cooler than Boston gives a location like Moncton, New Brunswick. Colder, yes, but not buried under half a mile of ice.

My brain says that a place covered by ice is far colder than current temps minus 4.5 C, and that since the ice sheets covered so much of the earth, I can safely skirt the "climate is global, you're looking at local temps" hangup. So what gives? How can a climate like Boston's cool by "only" 4.5 C and support such enormous glaciers? It would seem that the presence of such enormous ice sheets would imply that the average temperature must have been far colder than that...

I was able to dig up this (although without being able to find full sources):

It shows a pattern where the temperatures are dramatically lower where ice sheets have built up relative to today. Interestingly, a lower overall temperature means weaker mixing across latitudes, so some areas are actually warmer.  Boston gets chilled by -20 according to the map.

Also note the altitude effect. If the surface is raised by 1 kilometer, then due to the lapse rate, the temperature at the new surface will drop by 6.5 degrees. This is a very important factor in stabilizing large ice sheets.


European soil texture dataset according to USDA classification I'm looking for a dataset (in pretty much any format) of soil texture according to USDA classification (by U.S. Department of Agriculture). Is there anything that would cover the entirety of Europe?

I found the Topsoil physical properties for Europe (based on LUCAS topsoil data) dataset from the European Soil Data Centre (ESDAC), which would suit my needs perfectly, except that it only covers the EU member countries and thus some countries are missing.

After a lenghty unsuccessful search, I found an option to do my own mapping. There are global datasets with the percentages of clay, silt and loam available from the Land-Atmosphere Interaction Research Group at Sun Yat-sen University and I used the R soiltexture package for the classification. I ended up making a dataset covering my domain of interest in 2 km resolution. I attached my map and the original map mentioned in the question for comparison (some of the colours are a bit off, but they should more or less correspond to the same category in both images). If anyone is interested in this data, feel free to let me know. My custom mapping.

Original dataset from the European Soil Data Centre (ESDAC)


Could burning all fossil fuels (available on earth) render the atmosphere unbreathable? What if humanity burns all fossil fuels it can find? Putting the negative effects of climate change aside, would the enormous amount of $\small\mathsf{CO_2}$ in the atmosphere eventually make it unbreathable?

Not directly.  What possibly could happen is that rising temperatures turn the parts of the ocean anoxic, which leads to large releases of hydrogen sulfide, which is toxic: https://www.chemistryworld.com/news/ocean-chemistry-changes-triggered-earths-greatest-extinction-event/2500368.article


Saturation Index clarification I have a problem with my project and I was hoping I would find some clarification.

I did some modeling with phreeqc to calculate saturation indices and found that  calcite was saturated in an engineered aquifer. The time of sampling of groundwater was roughly 1 year after construction was completed. Gypsum is present in the aquifer, so there are high calcium concentrations. However, I don't think the mineral calcite is actually forming insitu. I think the concentrations of calcium and carbonate are just at the right combination to be in equilibrium with calcite, so it is not actually contributing to calcium concentrations. I should add that the pH of the aquifer is between 7-8. I just don't think any sufficient quantities of calcite would form in a system with lots of water moving through it.

Is this a correct interpretation?

Why don't you think calcite is forming in-situ? The saturation index does not guarantee that calcite has precipitated (or dissolved) but there are a number of reasons to think it has. First, calcite does not have a large kinetic barrier to precipitation. The kinetics are fairly rapid. Rapid is a relative term but the formation of calcite in caliche and speleothems indicates that it does not take much for it to precipitate. Secondly, are you suggesting that it is merely coincidental that the SI indicates saturation? Do you have a number of water samples from different locations that are all in equilibrium with calcite? How would that occur without reacting to form or dissolve calcite? What else could be buffering the pH to the value at equilibrium between your solution and calcite?

Have you looked at the gypsum SI? Does it remain undersaturated? If so you would expect it to be dissolving which would move calcite towards supersaturation.

One possibility is that you in equilibrium with both gypsum and calcite. In that case, they will fix the ion concentrations in solution and pH so you get no further precipitation (assuming the system is closed to carbon dioxide).


How can I find weather data for greenland sea during the 4 seasons? In the Greenland Sea or in Denmark's strait, near greenland's cost,

how can I find weather information for this place? Specifically, with respect to months (i.e, dec-feb, march-may, june-august, oct - nov). When it is warmest, coldest, etc.

An interactive website called earth has detailed weather data for the entire globe. Using this is similar to using Google Earth. You can adjust it for almost any weather data you need by clicking the "earth" icon and adjusting the date under each section. You can see the numerical data for a specific area by clicking the area on the globe with your mouse.


How much of arctic ice is from snow fall versus frozen sea water? How much of arctic ice is from snow fall versus frozen sea water? I presume arctic ice comes from both sources.

Is there a way to tell how the ice was formed? In other words, if you made a core through the arctic ice cap, could you tell how much of the core was from snow versus frozen sea water? What's the difference?

I'm assuming this question is asking about the sea ice in the Arctic Ocean as opposed to ice caps such as that over Greenland. The sea ice on the Arctic Ocean is predominantly (overwhelmingly!) frozen ocean water.

The Arctic Ocean loses 17 to 18 thousand cubic kilometers of ice every summer, only to regain most of that melted ice during the long Arctic winter when the ocean freezes at the surface. That corresponds to a layer of ice well over a meter thick that melts and reforms every year.

The Arctic is a desert, and an extreme desert during the Arctic winter. At 40 below zero (Fahrenheit or Celsius), it's simply too cold to snow. The amount of precipitation that falls on the Arctic Basin over the six to seven months or so when the ocean freezes is about a tenth of a meter.  Snowfall cannot account for anywhere close to the meter+ thick layer of ice that forms during the Arctic winter. The tiny amount of snow that falls during the Arctic winter can't accumulate the way it does over ice caps.

Compare with Antarctica. Antarctica, like the Arctic, is a desert. Unlike the Arctic, Antarctica is a continent. The little snow that does fall accumulates over the millennia, and longer. The Antarctic ice caps have existed for millions of years. Now look at the Arctic. There is very little Arctic sea ice that is over ten years old. (Thanks to global warming, there is very little Arctic sea ice that is over five years old nowadays.)


What are these clearings in Amazon rainforest? I was surfing around on Google Maps and found dozens of clearings amid a sea of vegetation.

What are they? Some look like rocks, others can't be made out due to the image resolution.

Here is one specific clearing:

Dozens of clearings (zoom in on dots of lighter color in forest)

Hard to say. Some could be clearings for log landings, some for small villages or outposts used by the military or others, some cleared due to natural disturbance in the area (e.g. fire from lightening strikes) though I'd expect the latter to have sparse canopy and not be totally clear.

Many of these patches don't have signs of good access routes (other than by air or through thick vegetation). No doubt there can be smaller trails and rivers under the canopy, but we don't see any substantial routes with canopy cleared overhead. Therefore, logging and mining seems less likely, though both occur in the region. Smaller scale operations, like a clearing for more sun-loving plants by a local human population, could account for some of these though.

On the village or outpost possibility

Consider these clearings:

Two relatively nearby clearings, one with what appears to be grainy rocks but could be thatched roofs of a village
Another nearby clearing that appears to have a significant amount of its soil covered in a darker shaded texture, again perhaps thatched roofs
And another clearing, partially open and partially with this same darker texture to it in a shape that could certainly be a spread of small buildings in a community

I searched for on-the-ground views of potential villages and found a few that could match the view from above.

Here's a large communal structure in a clearing which could match some of the textures we see. Some indigenous groups of the Amazon live in large structures like this as a community, and some just use large structures like this as ceremonial communal spaces.

Here's a set of buildings in a village clearing. Note how close the forest canopy comes to the buildings. Given how thick the forest is, it's probably not easy to manage, but that could be all the more reason to get to bare ground in these village clearings.

Here's a pretty amazing example of small scale clearings and manipulation of the forest landscape by indigenous communities. While we're not seeing this from a satellite, it points out how the lack of texture nearby and between these clearings doesn't necessarily mean there's no trails or human presence. It appears these structures are surrounded by unusual tree canopies - perhaps banana or another agroforest crop - which could be cultivated from nearby shelters.

In conclusion, a likely possibility is that these clearings are signs of relatively-isolated small-scale villages or outposts.


When will the Final Ice Age happen? As the Sun's luminosity slowly rises, the Earth's surface temperature will climb. Will Earth ever be too warm to have any more glacial periods? If so, when will that be?

Edit: The existing answer misunderstood the question. I'd like some boundary conditions, e.g. "when the sun's luminosity is 10% higher and the Earth becomes a 'moist greenhouse'" and "when the Sun turns Earth into a cinder". Those conditions would imply that the last Ice Age will happen 1-4 billion years from now. A better estimate would be awesome. Unless there's something I'm missing, with Stefan-Boltzmann and some reasonable assumptions (e.g. linear increase in luminosity) it should be possible to get a back-of-the-envelope calculation for this.

At the moment, nobody knows for sure whether or not changes in the Sun's luminosity can cause long-term climate changes. There have been various studies done, most since the advent of global warming, that have tried to address this. The conclusions have been interesting:

The Sun is not responsible for the recent warming of the Earth.
It's not yet known whether or not the Sun has influenced climate in the past.

Here are some studies (one supporting each side of the long-term debate):

A report by the National Research Council (available here) found that sunspot activity could be a major contributor to small changes in the Sun's brightness. There is a periodic trend in sunspot activity that lasts 11 years, and studies have considered this when looking at long-term trends. One target of inquiry is the Maunder Minimum, a period of low sunspot activity:

The Maunder Minimum coincided with the Little Ice Age, a short period of low temperatures. In fact, the Sun may be entering a similar period within the next few decades. Observations could show whether or not there is a link between the two events.

However, the NRC concluded that it is hard, if not impossible, to find any data supporting theories that there is a long-term patter. Hal Maring summarized it best:

  Hal Maring, a climate scientist at NASA headquarters who has studied the report, notes that “lots of interesting possibilities were suggested by the panelists.  However, few, if any, have been quantified to the point that we can definitively assess their impact on climate.”

In the paper Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model by Holger et al., periods called Dansgaard–
Oeschger events were studied. These are climate oscillations lasting 1,470 years. Holger et al. analyzed ice cores from Greenland and attempted to model solar forcing, the amount of energy absorbed by Earth or radiated into space. They also used the ocean and atmosphere to account for changes (the NRC report, too, concluded that solar effects can trickle down through the atmosphere and other parts of Earth). Their conclusion was that, despite the fact that no records of 1,470-year solar cycle exist, the analysis supported a connection between solar variability and changes in Earth's climate.

Before anyone gets too excited, I'll add this: 1) I haven't been able to find any comments from other scientists on the paper, so I'm not sure how well-received it was, and 2) The 1,470-year cycle can not account for long-term glacial periods, or the recent rise in global temperatures.

Another potentially interesting (and paywalled) paper can be found here. An informative website is here, but I'm not sure if it's entirely neutral. It does seem to present both sides, though.

I'll end on this: Whether or not the Sun severely impacts the Earth's climate, Milankovitch cycles are the biggest influence on ice ages.

It will take some pretty drastic changes in the Sun's luminosity to change the glacial periods . . . which the Sun will be undergoing in about billion years or so. It will still be on the main sequence, and will stay there for 4.4 billion years more, but it will have brightened by about 10%.

Once of the consequences of this will be that the Earth will lose its oceans. Through a process called the "moist greenhouse" effect, water heats up and reaches the atmosphere, where the hydrogen atoms are freed from the oxygen atoms and escape to space. This occurs at a tiny, tiny rate at present, but in about one billion years, the Sun will be bright enough that this will occur at a catastrophic rate.

That places the last glacial period somewhere between now and one billion years in the future. To figure this out, we have to look at long term patterns, such as Milankovitch Cycles. This graph illustrates them best:

From the present day to the far right, though, is only 800,000 years. That's unhelpful. This graph, while a bit clearer, shows only the variations without accounting for any changes in the Sun's luminosity (though that will not affect us during the next 800,000 years!).

Here's the actual answer to your question: We don't know. That's because some parts of the Earth will be affected more by the Sun's brightening that others. For example, the NRC found that the Pacific Ocean experienced a strong relationship with solar activity. So as the Sun gets brighter, some areas could still be strongly affected by Milankovitch cycles, while others might find themselves getting hotter than they would normally be.

We can be sure of one thing, though: It will certainly be before one billion years from now!


What is cluster situation with respect to sand mining? Guideline on handling cluster issues : The original Environmental  Impact Assessment ( EIA ) notification does not provide for the procedure to handle cluster situation, which has been proposed in this guideline and will become part of the notification. One EIA will be prepared for one cluster irrespective of number and size of mining leases in that cluster, if the area is more than 5 hectares.

Taken from a book am reading on Environment, the author isn’t internationally known but I will still mention his name, Shankar.

Cluster in this situation refers to a grouping or a number of mining operations within a giving area.

Sometimes deposits of minerals with sand deposits is such that a number of smaller deposits is created instead of one larger more continuous deposit. When this happens it sometimes makes more sense to mine the deposits as separate pits instead of one large pit. The result is a cluster of mines within a given region/area.


Methane leaks from biogas Lately, I have been thinking about biogas and the impact leaks might have on climate. Biogas is mostly methane, and we know that methane has a much higher global warming potential than $\sf{CO_2}$. There will inevitably be leaks from biogas production plants, vehicles running on biogas, and other infrastructure.

In Norway, sorting of food waste has been introduced in many areas. This food waste is taken to a treatment facility where biogas is produced, and the leftovers from the biogas production are used as bio-fertiliser. The biogas is used to power buses and dustcarts in and around Oslo. The climate effect is then positive, since you are using a resource that would otherwise be wasted, potentially turning into methane at a landfill.

My question is: how large would the leaks have to be to counteract the positive effects?

how large would the leaks have to be to counteract the positive effects?

Trying a ballpark estimate ... biogas replaces natural gas. For simplicity let's assume the replacement is 1:1, one mole of methane from biogas* replaces one mole of natural gas. This also means that one mole of biomethane "saves" one mole of CO2.

Methane is about 25 times more intensive in terms of cliamte change than CO2. So if 100/25 = 4% leaks, the positive effect would be offset.

The factors influencing gas leakage, from biggest to smallest influence (this is mostly from memory):

Retention time of substrate in gas tight system - depending on retention time in the digesters, the digestate could still have 10% or so of it's total biogas potential, when the digestate storage is open and the HRT is short. One of the later iterations of the German rennewable energy laws specifies 150 days retention time in the gas tight system for this reason & I think this is reasonable for many substrates.
Leaking foil roofs - foil roofs are common on large tanks, especially the connection foil roof/digester is a common point for leakage. This study found leakage rates from plants between 0 and 20 Nm³/h (median 5-10 Nm³/h), size of plants was not given but probably around 500 Nm³/h biogas production.
Methane slip - I don't have numbers to go by, but I think 0.5-1% of gas slip (unburnt gas in the exhaust) in IC motors is common. This regardless of wether you burn natural gas or biogas, AFAIK.
Manure storage - some wastes will ferment on their own, esp. manure.
Everything else - IMO the art of building gas pipes etc. is pretty well developed, if proper procedures are followed and proper materials used leakages from pipes should be neglible.

In summary, the methane loss of biogas plants may well be above the 4% cutoff point I mentioned above, or well below, depending on plant design and quality of building.

However, as you pointed out in comments to your question, you need to also look at what would happen to the feedstock without biogasification. Manure would ferment (but not as completely) in an open pit and emit gasses. Municipal wastes would be either incinerated (likely with additional fuel because of the high moisture content), composted or landfilled (landfilled wastes also ferment and produce biogas, if this goes to the atmosphere, is flared or used productivly depends on the site). I have worked in landfill supervision and design of biogas plants.

At this point, I lack good numbers to really compare biogasification to other disposal paths. Having worked in landfill supervision and design of biogas plants, I have more trust in a properly designed biogas plant to keep methane out of the atmosphere than in a typically, well maintained landfill. But I'm sure you can find shoddy biogas plants that leak, for the same amount of input, worse than some landfills!

Likewise, I'm still looking for hard numbers of fuel usage for incineration of biowastes, so I can't offer a good comparison here.

So IMO, while biogas from energy crops is highly questionable, biogasification of wastes is a net benefit if done properly.

*biogas is anything between 50 and 70% methane, the rest CO2 and traces.


Volcanoes and Lightning Just wondering about this question has been popped into my head many times and as what I have seen in some volcanic activities that when a volcano erupts there's a lightning, & i don't know if there's really a storm but I do think volcanoes do attracted to lightning or it produces it's own?

Do volcanoes attracts to lightning?

Volcanic lightning was documented by one of the earliest American volcanologists, Frank A. Perret in the 1940s. However, there was not much, if any, study of the phenomena until recently. According to this article, the electric charge develops close to the ground where the plume gas thrust region at a few hundred meters above the crater rim, where the overpressure of the turbulent volcanic jets determines the electrification of particles generating a complex charge structure in the growing plume."

The abstract of another journal article indicates that additional lightning can be generated in the stratosphere, "Observations and volcanic plume modeling further suggest that electrical activity was enhanced both by ice formation in the ash clouds >10 km above sea level and development of a low-level charge layer from ground-hugging currents."


Why is the diurnal temperature range on the Cascade volcanoes so small? Ski-mountaineering in the Pacific Northwest I am frustrated that the snow pack isn't refreezing at night.

There is about a 20F difference between the day and night temperatures in Seattle. Looking at forecasts for Mt. Rainier and Mt. Baker, the night temperature looks to be the same or sometimes even  warmer. I think I have seen these kinds of forecasts even when the sky is clear, when I would expect the snow pack to release a lot of longwave radiation.

What is going on here?

I think the answer to this question can be split into two parts. First, it is important to know which weather model you are using. Weather models use grids to predict the weather. The finer the grid, the better the topography (mountains) are represented by the weather model. To get a reasonable representation of the mountains that you mention, you would need a horizontal grid spacing of a few kilometers at most.

For the second part of the answer, we will assume that the weather model you are looking at has a fine grid. The only effect that I can think of explaining the strong difference in the daily cycle between Seattle and the mountains, is the wind. At higher altitudes, radiative cooling cannot effectively bring down the temperatures since the air is continuously being mixed with air from the free atmosphere which has a much less pronounced daily cycle.


A sedimentary rock with only minerals In my text book I came across this multiple-choice question

A sedimentary rock consists of only minerals and lacks fossils, it could be classified as:
i) a clastic sedimentary rock
ii) a chemical sedimentary rock
iii) a biochemical sedimentary rock

Of course I would exclude "a biochemical", but I am confused between clastic and chemical. I did some research on google but didn't find a precise answer. However, I found that both of them could contain only minerals.
So, I hope someone could help me here!

This is a really bad question, because all three can lack fossils, or all three can have fossils. The definition of "minerals" is also a bit unclear, because fossils are also made out of minerals. I'll assume that by minerals they mean non-biogenic minerals. Let's go through each one of them:

  a clastic sedimentary rock

This rock will have minerals, because this is what is being transported. Usually quartz, feldspars, clays, heavy minerals, etc. But, it can also have fossils. Fossils can be transported as well, and it is not uncommon to find fossils in clastic sedimentary rocks. They are usually not intact, but still fossils nonetheless.

  a chemical sedimentary rock

This will have minerals, obviously. This might also have fossils: what if there were organisms around while the chemical rock formed? Could be fossils falling from above into a carbonate precipitate, or insects in an evaporite basin. However, this is probably the least likely rock to contain fossils. If you have to choose only one, this would be it (unfortunately).

  iii) a biochemical sedimentary rock

This sounds like an obvious one to contain fossils, but it may not be. What about limestones where all of the fossils were broken down to unrecognizable fragments of calcite? Also known as a micrite? This would be biogenic, but it wouldn't be clear what fossils are there.


What controls the acidity of the ocean? I have learned that:

coral reefs are made up mostly of calcium carbonate
coral reefs are mainly distributed in the tropical zone
The calcium carbonate will be decomposed in the reaction as follows:
$$CaCO_3 + H_2CO_3 -> Ca^{2+} + 2HCO_3^-$$

Thus this reaction will be promoted in the environment with low pH.

The ocean in the tropic zone should have lower acidity (higher pH) for the coral reef to exist.

But in my opinion, the pH in the ocean is determined by the dissolution of CO2, and this process might be promoted in higher temperature?

How to explain this issue?

You have focused on corals (that have a much more lower biomass than for example foraminifera), and you have forgotten what controls carbonate levels at oceans at bigger scale is Henry's Law:

"In chemistry, Henry's law is a gas law that states that the amount of dissolved gas in liquid is proportional to its partial pressure above the liquid . The proportionality factor is called the Henry's law constant"
Source: Wikipedia

So answering your question what controls acidity on oceans is indeed carbonates, but it is atmospheric $\small\sf{CO_2}$ levels (and temperature, as Henry's constant is temperature dependent) what determine the concentration of carbonates.
The quaternary increase of $\small\sf{CO_2}$ leads to the generation of new $H^+$ and thus acidify the ocean, acording to the reaction:
$CO2 (aq) + H2O ⇌ H2CO3 ⇌ HCO3− + H+ ⇌ CO32− + 2 H+.$


Future super-continent What will the earth look like when the continents recollide? What will the climate be like? Assume global warming has been taken care of.

There are a couple of very cool animations on YouTube of the future supercontinent: Pangea Proxima. One is by Christopher Scotese (video) and the other is by Algol (YouTube or also a longer animation with a longer history). The PALEOMAP Project page contains a fair amount of information as to how they estimate the evolution. With regard to the future climate, that is a really tough question that I don't feel qualified to answer.

Also, even though it does not include the future supercontinent, I really like the EarthViewer interactive tool. It has lots of information and it is very intuitive to use.


In what way does the orientation of fossils help? What can we infer from that? Randomly oriented fossils may indicate an autochthonous deposit whereas parallelly oriented fossils indicate directionality of flow. How?

Lots of bones are long and thin and fairly heavy, to turn them all in the same direction water flow has to be fairly fast, we see the same thing today. fast flowing water turns bones and logs to present the least drag. This is important because it was one of the first ways used to establish bones whether had been moved by the environment after death.


How to calculate 3-hour flux values in ERA-Interim? Referring to the post:

https://www.myroms.org/forum/viewtopic.php?f=30&t=3003

I understood how to calculate the slhf and sshf for 03, 06, 09 and 12 time steps. But I have values for 00, 15, 18 and 21 time steps as well. If the accumulated fields have base time for forecast values at 00:00:00 and 12:00:00, then how average values for 00, 12, 15, 18 and 21 time steps are calculated. I need average flux values for every 3-hour.

Thanks for your inputs.

After my original answer, and some back and forth in the comments, turns out I got the answer right by a bit of fools luck, and we sorted it out...

The thing is, despite flux being commonly thought of in physics as BetterExplained.com suggests:

  Timing: We measure flux at a single point in time. Freeze time and ask
  “Right now, at this moment, how much stuff is passing through my
  surface?”. If your field doesn’t change over time, then all is well.
  If your field does change, then you need to pick a point in time to
  measure the flux.

But, fairly counter-intuitively to many, meteorological models often, despite naming their variables as flux (such as sshf... surface sensible heat flux), actually store them as accumulations.  This ECMWF whitepaper on archive data specifications explains:

  Physical fluxes archived by the ECMWF model are accumulated since the
  start of the relevant forecast, and therefore in units of
  $\mathrm{Jm^{−2}}$ (or $\mathrm{W m^{−2}\cdot s}$).  Thus, a daily
  mean (in $\mathrm{W m^{− 2}}$) is obtained by retrieving the
  accumulated fluxes at $\mathrm{t_1=t}$ and $\mathrm{t_2=t}+ \mathrm{24\;hours}$ (where
  $\mathrm{t}$ is the time of the start of the average), taking the difference
  and dividing by 86400, the number of seconds in a day.

So, though intuitively, you might think the surface sensible heat flux at 6 hours would just be the sshf variable in the 6 hour file, it isn't.  To get the best estimate of the flux, you'd need to calculate it as:

$$\mathrm{\frac{fluxvar_{(this\;timestep)} - fluxvar_{(previous\;timestep)}}{timestep_{(in\;hours)}\cdot3600}}$$

So if you want to find the average flux between hours 3 and 6, you'd do:

$$\mathrm{\frac{fluxvar_{(t=6hr)} - fluxvar_{(t=3hr)}}{3\cdot3600}}$$

A couple of questions that Vidhi asked about that may be worthwhile understanding to others:

Why did the website quoted show the calculation as $\mathrm{({fluxvar_{(t=6hr)} - fluxvar_{(t=3hr)})/10800}}$, but not $\mathrm{({fluxvar_{(t=3hr)} - fluxvar_{(t=0hr)})/10800}}$... instead just using $\mathrm{{fluxvar_{(t=3hr)}}/10800}$

Because indeed, in this strange accumulation form $\mathrm{fluxvar_{(t=0hr)}}$ by definition is zero.  The variable may or may not exist in the $\mathrm{t=0hr}$ file, but if it does, it should be pointless to include as it had better be 0 if it is indeed accumulation.

The site quoted only mentions hours 3, 6, 9, and 12.  I have 15, 18, and 21 as well, how do I deal with this?

The same math applies... but remember, if you're dealing with forecast model archive (rather than reanalysis data), you want to use the shortest future hour possible.  So actually, rather than use 00Z's $\mathrm{t=12hr}$, you want to be using 12Z's $\mathrm{t=0hr}$, such that, when calculating the 9Z to 12Z flux average, best is$\mathrm{({fluxvar_{(12Z\;t=0hr)} - fluxvar_{(00Z\;t=9hr)})/10800}}$.  Because you only need steps 0, 3, 6, and 9 before the next archived model/reanalysis file (for a twice a day model), the 12/15/18/21 values really are the 0/3/6/9 values (just from the next model run).

Anytime derived values (variables that aren't in the model itself, but require a formula to determine) need calculating, such as total surface heat flux, just make sure that when you combine the variables (in this case the shortwave, longwave, sensible, and latent heats), you only divide by the timestep once (don't divide by 10800 in the separate input variables beforehand, then divide by 10800 again after combining them).

The models are strange to many.  I just happened to incorrectly remember what a flux was, and get the "divide by 10800" math right (probably in part due to horror memories of working with similar files in years gone by!).  But hopefully this helps some confused people!


Mining and keeping UK minerals? Is it legal to mine/collect and keep minerals in the UK for educational purposes?

I would also like to know if there are any notable mineral deposits located in the UK midlands.

Can I go to forests, national parks or mineral deposits and mine

I think the basic answer to this question is No, or rather, not without the land owners permission.

For example it is illegal to remove pebbles from a beach: Woman who 'stole' pebbles from a BEACH to decorate in her garden given police warning

For more information on mineral ownership in the UK see: Legislation & policy: mineral ownership


Marine microfibres: less plastic than predicted Marine microfibres: less plastic than predicted (Phys.org)

  Microfibers are fine strands of thread used to make clothing, carpeting and household items like mops. They are found in the air we breathe, the water we drink, and throughout the world's oceans. Natural, rather than synthetic, microfibers, though, make up the majority of those found in the ocean's surface waters—despite the fact that currently two-thirds of all human-produced fibers are synthetic.

This is based on the paper: Microfibers in oceanic surface waters: A global characterization.

They seem to assume that all the "natural" fibres (wool, cotton) are "anthropogenic" (e.g. clothing, carpeting).

Do they consider the possibility that some of the "natural" fibres may come from plants or animals without human intervention? E.g., animals shedding hair or plant fibres washed into rivers.

They don't mention it explicitly. But they don't classify further than "natural" and "synthetic". And, may I say, animal husbandry as well as agricultural use of the producers of such natural fibres (e.g. jute, wool) are under human control as well. They are introduced into the ocean via waste-water, rivers, wash from the continents.

The study used samples from surface waters, if I understand it correctly from reading superficially. They say that too many fibres are prematurely seen as "microplastic" while they may actually be natural.

Other studies have come to the conclusion that the missing plastic-fibre in surface waters rests deeper in the water column, or may come in small(er) sizes than sampled.


Unwarranted claim of higher degree of accuracy in zircon geochronology The uncertainty in the half life of uranium-238 is stated at 0.05% [1]. The same paper gives the date 251.941 myr ± 31 kyr.
251.941 $\times$ 0.05% = 125 kyr.

How are the authors justified in claiming an accuracy of ± 31 kyr when the uncertainty in the half life alone is ± 125 kyr? On top of that, they list two other kinds of analytical uncertainties, which would only increase the overall uncertainty.

[1]  Burgess, S. et al, "High-precision timeline for Earth’s most severe extinction", Proceedings of the National Academy of Sciences USA, Volume 111, 2014.
https://www.pnas.org/content/pnas/111/9/3316.full.pdf

I can't be entirely sure but I'll make an informed guess:

That value doesn't come for a single measurement. Therefore, if the error in the age of a single sample is $\pm125$ kyr, you just need to average 16 samples to get it down to $\pm31$ kyr.

The uncertainty in the addition (or substraction) of two or more quantities is equal to the square root of the addition of the squares of the uncertainties of each quantity (assuming they arise from random errors). For example, if we have quantity A with uncertainty $\sigma_a$ and quantity B with uncertainty $\sigma_b$, the error in the quantity $C=A+B$ would be:

$\sigma_c=\sqrt{\sigma_a^2+\sigma_b^2}$

And if we call M to the average between A and B. The uncertainty in the average is

$\sigma_m=\frac{\sqrt{\sigma_a^2+\sigma_b^2}}{2}$

So if we average 16 samples with $\sigma=125$ kyr, the uncertainty in the average would be

$\sigma_m=\frac{\sqrt{16 \sigma^2}}{16}=\frac{\sqrt{16 \times 125^2}}{16}=31$ kyr

Uncertainty propagation can be seen in the abstract of the article you refer to:

  The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031
  Mya, an interval of 60 ± 48 ka.

Where the ±48 ka comes from?

$\sqrt{37^2+31^2}=48$

This treatment of uncertainties assumes that uncertainties are independent of each other. As @Mark pointed in the comments, this won't be the case if the uncertainty comes from "the length of your measuring stick (the half-life of U-238)".

This is: if you measure something with a "yard-stick" that have the wrong size, you can't reduce the resulting error by just averaging many measurements.

I don't know enough of geochronology to understand all the different errors they report. But the simple example in the abstract cite I presented above shows that they are indeed treating those errors as independent. Otherwise the reported interval error (±48 ka) would not make sense.

If one significant source of error is indeed the uncertainty in the half-life of $^{238}$U. However, it would be wrong to treat these errors as independent only if there exists an exact value for this half-life. Alternatively, maybe there is no exact value of the half-life, and what they meant is that the half-life value can truly vary a 0.05%. This is something to look into if you want to figure out if the treatment of errors they do is correct. However, after a quick google search I found that radioactive half-life can indeed vary by a small fraction due to environmental conditions, this article explains pretty well the phenomena. Here a short excerpt:

  ...radioactive half-life of an atom can depend on how it is bonded to
  other atoms. Simply by changing the neighboring atoms that are bonded
  to a radioactive isotope, we can change its half-life. However, the
  change in half-life accomplished in this way is typically small. For
  instance, a study performed by B. Wang et al and published in the
  European Physical Journal A was able to measure that the electron
  capture half-life of beryllium-7 was made 0.9% longer by surrounding
  the beryllium atoms with palladium atoms.

If the 0.05% uncertainty on the half-life of $^{238}$U comes from random environmental factors, it would indeed be acceptable to consider them as an independent source of error for each sample.


Minimum temperature on 15km height on equator in JJA? See this picture from the book Hartmann, Dennis L - Global Physical Climatology.
There is a minimum temperature point of 200K at 15km height above the  equator, in June/July/August.

I don't know why this happens. Can anyone explain this?

That's because the tropopause, the boundary between the troposphere and stratosphere, is highest in equatorial regions. The high amount energy from the Sun in equatorial regions makes for a lot of convection, which in turn pushes the tropopause to about 16 km above the surface (and sometimes to 18 km) in those equatorial regions. Near the poles, sinking air and reduced solar intensity makes the tropopause much closer to the surface, where it is only 8 km or so high.

The lapse rate in the upper troposphere is roughly the same as the dry adiabatic lapse rate, 9.8 °C/km. The 8 km difference between the tropopause height between equatorial and polar regions results in about 80 degrees more cooling in equatorial regions than polar ones.


What is the synoptic/atmospheric setup that is causing the U.S. severe weather outbreak in May 2019? I asked this in the chat and it was suggested I ask on the main site.

There's been a seemingly perpetual severe weather outbreak over the central and eastern U.S. over the past two weeks. Killer EF3s in Jefferson City, MO, Dayton, OH, and El Reno; flash flooding in Oklahoma; severe storms in Illinois/the Ohio Valley/Mid Atlantic; the tornadic supercells in northern NJ/Staten Island, the list goes on, and on, and on.

On top of this, the southeastern U.S. is seeing record high temperatures (earliest-ever triple digit temps for Alabama) and a heat wave is currently (as of today, Wednesday 5/29) smothering the east coast. What has been the synoptic and mesoscale (fronts, upper-air) setup that can explain this unusual pattern?

Summarizing the comments I made above in this question and in this one - Does this weather pattern have a name ? I believe significant parts of the US  are experiencing a  Stationary Front for the past one month. There has been plenty of media coverage of this event and if you google the term "stationary front" under news one will receive a lot of links to the TV news media with meteorologists giving detailed analysis of this event.

A few summarized below -

1) Week's bleak weather not an unusual spring occurrence

2)A stationary front is stuck across the middle parts of Illinois and Indiana

I will attempt to provide a synoptic scale explanation of the event from reanalysis data.

1) From JMA's site  -

an upper level look at the 200 hPa surface reveals that an equatorward trajectory of the wave activity flux vector(seen as small arrows) is seen  from the Upper North Pacific. Climatologically Rossby Wave Breaking can occur from boreal fall to boreal spring. The signal is seen at 30 day , 10 day period and 7 day period and 5 day period. The signal is present in the raw data as well as in the anomaly. Most importantly this wave activity flux is directed towards the continental USA all the way from New Mexico to the Great Lakes region.

A popular science version of the above information has been discussed over at this link - What's up with all this wet weird weather ?

2) At the surface level this "stationary front" presents itself as air masses of two different temperatures as seen from this plot and one can see the frontal boundary more or less coincides with the rising contour of the stream function plot in (1). Here the south easterlies are bringing in warm moist air from the Gulf coast and the Atlantic and the colder air masses are coming from Canada and North East Pacific. So the key question is whether the upper level influence is directing the surface level weather and that question can be answered by calculating PV anomalies when ERA 5 reanalysis data does become available.

Source - JMA reanalysis data

3) The moisture flux being pumped into the south eastern part of the USA can be seen from this plot over a seven day period - .
Again the signal is present over 30 day period, 10 day period and 3 day period and over a 1 day period. I would like to point out the moisture flux is seen at different levels of the atmosphere from surface level to the 300 hPa surface.

Source - NCAR NOAA reanalysis derived variables

4) Last year (2018) apparently a wavenumber - 7 was found to be causing weather stalls as shown in this link - Weather stalls becoming longer. This year in April  it is a wavenumber 5 pattern as seen in this site - Current Weather reports and summarized here

  From a global point of view, the weather pattern in the beginning parts of the 6-10 day (around day 7) will enter into a wavenumber 5 pattern. That's where you have 5 distinct upper-level troughs (areas where the weather is cool and stormy) around the globe. It's like a major traffic jam in the atmosphere and could lead to weather stagnation with little to no variation for days and/or weeks. This could also lead to extreme weather events such as droughts and severe weather/flooding across some parts of the world.

and I am able to pick up the wavenumber 5 or 6 as pointed by user Deditos (as well in this twitter feed - Wave number 6 planetary wave) from NCAR NOAA reanalysis data for the 500 hPa geopotential height anomaly for the month of May.