Why is the African Jet so Low (and in the opposite direction)?

The following is paraphrased from a talk Chris Thorncroft (of SUNY Albany) gave at Climatea today. Any mistakes are certain to be based on my misunderstandings.

The jet arises from thermal wind balance between the hot saharan air and the cooler sale atmosphere (The gradient points south, so the Jet is Easterly). But why is the jet at such a low altitude (600hPa?) - other jets are nearer the tropopause.

The answer stems from the unusually dry Saharan air. The dryness is such that the temperature profile is essentially a dry adiabatic - there is essential no latent heat released to counteract the cooling by expansion as air rises above the sahara.

Above the Sahel, the air is moist, so there is plenty of latent heating and the temperature drops less rapidly.

Thermal-Wind Balance requires that the wind is increases with height in proportion to (and perpendicular to) the horizontal temperature gradient. So, the Jet peaks when the temperature gradient vanishes - where the temperature above the Sahel and the Sahara are the same.

For other jets, there is moist convection on both sides of the jet, so the temperatures equalize much higher than over West Africa.

Abbott and Costello Buy A Computer

The first new joke forward worth repeating in a very long time...

In today's world, Bud ABBOTT and Lou COSTELLO's famous sketch "Who's on first?" might have turned out something like this....
COSTELLO CALLS TO BUY A COMPUTER FROM ABBOTT . . . .
ABBOTT: Super Duper computer store. Can I help you?
COSTELLO: Thanks. I'm setting up an office in my den and I'm thinking about buying a computer.
ABBOTT: Mac?
COSTELLO: No, the name's Lou.
ABBOTT: Your computer?
COSTELLO: I don't own a computer. I want to buy one.
ABBOTT: Mac?
COSTELLO: I told you, my name's Lou.
ABBOTT: What about Windows?
COSTELLO: Why? Will it get stuffy in here?
ABBOTT: Do you want a computer with Windows?
COSTELLO: I don't know. What will I see when I look in the windows?
ABBOTT: Wallpaper.
COSTELLO: Never mind the windows. I need a computer and software.
ABBOTT: Software for Windows?
COSTELLO: No. On the computer! I need something I can use to write proposals, track expenses and run my business. What have you got?
ABBOTT: Office.
COSTELLO: Yeah, for my office. Can you recommend anything?
ABBOTT: I just did.
COSTELLO: You just did what?
ABBOTT: Recommend something.
COSTELLO: You recommended something?
ABBOTT: Yes.
COSTELLO: For my office?
ABBOTT: Yes.
COSTELLO: OK, what did you recommend for my office?
ABBOTT: Office.
COSTELLO: Yes, for my office!
ABBOTT: I recommend Office with Windows.
COSTELLO: I already have an office with windows! OK, lets just say I'm sitting at my computer and I want to type a proposal. What do I need?
ABBOTT: Word.
COSTELLO: What word?
ABBOTT: Word in Office.
COSTELLO: The only word in office is office.
ABBOTT: The Word in Office for Windows.
COSTELLO: Which word in office for windows?
ABBOTT: The Word you get when you click the blue "W".
COSTELLO: I'm going to click your blue "w" if you don't start with some straight answers. OK, forget that. Can I watch movies on the Internet?
ABBOTT: Yes, you want Real One.
COSTELLO: Maybe a real one, maybe a cartoon. What I watch is none of your business. Just tell me what I need!
ABBOTT: Real One.
COSTELLO: If it's a long movie I also want to see reel 2, 3 & 4. Can I watch them?
ABBOTT: Of course.
COSTELLO: Great! With what?
ABBOTT: Real One.
COSTELLO: OK, I'm at my computer and I want to watch a movie. What do I do?
ABBOTT: You click the blue "1".
COSTELLO: I click the blue one what?
ABBOTT: The blue "1".
COSTELLO: Is that different from the blue w?
ABBOTT: The blue "1" is Real One and the blue "W" is Word.
COSTELLO: What word?
ABBOTT: The Word in Office for Windows.
COSTELLO: But there are three words in "office for windows"!
ABBOTT: No, just one. But it's the most popular Word in the world.
COSTELLO: It is?
ABBOTT: Yes, but to be fair, there aren't many other Words left. It pretty much wiped out all the other Words out there.
COSTELLO: And that word is real one?
ABBOTT: Real One has nothing to do with Word. Real One isn't even part of Office.
COSTELLO: STOP! Don't start that again. What about financial bookkeeping? You have anything I can track my money with?
ABBOTT: Money.
COSTELLO: That's right. What do you have?
ABBOTT: Money.
COSTELLO: I need money to track my money?
ABBOTT: It comes bundled with your computer?
COSTELLO: What's bundled with my computer?
ABBOTT: Money.
COSTELLO: Money comes with my computer?
ABBOTT: Yes. No extra charge.
COSTELLO: I get a bundle of money with my computer? How much?
ABBOTT: One copy.
COSTELLO: Isn't it illegal to copy money?
ABBOTT: Microsoft gave us a license to copy money.
COSTELLO: They can give you a license to copy money?
ABBOTT: Why not? THEY OWN IT!
A FEW DAYS LATER . . .
ABBOTT: Super Duper computer store. Can I help you?
COSTELLO: How do I turn my computer off?
ABBOTT: Click on "START" . . .

(c) 2004 by Tom King - Used by permission
Some Rights Reserved
twayneking@gmail.com
http://twayneking.blogspot.com

NETC Abstract

A Toy Model of the Instability in the Equatorially Trapped Convectively Coupled
Waves on the Equatorial Beta Plane

J Andersen and Z Kuang

Partially based upon Andersen, J. A., Z. Kuang, A toy model of the instability in the equatorially trapped convectively coupled waves on the equatorial beta plane, Journal of Atmospheric Sciences, 65,3736-3757, (2008)
http://swell.eps.harvard.edu/~joe/files/AndersenJA08.pdf


The equatorial atmospheric variability shows a spectrum of significant peaks in the wavenumber–frequency domain. These peaks have been identified with the equatorially trapped wave modes of rotating shallow water wave theory. This paper addresses the observation that the various wave types (e.g. Kelvin, Rossby, etc.) and wavenumbers show differing signal strength relative to a red background. It is hypothesized that this may be due to variations in the linear stability of the atmosphere in response to the various wave types depending on both the specific wave type and the wavenumber. A simple model of the convectively coupled waves on the equatorial beta plane is constructed to identify processes that contribute to this dependence. The linear instability spectrum of the resulting coupled system is evaluated by eigenvalue analysis. This analysis shows unstable waves with phase speeds, growth rates, and structures (vertical and horizontal) that are broadly consistent with the results from observations. The linear system, with an idealized single intertropical convergence zone (ITCZ) as a mean state, shows peak unstable Kelvin waves around zonal wavenumber 7 with peak growth rates of ~0.08 /day (e-folding time of ~13 days). The system also shows unstable mixed Rossby–gravity (MRG) and inertio-gravity waves with significant growth in the zonal wavenumber range from -15 (negative indicates westward phase speed) to +10 (positive indicates eastward phase speed). The peak n =0 eastward inertio-gravity wave (EIG) growth rate is around one-third that of the Kelvin wave and s at zonal wavenumber 3. The Rossby waves in this system are slightly unstable, and the Madden–Julian oscillation (MJO) is not observed. Within this model, it is shown that in addition to the effect of the ITCZ configuration, the differing instabilities of the different wave modes are also related to their different efficiency in converting input energy into divergent flow. This energy conversion efficiency difference is suggested as an additional factor that helps to shape the observed wave spectrum.

It is hypothesized that the MJO is better represented as a "moisture mode" where convection is much more directly coupled to variations in the atmospheric moisture content than to variations in atmospheric temperature (as in the "convective modes"). To this end, I will also discuss some preliminary results investigating this hypothesis and how it may be incorporated into convective wave models.

Can you see this trend in this data?

The data comes from ECMWF reanalysis projected/interpolated onto cloudsat orbits (y), and filtered OLR (x). The line in red is the result of a linear regression from matlab.

Because I'm a Nerd

I was queued up at whole foods behind a lady who was taking forever... and she took even longer once the cashier realized that she had transposed two digits between the register and the credit card charge - instead of $152.73, she charged the lady $125.73. When she realized this, she had to charge the lady an additional $27. Which took even more time, between explaining and doing...

All this is beside the point, except that I noticed that 27, while not round per se, was 3^3. I wondered if transpositions always gave interesting differences.

A little experimentation in my head lead me to conjecture that, rather than a cubic, the difference between two numbers that had a pair of adjacent digits swapped was multiple of 9.

A little more thought yielded a proof that is probably inelegant (but I'm a physicist not a mathematician, or a miracle worker!) and is also probably old news to all (but I don't care to look it up).

imagine a number n represented by ....def, where d, e, f are integers and the number is such that n = f+10*e+100*d + etc

now, consider the number m = ...dfe

m-n = e+10*f+100*d - (f+10*e+100*) = (1-10)*e + (10-1)*f = 9*(f-e)!

It is obvious that this still holds if there are digits to the right of our pair of transposees - everything written above is just multiplied by sufficient powers of ten.

What about when the pair of digits is separated by intervening digits?

eg m = ...fed

this can be considered the result of three transpositions:

def --> dfe --> fde --> fed

Each transposition provides a multiple of 9 to the difference, and so the statement still holds.

we can prove the statement for general separations through induction -

consider the difference between

...abc.....def

and

...aec.....dbf

where there are j+1 digits between the b and the e

consider the following chain of swaps:

...abc.....def --> ...acb.....def --> ...ace.....dbf --> ...aec.....dbf
This chain consists of two swaps of adjacent digits and one of digits seperated by j digits. All of these are known (or assumed) to satisfy the "multiple of nine" rule so the sum of the differences also obeys the rule.

QED!

I haven't proven anything in ages... it's actually a lot more fun when it isn't on an exam (and when its something trivial)

Obama on Science

Nature has an "interview" with the candidates on science (McCain's "responses" are taken from older statements - he declined to be involved).

http://www.nature.com/news/2008/080924/full/455446a.html

The final question was relevant to me:

Would it make sense for more overseas students who receive PhDs at American universities to stay in the country and contribute to its research base and its wealth? What immigration reforms would you support?

Obama: I believe that we must enact comprehensive immigration reform to restore our economic strength, relieve local governments of unfair burdens stemming from an inefficient federal immigration system, ensure that our country and borders remain secure and allow a path to citizenship for the 12 million undocumented immigrants who are willing to pay a fine, pay taxes, and learn English. A critical part of comprehensive immigration reform is turning back misguided policies that since 9/11 have turned away the world's best and brightest from America. As president, I will improve our legal permanent resident visa programmes and temporary programmes to attract some of the world's most talented people to America.

McCain, as a senator from Arizona, has long been involved in immigration issues, mainly through strengthening federal security at land border crossings. He supports immigration reforms to allow more highly skilled workers to stay and work in the United States after graduation.

Shame neither of them really answered the question - The question sounded like it was about F and J visa students, but they turned it into an illegal immigration question.

Another reason to be vegetarian...

People should consider eating less meat as a way of combating global warming, says the UN's top climate scientist.

Rajendra Pachauri, who chairs the Intergovernmental Panel on Climate Change (IPCC), will make the call at a speech in London on Monday evening.

UN figures suggest that meat production puts more greenhouse gases into the atmosphere than transport.

I was vegetarian quite some time before I realized this, but it is another good reason to stop eating meat.