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Gerrit Vanniekerk
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I've been reading a bit about SSW's, and the prevailing theory, namely that a slowed-down Rossby wave rises into the Stratosphere, blocking flow and thereby causing warming, just doesn't add up: If moving air is to slow down, it has to encounter a positive pressure gradient. This increase in pressure compresses the air, causing the temperature to rise. If it would come to a complete standstill, either by massive Rossby wave, turbulence, breaking waves, or whatever, it will reach stagnation temperature. It can't become warmer than that by dynamic effects. Now, to cause a 30K increase at 240K, an initial wind speed of .625M would be needed (that is average wind speed of 600km/h)... nope. Also, a rising stream of bone dry desert air is cooling at about 1K per 100m. Assuming it could manage to reach the Stratosphere by some mechanism, it would be at least 100K colder up there than down on the surface, and would rather have a cooling effect. The only plausible mechanism by which such a massive volume of air can heat up rapidly, is for it to decent, causing it to compress. The 30K warming will need a 50% pressure increase, meaning the air volume will have to drop by about 3000m. It is massive, but I can't see that it isn't possible, and it is also consistent with the notion of a lot of Arctic air spilling out. And it is consistent with the time of year - a rapidly cooling Arctic air mass, got to become more dense and start sinking. The question is just why all of a sudden, and not gradually as the Arctic starts cooling down in Autumn? There must be some meta-stable mechanism keeping it up, and maybe conditions above the Taklamakan sets this tipping process in motion, as Michael noted strongly descending air, as if plucking the first card from the card house, and then the rest of the house starts collapsing. Well, just a few more considerations to work into the theory. Hopefully those still reading aren't bored to death :)
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Apr 25, 2013