25 November, 2001
Antarctic weather is legendary for its extremes. For incoming flights carrying personnel and materials, the prediction of this weather is critical. This afternoon (Sunday) was slow in our lab, so I took a walk to the "nerve center" for meteorology in Antarctica, and spoke with Steve Pooler and Art Cayette about just how this all goes down.
As you can imagine, much has changed in the last ten years. They laughed out loud when I asked about how much of their predictions involved a "gut feeling." It was an inside joke that was the product of years of having to make predictions without the support of the data that would have helped. Why no data? It has to do with the sun's position relative to the satellite. Unfortunately, the "noise" produced by solar radiation coincides with the position of the satellite to produce about seven hours of silence from the technological heavens. Much of this has been resolved. Two major modern sources of satellite information are NOAA (National Oceanic and Atmospheric Administration) and DMSP (Defense Meteorological Satellite Program). An additional and highly useful source of information is the Antarctic Mesoscale Prediction System (AMPS-- which is visible to you online). This is not a satellite source, but a computer model of the continent's weather based on current meteorological data. Fially, SeaWiFS (Sea Viewing Wide Field of View Sensor Program) is an expensive subscribed source of data that helps to predict the weather.
I asked how their accuracy diminished over time, and was surprised to learn that in spite of Antarctica's notorious reputation for having weather blow up without warning, their two and three day forecasts were ironing out to about 75% to 80%, and a surprising 75% for four days. Twenty four hours yields a 90% correct prediction.
McMurdo is somewhat sheltered by the terrain that surrounds it. The topography also batters outlying areas through a phenomnon known as the Katabatic Wind. Cold, dense air high on mountains or plateaus (like the East Antarctic Ice Sheet) is either "pulled" down by local lows that rise (a weak Katabatic scenario) or pushed down by some intruding, overriding weather system. This dense air that is already prone to descend does so with a vengeance.
I should have talked to these folks sooner--it snowed two nights ago in a way that is rare in Antarctica. The wind was light, and perfect little snow crystals floated down. They knew it was coming! Hopefully, I will capture these the next time they fall. The chemicals are ready and waiting outdoors at the loading dock....
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