Air Weather Man

For the U.S. Air Force, the weather is of great and far-reaching concern. A strategic air fleet, taking off for destination X, will need to know what weather to expect 5,000 miles and 20 hours ahead. Last week the Air Force acquired one of the world's leading meteorologists, Dr. Sverre Petterssen of M.I.T.

Dr. Petterssen's job will be to appraise and utilize the new methods that are making meteorology something like an exact science. Modern meteorology was developed in his native country, Norway (whose Drs. Vilhelm and Jakob Bjerknes worked out the method of air-mass analysis), but now, says Dr. Petterssen; the U.S. is well in the lead.

The lower air levels are already pretty well watched by civilian weathermen. What interests the Air Force is the area far above--the clear, thin, cold upper atmosphere, where winds of enormous velocity blow around the world. The big job of meteorologists at present is to study these winds and learn how they stir up the atmosphere down below. The Air Force is charting atmospheric conditions up to 20,000 feet for the whole northern hemisphere. Soon it plans to extend the survey up to 40,000 feet.

Civilian scientists (many of them financed by the military) are helping. A group at the University of Chicago has discovered that pressure waves in the high atmosphere are different from those at lower levels. When the waves are comparatively short and fast-moving, they usually lead to nasty weather below. At M.I.T. and elsewhere, meteorologists are clocking high-level winds and trying to find out what makes them speed so fast. Most of the information comes from "sounding balloons," but a little is trickling in from rockets, which bring back important figures from 60 miles straight up.

Another approach to meteorological exactitude is through electronic computing machines: at Princeton's Institute for Advanced Study, scientists are feeding huge masses of figures on air velocity, temperature, pressure and humidity into intricate computers, and drawing off solved equations at the other end.

Until the world settles down, Dr. Petterssen's job will be mainly military. But if happier times ever come, his new methods will eventually reach the workaday Weather Bureau and be used to warn picnickers against sudden summer showers.

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