(7 of 9)
Everyone who has glanced aloft at the high, feathery cirrus clouds knows that they often move at impressive speed, but until the U.S. B-29s began bombing Japan, no one realized just how hard the high winds could blow. Sometimes the bombers were even blown backwards by head winds approaching 200 m.p.h.
When Rossby heard about these winds, he saw at once that they must be associated with the long, high-altitude waves that he had discovered. He named them the "jet stream." After the war he worked out a highly mathematical theory to account for the wind. Now the jet stream is used in the flight-planning of both civil and military airplanes. Its behavior can be predicted to a considerable extent by Rossby's theories.
Numbers Game. The most exciting postwar news for Rossby was the appearance of high-speed electronic computing machines. Meteorologists had often dreamed of "numerical forecasting," i.e., predicting the future actions of the atmosphere by applying mathematical equations to its current pattern, but they were stopped at once by two difficulties: 1) they did not know the proper equations, and 2) they would have to do so much figuring that they could not keep up with the weather, let alone forecast it. British Meteorologist L. F. Richardson described in 1922 a forecasting center built like a gigantic theater, with 64,000 mathematicians frantically busy with desk computers. A modern computing machine can figure as fast as 100,000 men.
Other men than Rossby noted this startling fact. Dr. Vladimir Zworykin, inventor of the iconoscope, the first effective television-camera tube, sold the idea to his Princeton neighbor, the great Mathematician John von Neumann. Teaming up with Rossby, who provided the meteorological knowledge, Von Neumann and his brilliant assistant Dr. Jule Charney devised ingenious mathematical tricks to shoehorn weather observations into computing machines.
Rossby's main contribution to numerical forecasting, besides his discovery of the long waves, is his simplified equations, which treat the atmosphere as if it were as two-dimensional as a sheet of paper. Looked at in the large, this is not far from true. The part of the atmosphere that concerns the weather is only some seven miles deep, and it covers the surface of a globe 8,000 miles in diameter. Proportionately, it is much thinner than the skin of an apple.
Electronic Editor. Electronic weather forecasting is now being done with steadily increasing success by the Joint Numerical Weather Prediction Unit at Suitland, Md., where the Air Force, Navy and Weather Bureau have pooled their forces. Weather information flows into the machines from both ground stations and upper-air probes. Some 1,400 punched cards cover North America. Other information equally important comes from the rest of the Northern Hemisphere, including Soviet Russia and Communist China. The machine even "edits" the raw data, selecting from masses of figures the special ones wanted, such as air pressure at 18,000 ft. over the Aleutian Islands.