## Richardsons Weather Factory

English meteorologist Lewis Fry Richardson (1881-1953) was determined to find a mathematical solution for weather forecasting. The son of prosperous Quaker (Society of Friends) parents, Richardson was the superintendent of Scotland's Eskdalemuir Observatory when World War I erupted. A pacifist, Richardson sought a leave of absence to provide noncombat assistance to the war effort. Denied leave, he resigned in 1916, volunteered to be a driver with the Friends' Ambulance Unit, and was assigned to a French infantry unit on the western front. Between ambulance runs, he decided to calculate temperature, pressure, and winds six hours into the future by using the basic equations of physics.

With paper and pencil, and an "office" of hay piled in a drafty barnlike building, Richardson spent every spare moment making his calculations with a slide rule and logarithm table. He was not actually making a forecast. He was making a hindcast. Richardson already knew the result because he was working with surface- and upper-air data from May 20, 1910, that had been analyzed by Vilhelm Bjerknes. Richardson wanted to see whether he could get the same answer by using equations.

The "primitive equations" that must be solved to predict the future state of the atmosphere cannot be solved analytically by using calculus;

Lewis Fry Richardson divided western Europe into checkerboard-like squares and then computed wind velocity for the dark squares and atmospheric pressure for the light squares.

they must be solved by using numerical analysis techniques. The mathematical problem is broken down into small increments, an initial solution is proposed, and then the mathematician solving the problem gradually narrows down the answer to a solution. It is unbelievably tedious without an electronic computer.

Because the observations were not evenly spaced across France, Richardson placed a "checkerboard" with squares 124 miles (200 km) on a side over the plotted map. Then he divided the upper atmosphere into five layers with the surfaces at sea level and then aloft at 1.2, 2.5, 4.3, and 7.5 miles (2, 4, 7, and 12 km) above sea level. There were 25 squares. He computed wind velocity in the black ones, and tem

RICHARDSON'S CHECKERBOARD

RICHARDSON'S CHECKERBOARD

perature or pressure in the white ones so the values would be evenly spaced. Richardson then calculated the pressure change in two of the squares (doing so far all 25 would have taken too long). After six weeks of calculations, Richardson forecasted a pressure increase of 145 millibars (mb). The actual increase was almost zero! Richardson's attempt had failed.

Most people do not tell others when they fail. Richardson wrote about his experiment in his 1922 book Weather Prediction by Numerical Process. The book was filled with difficult mathematics but in the conclusion Richardson wrote about his vision for a "forecast factory" where 64,000 "human computers" calculated the weather for their assigned part of Earth. He thought they might be able to keep up with the weather as it occurred if they worked 24 hours a day but would never be able to forecast in advance. Actually, not even 64,000 people would have been enough to keep up with the weatherâ€”200,000 is closer to being correct.

While Richardson's method was not the least bit practical in 1922 and attracted little attention from his fellow meteorologists, in the late 1940s the creation of electronic digital computers provided meteorologists with the opportunity to explore numerical weather prediction. They looked at Richardson's book for ideas on how to avoid the problems he had encountered. Lewis Fry Richardson was on the right pathâ€”he was just 25 years ahead of a way to bring it to life. In the meantime, work on a practical forecasting method was continuing at the Bergen School.

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