Geoscience Reference
In-Depth Information
ENIAC
Scientists first began to use digital computers during World War II to calculate
artillery firing tables and to break enemy codes. But even before the war ended,
some meteorologists and pioneering computer scientists realized that in principle a
digital computer could solve the complex equations needed for numerical weather
prediction.
The first attempts used the ENIAC (Electronic Numerical Integrator and Com-
puter), which had been built by scientists at the University of Pennsylvania
between 1943 and 1945. The “Giant Brain,” as the press dubbed the machine, had
at most ten words of read/write memory, yet its 18,000 vacuum tubes, six thousand
switches, and the like filled an entire room.
Even if scientists had perfected short-term weather modeling, they would still
have been a long way from modeling the climate, which is the average of weather
over a longer period and a larger area, ultimately the entire globe. For that purpose,
mid-1950s, Norman Phillips of the Institute of Advanced Study at Princeton built
the first general circulation model. His equations divided the atmosphere into an
upper and a lower layer. He changed the amount of heat in the lower layer and ran
the model through ENIAC to see the effect. Though today we take the jet stream
for granted, its existence was not confirmed until the high-altitude flights of World
War II. Phillips's ENIAC model reproduced a jet stream and also accurately re-
flected the way energy moves from the warmer equator toward the cooler poles.
The results “settled an old controversy over what processes built the pattern of cir-
culation. For the first time scientists could see, among other things, how giant ed-
dies spinning through the atmosphere played a key role in moving energy and mo-
mentum from place to place.”
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On the other hand, as the computer runs stepped forward in time, after a few
simulated weeks the results bore little resemblance to the actual conditions on
Earth. The main benefit of these earliest models was not the particular outcomes
butthe demonstration that climate modeling usingadigital computer was possible.
To replicate anything approaching reality, scientists would need more computer
power.
