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The next day was a windy one. Frank realized that the air over the sixteenth green was moving: no longer would it do to assume the air stayed in only one place, with only radiation and turbulence affecting it. Now it was possible that the temperature at the sixteenth green could change because colder or warmer air was coming. What would the weather computer need now?
It turned out that the computer asked for two things: the temperature of the air upstream and the wind speed. And furthermore, it wanted that information for ALL LEVELS!
Frank decided on a simple approach: He took the current temperatures and told the computer that those were the temperatures 100 feet upstream. That was all the weather computer asked for, and it cranked away at its forecast. The output came, and Frank was disappointed, but not surprised. The temperatures in the forecast hardly changed at all from the initial temperatures.
Checking the computer program, Frank saw that a new term had been added. The equation for predicting temperature now read:
The NEW TEMPERATURE is just like the OLD TEMPERATURE, except for subtracting a TINY AMOUNT to allow for radiative cooling of the air, allowing for a small change to account for a little bit of TURBULENT MIXING of air from above and below, and including a small amount to account for warmer or colder air being BLOWN IN.
Frank recognized that this last term was the temperature advection term. Its importance depended on how strong the wind was and how much warmer or colder the upstream air was.
Temperature advection question:
Suppose the temperature is 4 degrees warmer 100 miles to the south and 4 degrees cooler 100 miles to the north. What wind will tend to cause the temperature to rise at the rate of 0.8 degrees per hour?
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