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How Do Models Make Clouds?
for more advanced readers
CONVECTIVE ADJUSTMENT
In models that use convective adjustment, a critical lapse rate is determined. This rate of cooling with height is what we expect from each grid cell. Then, the actual temperature profile of a grid cell is used to calculate that cell's lapse rate. If the calculated cooling with height is greater than the critical lapse rate, there will be relatively cold air aloft. Cold air is dense and should sink, so the grid cell's temperature profile should be adjusted to account for the sinking air. The adjustment occurs through cooling at the surface and warming near the top of the profile. This process emulates convection by mixing warmer air near the surface up through the atmosphere.
For example, this graph shows two possible situations for the atmosphere in a grid cell. The blue line shows temperature only decreasing modestly with height, while the red line shows temperature decreasing rapidly with height. We expect convection to occur in the atmosphere represented by the red line.
Next page -> how do models make clouds, continued
Links and resources
for more advanced readers
CONVECTIVE ADJUSTMENT
In models that use convective adjustment, a critical lapse rate is determined. This rate of cooling with height is what we expect from each grid cell. Then, the actual temperature profile of a grid cell is used to calculate that cell's lapse rate. If the calculated cooling with height is greater than the critical lapse rate, there will be relatively cold air aloft. Cold air is dense and should sink, so the grid cell's temperature profile should be adjusted to account for the sinking air. The adjustment occurs through cooling at the surface and warming near the top of the profile. This process emulates convection by mixing warmer air near the surface up through the atmosphere.
For example, this graph shows two possible situations for the atmosphere in a grid cell. The blue line shows temperature only decreasing modestly with height, while the red line shows temperature decreasing rapidly with height. We expect convection to occur in the atmosphere represented by the red line.
Next page -> how do models make clouds, continued
Links and resources
