Two Column Models of Tropical Atmospheric Circulations

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Dr. Raymond will use a highly simplified two column model to better understand large-scale tropical circulations and to help test cumulus parameterizations for atmospheric global circulation models. The model involves the use of two embedded cumulus ensembles, one in each column, that are coupled by mass flows which tend to drive the two column's environments toward buoyancy equilibrium with each other. These mass flows are the two column analog of large scale tropical circulations where one column represents the ascending (moist, convective) branch of the Walker circulation and the other column is the descending (clear, driven by radiative cooling) branch. The convective ensemble calculations thus operate in a context that is close to that which actually occurs in the equatorial regions of the earth's atmosphere. Vertical velocities in the two columns are created by the model itself rather than being imposed. The cumulus ensembles can be replaced by candidate cumulus parameterizations for purposes of comparison with ensemble model calculations.