A Test of the Role of Long wave Radiative Transfer in a General Circulation Model

The dynamical consequences of systematic changes in longwave radiative transfer computations have been investigated using the NCAR six-layer General Circulation Model. The experiments were run for a period of 40 days each: the “control” case with an emissivity computation, and the “test” case using a 19-sepctral-interval calculation, in which the Curtis-Godson approximation is employed. The two calculations lead to substantially different cooling rates when applied to identical soundings, especially in the tropics. Significant differences are observed in the thermal structure of the two cases, and in the mean meridonal circulations. The total kinetic energy is somewhat higher in the test case, probably due to increased baroclinic activity in latitudes.