A Computation of the Stratospheric Diabatic Circulation Using an Accurate Radiative Transfer Model

Abstract

The global diabatic circulation is computed for the months of January, April, July and October over the altitude region 100 to 0.1 mb using an accurate troposphere-stratosphere radiative transfer model, SBUV and SME ozone data, and NMC temperatures. There is high correlation between the level of wave activity and the local departure of the atmosphere from radiative equilibrium. For example, the summer lower stratosphere is close to radiative equilibrium while the winter is not. We find much greater heating in the upper stratosphere at low latitudes in the summer hemisphere, and roughly a factor of two less heating in the lower stratosphere at low latitudes, than did Murgatroyd and Singleton. An excess in the globally averaged net stratospheric heating from 40 to 50 km is computed for all months, and a deficit from 50 to 60 km is computed during solstice. Roughly a 20% uniform reduction in ozone from 40 to 50 km, or a temperature perturbation with an increase of 5 K at 1 mb, will bring the atmosphere into global radiative equilibrium without significant impact on the diabatic circulation. In the transitional mouths of April and October, the net heating in the fall hemispheres are very similar, while substantial differences exist between the spring hemispheres.