CLIMATE IMPLICATIONS OF THE OBSERVED CHANGES IN OZONE VERTICAL-DISTRIBUTION

Satellite and ozone-sonde observations indicated a decreasing trend in the ozone concentration in the lower stratosphere and an increasing t rend in the troposphere, especially the upper troposphere. We have use d a one-dimensional radiative - convective model (RCM) to examine the climate implications of these observed changes in vertical distributio n of ozone. Instantaneous radiative forcing calculated by the one-dime nsional radiative transfer model indicated a net warming of the surfac e-troposphere system due to stratospheric ozone losses. The increase i n tropospheric ozone causes an additional positive forcing. However, t he radiative forcing due to increases in trace gases during the same p eriod is larger than the forcing due to ozone changes. There is marked decrease of the instantaneous solar and longwave heating rates in the lower stratosphere due to stratospheric ozone losses. Increases in tr opospheric ozone causes additional decrease in longwave heating rate, in the lower stratosphere. Consistent with the changes in the heating rates, the equilibrium temperature profile computed by the radiative-c onvective model predicted a cooling in the stratosphere of the order o f 0.6 degrees C and a very slight warming in the troposphere. The incr ease of tropospheric ozone causes an additional cooling in the stratos phere. The temperature decrease caused by ozone decrease in the lower stratosphere is larger than that caused by increase of trace gases con centration during the same period. The stratospheric cooling effect du e to trace gases is, however, better presented near 30 km altitude.