Stratospheric Sensitivity to Perturbations in Ozone and Carbon Dioxide: Radiative and Dynamical Response

Abstract

We have attempted to assess the stratospheric effects of two different perturbations: 1) a uniform 50% reduction in ozone; and 2) a uniform doubling of carbon dioxide. The primary studies employ an annual mean insulation version of the recently developed GFDL 40-level general circulation model (GCM). Supporting auxiliary calculations using purely radiative models are also presented. One of these, in which the thermal sensitivity is computed using the assumption that heating by dynamical processes is unaffected by changed composition, gives results which generally are in excellent agreement with those from the GCM. Exceptions to this occur in the ozone reduction experiment at the tropical tropopause and the tropical mesosphere. The predicted response to the ozone reduction is largest at 50 km in the tropics, where the temperature decreases by 25 K; at the tropical tropopause, the decrease is 5 K. The carbon dioxide increase results in a 10 K decrease at 50 km, decreasing to zero at the tropopause. The temperature change in the CO, experiment is remarkably uniform in latitude.