Recovery of the tropical lower stratospheric ozone layer

Abstract

Long-term time dependent simulations out to the year 2050 using the Goddard Space Flight Center interactive 2D chemistry-radiation-dynamics model are used to predict tropical lower stratospheric ozone. The model results show that when chlorine levels are enhanced, heterogeneous chemistry on the surfaces of middle and high latitude sulfate aerosols and polar stratospheric clouds induces circulation changes which lead to ozone depletion in the tropical lower stratosphere. We find that despite a return to background chlorine levels, the tropical lower stratospheric ozone layer will not recover because of a reduction in penetrating ultraviolet radiation. This reduction is due to the faster upper stratospheric ozone recovery with increasing carbon dioxide. With background aerosol amounts, tropical ozone at 50 hPa is reduced by ∼2% between 1980 and 1997 and remains at that level of depletion out to 2050. The simulations also suggest that tropical tropopause temperatures will be lowered by a maximum of 0.1 K between 1980 and 2015, resulting in a maximum reduction of tropical lower stratospheric water vapor of 2% between 1980 and 2018. These results may have important implications for recovery detection strategies. Copyright 2005 by the American Geophysical Union.