Dehydration in the antarctic stratosphere: Radiative effects

A two dimensional model is used to investigate the effects of polar stratospheric clouds on the water vapor budget in the Antarctic stratosphere. It is shown that loss of stratospheric water vapor through formation and sedimentation of large ice particles decreases infrared cooling. This cooling reduction partially compensates the decreased ozone heating due to the formation of the Antarctic hole. Such a conclusion is reached by comparing a control unperturbed situation with two cases in which an ozone hole is formed with and without polar dehydration. We show that in the case of substantial loss of stratospheric water vapor since the years of the ozone hole formation, a dynamical mechanism may be necessary to explain the observed stratospheric cooling during the Antarctic spring. In this case the combined radiative perturbation (H2O + O3) is too small to force this cooling. Instead, in the case of a negligible change of water vapor content, the O3 radiative perturbation could be entirely responsible for the observed secular cooling.