Environmental Science and Engineering Seminar

With rising levels of atmospheric CO₂, projections of regional climate change are increasingly demanded by society. Yet, our confidence in such projections and our understanding of the underlying atmospheric circulation changes remains limited. I will report on recent work on the role of cloud-radiative interactions for regional climate and the atmospheric circulation of the tropics and extratropics. In the tropics, shifts of the intertropical convergence zone (ITCZ) are strongly modulated by the radiative contrast between high and low clouds and its control on hemispheric differences in the atmospheric energy balance. This offers a way to improve climate models and to reduce model uncertainty in projections of tropical rainfall changes. In the extratropics, tropical and mid-latitude high clouds control the position of mid-latitude storm tracks and jet streams through their effect on meridional and vertical temperature gradients. These results highlight the need to better understand the radiative coupling between clouds and the circulation, as well as the benefits that such an understanding likely has to offer for regional climate projections.