Title: 'Impact of the cloud-radiative feedback on the shift of the inter-tropical convergence zone'

Abstract

The cloud-radiative feedback is at the heart of uncertainty in model estimates of climate sensitivity. Because clouds are generated by and feed back on the atmospheric circulation, current model limitations in the representation of clouds, however, might not only limit
our ability to project the global-mean surface temperature change under increased CO2 but might also be a dominant source of uncertainty in circulation changes and thus regional climate change.In this talk I will report on recent work that studies the impact of the cloud-radiative feedback on the shift of the inter-tropical convergence zone (ITCZ). To this end, four comprehensive atmosphere general circulation models in aquaplanet-slab ocean setup are used, and simulations with a free cloud-radiative feedback are compared to those in which the cloud-radiative feedback is disabled. The impact of the cloud-radiative feedback on the ITCZ shift is found to differ in sign and magnitude between models. As a result the feedback is responsible for half of the model spread. In the simulations presented here the feedback arises from tropical clouds, whose impact on the ITCZ shift is strongly linked to the dependence of tropical cloud-radiative properties on the circulation. The simulations do not only demonstrate the importance of the cloud-radiative feedback for circulation changes and regional climate change but also suggest a way to reduce model uncertainty in ITCZ shifts.

Speaker's website: https://sites.google.com/site/aikovoigt/