Seasonal variations of marine boundary layer clouds and climate warming sensitivity

Thursday, 18 December 2014
Chengxing Zhai, Jonathan H. Jiang and Hui Su, NASA Jet Propulsion Laboratory, Pasadena, CA, United States
It has been established that the large spread of climate model's warming sensitivities to increase of greenhouse gases is caused mainly by their differences in simulating marine boundary layer (MBL) clouds and the corresponding shortwave radiative feedback. We study the seasonal variations of the MBL clouds and explore their relations with local sea surface temperature (SST) variations using monthly data from 15 climate models that participated the Coupled Model Intercomparison Project Phase 5 (CMIP5). A spectral analysis method is used to compute the linear response of MBL cloud amount to SST. We found that the amplitude of this linear response at seasonal time scale is strongly correlated with the model's warming sensitivity. We evaluate the seasonal variations of MBL clouds from these 15 CMIP5 model using NASA/CloudSat data and constrain model warming sensitivity based on its relationship with the seasonal varations of MBL clouds in response to local SST.