Evaluating models response of tropical low clouds to SST forcings using CALIPSO observations

Abstract

Recent studies have shown that, in response to a surface warming, the marine tropical low-cloud cover (LCC) as observed by passive-sensor satellites substantially decreases, therefore generating a smaller negative value of the top-of-The-Atmosphere (TOA) cloud radiative effect (CRE). Here we study the LCC and CRE interannual changes in response to sea surface temperature (SST) forcings in the GISS model E2 climate model, a developmental version of the GISS model E3 climate model, and in 12 other climate models, as a function of their ability to represent the vertical structure of the cloud response to SST change against 10 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) observations. The more realistic models (those that satisfy the observational constraint) capture the observed interannual LCC change quite well ( " LCC / " SST Combining double low line - 3.49 ± 1.01 % K ĝ'1 vs. " LCC / " SST obs Combining double low line - 3.59 ± 0.28 % K ĝ'1) while the others largely underestimate it ( " LCC / " SST Combining double low line - 1.32 ± 1.28 % K ĝ'1). Consequently, the more realistic models simulate more positive shortwave (SW) feedback ( " CRE / " SST Combining double low line 2.60 ± 1.13