Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data

[摘要] Aerosol indirect effects are considered to be the most uncertain yetimportant anthropogenic forcing of climate change. The goal of the presentstudy is to reduce this uncertainty by constraining two different generalcirculation models (LMDZ and ECHAM4) with satellite data. We build astatistical relationship between cloud droplet number concentration and theoptical depth of the fine aerosol mode as a measure of the aerosol indirecteffect using MODerate Resolution Imaging Spectroradiometer (MODIS) satellitedata, and constrain the model parameterizations to match this relationship.We include here "empirical" formulations for the cloud albedo effect aswell as parameterizations of the cloud lifetime effect. When fitting themodel parameterizations to the satellite data, consistently in both models,the radiative forcing by the combined aerosol indirect effect is reducedconsiderably, down to−0.5 and −0.3 Wm⁻², for LMDZ and ECHAM4, respectively.

[学科分类] 大气科学