The features of cloud overlapping in Eastern Asia and their effect on cloud radiative forcing

Abstract

Characteristics of cloud overlap over Eastern Asia are analyzed using a three-year dataset (2007-2009) from the cloud observing satellite CloudSat. Decorrelation depth L*cf is retrieved, which represents cloud overlap characteristics in the simulation of cloud-radiation processes in global climate models. Results show that values of L*cf in six study regions are generally within the range 0-3 km. By categorizing L*cf according to cloud amount in subregions, peak L*cf appears near subregions with cloud amount between 0. 6 and 0. 8. Average L*cf is 2. 5 km. L*cf at higher altitudes is generally larger than at lower latitudes. Seasonal variations of L*cf are also clearly demonstrated. The sensitivity of cloud radiative forcing (CRF) to L*cf in Community Atmosphere Model 3. 0 of the National Center for Atmospheric Research (CAM3/NCAR) is analyzed. The result shows that L*cf can have a big impact on simulation of CRF, especially in major monsoon regions and the Mid-Eastern Pacific, where the difference in CRF can reach 40-50 W m-2. Therefore, accurate parameterization of cloud vertical overlap structure is important to CRF simulation and its feedback to climate. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.