ALBERT

Description: Liquid water path (LWP) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) is validated using the Advanced Microwave Scanning Radiometer-EOS (AMSRE) retrievals for global oceanic non-raining warm clouds, with focus on the vertically homogeneous (VH) model and adiabatically stratified (AS) model of liquid water content (LWC) profile used in MODIS retrieval. With respect to AMSRE-LWP that acts as ground truth under a series of constraints, the global average of MODIS-LWP VH and MODIS-LWP AS has a positive (11.8%) and negative (-6.8%) bias, respectively. Most of the oceanic warm clouds tend to have adiabatic origin and correspondingly form AS-like profiles, which could be well retained if drizzle is absent. Besides the presence of drizzle, cloud-top entrainment seems to be another cause that modifies the original LWC profiles to become VH-like, which is notable for the very low clouds that have rather small thickness. These factors jointly determine the appearance of LWP profiles and in turn their spatial pattern across global oceans, with AS-like profiles dominant in the areas where non-raining warm clouds occur very frequently in the form of stratocumulus. The modified MODIS LWP shows significant improvement compared with either MODIS-LWP VH or MODIS-LWP AS . This is achieved by using the two physically explicit models flexibly, in which the elementary MODIS retrievals of cloud top temperature, cloud optical thickness and droplet effective radius play a determinant role. A combined use of VH and AS model in the MODIS retrieval is demonstrated to be effective for improving the LWP estimation for oceanic non-raining warm clouds.