Cloud-type dependencies of MODIS and AMSR-E liquid water path differences

Abstract. Comparisons of cloud liquid water path (LWP) retrievals are presented from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Microwave Scanning Radiometer (AMSR-E) located aboard the Aqua spacecraft. LWP differences as a function of cloud top height, cloud fraction, cloud top temperature, LWP, cloud effective radius and cloud optical thickness are quantified in most geophysical conditions. The assumption of vertically homogeneous distributions of cloud water content in the MODIS LWP retrieval yields a slightly poorer agreement than the assumption of stratified cloud liquid water. Furthermore, for a fixed cloud top pressure, the cloud top temperature can lead to sign changes in the LWP difference. In general, AMSR-E LWP is larger than MODIS for small cloud fractions, low values of LWP, and warmer cloud top temperatures. On the other hand, clouds with optical thicknesses above 20 lead to larger MODIS LWP. Using cloud optical thickness as a proxy for cloud type, deep convective clouds and stratus are shown to have the poorest agreement between AMSR-E and MODIS LWP. Particularly large differences are also found at latitudes poleward of 50°. The results of this work help characterize the scene- and cloud-dependent performance of microwave and visible/near infrared retrievals of LWP.