Remote sensing of liquid cloud profiles based on an analytical cloud profiling model
摘要
The characteristics of microphysical profiles of liquid clouds (i.e., the cloud effective radius (ER) and liquid water content (LWC)) are important factors in understanding the aerosol-cloud-precipitation process and improving the evaluation of cloud radiative effects on a global scale. However, the profiling of clouds is limited to measurements such as radars or lidars, and retrievals from active sensors are influenced by the attenuation of signals and surface clutter. Even when vast amounts of cloud property retrievals that express column or cloud-top/base characteristics from passive sensors are generated, these two-dimensional cloud products are scarcely ever used to further produce three-dimensional cloud profiles because of the lack of a reasonable analytical model to bridge the gap. Thus, this study developed a cloud profile reconstruction model (CPRM) based on our previous analytical cloud profile model and evaluated the sensitivities of visible-to-infrared bands of passive cloud observation sensors to each parameter of the model. The results indicated that the optical thickness, cloud-top ER, and geometrical thickness can be derived from multiwavelength measurements, whereas the slope of the cloud droplet number concentration (CDNC) and the cloud-base ER could hardly be directly estimated. Meanwhile, the analytical model was utilized to rebuild cloud profiles seen by CloudSat and Aircrafts. The analytical model could capture the shape and the vertical variations of the cloud ER and LWC.