Studying Mixed-Phased Clouds Using Ground-Based Active and Passive Remote Sensors

Summary of the Algorithm Altocumulus cloud with ice virga can be generally regarded as two connected cloud layers where the top is the water-dominated source cloud and the bottom is an ice cloud, although it is also necessary to study ice within the water-dominated source cloud. First, we treat ice virga as an independent ice cloud, and apply an existing lidar-radar algorithm to retrieve ice water content and general effective size profiles (Wang and Sassen 2002). Then a new iterative approach is used to retrieve supercooled water cloud properties by minimizing the difference between atmospheric emitted radiance interferometer (AERI) observed radiances and radiances calculated using the discrete ordinate radiative transfer model at 12 selected wavelengths. The flowchart of the algorithm is given in Figure 1, and more information about the algorithm can be found from Wang et al. (2004). Case studies demonstrate the capabilities of this approach in retrieving radiatively important microphysical properties to characterize this type of mixed-phase cloud. The good agreement between visible optical depths derived from lidar measurement and those estimated from retrieved liquid water path (LWP) and effective radius provides a closure test for the accuracy of mainly AERI-based supercooled water cloud retrieval.