Characterizing Tropical Deep Convective Cloud Properties and Distribution by Fusing CloudSat/CALIPSO and MODIS Measurements

Abstract:

Tropical convective clouds play an essential role in global heat and moisture transport. CloudSat/CALPISO provide unique vertically resolved measurements of tropical deep convective clouds, but the small cross-track footprint sizes and 16-day repeating tracks could introduce significant sampling biases in statistical analysis as well as process-oriented studies. On the other hand, MODIS cloud retrievals may be significantly biased for optically thick part of deep convective clouds. Therefore, it is necessary to fuse MODIS and CloudSat/CALIPSO measurements together to fully characterize tropical convective clouds. By collocating wide swath MODIS passive measurements with CloudSat/CALIPSO active measurements, we developed a new MODIS–based tropical deep convective cloud dataset, evaluated the potential spatial/temporal sampling bias, and studied the 3D convective core and anvil properties. 3-year tropical convective cloud occurrence and spatial distribution are generated to evaluate potential CloudSat/CALIPSO small sampling volume biases and MODIS retrieval biases. The storm-related track position bias is characterized based on the properties of each convective system in terms of the raining core size, cloud optical depth, cloud water path and detrained ice mass in relationship to the total convective system. Statistics of brightness temperature at 11 for MODIS identified deep convection cluster and collocated CloudSat pixels indicate CloudSat sampled tropical convective storm structure well statistically (with 3K peak temperature warmer). For optically thick part of deep convective clouds, MODIS level 2 cloud ice water path and optical thickness are systematically biased lower compared to CloudSat 2C-ICE results. These provide a base on how to fuse MODIS and CloudSat/CALIPSO measurements to effectively characterize tropical deep convective clouds. By using MODIS measurements as a context, we characterize spatial and life stage dependent convective cloud properties with CloudSat/CALIPSO measurements. The contoured frequency with altitude diagram (CFAD) of radar reflectivity (Ze) for deep convective clouds shows that the high altitude large Ze mode shifts to smaller value and low level attenuation mode weakens as it gets farther away from the MODIS identified convective core.