An Empirical Study of Tropical Cloud cluters Using Special Sensor Microwave Imager Data

Fifteen cases of Tropical Cloud Clusters (TCCs) in the western Pacific were analyzed using infrared satellite imagery and microwave satellite data from the Special Sensor Microwave Imager (SSM/I). Microwave data yielded atmospheric parameters of integrated water vapor, liquid water path, ice water path, and surface rainrate. Analyzed fields of SSM/I-derived parameters were then compared with each other and with infrared blackbody cloud top temperatures of TCCs in various stages of development. It was found that TCCs form preferentially in regions of elevated integrated water vapor. It is hypothesized that this extremely humid pre-storm environment signals large scale ascent, contributing to favorable conditions for tropical convection. Areas of surface precipitation retrieved from SSM/I were found, in general, to correlate to infrared cloud top temperatures of -65 deg C, though the coldest cloud tops did not necessarily coincide with the heaviest rain. It was found that the microwave signature of a TCC changes over the course of its life cycle, from a balance of liquid water emission and ice scattering in the intensifying and mature phases, to a predominance of liquid water emission over ice scattering in the dissipating phase.