Satellite-Observed Latent Heat Release in a Tropical Cyclone

Abstract

Data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR) are used to make calculations of the latent heat release (LHR) and the distribution of rainfall rate in a case study of a tropical cyclone as it grows from a tropical disturbance to a typhoon. The results indicate that the latent heat release characteristics of tropical cyclones can be determined from the microwave data and that such observations are potentially useful in the monitoring of such storms. The LHR (calculated over a circular area of 4° latitude radius) increases during the development and intensification of the storm from a magnitude of 2.7 ? 1014 W (in the disturbance stage) to 8.8 ? 1014 W (typhoon stage). The later value corresponds to a mean rainfall rate of 2.0 mm h?1. Even during the disturbance stage, the LHR increases significantly. It is also shown that the more intense the cyclone and the greater the LHR, the greater the percentage contribution of the larger rainfall rates to the LHR. In the disturbance stage the percentage contribution of rainfall rates ? 6 mm h?1 is typically 8%; for the typhoon stage, the value is 38%. The distribution of rainfall rate as a function of radial distance from the center indicates that as the cyclone intensifies, the higher rainfall rates tend to concentrate toward the center of the circulation.