Tuesday, 4 June 2002: 4:15 PM
Radiative Characteristics of Precipitating Convective Systems in the Tropical Western Pacific
The radiative impacts of seventeen different systems observed by the Tropical Rainfall Measuring Mission (TRMM) satellite over the Manus and Nauru Island Atmospheric Radiation Measurement sites have been modelled. These cases represent both deep and mid-level convection. Reflectivity data from the TRMM Precipitation Radar and Geostationary Meteorological Satellite infrared radiometer measurements are used to parameterize the three-dimensional cloud microphysics of each precipitating cloud system. These parameterized cloud properties are used as input for a two-stream radiative transfer model. Comparisons to broad-band radiative fluxes at the top-of-atmosphere and at the surface show agreement to within 20%. In cases when the convective available potential energy (CAPE) is large, deep convective clouds with large anvil clouds form that contain thick layers of small ice particles and large optical depth at cloud-top. This results in shortwave heating and longwave cooling at heights of 12-14 km. When the CAPE is small, convective clouds extend only to mid-levels near the freezing level (5-7 km) and do not develop deep layers of small ice crystals. Maximum radiative heating and cooling in these cases is concentrated near the freezing level. A sensitivity analysis suggests that the small ice crystals near cloud-top play an important role in producing the high visible albedos of deep convective clouds. A comparison of the radiative heating profiles calculated in this study latent heating profiles in deep convection from previous studies indicates that for mature deep convection, near local solar noon, the maximum radiative heating is of similar magnitude to the maximum latent heating.