Reflectivity, Ice Scattering, and Lightning Characteristics of Hurricane Eyewalls and Rainbands. Part I: Quantitative Description

Abstract

Covering December 1997 through December 1998, 261 overpasses of 45 hurricanes by the Tropical Rainfall Measuring Mission (TRMM) satellite are used to document the observed radar reflectivity values, passive microwave ice scattering magnitudes, and total lightning (cloud to ground plus in cloud). These parameters are interpreted as describing convective vigor or intensity, with greater reflectivities (particularly aloft), greater ice scattering (lower 85- and 37-GHz brightness temperatures), and increased lightning frequency indicating more intense convection. For each parameter, the full distribution of values observed during the TRMM satellite's first year is presented for specific regions. Properties of three regions of the hurricane (eyewall, inner rainband, and outer rainband) are treated separately and compared to other tropical oceanic and tropical continental precipitation systems. Reflectivity profiles and ice scattering signatures are found to be fairly similar for both hurricane and nonhurricane tropical oceanic precipitation systems, although the hurricane inner rainband region yields the weakest of these convective signatures. When normalized by the area experiencing significant convection, the outer rainband region produces more lightning than the rest of the hurricane or nonhurricane tropical oceanic systems. As a whole, the tropical oceanic precipitation systems (both hurricane and nonhurricane) are dominated by stratiform rain and relatively weak convection.