Time and space variability of convective and stratiform rain in South Florida

Cirrus clouds, many generated from deep convective storms, make up an important component of the global heat balance particularly in the Tropics. The radiative properties of convectively-generated cirrus, and thus the role of cirrus clouds in regulating global climate, are poorly understood. The effect of cirrus clouds on the global energy balance represents one of the largest points of uncertainty in climate models. Improvements in our understanding of convectively-generated cirrus was one of the goals of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL-FACE) in South Florida, which took place during the month of July 2002.

This paper investigates the relative contribution to rainfall from convective cells versus stratiform anvil clouds during CRYSTAL-FACE. The approach was to use the network of NOAA/NWS WSR 88-D (NEXRAD) radars in South Florida, which provided continuous sampling of the three-dimensional structure of convective systems. We analyze the fraction of rainfall and rain area associated with convective and stratiform portions of precipitation systems, as well as time series of these quantities near the coast, inland, and offshore. The relative amount and pattern of convective and stratiform rainfall vary systematically in space and time during the month of July with changing synoptic conditions. These observations provide insight as to the growth and evolution of stratiform anvil cloud.