A Radar Study of Convective Cells in Mesoscale Systems in GATE. Part II: Life Cycles of Convective Cells

Abstract

This is Part II of a two-part paper describing the vertical profile of radar reflectivity in GATE convective cells. Time-height radar life histories for 42 cells over three GATE days are examined, using data from the Quadra radar with 5-minute resolution. Mean profiles and plots of cell characteristics are generated, and confirm that the mean profiles in Part I are representative of the active portion of the cell lifetime. There are marked differences between the cell life histories of isolated cells and the longer-lived cells associated with mesoscale systems. In contrast to cells sampled in organized systems, the isolated cells are often of very limited vertical extent and must be dominated by the warm rain process. When forcing features exist such as gust fronts and intersecting lines of convection, they appear to dominate the generation of new convection, and isolated strong echoes are not observed. Composite life histories for typical GATE cells are constructed. The typical radar echo forms first at an altitude of 2.5 km and reaches the surface about 5 minutes later, strongly suggesting early domination by the warm rain process. At the same time the echo top rises and the mid-to-late stages of cell lifetime involve both warm rain and ice processes. The reflectivity profiles of the longer-lived echoes change relatively little in the middle 50% of the life cycle.