Early Growth of Mesoscale Convective Complexes: A Meso-β-Scale Cycle of Convective Precipitation?

Abstract

Abstract The evolution of precipitation fields associated with several mesoscale convective complexes (MCCs) has been inferred from radar reflectivity data. In almost all cases examined, including those described in the literature, the system's convective ensemble undergoes a marked modulation in intensity, on a meso-β time scale, during the early growth stage of its meso-α-scale life cycle. This β-scale convective cycle is most evident in time series of volumetric precipitation rate due to convective echo, and is characterized by a temporal maximum, followed by a minimum ∼0.5-1 h later, superimposed on an otherwise several-hour, monotonically increasing trend. While the latter is due to a concurrent, several-hour increase in the areal extent of convective echo, the β-scale perturbation is dominated by a modulation in intensity of the existing convective entities that the system constitutes at that stage of growth. The β-scale cycle also marks the onset of a sustained, increased growth rate of the MCC's s...