A Moisture Analysis of the Meso β-Scale Thunderstorm Environment during AVE-SESAME V (20–21 May 1979)

Abstract

Meso ?-scale radiosonde data at 75 km spacings and 3 or 1.5 h intervals from the fifth day of AVE-SESAME 1979 (20?21 May) are employed to investigate moisture budgets in thunderstorm environments. Budget values are computed at nine times prior to, during, and after a convective outbreak over Oklahoma. The domain under investigation includes both convective and nonconvective areas, thereby allowing budget comparisons between the two regions. Findings show that the convective region is characterized by strong horizontal moisture flux convergence in the low levels and weak divergence aloft. Vertical motion carries moisture into the middle and upper troposphere. Magnitudes of the moisture fluxes are directly proportional to storm intensity. The vertically integrated source/sink term also is closely related to the presence and intensity of convective activity. When converted into equivalent precipitation amounts, values correspond closely with those from a rain gage network. Moisture budgets also are obtained from routine National Weather Service rawinsonde soundings. A comparison of results for similar locations, but derived from the two different resolutions, reveals several common processes. However, magnitudes from the mesoscale data are sometimes an order of magnitude greater than those at the synoptic scale, especially in the convective areas.