Cloud-to-Ground Lightning Characteristics in Mesoscale Convective Systems.

摘要

Cloud-to-ground (CG) lightning characteristics were examined in 25 Mesoscale Convective Systems (MCSs) that occurred during the warm season of 1986. Lightning strike locations were superimposed on infrared (IR) satellite imagery to examine lightning ground strike patterns relative to cold cloud-tops of MCSs. Lightning strikes frequently indicated thunderstorms more than 1 hr before cold clouds were apparent on IR satellite imagery. Time series of the area within various temperature contours were compared to time series of positive and negative flash rates. The patterns of variations in negative cloud-to-ground flash rates appeared most similar to variations in the area within temperatures of -60 deg C to -70 deg C on satellite imagery. Positive flashes occurred in two different modes, a stratiform/dissipating mode and a convective mode. In the stratiform/dissipating mode, positive flashes occurred during the mature and dissipating stages of an MCS and peaked near or after the peak in negative flash rates. Ground strike locations were generally dispersed across a large area and were usually associated with either a dissipating convective region or a stratiform region on radar and with decaying and warming cloud-top temperatures on satellite imagery. The stratiform/dissipating mode appeared during all months on the warm season.