Thunderstorm Vertical Velocities Estimated from Satellite Data

Abstract

Infrared geosynchronous Satellite data with an interval of 5 min between images are used to estimate thunderstorm top ascent rates on two case study days. A mean vertical velocity of 3.4 m s?1 for 23 clouds is calculated at a height of 8.7 km. This upward motion is representative of an area of approximately 10 km on a side. Thunderstorm mass flux of ?2?108 kg s?1 is calculated, which compares favorably with previous estimates. There is a significant difference in the mean calculated vertical velocity between elements associated with severe weather reports (w=4.9 m s?1) and those with no such reports (2.4 m s?1). Calculations were made using a velocity profile for an axially symmetric jet to estimate the peak updraft velocity. For the largest observed w value of 7.8 m s?1 the calculation indicates a peak updraft of ?50 m s?1.