Thunderstorm Vertical Velocities Estimated from Satellite Data

Robert F. Adler Laboratory for Atmospheric Sciences, Goddard Space Flight Center, NASA, Greenbelt, MD 20771

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Douglas D. Fenn GE/MATSCO, Beltsville, MD 20705

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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.

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.

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