Thunderstorm Cloud Top Observations Using Satellite Stereoscopy

Abstract

GOES stereoscopy is applied to the study of severe squall line cells. Short interval (3 min) GOES stereoscopic data from the 2?3 May 1979 SESAME case were used to measure cloud top heights of growing storms as a function of time. A one-dimensional cloud model was used to relate the stereoscopically derived cloud top ascent rates to thunderstorm updraft intensity. Results show ascent rates ranging from 4.4 to 7.7 m s?1 for intense cells in a squall line. These results compare well in magnitude with growth rates determined from simultaneous GOES infrared observations and previous estimates of visual cloud and radar echo top growth rates of other thunderstorms. Detailed stereoscopic cloud top height contour maps of the mature squall line on 2?3 May 1979 were constructed and are discussed here in terms of the small-scale structure and its variability. Results show that for small-scale features (e.g., 5 km diameter tropopause penetrating towers) the short-interval GOES data are not sufficient for studying the life cycle of such features. The stereoscopic height contours are compared to infrared cloud top temperature patterns observed with intense thunderstorms and used to evaluate various theories on the cause of the infrared V-shaped signatures.