National Weather Center Colloquium

Tropopause-Penetrating Convection from Three-Dimensional Gridded NEXRAD Data

Dr. Kenneth P. Bowman
David Bullock Harris Professor of Geosciences
Department of Atmospheric Sciences
Texas A&M University

Texas A&M University

21 April 2015, 4:00 PM

National Weather Center, Room 1313
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Convection can rapidly transport tropospheric air into the upper troposphere and, in some cases, across the tropopause into the lower stratosphere.  The stratosphere-troposphere exchange has a significant impact on the composition of the upper troposphere and lower stratosphere (UTLS).  The composition of the UTLS, in turn, affects the radiation budget, chemistry, and climate of the whole atmosphere. To understand the convective transport across the tropopause, it is necessary to know the frequency, magnitude, and location of overshooting convection events. A new method that combines radar reflectivities from individual radars into a three-dimensional composite with high horizontal and vertical resolution is used to estimate storm-top altitudes for the continental U.S. east of the Rocky Mountains. A pronounced seasonal cycle has been found in the tropopause-penetrating convection; the majority of overshooting systems occur during the warm season (March-August). There is also a strong diurnal cycle, with maximum overshooting occurring near 00 UTC. Radiosonde observations are used to evaluate the quality of the reanalysis of tropopause altitudes and the dependence of overshooting depth on environmental characteristics. The radar-radiosonde comparison reveals that overshooting is deeper in double-tropopause environments and increases as the stability of the lower stratosphere decreases.

Speaker bio

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