Speaker – Richard Clark, 2022 American Meteorological Society President (hosted by R. Philbrick)

Seminar Title – Blowin’ in the Wind:  Nocturnal Destabilization Associated with the Summertime Great Plains Low-Level Jet, and musings from the AMS President.  Please see your email for a Zoom link.

Bio – Richard Clark is the 2022 AMS President and Fellow and former member of the AMS Council and the UCAR Board of Trustees. Until his recent retirement, he was Chair of the Department of Earth Sciences and Professor of Meteorology at Millersville University where he created and coordinated the transdisciplinary M.S. in Integrated Scientific Applications program, which focuses on creating business-ready scientists, and the graduate certificate program in Space Weather and Environment: Science, Policy, and Communication.  His research interests span boundary layers and turbulence and air chemistry with a special emphasis on field observations and instrumentation using airborne and balloon-borne platforms. He is the recipient of the 2006 Unidata DeSouza Award for outstanding community service and the 2008 AMS Teaching Excellence Award (now the Lorenz Award). Rich has a Ph.D. in atmospheric science from the University of Wyoming (’87).

Abstract – The Great Plains low-level jet (LLJ) has long been associated with summertime nocturnal convection over the Central Plains of the United States. Climatological effects of the LLJ on summertime elevated nocturnal convection are examined using composite fields assembled from the North American Mesoscale Forecast System for June and July over the five-year period 2008-2012. Of critical importance are the large isobaric temperature gradients that become established throughout the lowest three kilometers in response to the seasonal heating of the sloping Great Plains. Such temperature gradients provide thermal wind forcing throughout the lower atmosphere, resulting in the establishment of a large background horizontal pressure gradient force at the level of the LLJ. The attendant strong background geostrophic wind is an essential ingredient for the development of a strong summertime LLJ. Evolving LLJ winds in the vicinity of large isobaric temperature gradients promote pronounced differential temperature advection within a vertical column of atmosphere between the level of the LLJ and 500 hPa. Such differential temperature advection destabilizes the nighttime troposphere above the nocturnally cooled near-surface layer on a recurring basis during warm weather months over much of the Great Plains and states situated just eastward. This destabilization process reduces the convective inhibition of air parcels near the level of the LLJ and may, at times, be of significance in the development of elevated nocturnal convection. A case from the Plains Elevated Convection at Night field program is used to demonstrate this destabilization process.

Any remaining time will be given to an informal dialogue with the 2022 AMS president in an “ask-me-anything” format.