613 SEMINAR SERIES: W. Greg Blumberg

Affiliation: NASA Postdoctoral Program/Climate & Radiation Laboratory
Event Date: Wednesday, December 18, 2019

Location: Building 33, Room H114
Time: 1:30 PM

Investigations into Planetary Boundary Layer (PBL) Changes During the Afternoon-to-Evening Transition - Local and Non-Local Processes

There are four ingredients (e.g. moisture, shear, instability, and lift) fundamental to understanding the life-cycle of deep, moist convection.  Past studies have strongly emphasized that in the U.S. Southern Great Plains (SGP), two of these ingredients - shear and static stability - undergo strong changes around sunset.  Although these changes do help explain the climatological increase of hazardous thunderstorms during this timeframe, a consideration of how other ingredients also evolve may lead to new insights to why storms develop or intensify during this PBL transition.

To do this, my doctoral research at the University of Oklahoma aimed to characterize the AET in the SGP with data produced by the Oklahoma Mesonet and Atmospheric Radiation Measurement programs.  With respect to moisture, rapid increases (1-4 g/kg) in water vapor mixing ratio are found to occur near the SGP Winter Wheat Belt (WWB) during the AET.  In some cases, these rapid increases can reverse the expected loss of conditional instability caused by the decrease in solar heating - a new finding highly relevant to understanding storm behavior around sunset.  By using a combined observation and modeling strategy, this study suggests that imbalances occur between local and non-local processes during the AET that influence the moisture and conditional instability distribution.

With this background in mind, this seminar will also provide an overview of some of my current activities at NASA Goddard to expand our understanding of the contributions from local and non-local processes to PBL behavior, particularly in environments where strong heterogeneity in land-surface properties and air quality may exist.

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