180 Documenting the variability of the afternoon-evening transition (AET) in the planetary boundary layer conference theme

Monday, 16 September 2013
Breckenridge Ballroom (Peak 14-17, 1st Floor) / Event Tent (Outside) (Beaver Run Resort and Conference Center)
Stephanie Mullins, Univ. of Alabama, Huntsville, AL; and K. Knupp

UAH's Atmospheric Boundary Identification and Delineation Experiment (ABIDE) field effort is in part focused on convection initiation occurring in the afternoon-evening transition (AET) time frame, especially in association with convergent boundaries. As a result of our operations in this part of the diurnal cycle, in addition to cases that exhibit behavior of interest for the CI objective, a myriad of BL events in the AET period are observed. Previous studies have noted an array of clear (or nearly clear) air changes in BL state variables and winds across the AET. Multi-dimensional kinematic and thermodynamic fields, observed and derived from a variety of platforms, are used here in identifying the processes that characterize the clear air BL AET as an additional goal of ABIDE. We present results from a selection of spring-summer 2012-2013 non-CI AET episodes that show these signatures of the BL's AET as well as chaotic progressions that have been rather unexpected. Applicability of previous work to our observations of the former will be discussed. Examples of the latter include the propagation and transition of various types of convergent boundaries initiated in some instances thousands of km away from the sampling domain.
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