Extended Abstract (736K)12A.7
An observational study of atmospheric bore formation from colliding density currents
David E. Kingsmill, DRI, Reno, NV; and N. A. Crook
Observations from east central Florida during CaPE are used to investigate the factors that influence atmospheric bore formation from colliding density currents. Ten cases involving the collision of a gust front with a sea-breeze front are analyzed with Doppler radar, sounding and surface mesonet data. The gust fronts in these collisions were generally deeper, denser and faster propagating than their sea-breeze front counterparts. Seven of the ten cases produced dual boundaries that moved away from each other in a relative sense after the collision. Post-collision boundaries moving in the same direction and oriented similar to the pre-collision gust front occurred in all ten cases. They transported mass in the manner of a density current in six cases while the others behaved more like bores or bore/density current hybrids as they were characterized by little or no mass transport. The seven sea-breeze front induced post-collision boundaries exhibited no purely mass transport behavior and were all categorized as bores or bore/density current hybrids. Application of hydraulic theory shows that bores or bore/density current hybrids occurred when the strength parameter (the ratio of stable layer depth upstream and downstream of the bore) was between 1 and 2.5 while density currents resulted when the strength parameter was greater than 2. This potential predictive ability may be of value to convective nowcasting as seventy percent of the post-collision boundaries in this study were judged to initiate new convection or enhance existing convection.
Supplementary URL: http://www.dri.edu/Projects/Radar/Collision.html
Session 12A, IHOP/Boundary Layer
Monday, 11 August 2003, 4:00 PM-6:00 PM
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