Tuesday, 17 September 2013
Breckenridge Ballroom (Peak 14-17, 1st Floor) / Event Tent (Outside) (Beaver Run Resort and Conference Center)
On 9 April 2013, an ABIDE-3* field deployment was conducted as part of special project exercise in the UAH graduate-level class Boundary Layer Meteorology. The goal was to acquire data from the late convective boundary layer cycle, through the afternoon-evening transition (AET), and into the early NBL regime. The full suite of UAH instrumentation was available for the project, including a dual Doppler (DD) network formed by the Mobile Alabama X-band (MAX) dual pol radar and the ARMOR C-band dual pol radar, with a baseline separation of 17.5 km. The MIPS instrument suite (915 MHz wind profiler, X-band profiling radar, microwave profiling radiometer, CL-51 ceilometer, radiosonde system, and 2 kHz sodar) along with the recently acquired scanning 1.5 μm Doppler wind lidar were located within one lobe of the dual Doppler radar network. The M3V mobile mesonet unit acquired surface measurements during the course of the 6-h experiment. The KHTX WSR-88D radar provided larger-scale surveillance over the meso-µµ-scale dual Doppler network. The measurements acquired revealed a surprisingly rich diversity of heterogeneous boundary layer structures, including (in order of appearance): a) a ducted gravity wave (of depression) with a 1 mb amplitude and a short period (<1 h) that exerted a significant influence on upper CBL circulations; b) development of horizontal convective rolls (following reduction in cloud cover) over a limited area of the dual Doppler domain; c) passage of a boundary of unknown origin (during the initial AET period), marked by a relatively low change in mean BL wind direction and a significant reduction in aerosol loading; d) an extended AET period with a gradual decrease in wind speed within the lower surface layer and the development of a modest low-level jet; e) a distinct change in biological flyers, with (migrating) birds emerging after sunset, flying at a wide range of altitudes up to 3 km AGL. This presentation will summarize the above listed phenomena, but emphasis will be placed on high-resolution kinematics of the gravity wave (using all instruments), which propagated along a prominent inversion capping the CBL.
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