Extended Abstract (2.0M)14.4
High Resolution Multi-Sensor Profiling of Gust Fronts
Haldun Karan, University of Alabama, Huntsville, AL; and K. Knupp
Fine-scale kinematic and thermodynamic properties of gust fronts associated with thunderstorm outflows are investigated using the UAH Mobile Integrated Profiling System (MIPS) and Doppler radar. The MIPS consists of a 915 MHz wind profiler, 2 kHz Doppler sodar, a 0.906 mm lidar ceilometer, a 12-channel microwave radiometer and surface station data. The gust fronts examined were sampled in two contrasting environments: Southeast Texas during 1999 Texas Air Quality Studies (TEXAQS), and the Florida Keys area during the 2001 CAMEX-4 Keys Area Microphysics Project (KAMP). While observed changes in surface thermodynamic and kinematic variables associated with gust frontal passage show similarities to earlier studies, our large database covers a wide range of gust front characteristics. Out of 32 gust front cases from the two locations, most occurred during the afternoon hours. Maximum gust front updrafts with (30-s integration time) vary between 1-6 m s-1, with a mean value of 2-3 m s-1. Observed surface and dew point temperature differences prior and after the gust frontal passages are as large as 5 to 6 oC and 1 to 3 oC, respectively. Gust frontal head tops, where the outflow intrusion above ceases, were found to be lower over the Keys region southeast Texas (0.4 - 0.8 km, 1.2 - 1.6 km respectively). Local high reflectivity from Bragg scattering, high spectral width and mean vertical velocities from the 915 MHz wind profiler are typical gust frontal signatures. Due to the "clear air echo" or Bragg scattering, noticeable K-H waves were observed in the region of the wake of gust fronts head for some cases. 15-minute sodar and 2-minute 915 MHz Doppler radar derived averaged wind fields show convergence at the gust front and one or more horizontal vortices following the gust fronts. Ceilometer data are combined with the kinematic data to show details of cloud base structure around the gust fronts. The 12-channel microwave radiometer profiler is also used to examine the temperature, water vapor and liquid water content profiles before and after gust frontal passage.
Session 14, Mesoscale Circulations
Friday, 27 June 2003, 10:45 AM-12:15 PM
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