Extended Abstract (212K)P5.12
Kinematics of a mesoscale convective system and its mesoscale convective vortex
Jason C. Knievel, Colorado State Univ., Fort Collins, CO; and R. H. Johnson
Often data from field projects prove useful in studies beyond those explicitly planned when a project is organized and executed. Although the formal subject of the Global Energy and Water Cycle Experiment's (GEWEX's) Continental-Scale International Project (GCIP) is the examination of climatic effects of energy and water exchanges between the atmosphere and land surface, the authors apply some of the GCIP data toward a mesoscale study.
During 1996's Enhanced Seasonal Observing Period of GCIP (ESOP-96), radiosondes were launched every three hours from sites in Oklahoma and Kansas. The authors use profiles of temperature and dew point from these soundings, and profiles of wind from the NOAA Profiler Network (NPN), to examine a mesoscale convective vortex (MCV), which was generated by a mesoscale convective system (MCS) that formed in northwestern Kansas and moved into Oklahoma. A few of the radiosondes ascended through the stratiform region of the MCS and through the MCV, providing a rare glimpse of the thermodynamics of such a vortex.
The data depict a maximum in potential vorticity along the axis of the MCV between approximately 3 and 8 km above mean sea level. Around this core of high potential vorticity are virtually closed streamlines of wind in the middle troposphere. The authors examine the balance between fields of mass and velocity in the MCV and compare it with results from numerical simulations that are based on the assumption that MCVs are balanced, or that produce balanced MCVs. The authors then examine the thermodynamic imprint that the MCS left in its wake is it advanced to the southeast and dissipated. Plots of soundings through the troposphere in the MCS's wake display the well-known onion shape: a cool, moist boundary layer, topped by an inversion at the base of a dry, warm layer, then from there to the tropopause a deep layer of nearly saturated air with and approximately moist adiabatic lapse rate. The authors suggest what implications the thermodynamics of this wake have on the potential for additional moist convection, which sometimes develops near the center of, or along the periphery of an MCV.
Poster Session 5, New insights regarding mesoscale structure based on recent field experiments and new observing platforms—with Coffee Break
Wednesday, 1 August 2001, 2:30 PM-4:00 PM
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