12A.2 Thermodynamic destabilization processes in ARW-WRF convection-permitting simulations during a 6-day IHOP_2002 retrospective period

Thursday, 4 June 2009: 8:15 AM
Grand Ballroom East (DoubleTree Hotel & EMC - Downtown, Omaha)
Stanley B. Trier, NCAR, Boulder, CO; and C. A. Davis

One of the key factors hampering the study of convection life cycles is the lack of routine detailed thermodynamic observations through the depth of the troposphere. Fortunately, improvements in the capabilities of research numerical models to perform cloud-resolving simulations of actual cases may allow us to supplement our understanding gained from the available observations. The current study focuses on warm-season convection over the central United States for a 6-day retrospective period (10-16 June) during the IHOP_2002 field experiment. Cloud resolving simulations with the Advanced Research Weather Research and Forecasting Model (ARW-WRF) are used to diagnose factors contributing to the evolution of potential temperature and water vapor, which effect the initiation and sustenance of organized deep convection during 24-h forecasts. In these simulations we find that both PBL air parcel changes and the evolution of the environment above the daytime PBL can strongly influence the inhibition energy for deep convection (CIN). In many cases, widespread regions of negligible CIN develop during the afternoon. However, significant convective triggering is typically limited to regions with mesoscale forcing, which influences thermodynamic profiles above the PBL. While CIN is typically reduced to small-to-negligble values prior to the onset of afternoon convection, the convection may persist and even intensify overnight despite significant convection available potential energy (CAPE) decreases and CIN increases occur over mesoscale regions in its advance. Examination of model soundings reveal signatures of strong localized lifting at the leading edge of these mature mesoscale convective systems (MCSs) at night. It is hypothesized that such localized lifting, which is supported by nocturnal increases in the low-level vertical wind shear, helps allow the convection to persist in a less favorable thermodynamic environment.
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