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Evolution of the Vertical Thermodynamic Profile during the Transition from Shallow to Deep Convection during CuPIDO 2006

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  • 1 Department of Atmospheric Sciences, Creighton University, Omaha, Nebraska
  • | 2 Division of Computing Studies, Arizona State University, Mesa, Arizona
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Abstract

The evolution of the vertical thermodynamic profile associated with two cases of deep orographic convection were studied with data from an instrumented aircraft, mobile surface based radiosondes, and stereo photogrammetric analyses. The data were collected during a field experiment [i.e., the Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) experiment in 2006] performed over the Santa Catalina Mountains in southern Arizona. In both cases the vertical thermodynamic profile was modified in a way that supported subsequent deep convection. In one case, a midtropospheric stable layer was eroded through low-level warming and cooling at the cloud-top level that was likely due to an adiabatic adjustment of the profile through the action of gravity waves. In the second case, dry air aloft was moistened through the action of the shallow convection thus preventing the erosion of the convective turrets through entrainment of dry air. These cases illustrate mechanisms for convective conditioning of the atmosphere that may organize deep convection in general.

Corresponding author address: Joseph A. Zehnder, Department of Atmospheric Sciences, Creighton University, Omaha, NE 68178. Email: zehnder@creighton.edu

Abstract

The evolution of the vertical thermodynamic profile associated with two cases of deep orographic convection were studied with data from an instrumented aircraft, mobile surface based radiosondes, and stereo photogrammetric analyses. The data were collected during a field experiment [i.e., the Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) experiment in 2006] performed over the Santa Catalina Mountains in southern Arizona. In both cases the vertical thermodynamic profile was modified in a way that supported subsequent deep convection. In one case, a midtropospheric stable layer was eroded through low-level warming and cooling at the cloud-top level that was likely due to an adiabatic adjustment of the profile through the action of gravity waves. In the second case, dry air aloft was moistened through the action of the shallow convection thus preventing the erosion of the convective turrets through entrainment of dry air. These cases illustrate mechanisms for convective conditioning of the atmosphere that may organize deep convection in general.

Corresponding author address: Joseph A. Zehnder, Department of Atmospheric Sciences, Creighton University, Omaha, NE 68178. Email: zehnder@creighton.edu

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