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Morning breakup of cold pools in complex terrain

Published online by Cambridge University Press:  10 December 2008

M. PRINCEVAC  and
H. J. S. FERNANDO
M. PRINCEVAC*
Affiliation:
Department of Mechanical Engineering, University of California, Riverside, CA 92521, USA
H. J. S. FERNANDO
Affiliation:
Center for Environmental Fluid Dynamics, Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287–9809, USA
*
†Email address for correspondence: marko@engr.ucr.edu
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Abstract

Under fair weather conditions, local flow patterns in areas of complex topography are driven by diurnal heating and cooling. If the topography is basin-shaped, downslope flows occurring at night accumulate (pool) in the basin valley to form a stable layer of cold air. During the morning transition, this cold pool is destroyed by the onset of turbulent convection and upslope flow. A series of laboratory experiments was conducted to identify mechanisms responsible for the breakup of cold pools. An idealized V-shaped tank filled with thermally stratified water and heated with an approximately uniform bottom heat flux was used. Temperature measurements and dye visualization were used for flow diagnostics. Mechanisms of cold pool destruction were identified and placed in the context of previously proposed mechanisms. A new mechanism was identified, wherein a dominant intrusion emanating from the upslope flow plays a dynamically important role in cold pool destruction. The results are expected to help develop subgrid parameterizations for meso-scale weather forecasting models, which are notorious for giving poor predictions during the morning transition period in complex terrain.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 616 , 10 December 2008 , pp. 99 - 109
Copyright
Copyright © Cambridge University Press 2008

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