Local Structure Parameters of Temperature and Humidity in the Entrainment-Drying Convective Boundary Layer: A Large-Eddy Simulation Analysis

Sylvain Cheinet Institut Franco-Allemand de Recherches de Saint-Louis, Saint-Louis, France

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Pierre Cumin Institut Franco-Allemand de Recherches de Saint-Louis, Saint-Louis, France

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Abstract

Many wave propagation applications depend on the local, instantaneous structure parameters of humidity and of potential temperature . This study uses a large-eddy simulation to explore and compare the variability of and in the shearless, entrainment-drying convective boundary layer (CBL). The predicted horizontal mean profiles of these quantities are shown to agree with corresponding observations. The results in the bulk CBL suggest that the largest occur in the entrained tropospheric air whereas the largest are within the convective plumes. There are distinct correlations between the vertical velocity and and between the vertical velocity and . It is shown that these correlations can significantly contribute to the mean vertical velocity biases measured from radars and sodars. A physical interpretation for these contributions is offered in terms of the CBL dynamics.

Corresponding author address: Sylvain Cheinet, Institut Saint-Louis, 5 rue du Général Cassagnou, 68 300 Saint-Louis, France. Email: sylvain.cheinet@isl.eu

Abstract

Many wave propagation applications depend on the local, instantaneous structure parameters of humidity and of potential temperature . This study uses a large-eddy simulation to explore and compare the variability of and in the shearless, entrainment-drying convective boundary layer (CBL). The predicted horizontal mean profiles of these quantities are shown to agree with corresponding observations. The results in the bulk CBL suggest that the largest occur in the entrained tropospheric air whereas the largest are within the convective plumes. There are distinct correlations between the vertical velocity and and between the vertical velocity and . It is shown that these correlations can significantly contribute to the mean vertical velocity biases measured from radars and sodars. A physical interpretation for these contributions is offered in terms of the CBL dynamics.

Corresponding author address: Sylvain Cheinet, Institut Saint-Louis, 5 rue du Général Cassagnou, 68 300 Saint-Louis, France. Email: sylvain.cheinet@isl.eu

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