Inclusion of Sensible Heating in Convective Parameterization Applied to Lake-Effect Snow

Gloria E. Ellenton Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

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Maurice B. Danard Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

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Abstract

A method has been designed for including the surface fluxes of water vapor and sensible heat from water surfaces in a convective parameterization scheme for a primitive equation numerical model of the atmosphere. The grid size is 48 km. Application of the model to Lake Huron and vicinity in the simulation of three lake-effect storm cases resulted in predictions of vertical transport of heat and moisture and the consequent alteration of air mass properties, as well as precipitation. The maximum grid-square-average observed precipitation over 6 h was 0.75, 0.86 and 0.54 cm for the three cases. These values may be compared to maximum predicted values for those grid squares where observations were available. The predicted maxima were 0.60, 0.76 and 0.57 cm, respectively.

The model was also employed to isolate the various physical influences on precipitation. While model results were not clear-cut, they indicated that for near-lake points, heat and moisture from the lake were the principal causes of precipitation. Orographic lift and shoreline frictional convergence appeared to be secondary factors.

Abstract

A method has been designed for including the surface fluxes of water vapor and sensible heat from water surfaces in a convective parameterization scheme for a primitive equation numerical model of the atmosphere. The grid size is 48 km. Application of the model to Lake Huron and vicinity in the simulation of three lake-effect storm cases resulted in predictions of vertical transport of heat and moisture and the consequent alteration of air mass properties, as well as precipitation. The maximum grid-square-average observed precipitation over 6 h was 0.75, 0.86 and 0.54 cm for the three cases. These values may be compared to maximum predicted values for those grid squares where observations were available. The predicted maxima were 0.60, 0.76 and 0.57 cm, respectively.

The model was also employed to isolate the various physical influences on precipitation. While model results were not clear-cut, they indicated that for near-lake points, heat and moisture from the lake were the principal causes of precipitation. Orographic lift and shoreline frictional convergence appeared to be secondary factors.

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