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Multiparameter Radar Study of a Microburst: Comparison with Model Results

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  • 1 National Center for Atmospheric Research, Boulder, Colorado
  • | 2 Colorado State University, Fort Collins, Colorado
  • | 3 South Dakota School of Mines and Technology, Rapid City, South Dakota
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Abstract

Radar observations and model results are used to investigate the microphysical evolution of an isolated, intense storm observed on 20 July during the Microburst and Severe Thunderstorm (MIST) experiment. The storm grew to a height of 14 km and upon collapsing, produced heavy rain, pea-sized hail, and a microburst at the surface. The storm was observed by three Doppler radars and one of the radars was equipped to collect differential reflectivity (ZDR) and dual-frequency measurements. The radar observations indicate that the initial precipitation development was by collision-coalescence. Later, as the storm intensified, accretional growth became dominant leading to rapid precipitation development. Radar-derived rainfall rates peaked around 150 to 190 mm h−1. The microburst developed as the precipitation core descended to the surface and was likely initiated by a combination of mass loading and cooling due to melting.

Each morning during the experiment, a two-dimensional, time-dependent cloud model, initialized with the morning sounding, was run. This provided the unique opportunity to predict the day's convection before it actually began. The model results from the 20 July sounding are compared to the radar observations. Good agreement is shown in some aspects of the storm development, although the numerical simulation predicted a more vigorous storm than actually developed.

Abstract

Radar observations and model results are used to investigate the microphysical evolution of an isolated, intense storm observed on 20 July during the Microburst and Severe Thunderstorm (MIST) experiment. The storm grew to a height of 14 km and upon collapsing, produced heavy rain, pea-sized hail, and a microburst at the surface. The storm was observed by three Doppler radars and one of the radars was equipped to collect differential reflectivity (ZDR) and dual-frequency measurements. The radar observations indicate that the initial precipitation development was by collision-coalescence. Later, as the storm intensified, accretional growth became dominant leading to rapid precipitation development. Radar-derived rainfall rates peaked around 150 to 190 mm h−1. The microburst developed as the precipitation core descended to the surface and was likely initiated by a combination of mass loading and cooling due to melting.

Each morning during the experiment, a two-dimensional, time-dependent cloud model, initialized with the morning sounding, was run. This provided the unique opportunity to predict the day's convection before it actually began. The model results from the 20 July sounding are compared to the radar observations. Good agreement is shown in some aspects of the storm development, although the numerical simulation predicted a more vigorous storm than actually developed.

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