Statistics of Radar Echoes on Day 261 of GATE

C. Warner Department of Environmental Sciences, University of Virginia, Charlottesville 22903

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G. L. Austin Department of Physics, McGill University, Montreal Quebec H3A 2T8, Canada

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Abstract

Statistics of echoes observed on day 261 of GATE, using the radar aboard the Canadian ship Quadra, are described. This is a case in which detailed observations have been obtained from many sensors during the growth of a cloud cluster.

Dividing the radar field of view into many “bins,” it was found that rainfall rates and echo top heights were log-normally distributed UP to a certain limit, with a few additional high values. After identifying echo cores, bounded by a reflectivity threshold 24 dB above 1 mm6 m−3, their area were found to be distributed in a similar manner.

Upper limits of log-normality before (and during) the growth of the cluster were about 5 (and 30) mm h−1 for rainfall rate, 7 (and 7) km for echo top height (at the 29 dB level of intensity) and 100 (and 400) km2 for area (within contours of intensity 24 dBZ). To echoes organized on a length scale of about 100 km for more, one attributes maximum rainfall rates reaching roughly 50 mm h−1, peak heights reaching 14 km, and maximum areas of elongated cores reaching 5000 km2.

Abstract

Statistics of echoes observed on day 261 of GATE, using the radar aboard the Canadian ship Quadra, are described. This is a case in which detailed observations have been obtained from many sensors during the growth of a cloud cluster.

Dividing the radar field of view into many “bins,” it was found that rainfall rates and echo top heights were log-normally distributed UP to a certain limit, with a few additional high values. After identifying echo cores, bounded by a reflectivity threshold 24 dB above 1 mm6 m−3, their area were found to be distributed in a similar manner.

Upper limits of log-normality before (and during) the growth of the cluster were about 5 (and 30) mm h−1 for rainfall rate, 7 (and 7) km for echo top height (at the 29 dB level of intensity) and 100 (and 400) km2 for area (within contours of intensity 24 dBZ). To echoes organized on a length scale of about 100 km for more, one attributes maximum rainfall rates reaching roughly 50 mm h−1, peak heights reaching 14 km, and maximum areas of elongated cores reaching 5000 km2.

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