Population Characteristics, Development Processes and Structure of Radar Echoes in South Florida

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  • 1 NOAA/ERL/Office of Weather Research and Modification, Boulder, CO 80303
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Abstract

Radar data from the Florida Area Cumulus Experiment were used to study the ensemble characteristics of echo populations and also the structure of echo systems and their phenomenological growth and development process. The diurnal development of the convective field was explored as well. The overall distribution of echoes turned out to be of the truncated lognormal type, which is indicative of growth process that favor the larger, more vigorous clouds. Three principal scales of convective activity were apparent: single cell echoes conglomerates of several individual cells, and large areas of convection that normally form by the joining of existing cloud conglomerates by growth of new cells in the intervening space. The distributions of the radar characteristics of the individual cells were found to be very skewed, which indicates that the large majority of the cells are small and weak, and that only sporadically do a few large and strong cells appear. A considerable number. of the cells originated below the -10°C level indicating that warm rain formation is common in south Florida. Growth curves for the cells indicate fast formation and dissipation stages. A study of the diurnal development of the field of echoes revealed a tendency with time toward more complex echo structures starting from isolated showers to large merged systems. It was also seen that the large multicelled systems are preferred area for the formation of new cells, even at the expense of the population of smaller echoes.

Abstract

Radar data from the Florida Area Cumulus Experiment were used to study the ensemble characteristics of echo populations and also the structure of echo systems and their phenomenological growth and development process. The diurnal development of the convective field was explored as well. The overall distribution of echoes turned out to be of the truncated lognormal type, which is indicative of growth process that favor the larger, more vigorous clouds. Three principal scales of convective activity were apparent: single cell echoes conglomerates of several individual cells, and large areas of convection that normally form by the joining of existing cloud conglomerates by growth of new cells in the intervening space. The distributions of the radar characteristics of the individual cells were found to be very skewed, which indicates that the large majority of the cells are small and weak, and that only sporadically do a few large and strong cells appear. A considerable number. of the cells originated below the -10°C level indicating that warm rain formation is common in south Florida. Growth curves for the cells indicate fast formation and dissipation stages. A study of the diurnal development of the field of echoes revealed a tendency with time toward more complex echo structures starting from isolated showers to large merged systems. It was also seen that the large multicelled systems are preferred area for the formation of new cells, even at the expense of the population of smaller echoes.

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