EVOLUTION OF A FLORIDA THUNDERSTORM DURING THE CONVECTION AND PRECIPITATION ELECTRIFICATION EXPERIMENT - THE CASE OF 9 AUGUST 1991/

The relationships among kinematic, microphysical, and electric field p roperties within a multicell Florida thunderstorm are investigated usi ng observations from three Doppler radars (one with multiple wavelengt h and polarization diversity capabilities), four instrumented penetrat ing aircraft, a surface-based electric field mill network, and other o bservation facilities. The storm was convectively active for about 1 h and at least five primary cells developed within the storm during thi s time, one of which went through three consecutive development cycles . The updrafts in this storm were 2-4 km wide, exhibited bubble-like e volution, and had lifetimes of 10-20 min. The maximum updraft determin ed by the multiple Doppler analysis was about 20 m s(-1). A differenti al reflectivity (Z(DR)) ''column,'' indicating regions containing mill imeter-size raindrops, extending above the freezing level, was associa ted with each cell during its developing stages. This column reached a ltitudes exceeding 6 km (-8 degrees C) in the stronger updrafts. As th e Z(DR) columns reached maximum altitude, a ''cap'' of enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength attenuation ( A(3)) formed, overlapping the upper regions of the Z(DR) column. These parameters indicate rapid development of mixed-phase conditions initi ated by freezing of supercooled raindrops. Lightning was observed only in the central and strongest convective cell. Electric fields exceedi ng 10 kV m(-1) were noted during aircraft penetrations in this as well as several other cells that did not produce lightning. Fields exceedi ng 1 kV m(-1) were noted by the instrumented aircraft at midcloud leve ls within a few minutes of development of mixed-phase conditions at th ese levels or aloft. The first intracloud lightning was detected by th e surface field mill network within 5 min of development of mixed-phas e conditions aloft in the first cycle of development in the central ce ll, and the first cloud-to-ground event was noted within 9 min of this development. Lightning continued through two additional cycles of upd raft growth in this central region and diminished as the convection su bsided after about 30 min. Aircraft-measured electric fields and light ning retrievals from the surface field meter network are consistent wi th a tendency for negative charge to accumulate above the 6.5 km (-12 degrees C) level within regions of radar reflectivity maxima and for p ositive charge to accumulate in the anvil region well above 9 km (-30 degrees C).