FLUX MEASUREMENTS OF PULSATING RAIN WITH A DISDROMETER AND DOPPLER RADAR DURING PHASE-II OF THE JOINT TROPICAL RAIN EXPERIMENT IN MALAYSIA

During the Joint Tropical Rain Experiment of the Malaysian Meteorologi cal Service and the University of Toronto, pulsating raindrop ensemble s, hereafter pulses, were observed in and around Penang Island. Using a Doppler radar on 25 October 1990, a periodic variation of precipitat ion aloft 30 km from the radar site, with an approximate 8-min period, was established and seemed to be caused by the evolution and motion o f horizontal inhomogeneities existing within the same cell. On 30 Octo ber 1990, using a new volume scanning strategy with a repetition cycle of 3.5 min, pulsations of the same frequency were observed up to 3 km above the radar and at the ground by a disdrometer. High concentratio ns of large dregs were followed by high concentrations of successively smaller drops at the ground. This provides observational evidence to support the recent argument for using a time-varying release of precip itation-sized particles to model observed pulsating rainfall. Many cas es of nonsteady rain from convective clouds displayed repetition perio ds of between 8 and 25 min.