Characteristics of Precipitation Systems Analyzed from Radar Data over Bangladesh :

At present, a low-dense rain-gauge network over Bangladesh is the only tool by which to measure rainfall, so there is no way of understanding the properties of the precipitation systems occurring there. To obtain precise rainfall distributions and to clarify the characteristics of precipitation systems, radar data from the Bangladesh Meteorological Department (BMD) were used in the first investigation in Bangladesh. The BMD radar collects rain status data in six ranges. The precipitation rate was retrieved from the rain status obtained from BMD radar data. Correlation between three-days-running averaged rainfall estimated by radar and rain-gauges ranged from 0.63-0.89 over the months of 2000. The radar data was systematically underestimated by about one-fourth the rain-gauge value. Small size (～80km^2) echoes contribute greatly to the total precipitation, but there were few large size echoes. The distribution of precipitation over Bangladesh obtained from radar data shows heavy precipitation in the northeast and southeast of the country, which is consistent with the rain-gauge rainfall data. Using the radar data characteristics of 185 analyzed convective systems, the development location, lifetime, shape, size, propagation speed, and direction were identified. The BMD radar data coverage (600km×600km) is divided into 3-regions : Northern, Central, and Southern, each being 600km east to west and 200km north to south. In general, precipitation systems develop in the Northern region and tend to move eastward. Precipitation system development in the Central and Southern regions is significant during the peak-monsoon months (June-August). Analysis of the radar data shows that the average time of maximum precipitation in the Northern region is 00-06 LST, in the Central region 06 LST and 15-18 LST, and in the Southern region 06-09 LST. The average lifetime of these systems is ～5.7 hours. Movement speed is ～5ms^<-1>.