Abstract
Characteristics of precipitation systems in and around Bangladesh are analysed using 6 years of radar data from the Bangladesh Meteorological Department (BMD). Precipitation systems are classified as arc, line, or scattered types according to their shape; then as small, medium, or large according to their length; and as stationary, slow, or fast according to their propagation speed. Arc‐, line‐, and scattered‐type systems are found 230 (29%), 117 (15%), and 442 (56%) times, respectively, from April to September during the analysis period (2000–2005). These arc‐, line‐, and scattered‐type systems have average speeds of 11.0, 7.1, and 5.8 m/s, horizontal lengths of 185, 184, and 268 km, and approximate lifetimes of 4.3, 4.0, and 4.8 h, respectively. Scattered‐type systems dominate in the monsoon period (June, July, August, and September), while arc‐type systems dominate in the pre‐monsoon period (April and May). Line‐type systems occur with nearly equal frequency in both periods. The monsoon systems are large and stationary or slow moving. In contrast, pre‐monsoon systems are small and fast moving. Pre‐monsoon systems propagate southeastward whereas monsoon systems propagate to the northeast, northwest, or southeast. A large number of systems occur in the southern, eastern, and northern parts of Bangladesh. Of the 442 scattered‐type systems, 244 are scattered‐type systems having wide areal coverage (SWAC), which extends out of radar range, and speeds too small to calculate. About 97% of SWACs develop during the monsoon period and contribute greatly to monsoon rainfall in this region. Copyright © 2009 Royal Meteorological Society