Hydrometeor structure of a composite monsoon depression using the TRMM radar

This paper addresses the use of a satellite-based radar for obtaining the composite structure (from several monsoon depressions) of the distribution of precipitation elements in the horizontal and the vertical. This composting is based on the use of a simple elliptical layout of coordinates along the major and minor axes of each storm as it passed over north central India. This satellite, called the Tropical Rainfall Measuring Mission (TRMM), carries onboard a microwave instrument known as the Precipitation Radar (PR). The vertical structure of hydrometeors provided by the radar is somewhat of the same quality as the ground-based Doppler radar units. The PR could identify many features such as the melting layers, height of convection, extent of anvils and types of precipitation over different sections of the composited monsoon depression. Furthermore, the asymmetric nature of surface rainfall that intensifies around the composited monsoon depression has also been mapped, which could provide several more details than was possible from other satellite-based estimates. It is found that the most intense precipitation occurs in the south-southwest region of the monsoon depression. The preponderance of stratiform rain and the coverage of fewer deep convective elements, especially over the orographic upslope region, are some other noticeable features obtained using the TRMM PR. The stratiform rain was noted to arise where the melting layers (in the radar reflectivity signatures) were located near 5 km. In those few occasions where tall rain clouds were discernible, the cloud tops were seen to extend all the way from 12 to 15 km. Rainfall amounts across the composite monsoon depression range from 10 to 100 mm d−1. The 3–4 d passage time of one of those disturbances resulted in local rainfall totals of the order of 200–300 mm d−1.