Characteristics of the Z-R Relationships Observed Using Micro Rain Radar (MRR-2) over Darjeeling (27.05 degrees N, 88.26 degrees E): A Complex Terrain Region in the Eastern Himalayas

摘要

The relationship (Z = AR(b)) between radar reflectivity factor,Z and rainfall rate, R is studied using the micro rain radar (MRR) observation located over Darjeeling (27.05 degrees N, 88.26 degrees E, 2194 m above the msl) in the foothills of the eastern Himalayan Mountains during Indian summer monsoon and post monsoon seasons (June-October) 2013. Observations from MRR are classified mainly into two types, stratiform and convective, based on the bright band and non-bright band signatures in the radar reflectivity, respectively. We have observed 12 and 7 cases for the stratiform convective rain events, respectively. In the present study MRR is operated mostly during low intensity rainfall rate (0.02-20 mm/h). During southwest monsoon season Z-R relation for the stratiform and convective rainfall types are found to be Z = 272R(1.78) and Z = 192R(1.54) respectively. Z-R relation for both stratiform and convective rain shows high temporal variation during different months of monsoon and post monsoon seasons. The coefficient A varies between 225 and 289 for stratiform rain and between 153 and 235 for convective rain. The exponent b varies between 1.4 and 2.1 for stratiform rain while between 1.2 and 1.8 for convective rain. Interestingly, we observed a distinct relation with smaller values of A and b for convective rain than stratiform rain over Darjeeling. The height dependence of A and b are also studied which is found to be very small up to similar to 1.5 km above the surface for both types of the precipitating systems.