Simulation of a heavy rainfall event in Pune using WRF-ARW with updated vegetation cover and urban canopy parameterization

Prediction of heavy rainfall events due to severe convective storms in terms of their spatial and temporal scales is challenging aspect for operational forecaster. The present study is about record-breaking heavy rainfall event observed in Pune(18° 31' N, 73° 55' E) on 4th October 2010. It had the maximum 24-h accumulated precipitation of 181.3 mm and caused flash floods in the city. The real time weather forecasting system which is operating on C-DAC's PARAM YUVA high performance computer has captured this intense convective event 4 hours before. Further this study is extended by changing high resolution AWiFS terrain data set prepared by National Remote Sensing Centre (NRSC), by using the urban canopy model option and assimilating the conventional and satellite derived sounding observations. Model runs were compared with observations from Automated Weather Stations (AWS) and radiosonde of IMD and Stability indices from Wyoming weather chart. Simulation with NRSC terrain data showed less vegetated cover over Pune surroundings indicating changes in the albedo values and leading to changes in sensible and latent heat fluxes which results in more precipitation than control run. With the inclusion of the Urban Canopy Model option, it was observed that decrease in the surface humidity content and an increase in the ground temperature which results in development of Urban Heat island effect which intern has led to better simulation of precipitation. With the inclusion of additional data using the FDDA technique, it enhanced the precipitation simulation over Pune. [Keywords: Heavy Rainfall, WRF, Land cover, Data Assimilation]