Performance of WRF’S Microphysics Options to Increase the Medium Range Rainfall Forecast Accuracy in Tamil Nadu Cauvery Delta Zone

Abstract

Weather plays a significant role in agricultural sector and the favourable weather enhance the opportunities and sustainability for crop production. Agriculture oriented Medium Range Weather Forecasts (3 – 10 days), particularly rainfall information in a week advance helps the farmers to overcome the aberrant weather conditions, reduces both input and output loss, thereby warranted higher benefit – cost ratio and net income. An attempt was made to improve the accuracy of medium range rainfall forecast (6 days) at Cauvery Delta Zone, the rice bowl of Tamil Nadu state, during South West Monsoon (June – Sep. 2020) and North East Monsoon (Oct. – Dec. 2020). The performance study of four microphysics schemes in WRF viz., Kessler, WSM3, WSM5 and WSM6 concluded that the WSM3 scheme produced more accurate forecast in Tamil Nadu's Cauvery Delta Zone (CDZ) during both the South West Monsoon (SWM) and North East Monsoon (NEM). The 2nd better choice was the Kessler scheme, where the WSM5 and WSM6 were bad performers in CDZ. The forecast usability was decreased with increasing lead time, irrespective of season and microphysics. Among the seasons forecast accuracy and usability were higher in NEM than SWM.