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WRF model and 3D-Var; ISRO AWS; rainfall; threat score.

The three dimensional variational data assimilation scheme (3D-Var) is employed in the recently developed Weather Research and Forecasting (WRF) model. Assimilation experiments have been conducted to assess the impact of Indian Space Research Organisation’s (ISRO) Automatic Weather Stations (AWS) surface observations (temperature and moisture) on the short range forecast over the Indian region. In this study, two experiments, CNT (without AWS observations) and EXP (with AWS observations) were made for 24-h forecast starting daily at 0000 UTC during July 2008. The impact of assimilation of AWS surface observations were assessed in comparison to the CNT experiment. The spatial distribution of the improvement parameter for temperature, relative humidity and wind speed from one month assimilation experiments demonstrated that for 24-h forecast, AWS observations provide valuable information. Assimilation of AWS observed temperature and relative humidity improved the analysis as well as 24-h forecast. The rainfall prediction has been improved due to the assimilation of AWS data, with the largest improvement seen over the Western Ghat and eastern India.

Prashant Kumar¹ Randhir Singh¹ P C Joshi¹ P K Pal¹

1. Meteorology and Oceanography Group, Space Applications Centre (ISRO), Ahmedabad 380 015, India.

Published

February 2011

Manuscript received

23 April 2010

Manuscript revised

1 October 2010

Accepted

5 October 2010