Investigation of Suitable Regions Determination for Drought Monitoring Using TRMM Satellite Data (Case Study: Khorasan Razavi Province)

Most of drought evaluation systems are based on precipitation data. However short period of measured data and inappropriate distribution of weather stations and undesirable quality of precipitation measurement networks reduce ability of showing the spatial pattern of drought. Therefore, it is necessary to recognize others reliable climatic data resources. Then to overpass the difficulty, after verification, the data is used to complete or substitute the existing data. Accordingly, in this research to monitor drought in Khorasan Razavi province using data from 10 synoptic stations and 107 rain gauges around the province, the monthly data of TRMM satellite was validated. To do this, standardized precipitation index (SPI) of 1, 3, 6 and 12 months are calculated for a 13 years period (1998-2010) and compared with those of satellite for the same period. The evaluation was measured using CSI (%) (Critical Success Index) and R2 (Coefficient of Determination). The results showed that there was a very good consistency between earth borne and satellite borne SPIs for all time scales except for 1 month time scale. Consistency value for all time scales over most regions of the province is more than 50%. Based on the results, for achieving the accuracy more than 60%, time scales of 1, 3, 6 and 12 months should be used as below: 1 month only for the northern regions, 3 month for all regions except the eastern part, 6 month for all regions except the northern part and 12 month for all regions except the northern region and central part of the province.