Abstract
In the present study assessment of Global Precipitation Mission’s (GPM) IMERG research and IMERG real time was carried out under varied climatic and topographic conditions in Pakistan. Three types of statistical indices were applied. First the Correlation Co-efficient (CC), describes the covenant between the satellite estimations and rain-gauge data. Second the BIAS, Relative-BIAS (RBIAS) and Root Mean Square Error (RMSE) that define the BIAS and errors of satellite-based products compared with rain-gauge estimates. The third Probability of Detection (POD), False Alarm Ratio (FAR), and Critical Success Index (CSI) used to pronounce the prospect of satellite-based rainfall products. The assessment was carried out at grid scale, for the entire study area and by dividing the study area in to five regions based on topography and climatic conditions. For this purpose daily accumulated rainfall data in mille meters, of eighty two rain gauges, for the period from March till December 2015 was obtained from Pakistan Meteorological Department. For inter comparison among the satellite based products TRMM TMPA 3B42 Real Time was also used. The result showed that a very good co-relation was not observed at regional as well as grid scale but the result of BIAS has been encouraging. Similarly value of POD varied from 50 to 100 percent. However the value of CSI remained up to 30 percent. It was observed that performance of satellite based products improved in plain areas and areas with sufficient rainfall. However in high altitude areas results were not satisfactory due to complex topography and climatic conditions. Inter comparison of satellite products showed that performance of IMERG research was better than IMERG real time and TMPA 3B42. However at mean daily basis, the performance of IMERG real time was better than the other two. The overall performance of IMERG products remained better than 3B42 RT. An inter comparison between spatial distribution of daily mean precipitation of the satellite based estimations and rain gauge values strongly encouraged application and further exploration of satellite based precipitation products.
Keyword(s)
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