Evaluation of GSMaP Data for Extreme Rain Events and Causing Floods in East Kotawaringin

On 12 May 2021, 12 August 2021, 6 September 2021 and 27 June 2022, extreme rain occured with an intensity of 58.85 mm/day, 101.3 mm/day, 124.4 mm/day and 176.8 mm/day respectively in East Kotawaringin. These phenomena occurred during the dry season and caused flooding, which is a rare condition during the dry season in East Kotawaringin. This study aims to evaluate extreme rainfall using GSMaP (Global Satellite Mapping of Precipitation) data, where analysis using GSMaP has never been done before in East Kotawaringin. These GSMaP data were processed and compared with the observation data from the Meteorological Station of H. Asan, East Kotawaringin. After that, the GSMaP rainfall results are verified using statistical methods, namely RMSE, correlation coefficient and bias. The verification results show that the bias gives underestimate results for all dates. In addition, the RMSE values on 12 May 2021, 12 August 2021, 6 September 2021 and 27 June 2022 are 10.83, 17.32, 12.41 and 34.03, respectively. These high RMSE values indicate that the GSMaP rainfall value is quite far from the observed rainfall value. The correlation value between GSMaP rainfall and observations has a high correlation with values of 0.84, 0.90, 0.96 and 0.98 for each date. These results show that the GSMaP data has a good correlation value and can be used for extreme rainfall analysis at the Meteorological Station of H. Asan, East Kotawaringin.