Evaluation of IMERG precipitation product in the investigation of drought events in the Kermanshah Province

Our world is facing new challenges due to the prolonged drought events that have occurred over the past decade. These events are affecting ecosystem services and Earth surface processes adding unpredictable responses to be managed. In this study, a comprehensive evaluation of integrated multi-satellite retrieval (IMERG) global precipitation measurement products was conducted to determine the drought situation in semi-arid and arid areas. Predicted precipitation values from the final IMERG from 2001 to 2020 were used to evaluate 3, 6, and 12 months of drought in 13 meteorological stations in the Kermanshah Province, a representative study area. The results showed that IMERG has a relatively good performance in detecting the spatial patterns of heavy and low precipitation, so that in the northern stations, where the rainfall amount is higher, IMERG has shown good performance. The drought results obtained from IMERG show that the SPI-3 index is close to the station data; therefore, the average of RMSE, R², and E_NS of the 3 month time step data is equal to 0.7, 0.5, and 0.6 compared to SPI-6 and 12 data. The results of drought frequency showed that drought intensity in the Kermanshah Province was higher than that in SPI-3 at 12 and 6 months, whereas the 3 month drought frequency closely matched that of the station data. In examining the time step of the drought event, it was found that the IMERG data showed the drought 1–2 years earlier than the station data, which can be used to evaluate early droughts. In this case, we demonstrated that the SPI-3 drought index obtained from IMERG data was the best indicator of drought. The overall findings indicate that IMERG data are able to simulate droughts earlier than station data and can be a useful tool for drought monitoring and disaster management in semi-arid and arid regions. This research can be applied in the use of satellite precipitation products for regional drought management.