Investigation of the Best Satellite Rainfall Data in Northern Iraq

Many watersheds lack reliable rainfall data due to limitations in ground-based meteorological stations, which is critical for accurate water resource modelling. This study evaluates the suitability of satellite precipitation data as an alternative source. Four data sources were compared: NASA-POWER, which is the Prediction of Worldwide Energy Resource dataset, ERA5-Land (European Re-analysis Land Component), which stands for ECMWF (European Centre for Medium-Range Weather Forecasts), the Climate Hazards Group Infra-Red Precipitation with Station dataset CHIRPSv.2, and Terra-Climate. The satellite precipitation data for the period (2010–2020) were validated against local rain gauge station data in the study region. The validation was performed using statistical metrics, including: R², NSE, and RMSE. Results showed that NASA-POWER data had the highest correlation with rain gauge data, with R² values of 0.8818, 0.8817, 0.7494, and 0.7768 for Haweejah, Altun Kopri, Zummar, and Mosul stations, respectively. ERA5-Land also showed strong correlations, though with slightly lower R² values between (0.8165 - 0.8395). While the CHIRPS and Terra-Climate data exhibited weaker correlations with lower R² values. Overall, the findings demonstrate that satellite-based precipitation data, particularly from NASA-POWER and ERA5-Land, can effectively simulate hydrological processes in the region.