Evaluation of the Satellite Rainfall Data in Central Region of Iraq

Several watersheds lack sufficient data coverage due to an ineffective network of ground meteorological stations. So, it is essential to identify a reliable alternative data source. The objective of this paper was to analyze the rainfall time series data for eight stations in the central region of Iraq, namely Baghdad, Rutba, Baiji, Karbala, Al-Hilla, Al-Hai, Al-Khalis, and Khanaqin from 2000 until 2022, then assess how well these observed data match with satellite-derived rain data for these selected stations. Four satellite-based rainfall datasets were evaluated NASA-POWER, CHIRPS, ERA5-Ag, and TerraClimate, then comparing that data with the rain gauge stations' data in the study region. Statistical tests were implemented to evaluate the validity of the techniques, including R2, RMSE, PBIAS, and NSE. The results obtained were concurrent, as R2 values were 0.8494, 0.885, 0.8302, 0.8320, 0.784, 0.777, 0.7695, and 0.8351 for selected stations Baghdad, Rutba, Baiji, Karbala, Al-Hilla, Al-Hai, Al-Khalis, and Khanaqin, respectively, when using the NASA-POWER. When using ERA5-Ag, R2 values ranged from 0.5271 to 0.8267. Based on the results of statistical comparisons, NASA gave the best concurrence, followed by ERA5-Ag, more than CHIRPS and TerraClimate for the rainfall data. The results showed a strong correlation of satellite and observed data, suggesting that the satellite data from NASA and ERA5-Ag were sufficient to predict the different hydrological processes in the study area.