Evaluation and comparison of the performance of two reanalysis and satellite climatological databases under data scarcity conditions

The present study aimed to evaluate the performance of CHIRPS and ERA5 reanalysis and satellite data from 2011 to 2020. This evaluation was carried out using 8 synoptic stations and 23 rainfall gauge stations within the Aras River basin, spanning four countries. The results indicated that the daily correlation coefficient for minimum and maximum daily temperature parameters in the ERA5 database exceeded 0.9 for all stations. This value improved for monthly and seasonal scales, with these coefficients reaching approximately 0.99. In terms of precipitation, the comparison between CHIRPS and ERA5 databases revealed that ERA5 exhibited higher accuracy in estimating precipitation with an RMSD coefficient below 0.3. This trend was consistent at monthly and seasonal time scales. At the basin level, the analysis demonstrated that ERA5 had significantly higher accuracy compared to point-based data, as confirmed by the obtained statistical coefficients. Therefore, ERA5 products, particularly at monthly scales or at the basin level, can serve as suitable alternatives for data-scarce regions, especially in the Aras River basin.