Evaluation of CHIRPS rainfall estimates over Iran

Abstract

The Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) dataset, first released in 2014, is a high-resolution blended rainfall product with quasi-global coverage that has not previously been evaluated over Iran. Here, we assess the performance of the CHIRPS rainfall estimates against ground-based rainfall observations across Iran over the time period 2005–2014 inclusive. Results show that performance of CHIRPS is best over areas and during months of predominantly convective precipitation, with the highest correlations in the southern coastal lowlands, which are characterized by heavy rains of convective origin. Correlations are stronger with variables such as altitude, particularly alongside coastal regions in the north and south, where surface water produces more moisture in the atmosphere. Results of pairwise comparison statistics and categorical skill scores reveal the influence of altitude and precipitation amount, while categorical skill metrics vary more with changes in precipitation amount than with latitudinal or longitudinal changes.