Evaluation of long-term satellite-based retrieved precipitation estimates and spatiotemporal rainfall variability: The case study of Awash basin, Ethiopia

Abstract Obtaining near-real time rainfall data from rain gauge stations are not easy in most developing countries like Ethiopia. Alternatively, satellite rainfall estimates have a solution to address the limitation of the conventional in situ-based rainfall measured datasets. They can also provide reliable rainfall data at different spatiotemporal scales. The performance of satellite-based rainfall estimates including Climate Hazards Group Infrared Precipitation with Station Data (CHIRPS v.2), Tropical Applications of Meteorology using SATellite and Ground-based Observations (TAMSAT), and African Rainfall Climatology (ARC v2.0) were evaluated. Subsequently, rainfall variability trend analysis was carried out over the Awash basin. TAMSAT has good agreement with station data in monthly scale. However, CHIRPS has better performance in seasonal and annual scale. Besides, the performance of CHIRPS had better than TAMSAT and ARC-based satellite-based rainfall estimates at the annual scale. The analysis of satellite-based rainfall estimates and rain gauge rainfall data revealed an increasing trend during the heavy rain falls Kiremt season (June, July, August, and September) except for ARC product. For Belg season with occasional rainfall (February, March, April, and May), the correlation analysis result using measured and satellite-based rainfall estimates showed decreasing trend; however, the result of the analysis indicated an increasing trend during the dry season of Bega (October, November, December, and January). The decreasing or increasing trend was not statistically significant. On the other hand, the downstream part of the basin exhibited high spatiotemporal variability of rainfall. Generally, the findings of the study confirmed that satellite based-rainfall estimates can be used as an alternative data source for different hydro-meteorological applications, in regions where evenly distributed and continuously recorded rain gauge data are almost lacking in Ethiopia.