Rainfall retrieval and drought monitoring skill of satellite rainfall estimates in the Ethiopian Rift Valley Lakes Basin

Satellite-based rainfall products are essential for retrieving rainfall, particularly in data-scarce and drought-prone countries like Ethiopia. However, their quality needs to be validated prior to their use. Therefore, we evaluated the performance of the Climate Hazards group Infrared Precipitation with Stations version 2.0 (CHIRPS), the Tropical Applications of Meteorology using Satellite data version 3.0 (TAMSAT3), and the African Rainfall Climatology version 2 (ARC2) satellite rainfall estimates in the Ethiopian Rift Valley Lakes Basin. Their skill of retrieval was evaluated against ground-measured rainfall at dekadal, monthly, and seasonal scales across agroclimatic zones over 2001 to 2017. Finally, these satellite products have demonstrated different levels of agreement with the reference data, being the highest for CHIRPS and the lowest for ARC2. At all timescales and agroclimatic zones, ARC2 has severely underestimated the actual rainfall while TAMSAT3 has persistently overestimated it. However, TAMSAT3 has demonstrated better performance than ARC2. Generally, except for its slightly larger dekadal false alarm ratio, CHIRPS has achieved the highest and most consistent agreement with the reference data at all the timescales and agroclimatic classes. Consequently, CHIRPS was further assessed for its suitability of drought monitoring, and it has exhibited promising skill in detecting specific historical drought events. Therefore, to overcome the scarcity of ground-measured rainfall data in the study area, we recommend the CHIRPS rainfall estimate to be used as an alternative data source for drought monitoring. Conversely, owing to its overestimation tendency, TAMSAT3 could be used for flood monitoring in this region.