GIRHAF (Gridded hIgh-resolution Rainfall for the Horn of AFrica): a new rainfall product for detailed applications in a region beset by climate hazards

Rainfall is one of the most important inputs for applications such as hydrological modelling, water resource allocation, flood/drought analysis, and climatic risk assessments. Currently, there exist numerous (global) products offering rainfall estimates at various spatio-temporal resolutions. Nevertheless, there are still places on Earth where the coverage and/or quality of such products is limited due to sparse ground-control data, thus constraining the robustness of input rainfall for hydrological and climate applications. Located in Eastern Africa, the Horn of Africa (HOA) is a place where climate impacts like droughts and floods frequently inflict a huge toll on the lives and livelihoods of millions residing in subsistence rural communities. For places like this, high resolution rainfall data are fundamental to understanding the availability of water resources, flood hazard, and soil moisture dynamics relevant to crop yields and pasture availability.

Here we introduce GIRHAF (Gridded hIgh-resolution Rainfall for the Horn of AFrica), which is a 20-year rainfall product, with a spatio-temporal resolution of 0.05°×0.05°, every 30 minutes. GIRHAF is based on downscaling CHIMES (Climate Hazards center IMErg with Stations) a pentad operational rainfall product which corrects microwave signals in IMERG (Integrated Multi-satellitE Retrievals for GPM -Global Precipitation Measurement mission-) by in situ rain gauging networks. The goal of this product is to offer the HOA region high-resolution rainfall fields that can support more detailed mechanistic analyses of historical rainfall and can also provide the base dataset required to develop stochastic rainfall models capable of simulating forecasted or projected climate scenarios. It is our aspiration that GIRHAF will enable improved responses to climatic hazards as well as better water resources management in the HOA region, and perhaps to allow people of this region to better prepare to future climate scenarios.