3.2.1. Precipitation Datasets

IMERG (Integrated Multi-satellitE Retrievals for GPM) is a high resolution global precipitation product produced by NASA as part of the Global Precipitation Measurement (GPM) mission [36–38]. IMERG merges several satellite estimates from infrared, passive-microwave and satellite-radar. Three versions are available at half-hourly and 0.1◦ lat/lon resolution: the Early, Late and Final runs. The Final run is gauge-adjusted at monthly scale with the GPCC (Global Precipitation Climatology Centre) gauge product. This product is not available for the Early and Late runs, which have

respectively 5 h and 15 h latency. Instead, they are climatologically adjusted to the Final run. So, they indirectly incorporate past gauge data through this climatological adjustment, but are independent of recent rainfall measurements. The warping will be applied to IMERG-Late run, on a 37 × 37 grid points area corresponding to the study domain.

The Trans-African Hydro-Meteorological Observatory (TAHMO [39]) initiative aims to develop a dense network of 20,000 hydro-meteorological stations in sub-Saharan Africa (equivalent to one station each 30 km). These low-cost stations measure the standard meteorological variables, including precipitation, at a high temporal resolution (5 min). The current TAHMO network contains over 500 stations, mainly in West and East Africa. Data from 66 TAHMO stations are available within the study area for the selected hour.

IMERG-Late estimates and TAHMO measurements for the selected hour, i.e., for the 22 April 2018 between 18:00:00 and 19:00:00, can be seen in Figure 4. Both show one main rainfall event, with a maximum of 45 mm/h according to IMERG-Late. TAHMO recorded a slightly higher maximum of 53.45 mm/h at a gauge located South-West of IMERG's peak.

**Figure 4.** IMERG-Late (background) and TAHMO (circles) accumulated rainfall between 18:00:00 and 19:00:00, within the study domain (dotted line).
