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Figure 3.9 shows mean annual rainfall based on two products, CHIRPS2 and raw gauge data in the NIC131 archive. The raw gauge data are averaged for the period 1945 to 1984, the period with the greatest number of gauges in the Congo Basin. CHIRPS2 was averaged over the time period 1981 to 2019. A comparison with gauge data during that time period would be desirable, but the station density over the Congo Basin is too low. In that the averaging period for both data sets is roughly four decades, the long‐term means derived from the two should be comparable. In fact, there is excellent agreement between the two analyses, despite the much lower resolution of the gauge data. There is, likewise, excellent agreement with the analysis of Bultot (1971) for 1930–1959, which is based on some 500 stations in the Congo (Camberlin et al., 2019).

Figure 3.9 (a) Mean annual rainfall (mm) based on gauge data for the period 1945 to 1984 and CHIRPS2 data for the period 1981 to 2019. (b) Mean rainfall for four individual months from CHIRPS2 for the period 1981 to 2019.

Throughout the basin mean annual rainfall exceeds 1250 mm, but it exceeds 1500 mm over most of the region. In the core of the basin, annual rainfall exceeds 1750 mm. Within that area are three maxima, located at roughly the equator and 20°E, 2°S, and 28°E, and 3°N and 28°E. CHIRPS2 shows the maximum at 2°S and 28°E to be the strongest. Mean annual rainfall exceeds 2000 mm in at least some areas. Rainfall maxima are also evident along the Atlantic coast between roughly the equator and 7°N, over the Ethiopian highlands, over the western portion of Lake Victoria, and in a small sector of western Kenya (northeast of Lake Victoria). The aridity of eastern Africa contrasts sharply with the high rainfall over the Congo Basin.