# Precipitation Products' Inter-Comparison over East and Southern Africa 1983-2017
## 3 Regions of Study and Precipitation Climatology
### Southern Africa  
The second investigated African region is Southern Africa (10-35S, 10-51E) including Madagascar, the Republic of South Africa (RSA), Lesotho, eSwatini, Mozambique, Zimbabwe, Botswana, Namibia, Angola, Zambia, and Malawi (Figure 3). The Central Plateau covers most of the region. Its altitude is highly variable, from 3000 m in Lesotho and the eastern part of the RSA to 1000 m in Botswana, with the lowest values corresponding to the larger river valleys, and some particularly depressed basins such as that of Kalahari extending into Botswana, Namibia and RSA and encroaching into part of Angola, Zambia and Zimbabwe. The Great Escarpment is the prominent topographical feature of this region and consists of steep slopes from the Central Plateau downward in the direction of the oceans surrounding SA on three sides. The most well-known section of the Great Escarpment and one of the most remarkable mountain range of  
Figure 2: EA monthly mean precipitation relative to the period 1983–2017. Monthly climatology has been obtained from the ensemble mean of the three precipitation products. the region is the Drakensberg, which delimits the edge of the plateau in the south-east of RSA with peaks up to 3500 m of altitude. In the eastern part (i.e., Zambia and Mozambique) the plateau runs along the Rift Valley region (Section 3.1) via a sharp border highlighted by the Lake Malawi. In western SA the Central Plateau runs north to south, bordered by the Skeleton Coast to the northwest, with the Namib Desert and its coastal plains to the southwest. Finally, Madagascar completes the analyzed region, the largest island in the Indian Ocean, separated from the African continent by the Mozambique Channel with a width of 400 km. It is mainly mountainous, crossed latitudinally by a mountain ridge with an average altitude between 1200 and 1500 m and peaks exceeding 2600 m.  
Precipitation in this area is characterized by great spatial and temporal variability, mainly attributable to the interaction of multiple factors among which are the geographical location, variations in the regional topography, sea surface temperature, and southward tapering of the subcontinent. Because of the very steep topography of the eastern part, the subtropical easterly flow, and the contrast between the warm Indian Ocean and the cold Atlantic Ocean, SA is characterized by a strong longitudinal precipitation gradient, with more intense precipitation on the eastern side and semi-arid conditions on the western side [16]. The mean annual precipitation obtained by averaging the time series of the three products ranges from less than 200 mm year\({}^{-1}\) in the Namib Desert to more than 1000 mm year\({}^{-1}\) in northern Mozambique and Angola. In general, northern SA, including Angola, Zambia, Malawi and northern Mozambique, receives more precipitation due to its location within the tropical belt, in an area characterized by the presence of plateaus and escarpments that encourage the development of orographic precipitation. Furthermore, a recent study has attributed 31% of total precipitation in Angola and Zambia to the formation of tropical lows, i.e., synoptic-scale cyclonic vortices that propagate westward across SA during the austral summer with the peculiar tendency to become semi-stationary over Angola, where their aggregation creates a local pressure minimum called the Angola Low [49]. The RSA is characterized by a strong longitudinal precipitation gradient from less  
Figure 3: SA region and elevation map (m). than 200 mm year\({}^{-1}\) on the west coast up to 1000 mm year\({}^{-1}\) on the eastern one, following the profile of the Drakensberg Mountain range. Marked N-S differences are present in Mozambique. Despite its proximity to the Indian Ocean and the prevalence of easterly winds, the high mountains of Madagascar partially prevent the flow of moist air masses toward Mozambique [50].