Looking at equatorial Africa in Google Maps, the western part – Guinea, the Congo – is the dark green of tropical rain forest that I would expect of a wet equatorial region, by analogy with the Amazon basin and similar latitudes in east Asia.

By contrast, the eastern part – Kenya, Tanzania – is the light green of savanna and the light brown of semidesert or desert, indicating much drier conditions that at other longitudes, are more associated with the edges of the Hadley cells, 20-30 degrees away from the equator.

That's not at all the pattern I would've expected. By the basic logic of convection cells, plus analogy with other continents, I would've expected moist conditions across the width of equatorial Africa, but failing that, because the prevailing winds in the tropics blow from the east, I would've expected the eastern part of the continent (which gets wind from the Indian Ocean) to be wet and the western part (which gets wind that has blown some distance over land) to be drier.

Why is it that the western part of equatorial Africa is wet and the eastern part is dry?

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    $\begingroup$ Part of the answer probably has to do with topography: if you look at any topographic map of Africa (for instance here: commons.m.wikimedia.org/wiki/Category:DEM_maps_of_Africa), you'll see that Congo is in the lowlands, while Kenya and Tanzania are mountainous. Elevation has an impact on temperature and thus on vegetation. $\endgroup$ Aug 31, 2021 at 16:44
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    $\begingroup$ Indeed there's already a question here: Why is Somalia so dry? $\endgroup$ Aug 31, 2021 at 17:38
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    $\begingroup$ @JeopardyTempest should we mark this as duplicate? $\endgroup$
    – f.thorpe
    Aug 31, 2021 at 22:13
  • $\begingroup$ @f.thorpe You're the moderator, you tell me :-p Yeah, maybe... it's supposed to be a little different by focusing on the opposite question, but in the end the key looks to be Somalia's difference from the rest of that latitude around the globe $\endgroup$ Aug 31, 2021 at 22:21
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    $\begingroup$ @nwallace tropical easterly waves for the west and for the eastern part read my why is Somalia dry answer $\endgroup$
    – user1066
    Sep 1, 2021 at 2:06


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