Sem-arid conditions in Save Valley are due to the Rain-shadow effect. Image by Youth Delegates

Sem-arid conditions in Save Valley are due to the Rain-shadow effect. Image by Youth Delegates

ZIMSEC O Level Geography Notes: Rain Shadow Effect

We have already looked at the formation of relief rainfall elsewhere. The diagram below shows the formation of relief rainfall and the resulting rain-shadow effect.

Rain-shadow Effect. Image by Wikispaces

Rain-shadow Effect. Image by Wikispaces

  • As the air descends it becomes drier and warm
  • This results in semi-arid conditions.
  • Examples of such places include Bocha/Marange and Save valley.
  • Zimbabwe’s mountain ranges including Mt Inyangani and the Chimanimani mountains are located to the east of the country.
  • They force the Easterly winds to rise as they impede the wind’s path.
  • These winds carry moisture from the Indian Ocean after blowing across the warm Mozambique current.
  • The air is forced to rise condenses and relief rain is formed.
  • Most of the rainfall falls on the windward/eastern slopes of the mountains.
  • Little to no rainfall falls on the leeward slopes and valley.
Rainfall patterns of Zimbabwe. Image by Runyamhere.

Rainfall patterns of Zimbabwe. Image by Runyamhere.

  • As the rainfall map above clearly shows most of the rainfall in Zimbabwe falls within the vicinity of Zimbabwe’s Eastern Highlands range
  • As said this because the mountains impede the flow of the air, force it to rise thus resulting in relief rainfall.
  • The amount of rainfall decreases as one moves to the west.
  • Mountains thus block precipitation from happening on the leeward side.

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