These images show the vicinity of the Elburz Mountains in northern Iran. Tehran lies in the south, and the Caspian Sea is to the north.
The Elburz Mountains run parallel to the southern coast of the Caspian Sea, and these mountains act as a barrier to rain clouds moving southward; as the clouds rise in altitude to cross the mountains they drop their moisture. This abundant rainfall supports a heavy rainforest (the bright red area) on the northern slopes. The valley to the south receives little precipitation because of this rain-shadow effect of the mountains.
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Helen Chapin Metz (ed.), 1989, Iran: a country study: Federal Research Division, Library of Congress, Washington, D.C., 342 p.
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UNEP, 2005, Tehran—Impacts of Urban Expansion on Water Resources: UNEP, Division of Early Warning and Assessment, available online at https://na.unep.net/atlas/onePlanetManyPeople/downloads/urbanPosters/Teh.... (Accessed April 3, 2014.)