from newscientist.com

"Scientists have known for some time that forests recycle rain. Up to half the precipitation falling on a typical tropical rainforest evaporates or transpires from trees. This keeps the air above moist. Ocean winds can spread the moisture to create more rain. But now Victor Gorshkov and Anastassia Makarieva of the St Petersburg Nuclear Physics Institute in Russia say that forests also create winds that pump moisture across continents.

How can forests create wind? Water vapour from coastal forests and oceans quickly condenses to form droplets and clouds. The Russians point out that the gas takes up less space as it turns to liquid, lowering local air pressure. Because evaporation is stronger over the forest than over the ocean, the pressure is lower over coastal forests, which suck in moist air from the ocean. This generates wind that drives moisture further inland. The process repeats itself as the moisture is recycled in stages, moving towards the continent's heart (see diagram). As a result, giant winds transport moisture thousands of kilometres into the interior of a continent."

read more by clicking on the link http://www.newscientist.com/article/mg20227024.400-rainforests-may-pump-winds-worldwide.html?full=true&print=true