Science, Tech & Environment

Rainmaking in the Amazon

Moving into the rainforest is to feel the trees closing in around you. The road disintegrates into a muddy track and tree branches reach into your face. We switch to an all terrain vehicle. Finally, we climb from green to blue. Every direction I look, all I can see is forest, nothing else. We are about 60 kilometers into the forest, only 40 miles outside a major city but in a different planet. This scientist has brought me here to this tower, one of a series that form the large scale biosphere atmosphere experiment in the Amazon. This tower has been monitoring the forest since 1999 and it's helped discover some things that were undiscovered in the forest up until that point. It measures many different aspects of the forest including rainfall and concentrations of CO2 and water vapor in the air and forest temperature. This data will help form the backbone to argue against deforestation�data from towers like this one help show exactly what rainforests do. This researcher and scientist says rainforests act like giant air conditioners. So when rain falls on the forest, much of it gets caught by the leaves at the top but the rain that gets through that get caught by roots, which sends the water up the tree and pulled as if by a giant straw and the sucking is actually coming from those leaves and as they lose water into the sunlight from evaporation they draw up more water from the roots. The water vapor helps create new rain. But there was this mystery, says this scientist because you need water vapor but also tiny particles to latch onto the vapor to create condensation and make it rain. The problem is that the air above rainforests is clean, there aren't many solid particles. Measurements conducted at the towers helped produce the answer: they found forests are emitting something else into the air: gasses, organic gasses created by foliage. And the sunlight transforms that into small crystals. Elsewhere in the world it takes clouds a bit of time for clouds to form, but in rainforests it takes only a few hours. The clouds then travel east to west and then they hit the wall which is the Andes and some of the clouds then head south and they'll drop their moisture in the South American grainbelt and some of the vapor makes it to the southern part of the continent and eventually some of it to Africa. Deforestation disrupts that process�there will be less rain clouds forming. That's just a slice of what's going on in this part of the rainforest.

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