The ATTO site is located in the central Amazon rainforest of Brazil. Scientists chose it for the pristine quality of the area, up till now mostly unaffected by deforestation or other human interference. In fact, it is situated within the Uatumã Sustainable Development Reserve, guarantying that it will remain undisturbed for some years to come. At the same time, the relative proximity of the site to this metropolitan area of Manaus makes it accessible for scientists and technicians. It takes about five to six hours to travel the 150 km air-line distance: first by car north and east from Manaus to Porto Morena, then by boat along the Rio Uatumã, a tributary of the Amazon river, to Porto ATTO and then again by car on dirt-road to finally reach ATTO.
In this part of the world, the predominant wind direction is North-East, due to trade winds blowing from the Atlantic Ocean. This puts ATTO upwind from Manaus and its air pollution. During the wet season, the air masses reaching the site from to the East and North-East are near-pristine, mainly unaffected by human activities. The closest cities in that direction are Santarém and Belém, at distances of 500 and 900 km away. The rest of the area is covered in rainforest. During the dry season, however, the wind direction shifts more often to South-West and the frequency of natural and man-caused fires increases. Thus, the wind brings more pollutants to ATTO from the so-called deforestation belt.