As a location for the ATTO site we chose a spot in the central Amazon rainforest of Brazil, in a pristine area, up till now mostly unaffected by deforestation or other human interference. In fact, it is situated within the Uatumã Sustainable Development Reserve. This ensures 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.
Observing pristine rainforest - or do we?
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. Air masses reaching the site from to the 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. But this is only true during the wet season.
During the dry season, the wind direction shifts more often to East and South-East. Air masses from this direction pass over agricultural areas and regions more affected by deforestation. Additionally, this is the time of year when the frequency of natural and man-caused fires increases. Thus, the wind brings more pollutants to ATTO.
These contrasting regimes allow us to compare a near-pristine atmosphere to one notably influenced by human activity.