Science for Brazil (Reino Unido)

Balloons “sniff” Amazon Skies

Publicado em 03 novembro 2014

Researchers from the United States and Brazil are using high-altitude balloons to help them measure aerosols in the atmosphere high above the Amazon rainforest in the Atmospheric Boundary Layer.

This so-called Amazon Boundary Layer (ABLE) is the new frontier in the race to fully understand the role the rainforest plays in global climate change. As well as towers rising above the pristine forest, and aircraft equipped with “sniffer” equipment, the balloons form part of a massive experiment called Green Ocean Amazon (GOAmazon). The experiment is partly funded by the US Department of Energy.

You can read more about the GOAmazon project by clicking here.

The focus of sensors borne 1,800 meters aloft by balloons are secondary aerosols generated by healthy forest. In recent months huge controversy has been generated by a US “climate change skeptic” scientist from Yale University who wrote in the New York Times that aerosols generated by healthy forest actually contribute to global warming, and that deforestation could help cool the planet. You can read about this by clicking here.

The two scientists leading the balloon experiment –  Celso von Randow from Brazil’s Institute of Space Research (Inpe), and Marcelo Chamecki, professor at Pennsylvania State University –  presented their early findings at a high-level seminar held at Washington’s Woodrow Wilson Center on October 28th. You can read more about the seminar by clicking here.

The seminar, which was opened by US Energy Secretary Ernest Moniz, heard that aerosol-measuring balloons have been sent aloft near the industrial city of Manaus, and above pristine forest.

Wind-borne aerosols have various natural and man-made sources. Natural aerosols can come from desert or volcanic dust, as well as chemical cocktails released as a product of condensation or photosynthesis. Man-made sources are chiefly the product of combustion of carbon and chemical derivatives included sulphur-based impurities.

The chemical composition of the atmospheric mixed layer over the Amazon Basin ecosystem during both wet and dry seasons reflects interacting influences from biogenic gas and aerosol sources and sinks, photochemistry, exchange with the free troposphere, influx of marine air from the tropical Atlantic, and long-range transport of pollutants from distant industrial and agricultural activities.

These aerosols influence the surface dynamics of water droplets during the process o cloud formation and precipitation. Very pure water with low aerosol content tends to produce large raindrops characteristic of tropical downpours. Water with higher aerosol content generates smaller droplets or even a finer mist that can resist falling as rain, thereby leaving the forest below to dry out and as a consequence contribute less evaporation.

The breaking of this “virtuous circle” of rainfall and evaporation could lies behind the periodic drying out of Amazon basin, the noted changes to regional weather in South America – and perhaps even the process of global climate change.

During the wet season, the northern hemisphere becomes a source of pollution to the Amazon as a result of episodic inputs associated with changes in the large-scale atmospheric circulations associated with subtropical anticyclones. Seasonal variations in biogenic emissions are important in determining the photochemical characteristics of the Amazon mixed layer. The undisturbed regions of the Amazon are potentially a globally significant sink for ozone during wet-season conditions.

The region is an important source of both methane and nitrous oxide. The extensive area of undisturbed tropical forests in the Amazon Basin and the relatively pristine atmospheric chemical conditions during much of the wet season are an important resource for understanding the role of biosphere-atmosphere interactions in global atmospheric chemistry.

Chemicals being monitored by the balloons include ozone, carbon monoxide, CO2, sulphur dioxide, hydrocarbonates and oxides of nitrogen. As well as aerosols, the balloons measure atmospheric turbulence high above the forest cover in the Atmospheric Boundary Layer.

The results will provide data for computer modelling of the complete cloud and water transfer cycle in the Amazon Basin’s atmosphere. This will feed into the Climate Change Model being developed by Brazilian researchers, and will be integrated into the large-scale GOAmazon Project involving scientists from several countries and financed by the US Department of Energy, by the São Paulo Research Foundation (FAPESP) and other Brazilian federal and regional funding sources.

The results build on a decade of sampling by a precursor project named ABLE.

The Amazon Boundary Layer Experiment (ABLE 2B) used data from aircraft, ground-based, and satellite platforms to characterize the chemistry and dynamics of the lower atmosphere over the Amazon Basin during wet season (April–May 1987) conditions.

Portuguese speakers can read a detailed article by Brazilian journalist Heitor Shimizu by clicking here. Further Portuguese language links are available below: