Task force investigates whether Amazonia’s ‘Green Ocean’ is at risk

The GOAmazon Project will collect data for two years to understand how pollution can alter cloud characteristics and affect rainfall patterns.

By Karina Toledo

Agência FAPESP – The clouds that hang over the Amazon rainforest have characteristics similar to those of clouds found over oceans. Because there is a great deal of moisture in the air and an extremely low concentration of particulate matter – which offers a surface for water vapor condensation – raindrops rapidly increase in size and soon acquire sufficient mass for precipitation.

This particular feature of a tropical forest was first described in 2004 in an article published in the journal Science by researchers who took part in the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), an international collaborative program led by Brazil. The discovery gave the Amazon the nickname the ‘Green Ocean.’

The same study suggested, however, that the Amazon’s efficiency in producing rain would be jeopardized by the growing pollution resulting from urbanization and the burning of biomass. This is because the increased particulate matter (aerosol particulates) in the atmosphere would create a larger number of water condensation nuclei and, consequently, reduce the size of the drops, slowing the entire process of precipitation.

“If pollution is in fact altering the characteristics of the clouds in Amazonia, the consequence will be a significant change in rainfall patterns. In addition, altering the hydrological equilibrium of a huge region responsible for controlling the transport of humidity to the country’s south could have a significant impact on the Southeastern and Central-Western regions,” stated Paulo Artaxo, a professor at the Physics Institute of the University of São Paulo (USP) and coauthor of the study published in Science.

To test the hypothesis regarding the effect of pollution on clouds and to increase the knowledge about the process of rain formation and the interaction dynamic between the Amazon biosphere and the atmosphere, the scientific campaign known as Green Ocean Amazon (GOAmazon) began in January 2014. The program brings together researchers from several Brazilian and North American universities and institutes and is financed by the U.S. Department of Energy (DOE), FAPESP and the Amazonas Research Foundation (FAPEAM), among other partners.

“Man’s use of natural resources has accelerated in the last 30 or 40 years. The questions that we’re trying to answer with this experiment are: up to what point can we pollute, extract timber and change the climate? How long will the Earth withstand this?” asked Scot Martin – a Harvard University professor and the mastermind of GOAmazon, along with Artaxo – during the program’s official launch in Amazonas on February 18.

According to Martin, the city of Manaus and its surrounding areas constitute an ideal laboratory for this type of research. This is because the Amazonas capital, with a number of thermoelectric plants, nearly two million inhabitants and 600,000 cars, is surrounded by 2,000 kilometers (km) of forest. During the rainy season, the levels of particulate material in the region are as low as those in pre-industrial times.

In 2010, Martin submitted a proposal to the DOE to bring the infrastructure of the Atmospheric Radiation Measurement (ARM) Facility – a mobile set of terrestrial and aerial equipment for climate studies, especially those geared to the process of cloud formation and radiation transfer – to Brazil.

With the project approved, a partnership involving the DOE, FAPESP and FAPEAM was established to maximize the use of the mobile observatory by Brazilian and US scientists. The result was a joint call for proposals launched in 2013, with a total financing budget of R$24 million.

Six projects were approved, and others are already underway, such as the thematic project “Cloud processes of the main precipitation systems in Brazil: a contribution to cloud-resolving modeling and to the GPM (Global Precipitation Measurement),” which is coordinated by Luiz Augusto Toledo Machado of the National Institute for Space Research (Inpe), and the thematic project “GOAmazon: interactions of the urban plume of Manaus with biogenic forest emissions in Amazonia,” which is coordinated by Paulo Artaxo and Maria Assunção Faus da Silva Dias of the USP Institute of Astronomy, Geophysics and Atmospheric Sciences.

FAPEAM currently has a call for proposals out to Amazonas researchers interested in joining the GOAmazon campaign.

In January 2014, the ARM Mobile Facility (AMF) began to be installed in the city of Manacapuru, nearly 100 km west (downwind) of Manaus. The site was selected because for nearly half the year, it receives the pollution plume from the capital carried by tropical winds that blow from east to west. The rest of the time, the region receives only very clean air; thus, it is possible to compare the two situations.

The mobile observatory consists of 11 containers full of sensors, radars and other equipment for collecting and analyzing aerosol particulates and the variety of gases present in the atmosphere, in addition to measuring cloud properties and meteorological parameters, such as temperature, humidity and wind speed. Four additional containers were installed at the research site, which was given the name T3, by the Brazilian partners of the GOAmazon program.

ARM containers installed in the municipality of Manacapuru
(click on the photo to enlarge)

In total, 50 researchers work at the site and monitor measurements daily to ensure that the best and most complete set of data is obtained during the operation. Extensive data will be gathered continuously until December 2015, which is when the experiment is slated to end.

“The ARM-AMF has already been to Germany, China, India and African countries such as Nigeria, but never in Brazil, where it will stay for the longest period. It’s the largest experiment that we at the DOE have ever conducted,” said Wanda Ferrel, the ARM program director.

Complementary sites

During the time that the Manaus pollution plume travels nearly 100 km to reach Manacapuru, the particulates interact with atmospheric gases and arrive quite differently at their final destination. The location of the T3 site has the advantage of enabling scientists to study the results of this transformation and its impact on clouds and the local climate. However, the data need to be compared to measurements obtained at sites that are more directly exposed to the pollution from Manaus.

With FAPESP funding through the thematic project coordinated by Artaxo, a container with equipment similar to that in Manacapuru was installed in the municipality of Iranduba, which is situated on the banks of the Rio Negro across from the city of Manaus. This research site, housed inside the Tiwa jungle hotel, is referred to by the GOAmazon participants as T2.

Paulo Artaxo shows North American researchers the container equipment
installed in the municipality of Iranduba (click on the photo to enlarge)

In an initial analysis of the data that have been collected since January; Artaxo’s group of 10 researchers has already obtained impressive results.

“At T2 in Iranduba, we noted significant concentrations of sulfur dioxide that were not detected at T3 in Manacapuru. We also noted a strong predominance of organic aerosols – responsible for up to 85% the particulate mass – at both research sites, although the chemical composition changes radically from one site to the other as a result of atmospheric chemical processes. We also noted that the ozone levels in Manacapuru are twice as high as those found in Iranduba,” Artaxo explained.

According to the researcher, the ozone concentration registered in Manacapuru, which was on the order of 40 parts per billion (ppb), is high enough to damage the stomata of the leaves and, as a result, hinder the process of photosynthesis and the emission of water vapor.

“The impact of air pollution are not the same everywhere. There are peculiarities to the processes of atmospheric chemistry that appear as a result of the urban plume’s interaction with the volatile organic compounds (VOCs) released by vegetation,” Artaxo stated.

VOCs correspond to hundreds of substances (the best known of which are isoprenes and terpenes) that are released by vegetation in response to oxidative stress. One of the objectives of Artaxo’s project is to discover how much this vegetative stress is intensified by pollution because VOCs can also be transformed into aerosol particulates, function as cloud condensation nuclei in the atmosphere and interfere with the processes of cloud and rain formation.

Another project underway within the scope of GOAmazon, coordinated by Jeff Chambers of the Lawrence Berkeley National Laboratory, an entity associated with the DOE, is designed to further study the functions of VOCs on plant physiology and understand how the emissions change according to the amount of sunlight and rain and how all of this affects the forest ecosystem. Measurements are being taken at a set of towers located 50 km north of Manaus, near kilometer 34 of a dirt road known as ZF2.

One of the towers used to measure volatile organic compound emissions
(click on the photo to enlarge)

Another set of towers used by the group is located at the Uatumã Biological Reserve, a forest area 160 km northeast of Manaus, an area untouched by urban pollution. At that site, called T0, a 320 meter-high observation tower is under construction, part of the Amazonian Tall Tower Observatory (ATTO), a partnership between the National Institute for Research in the Amazon (Inpa) and the Max Planck Institute of Chemistry, Germany.

The infrastructure for GOAmazon data collection also includes two towers installed in Manaus, two weather balloons and two research planes.