Balloons hunt for air particles to study cloud formation

Brazilian and U.S. researchers are investigating aerosols and regions with and without pollution in the Amazon to understand their influence on cloud formation   

By Heitor Shimizu, in Washington, DC

Agência FAPESP — An international research project investigating the aerosols that result from hydrocarbon emissions and their influence on the formation of clouds and rain in the Amazon was presented by its coordinators at the symposium FAPESP-U.S. Collaborative Research on the Amazon, held October 28-29, 2014 in Washington, DC.

The project is part of the scientific initiative known as Green Ocean Amazon (GOAmazon), a U.S. Department of Energy (DOE) program conducted in partnership with FAPESP and the Amazonas Research Foundation (FAPEAM).

In a project called Goble (forGOAmazon Boundary Layer Experiment), researchers are studying secondary aerosols in pristine and polluted environments as well as in the atmospheric boundary layer (ABL) of the Amazon region.

Aerosols are particulate matter found in the atmosphere that can become primary sources — be they natural, such as dust from deserts or volcanic eruptions, or anthropogenic, derived from fires or fossil fuels — or secondary sources, resulting from the condensation of gaseous products such as sulfate, nitrate or organic aerosols.

The project — coordinated by Celso von Randow from the National Institute for Space Research (INPE) and Marcelo Chamecki, professor at Pennsylvania State University — seeks to study the lifecycle of secondary aerosols, and has been conducted in two regions of the Central Amazon: one with pristine air and primitive forest landscape, and the other near the city of Manaus, which is greatly influenced by a pollution plume. The research is part of the FAPESP Research Program on Global Climate Change .

The researchers are using flux towers and balloons to measure the vertical distribution of aerosols and cloud condensation nuclei in the ABL. One goal of the project is to better understand how the forest land cover influences cloud formation, with emphasis on how boundary-layer air is injected into the cloud layers, and how these processes are altered by the influence of the pollutant outflow from a city like Manaus.

“In addition to the flux towers, we are also using tethered balloons, which offer an interesting perspective to the project because they allow us to bridge the gap between surface measurements conducted in the towers and those obtained by the balloons,” Randow said.

“We are investigating the entire ABL aerosol profile and working with a computer model to analyze the turbulent transport of these elements through the cloud layers,” he said.

The researchers have conducted balloon measurements in the GOAmazon area known as T1, which is primitive forest. The balloon can reach altitudes of 1,800 meters. Soon a second unit will be acquired for measurements at another site. They have also used other instruments — such as sonic anemometers for measuring turbulence — and combined measurements collected by other projects to obtain more complete results.

“Much of this effort is made to understand the forest turbulence structure, which is how the forest really influences the flow of air over and through the tree canopy. Because we wanted to better understand the atmospheric chemistry and the formation of aerosols, we have conducted a lot of measurements. We installed sensors for ozone, sulfur dioxide, nitrogen oxides and hydrocarbons and we have also measured aerosols and how these particles become cloud condensation nuclei,” Randow said.

“Using the balloon, we also assessed the thermodynamic conditions in the atmospheric boundary layer. The results of all these measurements are then combined with high-resolution computer simulations to allow us to study the complete cycle of gases and particles in the ABL, from emission to transport to the cloud layer,” he said.

Randow pointed out that another important outcome of the Goble project has been the training of personnel since more than 20 students have been involved. The results of the project will also be used in the Brazilian Climate Model that is being developed by the Brazilian scientific community.