Numerical models enrich scientific knowledge of climate change in Amazonia

Research findings were presented at the Annual Project Meeting of FAPESP's Research Program on Global Climate Change.

By Diego Freire  |  Agência FAPESP – The impact of El Niño on the Amazon, which is associated with rising temperatures and drought in the region, may be intensified or moderated by another climate phenomenon originating in the Indian Ocean, the Madden-Julian Oscillation (MJO), which could increase or decrease rainfall. To understand the pattern of interactions between these phenomena, researchers supported by FAPESP have developed advanced numerical computer models that generate more precise projections of climate change.

Researchers in the field presented findings at the Annual Project Meeting of FAPESP’s Research Program on Global Climate Change (RPGCC), held at the institution’s headquarters in São Paulo, Brazil, on February 18-19. Scientists from different institutions in Brazil and other countries assembled there to present and discuss ongoing research projects linked to the program.

The projects involving numerical models presented at the meeting were the result of collaborations between researchers at the University of São Paulo (USP) and researchers at the University of California, Los Angeles (UCLA), in the United States. The models simulate interactions between Earth’s surface and atmosphere, among other phenomena.

“The idea is to test and enhance these models by enriching them with data obtained from different research projects, so that long-term simulations can be performed on how the climate is changing in the Amazon, with highly accurate reproduction of all climate conditions,” said Tercio Ambrizzi, from the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP). Ambrizzi is a principal investigator for the project “Multiscale processes driving tropical convection and influence of aerosols” in Brazil, supported by FAPESP.

Once they have completed the observational analysis now under way, the researchers will work on numerical modeling of the patterns of interaction between El Niño, an atmospheric-oceanic phenomenon characterized by abnormal warming of sea surface water in the equatorial Pacific Ocean, and the MJO, a large complex of clouds and rain initiating over the Indian Ocean and slowly progressing around the world along the equator. Its propagation generates waves of convective clouds that reach Amazonia and can affect precipitation patterns.

“The MJO propagates along the equator, starting over the Indian Ocean and passing over the western Pacific,” Ambrizzi said. “Although the volume of clouds decreases and almost disappears in the western Pacific because the sea there is cooler, the wave continues eastwards. When the cloud mass arrives over the Amazon in northern South America, it builds up again and travels back to the Indian Ocean. The entire cycle lasts 40-50 days.”

Because the MJO is a wave of convective clouds, its arrival over the Amazon region may increase or decrease the amount of rainfall depending on its interactions with other phenomena, such as the El Niño Southern Oscillation (ENSO). In fact, the MJO can foster the occurrence of more rain or extreme drought, depending on the phase in which the interaction occurs.

The researchers are comparing the data with observations in other parts of the world, such as the Pacific Islands. “The aim is to see whether the start of the convection that takes place in the Pacific has similarities with what happens in the middle of the Amazon forest, determining the differences between the ocean and forest environments,” Ambrizzi said. “These similarities are important because they can be a basis for adjustments that enable the models to represent growth of the cloud wave more realistically by considering the environment in which it forms.”

Ambrizzi’s group is also working on simulations of pollution in Manaus, the capital of Amazonas State. A chemical model will simulate the sources of pollutants using interactions with the numerical models of cloud formations. The goal is to enrich scientific knowledge of how aerosols – tiny liquid or solid particles suspended in the atmosphere – and different gases interact with these clouds and may modify their growth.

The numerical models tested by the researchers use data from the international scientific collaboration Green Ocean Amazon (GOAmazon), which studies the interactions between the Amazon forest and the atmosphere, in addition to measuring pollution in Manaus and its influence on cloud lifecycles and rain formation.

The initiative includes research supported by FAPESP and presented at the meeting by Paulo Eduardo Artaxo Netto, Full Professor and Head of the Department of Applied Physics at USP’s Physics Institute and a member of RPGCC’s steering committee.

“Manaus is an urban area with some 2 million inhabitants, surrounded by hundreds of square kilometers of forest,” Artaxo Netto said. “Studying the atmospheric processes arising from this interaction is important so that we can understand more about not just regional but also global climate change.”

The scope of the research includes measurements at six different sites, followed by detailed studies of atmospheric transport and processing. Three sites measure atmospheric properties of the wind before the Manaus plume; two near the Negro River and the town of Manacapuru collect measurements downwind of the Manaus plume; and a sixth operates in the center of the state capital.

The presentations delivered at the Annual Meeting of the RPGCC covered only some of the 38 ongoing research projects supported by the program, apart from 71 completed projects. A new call for proposals ended on February 26 and will select projects on “Climate change and its relations with energy, water and agriculture”.

“The problems caused by climate change were identified by scientists over 40 years ago and have become an important element of public policy all over the world. Science has played a key role in bringing to light this understanding of the problems, and FAPESP is directly addressing the challenge of presenting solutions,” FAPESP President José Goldemberg said in his opening remarks at the meeting.

FAPESP Science Director Carlos Henrique de Brito Cruz recalled the São Paulo scientific community’s participation in formulating the voluntary greenhouse gas emission reduction targets presented by Brazil at the United Nations Climate Change Conference (COP21) in Paris.

“The research done with support from the RPGCC contributes to the discovery of scientific pathways to the achievement of these targets,” Brito Cruz said. “We need to understand clearly which directions to take on the basis of what has been proposed, and science plays a key role in this.”