PNNL

The Science

As the heat engine of our planet, storm systems from the tropics drive climate and weather patterns around the globe.

A new paper summarizes the two-year, multi-agency effort for routine collection of cloud observations and environmental conditions during the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) field campaign led by the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility, a scientific user facility.

This effort quantifies the propensity for convective clouds to initiate, deepen, and organize across the Amazon basin, the radiative impacts of those clouds, and increases in clouds and precipitation observed during the Amazon wet season (December through April).

The Impact

The long-term Amazonian ground deployment and two short-term aircraft intensive observing periods provide a rich data set for studies of cloud and aerosol life cycles, including cloud-aerosol-precipitation interactions and the influences of a pollution plume from the Brazilian city of Manaus. The observations help characterize the cloud life cycle, the effects on Earth's energy balance, and cloud-aerosol interactions for an undersampled yet climatically important Amazon basin region in support of improving Earth system modeling capabilities.

Summary

The Amazon forest is the largest tropical rainforest on Earth, featuring prolific and diverse cloud conditions. GoAmazon2014/5, which involved observations collected from ARM mobile and aerial facilities, was motivated by the need for scientists to gain a better understanding of how aerosol and cloud interactions influence climate and the global circulation. Researchers summarized the routine ARM observations from this two-year campaign to help quantify large-scale environmental controls on clouds and precipitation over an undersampled Amazon basin region.

Covering both wet and dry seasons, the study contrasted daily cycles of large-scale environmental conditions, cloud fractions classified by cloud types, their surface radiative effects, and associated precipitation. It also documented substantial increases in wet season cloud frequency, propensity for widespread precipitation, and precipitation accumulation.

Researchers found that shallow cumulus clouds played a dominant role in affecting energy balance at the surface during both wet and dry seasons. Aircraft observations also showed the increased aerosol concentrations during the dry season reduced cloud particle sizes and increased cloud particle concentrations compared to the wet season, ultimately altering shallow clouds' impact on the surface energy balance.

The rich GoAmazon2014/5 data set supports future opportunities for process studies to better understand coupled cloud-aerosol interactions.

Acknowledgments

Sponsors: Zhe Feng of Pacific Northwest National Laboratory is supported by the U.S. Department of Energy (DOE) as part of the Atmospheric System Research (ASR) program. Lawrence Livermore National Laboratory was supported by the DOE ARM program. Funding was also obtained from DOE, the São Paulo Research Foundation (FAPESP - 2009/15235-8), the Amazonas State University (UEA), and the Amazonas Research Foundation (FAPEAM - 062.00568/2014). The work was conducted under scientific licenses 001030/2012-4, 001262/2012-2, and 00254/2013-9 of the Brazilian National Council for Scientific and Technological Development (CNPq). Institutional support was provided by the Central Office of the Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA), the National Institute of Amazonian Research (INPA), the National Institute for Space Research (INPE), and the Brazil Space Agency (AEB).

Facilities: The ARM Climate Research Facility, a DOE Office of Science user facility sponsored by the Office of Biological and Environmental Research

Reference: S.E. Giangrande, Z. Feng, M.P. Jensen, J.M. Comstock, K.L. Johnson, T. Toto, M. Wang, C. Burleyson, N. Bharadwaj, F. Mei, L.A.T. Machado, A.O. Manzi, S. Xie, S. Tang, M.A.F. Silva Dias, R.A.F. de Souza, C. Schumacher, S.T. Martin, "Cloud Characteristics, Thermodynamic Controls and Radiative Impacts During the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) Experiment." Atmospheric Chemistry and Physics 17, 14519-14541 (2017). [DOI: 10.5194/acp-17-14519-2017]