Processes influencing rainfall features in the Amazonian region

Monday, 15 December 2014: 8:30 AM
Tobias Gerken1, Marcelo Chamecki2, Jose D Fuentes1, Gabriel George Katul3, David R Fitzjarrald4, Antonio O Manzi5, Rosa M Nascimento dos Santos6, Celso von Randow7, Paul C Stoy8, Julio Tota9, Amy Trowbridge10, Courtney Schumacher11 and Luiz Machado7, (1)Pennsylvania State University, University Park, PA, United States, (2)Pennsylvania State University, Department of Meteorology, University Park, PA, United States, (3)Duke University, Durham, NC, United States, (4)State University of New York at Albany, Albany, NY, United States, (5)Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil, (6)University of the State of Amazonas (UEA), Manaus, Brazil, (7)Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil, (8)Montana State University, Bozeman, MT, United States, (9)Federal University of West Para, Institute of Engineering and Geoscience, Santarem, PA, Brazil, (10)Indiana University Bloomington, Bloomington, IN, United States, (11)Texas A&M Univ, College Station, TX, United States
The Amazon is globally unique as it experiences the deepest atmospheric convection with important teleconnections to other parts of the Earth’s climate system. In the Amazon Basin a large fraction of the local evapotranspiration is recycled through the formation of deep convective precipitating storms. Deep convection occurs due to moist thermodynamic conditions associated with elevated amounts of convective available potential energy. Aerosols invigorate the formation of convective storms in the Amazon via their unique concentrations, physical size, and chemical composition to activate into cloud condensation nuclei (CCN), but important aspects of aerosol/precipitation feedbacks remain unresolved. During the wet season, low atmospheric aerosol concentrations prevail in the pristine tropical air masses. These conditions have led to the Green Ocean hypothesis, which compares the clean tropical air to maritime air-masses and emphasizes biosphere-atmosphere feedbacks, to explain the features of the convective-type rainfall events in the Amazon. Field studies have been designed to investigate these relationships and the development of mesoscale convective systems through the Green Ocean Amazon project and the GOAmazon Boundary Layer Experiment.

From March to October 2014 a field experiment was conducted at the Cuieiras Biological Reserve (2°51' S, 54°58' W), 80 km north of the city of Manaus, Brazil. This investigation spans the biological, chemical, and physical conditions influencing emissions and reactions of precursors (biogenic and anthropogenic volatile organic compounds, VOCs), formation of aerosols and CCNs and transport out of the ABL, and their role in cloud formation and precipitation triggers. In this presentation we will show results on the magnitude turbulent fluxes of latent and sensible heat, CCN concentrations, and rain droplet size distribution for both the wet and dry season. Such influencing factors on precipitation, will be contrasted with the vertical contoured frequency-by-altitude diagrams (CFADs) for representative mesoscale convective systems for dry and wet seasons. Rainfall yields from mesoscale convective storms will be linked to the antecedent thermodynamic conditions derived from analyses of upper air soundings.