Meteorology, turbulence and air chemistry in the Amazonian rainforest
Authors
Marcelo Chamecki — University of California, Los Angeles
David Roy Fitzjarrald — University of Albany
Gabriel George Katul — Duke University
Paul Christopher Stoy — Montana State University
Jose D Fuentes — Pennsylvania State University
Antonio Ocimar Manzi — Instituto Nacional de Pesquisas da Amazonia
Tobias Gerken — The Pennsylvania State University
Rosa Maria Nascimento dos Santos — Universidade do Estado do Amazonas (UEA)
Celso Von Randow — National Institute for Space Research (INPE)
Livia Souza Freire —
Category
General Topics – Aerosol
Description
This presentation provides an overview of a field project in the Brazilian rainforest conducted during April to December 2014. Objectives were to investigate turbulent transport and chemical processing of hydrocarbons to assess the role of the forest in aerosol production. Ten sonic anemometers were deployed on a 50-m tower to study turbulence. Distribution of plant-emitted hydrocarbons, and reactive chemical species such as ozone, carbon monoxide, sulfur dioxide, and nitrogen oxides were determined using gas analyzers and mass spectrometers to estimate aerosol yields. Particle sizes and concentrations were investigated with aerosol spectrometers. The upper canopy experienced strong turbulence, with standard deviation of vertical velocity normalized by the friction velocity similar to values above the forest. The lower canopy maintained a quiescent state with turbulence being four times weaker than near the canopy top. Such weak turbulence is conducive to the development of strong and pronounced hydrocarbon mixing ratio mean gradients within the canopy, with highest gas levels within the forest crown responding to strong emissions. Different levels of atmosphere-forest coupling were observed, indicating a broad range of mixing conditions. Periods of strong coupling favor fast transport of hydrocarbons out of the canopy, but also provide conditions for enhanced ozone levels in the forest. The forest emitted monoterpenes, resulting in a total sum exceeding one parts per billion (ppb). During the wet season, ozone levels ranged from 5 to 10 ppb due to the frequent presence of clouds and precipitation. However, following the passage of mesoscale convective storms, ozone levels abruptly increased in response to downward transport from aloft. Such enhancements can be as high as 30 ppb. Photochemical process resulted in low particle concentrations (<104 particles cm-3), dominated by small diameter (< 400 nanometers) particles. One conclusion is that the rainforest produces necessary and sufficient precursors to form particles.
