Oxygenated volatile organic compounds in the Tropical Atmosphere: Variability and Exchanges (OCTAVE)
Earth and related Environmental sciences
MetadataShow full item record
Oxygenated Volatile Organic Compounds (OVOCs) have a significant impact on the atmospheric oxidative capacity and climate. Methanol, acetaldehyde and acetone are among the most abundant OVOCs, especially in the marine atmosphere where they make up 37-63% of the total non-methane volatile organic carbon. Their sources include terrestrial vegetation, oceans, the oxidation of VOCs, biomass burning and anthropogenic emissions. However, large discrepancies in OVOC budget estimates still exist, mostly due to incomplete representation of photochemical OVOC production, and uncertainties in terrestrial emissions and ocean/atmosphere exchanges of OVOCs and their precursors. The paucity of OVOC observations in tropical regions strongly contributes to those uncertainties. Although ocean/atmosphere exchanges of OVOCs are significant, their magnitude and direction remain poorly constrained. Very large, yet unexplained model underestimations of observed acetaldehyde concentrations have been reported at remote tropical locations, which might imply the existence of so far unknown sources of acetaldehyde or its precursors. Also, for methanol, a large photochemical source has been recently identified, the CH3O2+OH reaction, of magnitude comparable to the combined terrestrial emissions. Although this source might provide a long-needed explanation for persistent model underestimations over remote tropical oceans, its precise magnitude and its implications for global budget assessments remain unclear. For acetone as well, models fail to predict their observed seasonal variability. A better understanding of OVOC sources and sinks is required to quantify their impact on atmospheric oxidants, on the lifetime of methane and consequently on climate.