Assessing acetone for the GISS ModelE2.1 Earth system model

Abstract. Acetone is an abundant volatile organic compound in the atmosphere with important influence on ozone and oxidation capacity. Direct sources include anthropogenic, terrestrial vegetation, oceanic, and biomass burning emissions. Acetone is also produced chemically from other volatile organic compounds. Sinks include deposition onto the land and ocean surfaces, as well as chemical loss. Acetone’s lifetime is long enough to allow transport and reactions with other compounds remote from its sources. The latest NASA Goddard Institute for Space Studies (GISS) Earth System Model, ModelE2.1, simulates a variety of Earth system interactions. Previously, acetone had a very simplistic representation in the ModelE chemical scheme. This study assesses a more sophisticated acetone scheme, in which acetone is a full 3-dimensional tracer, with explicit sources, sinks and atmospheric transport. We evaluate the new global acetone budget in the context of past literature. Anthropogenic emissions, vegetation emissions, biomass burning, and deposition representations agree well with previous studies. Chemistry and the ocean contribute to both sources and sinks of acetone, with their net values agreeing with the literature, although their individual source and sink terms appear to be overestimated for chemistry and underestimated for ocean fluxes. We find the production of acetone from precursor hydrocarbon oxidation has strong leverage on the overall chemical source, indicating the importance of accurate molar yields for this source. Spatial distributions reveal that ocean uptake of acetone is strongest in northern latitudes, while production is mainly in mid-southern latitudes. The seasonality of acetone-related processes was also studied in conjunction with field measurements around the world. These comparisons show promising agreement, but have shortcomings at urban locations, since the model’s resolution is too coarse to capture behavior in high-emission areas. Overall, our analysis of the acetone budget aids the development of this tracer in the GISS ModelE2.1, a crucial step to understanding the role of acetone in the atmosphere.