Isoprene is the dominant volatile organic compound emitted by the biosphere into the atmosphere, and its oxidation by OH is a major formaldehyde (HCHO) source within the continental boundary layer. Both species are short-lived, with HCHO removed by photolysis as well as by OH, giving rise to a tight, near-linear correlation between the isoprene:HCHO column ratio and 1/[OH] over isoprene-dominant regions. In this work, we use variations and trends in this column ratio to assess changes in atmospheric oxidation across key source regions from 2012-present using measurements from CrIS and OMPS onboard Suomi-NPP. Using a chemical transport model (GEOS-Chem) to help guide interpretations, we observe an influence of El Niño on atmospheric OH over tropical Amazonia and Southeast Asia in 2015-2016. Additionally, in a more anthropogenically-influenced isoprene source region such as the southern USA, a modeled OH decrease from 2012-present is contradicted by satellite observations which shows no consistent OH trend. Overall, the isoprene:HCHO column ratio provides a framework to assess how the biosphere in a changing climate is influencing the atmosphere’s oxidizing capacity across time and space.

Determining changes in atmospheric oxidation over biogenic source regions using satellite-derived measurements of isoprene and formaldehyde

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