Glyoxal yield from isoprene oxidation and relation to formaldehyde: chemical mechanism, constraints from SENEX aircraft observations, and interpretation of OMI satellite data

摘要: Abstract. Glyoxal (CHOCHO) is produced in the atmosphere by oxidation of volatile organic compounds (VOCs). Like formaldehyde (HCHO), another VOC product, it measurable from space solar backscatter. Isoprene emitted vegetation dominant source CHOCHO and HCHO most world. We use aircraft observations SENEX campaign over southeast US summer 2013 to better understand time-dependent yield isoprene oxidation, its dependence on nitrogen oxides (NOx  ≡  NO + NO2), behavior CHOCHO–HCHO relationship, quality OMI satellite observations, implications for using as constraints emissions. simulate with Goddard Earth Observing System chemical transport model (GEOS-Chem) featuring a new mechanism formation isoprene. The includes prompt under low-NOx conditions following isomerization peroxy radical (ISOPO2). provide support this pathway, are generally consistent GEOS-Chem mechanism. Boundary layer strongly correlated model, some departure due formation. vertical profiles indicate free-tropospheric background that absent model. data show enhancements but factor 2 too low. Part bias excessive surface reflectivities assumed retrieval. seasonal tightly redundant proxies Higher temporal resolution future geostationary may enable detection production apparent data.