Preview

PDF, English Download (13MB) | Terms of use

Abstract

Tropospheric glyoxal mixing ratios and vertical column densities were measured during 72 research flights with the German research aircraft DLR HALO over different regions etween 2014 and 2019. Over the Amazon rainforest, the bservations are complemented by simultaneous formaldehyde and methylglyoxal measurements. The glyoxal measurements are confirmed by same-day observations of the TROPOMI satellite instrument and compared to simulations of the photochemical transport model EMAC. Deviations of air- and spaceborne glyoxal are found for spatially small pollution plumes and those located near the surface. This causes smaller satellite glyoxal measurements around urban centres. Unexplained glyoxal enhancements are detected repeatedly in aged biomass burning plumes and the tropical marine boundary layer. Over the rainforest, emission factors are estimated for tropical forest fires (0.11–0.52 gglyoxal kg−1 fuel, 0.50–8.64 gmethylglyoxal kg−1 fuel) and isoprene is identified as a potential glyoxal and methylglyoxal precursor above the boundary layer. The comparison to EMAC shows an underestimation of modelled glyoxal in most regions, especially in the boundary layer and pollution plumes. This is indicative of an underestimation of glyoxal and its precursors by EMAC, with consequences for the tropospheric oxidative capacity as well as the formation of ozone and secondary organic aerosols and hence for the radiative forcing.