Temporal and spatial variability of glyoxal as observed from space

Abstract

Abstract. Glyoxal, CHO.CHO, is produced during the oxidation of volatile organic compounds, VOC, released by anthropogenic activities, biogenic processes and biomass burning. It has a short chemical lifetime of a few hours in the boundary layer and lower troposphere and therefore serves as an indicator and a marker of photochemical hotspots and their response to changing atmospheric conditions around the globe. For this reason more than five years of CHO. CHO observations (2002CHO observations ( -2007, retrieved from the radiances measured by the satellite instrument SCIAMACHY, were obtained and analyzed both temporally and spatially. The largest columns of CHO.CHO (>6.10 14 molec cm −2 ) are found in the tropical and sub-tropical regions, associated with high biological activity and the plumes from vegetation fires. The majority of the identified hot spots are characterized by a well-defined seasonality: the highest values being observed during the warm and dry periods as a result of the enhanced biogenic, primarily isoprene, emissions and/or biomass burning from natural or man-made fires. The regions influenced by anthropogenic pollution also encounter enhanced amounts of glyoxal. The ratio "CHO.CHO to HCHO, R GF " over the biogenically influenced photochemical hot-spots is approximately 0.045. For the studied regions, the presence of pyrogenic and anthropogenic emissions increases and decreases this number respectively. Although the 2002-2007 period of observation is limited, over the northeastern Asia a significant annual increase in CHO.CHO in addition to a seasonal cycle is reported.

Measurements of volatile organic compounds over West Africa

“…Recent satellite observations indicate that the column density in this region and season is approximately 5×10 14 molec cm −2 (Stavrakou et al, 2009). To give an upper estimate for a mixing ratio, if one assumes this resides entirely in a 1 km deep mixed layer at the surface, this results in a mixing ratio of ∼200 ppt, in the same range as in situ measurements compiled in Vrekoussis et al (2009). While we cannot rule out the possibility that this compound makes a contribution at m/z=59, it is likely minor compared to the significant amounts of acetone.…”

Glyoxal vertical columns from GOME-2 backscattered light measurements and comparisons with a global model

“…However, discrepancies arise when comparing model results with the space-based glyoxal column data set from the SCIAMACHY instrument (Wittrock et al, 2006;Vrekoussis et al, 2009). It turns out that models generally underpredict the observed glyoxal columns over both continental and oceanic regions.…”

Systematic analysis of tropospheric NO<sub>2</sub> long-range transport events detected in GOME-2 satellite data

“…NO 2 and glyoxal (CHOCHO) from large bush fires such as the Black Saturday fires are routinely observed in satellite data (Wittrock et al, 2006;Vrekoussis et al, 2009) and GOME-2 data show elevated NO 2 vertical column densities over southwestern Australia on 25 and 26 April 2008 -on the order of 3 × 10 15 molecules cm −2 , a factor 2 higher than background levels. It is likely, that our data product underestimates these values due to a lowered air-mass factor in the presence of black carbon aerosol in bush fire smoke plumes (Martin et al, 2003;Leitão et al, 2010;Giles et al, 2012).…”