Investigating Temporal VOC Variation with Homogenized Glyoxal Retrieval

1. Investigating the temporal variation of VOCs using a homogenized glyoxal retrieval for different satellite platforms L.M.A. Alvarado1, A. Richter1, M. Vrekoussis1,2, F. Wittrock1, A. Hilboll1, S. F. Schreier1, and J. P. Burrows1 1Institute of Environmental Physics, University of Bremen, Bremen, Germany 2Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia, Cyprus, Greece DOAS workshop 8 July 2015

2. Outline • Motivation • Glyoxal retrieval • Satellite inter-comparison • Correlation with different sources • Summary Homogenized glyoxal retrieval

3. Motivation Retrieval Comparison Correlation Summary Motivation Volatile Organic Compounds (VOC) Secondary organic aerosol formation O3 formation VOC NOx (NO + NO2) Photochemical smog Human health effects Homogenized glyoxal retrieval

4. Motivation Retrieval Comparison Correlation Summary Glyoxal (CHO.CHO) intermediate product in the oxidation of most VOCs indicator of secondary aerosol formation in the atmosphere Deposition VOC (e.g., Aromatics, isoprene, terpenes, …) Major sinks: OH, photolysis, dry andwetdeposition. 27% 18% 55% Homogenized glyoxal retrieval

5. Motivation Retrieval Comparison Correlation Summary Glyoxal retrieval • The glyoxal columns are retrieved by the Differential Optical Absorption Spectroscopy (DOAS) method. • Instruments: SCIAMACHY, OMI, GOME-2(A&B) • Very sensitive to spectral interferences • Weak absorption in comparison to others species • The retrieval has been developed for OMI in 2014 (Alvarado et al., 2014) • Adapted and extended to SCIAMACHY and GOME-2(A&B) Homogenized glyoxal retrieval 5 5

6. Motivation Retrieval Comparison Correlation Summary • Using a high temperature NO2 cross-section reduces the high glyoxal values over regions with large anthropogenic NOx emissions. • A liquid water cross-section is introduced to reduce the number of negative glyoxal SCs over Pacific ocean. Two-step aproach as in Lerot et al., 2010 Homogenized glyoxal retrieval

7. Motivation Retrieval Comparison Correlation Summary • NormalizationoverthePacific ocean: constantoffsetof 8x1013 molec/cm2 • Mg II index is frequently used as a proxy for spectral solar irradiance variability from the UV • Instruments using an imaging spectrometer such as OMI, offsets (”stripes”) are sometimes observed between viewing directions • Destriping correction needs to be applied to the OMI measurements Homogenized glyoxal retrieval

8. Motivation Retrieval Comparison Correlation Summary Pacific region as reference spectrum I0 I absorption term residual polynomial spectra • Stripes are cancelled out Homogenized glyoxal retrieval

9. Motivation Retrieval Comparison Correlation Summary • Advantages • Cancellation of stripes • Significant reduction in the residual • The number of negative SCs is reduced and no seasonal variability is observed over the Pacific Pacific region as reference spectrum has been already used in other studies (e.g. NO2: Anand et al., 2015; HCHO: De Smedt et al., 2008; IO: Schönhardt et al., 2008) Homogenized glyoxal retrieval

10. Motivation Retrieval Comparison Correlation Summary Sun vs Pacific region CHN NA IND AFC SA AUS • Good temporal agreement between datasets • Some differences are found between datasets for January • High correlation between retrievals Homogenized glyoxal retrieval

11. Motivation Retrieval Comparison Correlation Summary Satellite intercomparison *Onlyfor GOME-2 (A&B) • Consistency between the global fields of glyoxalcolumns for all instruments • Strong glyoxal signal in the Tropics where the most important biogenic emissions and fire events take place Homogenized glyoxal retrieval

12. Motivation Retrieval Comparison Correlation Summary CHN NA IND AFC SA AUS • Similar temporal variability • In some regions OMI CHOCHO VC are lower than those from SCIAMACHY and GOME-2(A&B) Homogenized glyoxal retrieval

13. Motivation Retrieval Comparison Correlation Summary Correlation with different sources • Enhanced Vegetation Index (EVI) and Fire Radiative Power (FRP) from MODIS on board of NASA’s Aqua and Terra satellites can be used as indicators of biogenic and pyrogenic emissions, respectively. • Similar seasonal behaviour between CHOCHO and FRP and EVI where high correlations between them are found Homogenized glyoxal retrieval

14. Motivation Retrieval Comparison Correlation Summary Monthly mean of NO2 VC from OMI measurements. This is an indicator of anthropogenic emissions 2011 • Good correlation between CHOCHO and NO2 over PRD, but low for NE. China • Correlation between CHOCHO and NO2 is improved if summer is excluded • Less CHOCHO is removed by photolysis Homogenized glyoxal retrieval

15. Motivation Retrieval Comparison Correlation Summary Ratio of Glyoxal to Formaldehyde (RGF) for GOME-2A • Large RGF over regions with large fire emissions and small for regions dominated by biogenic activities • The ratioGF behaves similar to the glyoxal over the seasons • Close to the equator, the CHOCHO seasonal variation is quite smooth • CHOCHO from biogenic sources at higher latitudes has a clear seasonal cycle with maximum in JJA • No significant differences are observed between seasons over highly polluted regions Homogenized glyoxal retrieval

16. Motivation Retrieval Comparison Correlation Summary Summary • A homogenized glyoxal retrieval has been developed for four different satellite instruments • Most glyoxal is located over (sub)tropical regions, where abundant vegetation is found and fire events occur • Hot-spots can also be identified over polluted areas • The maximum production of glyoxal is found in the warm season, which corresponds to the major growing period of plants • Good correlations are found between glyoxal columns and indicators of biogenic, pyrogenic, and anthropogenic emissions Homogenized glyoxal retrieval

17. Acknowledgements • DAAD and University of Bremen for funding this project • ESSRES for support • OMI lv1 and MODIS FRP and EVI data have been provided by NASA. • DOAS group at the Institute of Environmental Physics Bremen (IUP-Bremen) Thankyouforyourattention! Homogenized glyoxal retrieval