Atmos. Chem. Phys. Discuss., 13, 6165-6218, 2013
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Atmospheric inversion of SO2 and primary aerosol emissions for the year 2010
N. Huneeus1, O. Boucher1, and F. Chevallier2
1Laboratoire de Météorologie Dynamique, IPSL, UMR8539, CNRS/UPMC, Paris, France
2Laboratoire des Sciences du Climat et de l'Environnement, IPSL, UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, France

Abstract. Natural and anthropogenic emissions of primary aerosols and sulphur dioxide (SO2) are estimated for the year 2010 by assimilating daily total and fine mode aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument into a global aerosol model of intermediate complexity. The system adjusts monthly emission fluxes over a set of predefined regions tiling the globe. The resulting aerosol emissions improve the model performance, as measured from usual skill scores, both against the assimilated observations and a set of independent ground-based measurements. The estimated emission fluxes are 67 Tg S yr−1 for SO2, 12 Tg yr−1 for black carbon (BC), 87 Tg yr−1 for particulate organic matter (POM), 17 Pg yr−1 for sea salt (SS, estimated at 80% relative humidity) and 1206 Tg yr−1 for desert dust (DD). They represent a difference of +53%, +73%, +72%, +1% and −8%, respectively, with respect to the first guess (FG) values. Constant errors throughout the regions and the year were assigned to the a priori emissions. The analysis errors are reduced for all species and throughout the year, they vary between 3% and 17% for SO2, 1% and 130% for biomass burning, 25% and 89% for fossil fuel, 1% and 200% for DD and 1% and 5% for SS. The maximum errors on the global-annual scale for the estimated fluxes (considering temporal error dependence) are 12% for SO2, 39% for BC, 41% for POM, 43% for DD and 40% for SS. These values represent a decrease as compared to the global-annual errors from the FG of 12% for SO2, 42% for BC, 47% for POM, 50% for DD and 95% for SS. The largest error reduction, both monthly and yearly, is observed for SS and the smallest one for SO2. The sensitivity and robustness of the inversion system to the choice of the first guess emission inventory is investigated by using different combinations of inventories for industrial, fossil fuel and biomass burning sources. The initial difference in the emissions between the various setups is reduced after the inversion. Furthermore, at the global scale, the inversion is sensitive to the choice of the BB inventory and not so much to the industrial and fossil fuel inventory. At the regional scale, however, the choice of the industrial and fossil fuel inventory can make a difference. The estimated baseline emission fluxes for SO2, BC and POM are within the estimated uncertainties of the four experiments. The resulting emissions were compared against projected emissions for the year 2010 for SO2, BC and POM. The new estimate present larger emissions than the projections for all three species, with larger differences for SO2 than POM and BC. These projected emissions are in general outside the uncertainties of the estimated emission inventories.

Citation: Huneeus, N., Boucher, O., and Chevallier, F.: Atmospheric inversion of SO2 and primary aerosol emissions for the year 2010, Atmos. Chem. Phys. Discuss., 13, 6165-6218, doi:10.5194/acpd-13-6165-2013, 2013.
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