Corinne Vigouroux

Analysis of the origin of the distribution of CO in the subtropical southern Indian Ocean in 2007

We show carbon monoxide (CO) distributions at different vertical levels over the subtropical southern Indian Ocean, analyzing an observation campaign using Fourier transform infrared (FTIR) solar absorption spectrometry performed in 2007 at Reunion Island (21°S, 55°E). The CO pollution levels detected by the FTIR measurements during the campaign show a doubling of the CO total columns during the Southern Hemisphere biomass burning season. Using correlative data from the Measurement of Pollution in the Troposphere instrument and back trajectories analyses, we show that the potential primary sources for CO throughout the troposphere in 2007 are southern Africa (June-August) and South America (September-October). A secondary potential contribution from Southeast Asia and Indonesia-Malaysia was identified in the upper troposphere, especially in July and September. We examine the relation between the Asian monsoon anticyclone seasonal cycle and this result. We also investigate the relative contribution of different areas across the globe to the CO concentration in the subtropical southern Indian Ocean in 2007 using backward simulations combining the Lagrangian model FLEXPART 6.2, the Global Fire Emissions Database (GFEDv2.1) and the Emission Database for Global Atmospheric Research (EDGARv3.2-FT2000). We confirm the predominance of the African and South American contributions in the CO concentration in the southern subtropical Indian Ocean below 11 km. We show that CO transported from Australia makes only a small contribution to the total CO concentration observed over Reunion Island, and that the long-range transport of CO coming from Southeast Asia and Indonesia-Malaysia is important, especially from June until September in the upper troposphere.

The exploitation of ground-based Fourier transform infrared observations for the evaluation of tropospheric trends of greenhouse gases over Europe

Abstract Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such observations have regularly been made for many years as a contribution to the Network for the Detection of Stratospheric Change (NDSC). They are the only ground-based remote sensing observations available nowadays that carry information about a number of greenhouse gases in the free troposphere. This work focuses on the discussion of the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3 and CO and C2H6, respectively), at six NDSC stations in Western Europe. This European FTIR network covers the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances for the above-mentioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series are being made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model and, in particular, to optimize emission estimates that are used as inputs to the model simulations. The work is being performed within the EC project UFTIR. The paper focuses on N2O for which the first trend results have been obtained.