Co-located column and in situ measurements of CO2 in the tropics compared with model simulations
1Institute of Environmental Physics, University of Bremen, Bremen, Germany
2Max Planck Institute for Biogeochemistry (MPI-BGC), Jena, Germany
3Alfred Wegener Institute for Polar and Marine Research (AWI), Bremerhaven, Germany
Abstract. The first ground-based remote sensing measurements of the column averaged volume mixing ratio of CO2 (XCO2) for the inner tropics have been obtained at Paramaribo, Suriname (5.8° N, 55.2° W). The remote sensing observations are complemented by surface air-samples collected at the site, analyzed for CO2 and 13CO2. The surface in-situ measurements are strongly influenced by local sources. From the isotopic composition of the air samples the local source component is suggested to be dominated by the terrestrial biosphere. Using δ13C from the NOAA/ESRL stations Ascension Is. (ASC), 7.9° S, 14.4° W, and Ragged Point (RPB), 7.9° S, 14.4° W, the data has been corrected for the local source component. Due to the migration of the ITCZ over the measurement site the probed air masses belong to the Northern or Southern Hemisphere depending on the time of the year. Comparison to analyzed CO2 fields based on TM3 model simulations using optimized fluxes indicate agreement for XCO2 as well as for the corrected CO2 mixing ratios at the surface for the long dry season, when Paramaribo belongs to the Southern Hemisphere. A slightly worse agreement during the short dry season is attributed to a larger representation error during this time of the year. Overall the comparison demonstrates that the TM3 model is capable to simulate surface concentrations as well as column densities of CO2 correctly at the same location.