Evaluation of CO Simulations and the Analysis of the CO Budget for Europe

Carbon Monoxide (CO) is a well-suited indicator for the transport of pollutants in the troposphere on a regional and global scale. For the study presented here, simulations of CO concentrations from a global chemistry-transport model (MOZART-2) have been used to diagnose the contributions of different processes and sources on the CO load over Europe. The CO molecules in the model were tagged according to the emission type and the source region. A set of optimized surface emissions has been incorporated in the model runs derived by inversion of modeled CO concentrations with CO data from the Measurements of Pollution in the Troposphere (MOPITT) remote-sensing instrument. The evaluation of the model simulations is based on an extensive comparison with remote-sensing, aircraft, and ground-based CO measurements. The results indicate that the model values represent the background conditions as well as the large scale transport over Europe relatively well, and, therefore, are suited for studying the CO budget over Europe. The analysis of the tagged model simulations shows the predominating impact of European emissions on CO concentrations over Europe near the surface, and a strong influence of sources from North America and Asia on the CO load in the free troposphere. Focus has been set mainly on CO emitted from technological sources, biofuel use, and biomass burning, which together contribute to the total CO concentrations over Europe by about 40-70% near the surface, and by about 30-60% at 500hPa. The contributions from other sources (e.g. biogenics, photochemistry,...) on the CO burden over Europe are outlined too.