The assessment of the seasonal contribution of the anthropogenic sources to the carbon monoxide budget in Europe

This study aims to obtain a simplified understanding of the European carbon monoxide (CO) budget, specifically focusing on the seasonal variability of sources and sinks with the help of a box-model. The information provided by such a model can be meaningful as a first order estimate for the CO budget in Europe, which is one of the main source regions of anthropogenic CO. The model allows the assessment of the incremental change in atmospheric CO concentration caused by the CO direct emission and CO chemical production in Europe. The output of the model is validated against available observational data, both in absolute terms and with respect to the seasonal variation of CO mixing ratio. Furthermore, the first order source apportionment provided by the model is compared to those retrieved from global 3D chemical-transport models (CTMs). The total incremental change caused by the European sources is estimated to be 91.4±21.1 Tg CO yr−1, while the inward advection is 52.2±13.8 Tg CO yr−1. The annual share of the primary and secondary anthropogenic sources is about 85±10% in the total. The total sink strength, including outward advection, reaction with hydroxyl radicals and dry deposition, is calculated to be 150.0±49.4 Tg CO yr−1. It should be noted that the outward advection represents 80±10% of the total sink strength.