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Model simulations and aircraft measurements of vertical, seasonal and latitudinal O3 and CO distributions over Europe
During a series of 8 measurement campaigns within the SPURT project (2001-2003), vertical profiles of CO and O3 have been obtained at subtropical, middle and high latitudes over western Europe, covering the troposphere and lowermost stratosphere up to ~14 km altitude during all seasons. The seasonal and latitudinal variation of the measured trace gas profiles are compared to simulations with the chemical transport model MATCH. In the troposphere reasonable agreement between observations and model predictions is achieved for CO and O3, in particular at subtropical and mid-latitudes, while the model overestimates (underestimates) CO (O3 in the lowermost stratosphere particularly at high latitudes, indicating too strong simulated bi-directional exchange across the tropopause. By the use of tagged tracers in the model, long-range transport of Asian air masses is identified as the dominant source of CO pollution over Europe in the free troposphere
Ozone production and trace gas correlations during the June 2000 MINATROC intensive measurement campaign at Mt. Cimone
An intensive measurement campaign was performed in June 2000 at the Mt. Cimone station (44°11' N-10°42' E, 2165 m asl, the highest mountain in the northern Italian Apennines) to study photochemical ozone production in the lower free troposphere. In general, average mixing ratios of important trace gases were not very high (121 ± 20 ppbv CO, 0.284 ± 0.220 ppbv NOx, 1.15 ± 0.8 ppbv NOy, 58 ± 9 ppbv O<sub>3</sub>), which indicates a small contribution by local pollution. Those trace gas levels are representative of continental background air, which is further supported by the analysis of VOCs (e.g.: C<sub>2</sub>H<sub>6</sub> = (905 ± 200) pptv, C<sub>3</sub>H<sub>8</sub> = (268 ±110) pptv, C<sub>2</sub>H<sub>2</sub> = (201 ± 102) pptv, C<sub>5</sub>H<sub>8</sub> = (111 ± 124) pptv, benzene = (65 ± 33) pptv). Furthermore, significant diurnal variations for a number of trace gases (O<sub>3</sub>, CO, NOx, NOy, HCHO) indicate the presence of free tropospheric airmasses at nighttime as a consequence of local catabatic winds. Average mid-day peroxy radical concentrations at Mt. Cimone are of the order of 30 pptv. At mean NO concentrations of the order of 40 pptv this gives rise to significant in situ net O<sub>3</sub> production of 0.1-0.3 ppbv/hr. The importance of O<sub>3 </sub>production is supported by correlations between O<sub>3</sub>, CO, NOz, and HCHO, and between HCHO, CO and NOy