Aircraft measurements of nitrogen oxides, ozone, and carbon monoxide during MINOS 2001: distributions and correlation analyses

Abstract. We present mean altitude profiles of NO_x, NO_y, O₃, and CO as measured by the DLR Falcon aircraft during the MINOS 2001 campaign over the Mediterranean in August 2001 and compare the data with results from other aircraft campaigns, namely the SIL 1996 (North Atlantic flight corridor), the POLINAT-2 (North Atlantic flight corridor), and the EXPORT 2000 (central Europe) campaigns. The MINOS NO_y, O₃, and CO mixing ratios in the free troposphere, especially between 4–8 km, are very similar to those measured during the EXPORT 2000 campaign. However, compared to the other campaigns the MINOS O₃ and CO were significantly higher in the boundary layer, by about 20 ppbV and 50 ppbV, respectively. In the second part of the paper the D[O₃]/D[NO_y], D[O₃]/D[CO], D[CO]/D[NO_y], and D[NO_x]/D[NO_y] trace gas correlations were calculated for the MINOS 2001 campaign. It was found that, within the scatter of the data, the overall average altitude profiles of the correlations compared well with data from a literature survey. The analysis of the mean vertical correlation profiles as measured during MINOS 2001 does therefore not single out special meteorological conditions and air mass origins over the Mediterranean in summer but reflects a more general condition of the free troposphere in the northern hemisphere. Correlation analyses for single flights at different altitudes, however, unambiguously identify air masses influenced by the stratosphere, whereas pollution plumes could only be identified with the help of back trajectories.