Figure 2-6: (a) Median NOx mixing ratios measured between
9 and 12 km during a number of in situ aircraft campaigns (compiled in Emmons
et al., 1997); (b) NOx concentration field in the altitude regions between
300 and 190 hPa obtained by the measurements of NOxAR. As an example, the
results for summer are shown. The aircraft carrying the NOxAR instruments
operated from Z�rich to destinations in the USA and the far East (Beijing
and Bombay-Hong Kong) from spring 1995 to spring 1996.