The NOy budget above Jungfraujoch: long-term evolution, family partition and model comparison

Based on high-resolution solar spectra recorded with FTIR instruments at the University of Liège laboratory located at the Jungfraujoch NDSC station (Swiss Alps, 46.5ºN, 8ºE, altitude 3580 m), the most important constituents making up the NOy family have been measured consistently since the mid-1980s. They include HNO3, NO, NO2 and ClONO2, which are analyzed in terms of their vertical column abundances above the site. Related trends have been determined and assessed statistically. Among these, only ClONO2 and NO2 reveal significant long-term trends. The combined column evaluation of NOy indicates a rate of change equal to (0.1+/-0.2) %/year, thus statistically undefined and barely consistent with the evolution of the source gas N2O. Trends derived from the observations will be compared critically with those deduced from a long-term run of a 2-D stratospheric model developed at the University of Oslo. The model includes full gaseous chemistry, PSCs and sulfate particles, which vary from year to year. Comparisons with similar data found in the literature are also discussed.