TREND ANALYSIS OF TROPOSPHERIC OZONE CONCENTRATIONS UTILIZING THE 20-YEAR DATA SET OF OZONE BALLOON SOUNDINGS OVER PAYERNE (SWITZERLAND)

The 20-year record of ozone balloon soundings from Payerne, Switzerland (2841 single ascents) shows a significant trend of rising tropospheric O3 since 1969, with averaged increases in annual mean concentrations of about 1% per year throughout the upper troposphere. To calculate O3 trends for the lower troposphere, one must apply a correction for the diurnal variation of the concentration of O3, because of several changes in balloon launch time. Corrected trend results reveal strongest increases just above the planetary boundary layer (800 mbar: mean annual increase of 1.6% per year) and in the planetary boundary layer (900 mbar: 1.4% per year). The trends were stronger for the cold season than for the summer months. Observed trends were large during 1982-1988 (3-4% annual increase above 2 km MSL). During 1969-1981 these trends were much less; they were statistically not significantly different from zero. The results of these trend analyses are discussed in the context of tropospheric O3 formation and atmospheric physics.