G. Ancellet et M. Beekmann, EVIDENCE FOR CHANGES IN THE OZONE CONCENTRATIONS IN THE FREE TROPOSPHERE OVER SOUTHERN FRANCE FROM 1976 TO 1995, Atmospheric environment, 31(17), 1997, pp. 2835-2851
Tropospheric ozone measurements were performed at the Observatoire de
Haute Provence (OHP) in Southern France by three instruments during th
e last 10 yr: Brewer Mast (BM) ozonesondes 1985/1991, ECC ozonesondes:
1991/1995, lidar: 1990/1995. The error analysis shows an overall accu
racy of 10% for the BM sondes and lidar data, and 5% for the ECC sonde
s. A comparison of the tropospheric seasonal means above 3 km shows th
at the differences between the three instruments are within the instru
ment accuracy. The OHP ECC data are also compared to the 1976/1983 ozo
ne measurements performed with BM sondes at the Biscarosse station als
o in Southern France to estimate possible tropospheric ozone changes d
uring the 1980s. Yearly mean values imply a maximum annual ozone incre
asing rate of 8 +/- 2% per decade in the 1980s, but this trend becomes
insignificant if one includes the usual - 15% bias between BM and ECC
. The shift of the seasonal variation from a spring maximum to a sprin
g/summer maximum is however statistically significant during the 1980s
. In the upper troposphere, the seasonal means are studied using a hei
ght scale relative to the tropopause, showing a similar seasonal varia
tion than in the mid-troposphere, Also an increase of the ozone spring
/summer maximum with the altitude is shown. A negative trend of - 10%/
decade is inferred at the tropopause level using the OHP and Biscaross
e data. (C) 1997. Published by Elsevier Science Ltd.