TREND OF OZONE IN THE FREE TROPOSPHERE ABOVE EUROPE

Ozone observations were made one century ago by the Schonbein technique at meteorological observatories in the alpine region. Within the intrinsic limitations of the technique, historical readings have been converted to present-time concentrations (p.p.b.v.). The evaluated ozone level in the free troposphere (17 p.p.b.v.) was twice as large as at the surface; comparable values were obtained by chemical and spectroscopic technique in the first half of our century. Furthermore, the reconstructed ozone trend in the free troposphere shows a sharp increase after the '50s, as already observed at the surface at midlatitudes of the northern hemisphere.