SURFACE OZONE IN ATHENS, GREECE, AT THE BEGINNING AND AT THE END OF THE 20TH-CENTURY

Atmospheric ozone at the surface was monitored in Athens, Greece during the first four decades of the twentieth century using De James colometric papers. This historic record is analysed in conjuction with present ozone measurements in Athens (1987-1990) to show an increase of the ozone mixing ratio from 28.2 to 57.4 ppb for daytime, and from 26.6 to 48.5 ppb for nighttime. The annual cycle of surface ozone contains one maximum for the daytime data and two maxima for the nighttime data, the situation being reversed when a subperiod (1901-1907) of the historic record is considered. Comparison of this subperiod to the Montsouris data show higher ozone levels in Athens, and in phase annual cycles. Finally, harmonic analysis of the historic and present records for Athens, shows-in addition to the well known 12-month and 6-month waves-a relatively strong 4-month wave in surface ozone, and a shift in the time of ozone maximum for both daytime and nighttime ozone data.