THE OZONE RECORD AT PAYERNE - AN ASSESSMENT OF THE CROSS-TROPOPAUSE FLUX

Ozone soundings from the 21-year record at Payerne (47-degrees-N, 7-degrees-E) are analysed. At the 300 mb level a simple statistical technique makes it possible to distinguish between the ozone of tropospheric photochemical origin and that in stratospheric intrusions. It is estimated that stratospheric intrusion is the source of 25% of the observed ozone mixing ratio at 300 mb. The maximum stratosphere to troposphere flux of ozone occurs in late winter/spring. A box model is developed for a Northern Hemisphere troposphere with stratosphere-troposphere exchange parameterized in terms of the baroclinic eddy activity but no tropospheric in situ source of ozone. It shows the same seasonality in ozone mixing ratio as the Payerne data, suggesting the assumed exchange mechanism to be reasonable.