THE CLIMATOLOGY OF THE JET-STREAM AND STRATOSPHERIC INTRUSIONS OF OZONE OVER JAPAN

The strongest jet stream in the Northern Hemisphere winter is located over Japan. Associated stratospheric instrusions make an important contribution to the local tropospheric ozone budget; these intrusions are studied on a seasonal basis using ozonesonde and TOMS data The northernmost station at Sapporo (44N, 141E) is the most affected by stratosphere/troposphere exchange. This exchange is observed to be associated with the advection of laminae of high and low ozone mixing ratio in the stratosphere. A case study is made of a cut-off low over Tateno on 12 April 1989. Between 10 and 11 April, there was increase in total column ozone of 71 DU over Tateno, due to an increase of ozone mixing ratio between 400 and 200 mbar. Dynamical analysis showed that vortex stretching alone could account for only about half of this increase; advection of a lamina of high ozone concentration from the north made up the difference. Thus, to model the cross-tropopause flux of trace gases correctly, the dynamics of the lower stratosphere must be included.