Bremen 2000 – scientific programme

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UP: Umweltphysik

UP 1: Instrumente (Atmosph
äre)

UP 1.1: Invited Talk

Tuesday, March 21, 2000, 15:00–15:30, H2

Stratosphere-troposphere Exchange — •Jos Lelieveld — IMAU Univ. Utrecht

Stratosphere-troposphere exchange (STE) is predominantly upward at low latitudes and downward at middle and high latitudes. The latter carries ozone (O3) rich air from the stratosphere into the troposphere. This circulation is primarily driven by wave disturbances that originate in the troposphere. This wave forcing is most efficient in the winter. Furthermore, during spring, the tropopause altitude increases, which entrains stratospheric air into the troposphere. The combined effect is that downward O3 transports reach a maximum in late winter and early spring. Since this almost coincides with an O3 maximum observed at background monitoring stations, an important role has been assumed for STE, even at the surface. It will be shown, however, that this view needs much refinement.