EGS XXV General Assembly, Nice, France, April 2000

ST6.01 Processes and issues of the upper troposphere and lower stratosphere (co-sponsored by OA): New chemistry of the upper troposphere

Event Information

Ozone in the upper troposphere (UT) plays an important role as a greenhouse gas; studies have shown that radiatively forced temperature increases at the earth's surface are particularly sensitive to its concentration in this part of the atmosphere. Measurements of the vertical distribution of O3 have revealed a negative trend in lower stratospheric ozone over the last few decades and an increase in ozone in the free troposphere in Northern mid-latitudes, with ozone over Europe showing the largest increases. There are however also observations of severe ozone loss in the upper troposphere. Factors that may directly influence the abundance and variability of upper tropospheric ozone and the photochemistry of the upper troposphere are: 1) Emissions from subsonic aircraft 2) Stratosphere-troposphere exchange 3) Convective transport of organics, NOx and other trace gases from the boundary layer 4) Oxidation of organics and formation of HOx 5) NOx / NOy / HOx gas-phase cycling reactions and reactions of halogenated species 6) Heterogeneous reactions on surfaces (esp. cirrus ice) In this session we expect to discuss recent research on the various phenomena that influence the seasonal and latitudinal variability of ozone in the upper troposphere, and in particular the extent to which the natural chemistry of the upper troposphere is being impacted by growing atmospheric pollution, both in the boundary layer and directly emitted into the upper troposphere by aircraft emissions. Accordingly we invite contributions from the following areas: Modelling studies of transport phenomena and chemistry of the UT Field measurements of UT trace gas- and particle concentrations Laboratory studies of homogeneous and heterogeneous processes relevant to the UT.

Preliminary List of Solicited Speakers

Co-Sponsorship