High-resolution lidar measurements of stratosphere-troposphere exchange

The tropospheric ozone lidar at the Fraunhofer-Institut fur Atmospharische Umweltforschung has been upgraded for measurements in an extended range wit h high accuracy (mostly 5%), high vertical resolution (50-500 m within the troposphere), and under automatic control. The operating range is now from 0.15 to about 16 km, the upper limit varying by +/-2 km depending on the av erage ozone density in the troposphere. Routine measurements were resumed i n January 1996. The current research efforts are concentrated mainly on an optimum observational coverage, of tropopause folds and on evaluating more details of stratosphere-troposphere exchange. Ozone tongues associated with tropopause folds may be as narrow as 300 m. Their detection and correct an alysis greatly benefits from the improved instrumental performance of the l idar. From the data acquired during the first 23 months of this project it is Concluded that roughly 98% of the stratospheric air intrusions reach the Zugspitze summit station (2962 m above sea level). Many of the examples of stratospheric intrusions show pronounced secondary ozone maxima in the upp er troposphere starting a few hours to one day after the subsidence of a tr opopause fold and have been tracked with the lidar under automatic control for up to four consecutive days. More work is needed to understand and to a nalyze the contribution of these ozone structures to the overall downward A ux during such an episode.