Results: Transport of Stratospheric Ozone into the Troposphere

Contact: Thomas Trickl

Since 1996 focussed measurements with the IMK-IFU ozone lidar during predicted stratospheric air intrusions into the troposphere (see figure below) have yielded a very high probability of deep intrusions to reach the Zugspitze summit where they have been observed over several decades (VOTALP , STACCATO  and ATMOFAST projects). From the long-term measurements at the summit station a positive trend of the stratospheric component since the mid-seventies has been determined that has resulted in a surprisingly high stratospheric fraction of the ozone at 3000 m. The lidar measurements have also served as a reference for numerical model simulations. There are, still, important deficiencies in the results of quite a few coarse-grid models used for hemispheric and global studies, which prevents a full quantification of stratosphere-troposphere exchange.

Lidar measurements (upper panel) during a complex intrusion case in June 2001, showing three descending stratospheric layers (S); two of these intrusions were nicely reproduced with the fine-grid FLEXPART  transport model (lower panel), the third one (morning of June 20) originated outside the model domain. "USA" denotes ozone import from the United States.

Reference:

P. Zanis, T. Trickl et al.: Forecast, observation and modelling of a deep stratospheric intrusion event over Europe, , Atmos. Chem. Phys., 3, 763-777, 2003