Long-range transport and its impact on the vertical distribution of trace constitutents in the central European free troposphere

Abstract

Numerous case studies in recent years based on lidar sounding series at IMK-IFU extended to up to four days have established characteristic patterns of the transport routes and the source regions contributing to the observed ozone and aerosol structures in the free troposphere. The most important source regions were found to be the Sahara desert (particles), the stratosphere over the Northwest Atlantic and Northwest Pacific, the boundary layers in North America and East Asia (characterized by an ozone import of typically 80 to 110 ppb), and the (sub)tropical Atlantic (yielding ozone mixing ratios between 20 and 40 ppb). The export of polluted air masses from the boundary layer is dominated by lifting in warm conveyor belts. In the vicinity of the frontal systems mixing of the contributions from different source regions in the United States and Mexico is observed. The most striking recent result is repeatedly verified mixed ozone import from East Asia and the stratosphere in adjacent areas in rapid and dry middle and upper tropospheric air streams partly as thick as 6 km.