The impact of free convection on late morning ozone decreases on an Alpine foreland mountain summit
- 1Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
- 2Department of Micrometeorology, University of Bayreuth, Bayreuth, Germany
- 3German Meteorological Service, Observatory Hohenpeißenberg, Hohenpeißenberg, Germany
- 4Department of Physics, University of Zimbabwe, Harare, Zimbabwe
Abstract. Exceptional patterns in the diurnal course of ozone mixing ratio at a mountain top site (998 m a.s.l.) were observed during a field experiment (September 2005). They manifested themselves as strong and sudden decreases of ozone mixing ratio with a subsequent return to previous levels. The evaluation of corresponding long-term time series (2000–2005) revealed that such events occur mainly during summer, and affect the mountain top site on about 18% of the summer days. Combining (a) surface layer measurements at mountain summit and at the foot of the mountain, (b) in-situ (tethered balloon) and remote sensing (SODAR-RASS) measurements within the atmospheric boundary layer, the origin of these events of sudden ozone decrease could be attributed to free convection. The free convection was triggered by a rather frequently occurring wind speed minimum around the location of the mountain.