The impact of free convection on late morning ozone decreases on an Alpine foreland mountain summit

J.-C. Mayer (1) , K. Staudt (2) , S. Gilge (3) , F. X. Meixner (1, 4) , T. Foken (2)

1 Biogeochemistry Department [Mainz]
2 Micrometeorology Group [Bayreuth]
3 DWD - German Meteorological Service
4 Department of Physics

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 levels with a subsequent return to previous levels. Considering corresponding long-term time series (2000?2005) it was found, that such events occur mainly during summer, and affect the mountain top site in 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, triggered by a rather frequently occurring wind speed minimum around the location of the mountain.

Domaines: Océan, Atmosphère

J.-C. Mayer, K. Staudt, S. Gilge, F. X. Meixner, T. Foken. The impact of free convection on late morning ozone decreases on an Alpine foreland mountain summit. Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.5437-5476. ⟨hal-00304038⟩