Lidar measurements of tropospheric ozone over Reunion Island: influence of the synoptic situations

A tropospheric ozone lidar located at Reunion Island has provided an opportunity to investigate the daily vertical ozone distribution in the latter part of biomass burning season, during November-December 1999. The comparison with austral winter 1998 daily ozone profiles show that each daily ozone profile is very stratified with ozone enhancements (<100 ppbv) spaced at different heights within the whole free troposphere. The dynamical context of the profiles is different in comparison with the austral winter period where the effect of the subtropical jet stream is predominant. The analyses of the meteorological data show that the daily variability of ozone profiles is influenced by the movement of the synoptical situations. During the interseasonal period, multiple ozone sources including stratosphere-troposphere exchanges, convection and biomass burning contribute to tropospheric ozone at Reunion Island through sporadic events characterized by a large spatial and temporal variability.