Cumulus Cloud Venting of Mixed Layer Ozone

摘要

Observations are presented which substantiate the hypothesis that significant vertical exchange of ozone and aerosols (and possibly other compounds) occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments conducted in July 1981, utilized the airborne UV-DIAL (Ultra-Violet Differential Absorption Lidar) system developed by NASA. This system provides simultaneous range resolved ozone concentration and aerosol back scatter profiles with high spatial resolution. Data were obtained during the afternoon along 80 mi East to West and South to North intersecting transects over North Carolina when cumulus clouds were most active, although nonuniformly distributed. Evening transects were obtained in the downwind area where the air mass had been advected. Space-height analyses for the evening flight show the cloud 'debris' as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approximately the value of the concentration difference between the mixed layer and free troposphere determined from independent vertical soundings made by another aircraft in the afternoon.