Ozone Profile Observations at Huntsville: Toward Understanding Southeast North American Chemistry

Southeastern North America atmospheric chemistry has attracted significant interest in the atmospheric chemistry community due to numerous unsolved scientific questions. We examine ozone seasonal and intra-annual variability and tropopause characteristics by using weekly ozonesonde and lidar data over Huntsville from 1999 to present. We present the unique temporal and vertical ozone distribution in the southeast by comparing Huntsville with another midlatitude, continental site, Boulder. Ozone above Huntsville shows a larger influence from stratosphere-to-troposphere exchange in winter and spring, especially the cross-tropopause upward motion, however, with a shorter time period compared to Boulder. Consequently, the deseasonalized anomaly of tropospheric ozone above Huntsville shows a larger positive trend associated with the 2010 stratospheric sudden warming. Both the ozonesonde and EPA surface data suggest a slightly negative trend for the PBL ozone in summer, which might be attributed to the reduction in NOx as suggested by recent findings. The summertime upper-tropospheric (6-11 km) ozone maximum, especially in July and August, appears to be a permanent feature above Huntsville as suggested by the previous IONS campaign, and is little affected by direct stratospheric intrusion or tropopause folds. By investigation of the intra-annual anomaly of the height field, only half of the variability of the upper-tropospheric ozone can be explained by the consistent anticyclones over North America, which can convectively lift polluted air from the PBL. We, therefore, employ the UAHuntsville high-resolution ground-based ozone lidar (Figure 1) and collocated meteorological instruments to study the favorable conditions for the enhanced upper-tropospheric ozone layers. The simultaneous ozone lidar and HSRL aerosol lidar measurements to support the 2013 SENEX and SEAC4RS field campaigns will be also introduced.