Stratosphere-Troposphere Exchange studies using SAGE II data

Stratosphere-Troposphere Exchange (STE) is of significant importance to the chemistry and dynamics of the troposphere and the stratosphere yet many aspects are not well understood. Stratospheric Aerosols and Gas Experiment II (SAGE II) version 6.2 data, with improved water vapor, near global coverage, and excellent vertical resolution, is ideal to investigate stratosphere-troposphere exchange. The SAGE II 6.2 water vapor and ozone data together with United Kingdom Meteorological Office (UKMO) assimilated data are utilized to identify air of tropospheric characteristics in the stratosphere and air with stratospheric characteristics in the troposphere. Air that may be of stratospheric origin residing in the troposphere is identified by high ozone and low water vapor mixing ratios relative to tropospheric averages while tropospheric air in the stratosphere is identified by high water vapor and low ozone content relative to the stratospheric averages. For these determinations, the cold point tropopause is utilized in the tropics and the 3.5 x 10^-6 m² s^-1 K kg^-1 potential vorticity surface defines the tropopause in the mid-latitudes. The frequency of stratosphere-troposphere exchange is calculated globally and regionally to determine STE activity and the vertical structure of the exchange is investigated. In this paper, the data analysis approach, results, and interpretations of this investigation will be discussed.