| The quantification method to estimate the isentropic cross-tropopause ozone transport is based on the potential vorticity mapping of Stratospheric Aerosol and Gas Experiment II ozone measurements and contour advection calculations using the NASA Goddard Space Flight Center Global and Modeling Assimilation Office analysis for 1990 and 1999. The magnitude of the annual isentropic stratosphere-to-troposphere ozone flux is calculated to be approximately twice the flux that is directed from the troposphere to the stratosphere. The net effect is that ∼92 x 109 kg yr -1 and ∼118 x 109 kg yr-1 of ozone are transferred isentropically from the extratropical lower stratosphere into the subtropical upper troposphere between 330 K and 370 K in 1990 and 1999 respectively. The isentropic ozone fluxes are found to occur preferentially over the eastern Atlantic Ocean and northwest Africa in winter and over the Atlantic and Pacific Oceans in summer and they are shown to be associated with Rossby wave breaking events. This research shows that isentropic transport is important for determining ozone levels in the subtropical upper troposphere especially in summer. Remaining challenges are to gather new observational data to better estimate isentropic ozone transport, to assess the influence of isentropic transport on photochemistry in the upper troposphere, and to investigate the reversibility in the cross-tropopause transport. |
