Strat-Trop exchange: recent evidence from in situ observations of isotopes, water and reactive intermediates

An array of new observational strategies is emerging that provide unique insight into the coupled problem of strat-trop exchange, the source and transport of water into the upper tropical and sub-tropical troposphere, and secular trends in the column concentration of ozone in response to climate forcing. The combination of integrated cavity output spectroscopy (ICOS), photofragment laser induced fluorescence (PF-LIF) on the one hand, and GPS occultation on the other, is used to link a new generation of in situ spectroscopic tools with high accuracy remote soundings of the upper troposphere and lower stratosphere.