ATMOS measurements of H2O+2CH(4) and total reactive nitrogen in the November 1994 Antarctic stratosphere: Dehydration and denitrification in the vortex

Simultaneous stratospheric volume mixing ratios (VMRs) measured inside and outside the Antarctic vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument in November 1994 reveal previously unobserved features in the distributions of total reactive nitrogen (NOy) and total hydrogen (H2O+2CH(4)). Maximum removal of NOy due to sedimentation of polar stratospheric clouds (PSCs) inside the vortex occurred at a potential temperature (Theta) of 500-525 K (similar to 20 km), where values were 5 times smaller than measurements outside. Maximum loss of H2O+2CH(4) due to PSCs occurred in the vortex at 425-450 K, VMRs inside the vortex were similar to 70% of corresponding values out side. The Antarctic and April 1993 Arctic measurements by ATMOS show no significant differences in H2O+2CH(4) VMRs outside the vortices in the two hemispheres. Elevated NOy VMRs were measured inside the vortex near 700 K. Recent model calculations indicate that this feature results from downward transport of elevated NOy produced in the thermosphere and mesosphere.