Trends of HF, HCl, CCl2F2, CCl3F, CHClF2 (HCFC-22), and SF6 in the lower stratosphere from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements near 30 degrees N latitude
[en] [ 1] Volume mixing ratios ( VMRs) of HF, HCl, CCl2F2, CHClF2 ( HCFC-22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution Fourier transform spectrometers. Atmospheric Chemistry Experiment ( ACE) VMRs measured during 2004 have been compared with those obtained in 1985 and 1994 by the Atmospheric Trace MOlecule Spectroscopy ( ATMOS) instrument. Trends are estimated by referencing the measured VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled air masses. Pressure-gridded measurements covering 10-100 hPa ( similar to 16 to 30 km altitude) were used in the analysis that includes typically 25 degrees N-35 degrees N latitude. The VMR changes provide further evidence of the impact of the emission restrictions imposed by the Montreal Protocol and its strengthening amendments and adjustments and are consistent with model predictions and known sources and sinks of halocarbons. Decreases in the lower stratospheric mixing ratios of CCl3F and HCl are measured in 2004 with respect to 1994, providing important confirmation of recent ground-based solar absorption measurements of a decline in inorganic chlorine. Trends estimates are compared with other reported measurements and model predictions.