The evolution of inorganic chlorine above the Jungfraujoch station: an update.

Within the frame of the NDSC, the total vertical column abundances of HCl and ClONO2, by far the two most important inorganic chlorine reservoirs at northern mid-latitudes, have been further monitored above the Jungfraujoch station (Swiss Alps, 46.5ºN, 8.0ºE, 3580m a.s.l.), by analyzing infrared solar absorption spectra recorded with very high-resolution Fourier spectrometers. The mean temporal evolution of the sum of their monthly mean abundance time series indicates that the total stratospheric inorganic chlorine loading (Cly) has decreased slowly (-0.7+/-0.3%/yr, 1-sigma) since it peaked in late 1996, at the limit of being statistically significant at the 2-sigma level. Comparison with model calculations and with the evolution of surface total organic chlorine will also be discussed.