In the paper “Very early chlorine activation and ozone loss in the Arctic winter 2002–2003” by S. Tilmes et al. (Geophysical Research Letters, 30(23), 2201, doi:10.1029/2003GL018079, 2003), the footnote was inadvertently omitted from paragraph . The correct version of paragraph  and its footnote appear below.
  The TRAC technique considers the relation between gases (here HCl and O3) that may be changed chemically during the course of the Arctic winter and long-lived tracers (here HF) that are known to be chemically inert in the Arctic stratosphere [Tilmes et al., 2003]. Using the TRAC technique, chlorine activation can be identified from changes in the HCl-tracer relation during winter and spring [Müller et al., 1996, 2002]. Further, changes from an O_3-tracer reference relation can be identified as chemical ozone loss. In addition to HALOE and MkIV measurements, we employ observations of high clouds from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT [Fischer and Oelhaf, 1996]. These data are useful for investigating the development of PSC (polar stratospheric cloud) occurrence over the course of the winter. Further information about the development of the Arctic polar vortex in winter 2002–2003 and about the occurrence of APSC detected by MIPAS may be found in the auxiliary material.