Validation of NOAA‐9 SBUV/2 total ozone measurements during the 1994 Antarctic Ozone Hole

The Solar Backscatter Ultraviolet (SBUV/2) instrument on the NOAA‐9 spacecraft made total ozone measurements over Antarctica during the 1994 Austral Spring depletion. These measurements continue those made by the SBUV/2 on NOAA‐11. In recent years NOAA‐9 drifted from a poor orbit to one where earth observations and calibration capabilities are not restricted. An interim calibration of the NOAA‐9 SBUV/2 instrument was established with data from June 1994 and applied to observations during September, October, and November 1994. To validate the NOAA‐9 ozone measurements, daily zonal ozone averages from NOAA‐9 and NOAA‐11 measurements in the Northern Hemisphere have been compared. Comparisons have also been made with ground‐based measurements from five Dobson stations dispersed on the Antarctic continent. The results show that, on average, the NOAA‐9 data agree to within 1–2 percent with the Dobson stations with standard deviations of the difference ranging from 5.3 to 7.7% and to within several percent with NOAA‐11 Northern Hemisphere data when restricted to solar zenith angles less than 80 degrees. This agreement makes possible not only a continuation of the Antarctic measurements without a large instrument‐related bias, but also establishes the NOAA‐9 data as a suitable transition data set during the replacement of NOAA‐11 by NOAA‐14.