Recalculation of 11-year total ozone of Brewer spectrophotometer 115

Ground-based total ozone (O₃) has been measured by Brewer 115 at Hong Kong (Cape D'Aguilar, 22°13′N, 114°15′E, 64 m above mean sea level). Long-term observations between 1995 and 2005 show that the sensitivity of outdoor spectrophotometers exhibit long-term drift. Despite the undesirable sensitivity shift, high-quality total ozone observations can still be achieved so long as the spectrophotometer is well maintained and calibrated regularly, and appropriate corrections applied to the data. The recalculated ground-based total ozone also shows good agreement with the satellite (Total Ozone Mapping Spectrometer (TOMS) version 8) data and Brewer 61 (Chengkung: 23°05′, 121°21′). The procedures and experience of a total ozone trend analysis using multiple linear regression that account for upper level temperatures, QBO, AOD, sun spot activities, and El Niño were reported for future reference. It can be concluded that no ozone depletion was observed over Hong Kong in this time period.