The Long History of Ozone Measurements: Climatological Information Derived from Long Ozone Records

Abstract

Long-term measurements of total ozone started in the 1920s and a large number of column ozone observations using different techniques were performed prior to the International Geophysical Year (IGY 1957/58) when the presently used method for Dobson spectrophotometry (using two wavelength pair measurements) was introduced as a standard method. Only for a few series the prerequisites (considering, e.g. length of the record, sufficient documentation of observations including wavelengths used, calibration, etc,) are given for a useful and successful re-evaluation of pre-IGY total ozone measurements. In this chapter we summarize the re-evaluation and homogenization of the record of Oxford, performed in the laboratory of Dobson who is one of the most outstanding pioneers of the early atmospheric ozone research history. The Oxford series adds to a few other long-term series extending backwards beyond the IGY which were either recently re-evaluated and homogenized or tested for their reliability. The European sites Arosa (Switzerland), Oxford (United Kingdom), Lerwick (UK), Tromso (Norway), Svalbard (N), and Vigna di Valle (Italy) allow constructing a long-term interannual ozone climatology extending over more than 4 decades prior to start of the anthropogenic ozone depletion. (However, we only recommend the use of a subset of these series for long-term trend analysis.) The re-evaluated data sets are believed to be particularly useful to compare long-term ozone variability with anthropogenic forcings of the ozone layer (such as anthropogenic ozone depletion, its expected recovery from ozone depleting substances and stratospheric temperature decrease as a consequence of climate change) and to test numerical simulation performance for the pre-CFC era. Examples of other scientific applications of the ozone series related to the study of climate variability are highlighted as well.