Comparison of Re-calibrated TOMS Total Ozone Data with Dobson Network

Nine years of reprocessed Version 6 total ozone data from the Total Ozone Mapping Spectrometer (TOMS) are compared with selected subsets of the Dobson ground based Network. A small long-term drift of -0.11 ± 0.09 %/yr (95% confidence) is identified in the first nine years of TOMS data relative to Dobson. This small change in bias (amounting to 1% over the nine year period) is of the order of the long-term stability of the calibration of both measurement systems. However, a possible mechanism for the drift is identified. Changes in tropospheric ozone are only partly measured by the backscattered ultraviolet (BUV) method [Klenk et al., 1982]. Based on recent estimates of the change in tropospheric ozone [Bojkov, 1987] and of the BUV sensitivity to changes in tropospheric ozone [Fleig et al., 1989], about half of the observed drift would be attributed to this effect. The reprocessed Version 6 TOMS data set is available through the National Space Science Data Center, GSFC/NASA, Greenbelt Maryland.