An assessment of long-term ozone trend uncertainties using Total Ozone Mapping Spectrometers ( TOMS).

We provide here an estimate of the uncertainties that would result when combining multiple Total Ozone Mapping Spectrometer (TOMS) datasets to produce a long-term column ozone record. We use calibration results and various post-launch validations to estimate calibration-related uncertainties for each of the instruments. Two basic methods for combining the individual data records are examined. We assess the combined uncertainty in the global column ozone data record for the period 1978-2000 for both methods using a Monte Carlo model with basic Gaussian statistics. In the case where TOMS data are combined without relative adjustments we estimate a trend uncertainty of slightly less than 1% per decade in the column ozone time dependence. The recently re-calibrated Solar Backscattered Ultraviolet 2 (SBUV2) datasets can be utilized to bridge a gap between TOMS datasets that occurred in the mid-1990s. With our current understanding of the sensor comparisons, we estimate a small improvement in the combined TOMS trend uncertainty. A more significant improvement comes from considering an extended TOMS data record, out to 2007. We estimate an extended ozone trend uncertainty as low as 0.5% per decade. [ABSTRACT FROM AUTHOR]