Recent changes in total column ozone based on the SBUV Version 8.6 Merged Ozone Data Set

The Solar Backscatter Ultraviolet (SBUV) Merged Ozone Data Set (MOD) provides the longest available satellite-based time series of profile and total ozone from a single instrument type. The data span a 44 year period from 1970 to 2013 (except a 5 year gap in the 1970s). Data from nine independent SBUV-type instruments are included in the record, one of which is still operating. Although modifications in instrument design were made in the evolution from the Nimbus-4 Backscattered Ultraviolet instrument to the modern SBUV(/2) model, the basic principles of the measurement technique and retrieval algorithm remain the same, lending consistency to this record compared to those based on measurements using different instrument types. Nevertheless, each instrument has specific characteristics, and known anomalies must be incorporated in the MOD uncertainty estimates. In this study we describe the latest version of the MOD data set based on SBUV data processed using the Version 8.6 algorithm. We assess the measurement consistency across instruments and use this information to assign a drift uncertainty to the MOD. We then fit a multiple regression model to the MOD time series alternately using Equivalent Effective Stratospheric Chlorine (EESC) or linear trend fits over varying time series segments to analyze trends. Regression results indicate a statistically significant positive trend in total ozone outside the tropics based on the EESC proxy fit to the full record, but a linear trend fit to the last 13 years of data does not yield a statistically significant ozone increase.