AOe07 Variance-Covariance-Matrix

The Atmosphere and Ocean non-tidal De-aliasing Level-1B (AOD1B) product is widely used in satellite gravimetry to correct for transient effects of atmosphere-ocean mass variability that would otherwise alias into monthly-mean global gravity fields. The most recent release is based on the global ERA5 reanalysis and ECMWF operational data together with simulations from the general ocean circulation model MPIOM consistently forced with fields of the same atmospheric data-set. As background models are inevitably imperfect, residual errors due to aliasing remain. Accounting for the uncertainties of the background model data has, however, proven to be a useful approach to mitigate the impact of residual aliasing. In light of the changes made in the new release of AOD1B, previous uncertainty assessments are deemed too pessimistic and have been revised in the new time-series of true errors: AOe07. One possible way to include the uncertainty information of background models in gravity field estimation or simulation studies is through the computation and application of a variance-covariance matrix that describes the spatio-temporal error characteristics of the background model. The AOe07 variance-covariance-matrix provides this information through (1) a fully populated matrix up to degree and order 40 as well as (2) a diagonal matrix up to degree and order 180.