A new release 06 of the GRACE Atmosphere and Ocean De-aliasing Level-1B (AOD1B) product

Abstract:

We present a new release 06 of the GRACE AOD1B product, intended to serve as a background model for the removal of high-frequency non-tidal mass variations due to short-term (daily and sub-daily) mass transport in the atmosphere and oceans. AOD1B shall avoid aliasing of these high frequency signals into monthly gravity models derived from modern gravity missions (CHAMP, GRACE or GRACE-FO) and shall help to consistently reprocess altimetry and SLR satellites for later combination of gravimetric and geometric results. Therefore, AOD1B RL06 will be provided for an extended time-range (from 1976 till present). Some results on the use of the new and previous releases of the AOD1B product for precise orbit determination (POD) of these satellites are presented as well.
For AOD1B RL06 the ocean part is the same as in RL05, while the atmospheric one includes an improved algorithm for the vertical integration of the atmospheric columns as well as a correction strategy for errors (jumps) present in the atmospheric input data. These errors are estimated by comparing the standard atmospheric coefficients based on the ECMWF operational analysis with independently generated coefficients based on the ECMWF ERA-Interim reanalysis. With this, we are able to correct the 6-hourly AOD1B data sets applied during GRACE POD. The derived gravity solutions, as well as the monthly averages 'GAA' (atmosphere only) and 'GAC' (atmosphere combined with ocean), are then free from errors present in the atmospheric input data. Furthermore, we are checking routinely processing changes at ECMWF, since they are strictly associated with the above mentioned errors, and will estimate new correction coefficients, if necessary.