| Uncertainty quantification plays a key role in the establishment of fundamental climate data
records. Requirements are long-term stability, reproducibility, global coverage, accuracy,
resolution in space and time, description and validation of the products. GPS radio
occultation (RO) is a promising source for atmospheric climate records with best quality in
the upper troposphere and lower stratosphere (UTLS). Its properties comprise global
coverage, nearly all-weather capability, good vertical resolution, long-term stability, and
homogeneity. RO errors are well characterized for single profiles as well as for climatological
fields.
In this study we quantify the structural uncertainty of the RO record, which arises from
current processing schemes of six international RO processing centers, DMI Copenhagen,
EUM Darmstadt, GFZ Potsdam, JPL Pasadena, UCAR Boulder, and WEGC Graz. We
analyze atmospheric variables based on monthly 5-deg zonal mean fields at 8Â km to
30Â km for the CHAMP RO record 09/2001–09/2008. Anomaly time series are
computed and their difference to the all-center mean. Anomaly difference trends and the
standard deviation of the all-center mean trend are used as an estimate of the structural
uncertainty.
We find that structural uncertainty is lowest in the tropics and mid-latitudes from 8Â km to
25Â km for all inspected RO variables. In this region, the structural uncertainty in trends over
7Â years is |