The analysis was performed for monthly and zonal means for four regions, one global region (more precisely quasi-global, 70°S to 70°N), and three sub-regions: tropics (20° S to 20°N), Northern Hemisphere (NH) extratropics (30°N to 70°N) and Southern Hemisphere (SH) extratropics (30°S to 70°S), respectively (see Fig. 2). The comparison was made for the years 2001-2006.

The different data sets were brought to the same basic setup. RO climatologies were provided as 10° zonal means based on averaging of individual RO profiles weighted by the cosine of the latitude (Foelsche et al. 2008b). We note that in case of fewer and irregularly distributed occultations (e.g., GPS/MET) spatial mapping functions might be used in such zonal bands (Schr0der et al. 2003). MSU/AMSU data from UAH and RSS were averaged to 2.5° zonal means. Then weighted averages (weighted by the cosine of the latitude) for the four regions were produced.

Synthetic TLS temperatures were calculated for RO and ECMWF data by applying global weighting functions to zonal-mean monthly-mean temperature climatology profiles and alternatively by applying the RTTOV8.5 radiative transfer model to the individual profile data set. TLS temperature anomalies were calculated for each data set using the monthly-mean averaged over the years 2002-2005 as reference. The CHAMP averages were used as basis for the computation of the anomaly values of the SAC-C, GRACE, and COSMIC months as well. A detailed description on the calculation procedure is given in Steiner et al. (2007).

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