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N.H. Schade et al.: Regional Evaluation of ERA-40 Reanalysis Data 
Meteorol. Z, 22, 2013 
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OBS, 1961-1980/1981-2000 ERA-40, 1961-1980/1981-2000 
0 1 2 3 0 1 2 3 
Grid boxes 
Grid boxes 
OBS, JJA 1961-1980/1981-2000 
OBS, DJF 1961-1980/1981-2000 
ERA-40, JJA 1961-1980/1981-2000 
Figure 5: Box plots of 2 m air temperatures from measurements (left) and ERA-40 (right) for the time periods 1961-1980 and 1981-2000 
(first row), and file respective summer (second row) and whiter seasons (third row) for file North Sea Boxes 1 & 2. Median values and 
percentiles as described in Fig. 3. 
pronounced and have to be accounted for. Improvements 
could be made by further analyses including an 
independent data set for triple collocation error model 
ling. Finally, measurements have to be continued on a 
high quality basis to ensure the availability of a reference 
data base in the future. 
Acknowledgments 
The BSH/DWD KLIWAS team, and a special thanks to 
Wolfgang Gloeden and his staff at Seewetteramt 
Hamburg for the help with the preparations of the GZS 
database and its system.