680 
N.H. Schade et al.: Regional Evaluation of ERA-40 Reanalysis Data 
Meteorol. Z. 22, 2013 
Downloaded from www.schweizerbart.de 
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1961-2000 
Box2, 1961-2000 
DJF, 1961-2000 
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Grid boxes 
Box2, DJF, 1961-2000 
0 1 2 3 4 5 
Sub grid boxes of box 2 
Figure 3: Box plots of 2 m air temperatures from measurements (black) and ERA-40 (grey) for the period 1961-2000. Above left: Annual 
values, above right: Whiter month DJF for Box 1 and 2. Median values and the 25 and 75 percentiles are marked by the box, the whiskers 
show the 10 and 90 percentiles, the plus the percentiles 1, 5, 95 and 99. Below: Same as above but for the four subgrid boxes of Box 2 (see 
Fig. 1). Boxes facing to the open sea have odd, land side boxes even numbers. 
Mean Air Temperature, December/August, 
1961-2000, Box2 
Observations [°C] 
Mean Sea Level Pressure, December/August, 
1961-2000, Box2 
1025 
1020 
1015 
1010 
1005 
1000 
995 
.-'Qi * 
±.'<T 
6 
☆ . 
4M 
w ^ ☆ December 
☆ 0 August 
(tJ&f* 
> tr 
V*' 
/ir 
995 1000 1005 1010 1015 1020 1025 
Observations [hPa] 
Figure 4: Scatter plot of monthly mean 2 m ah temperatures (left) and sea level pressures (right) of measurement and ERA-40 data pahs hi 
Box 2 hi December (black stars) and August (grey diamonds). Base period: 1961-2000. 
The values of mean SLP in contrast show no system 
atic differences between December and August. The 
December values differ more from the optimum accor 
dance line and show a larger spread than the August 
values, but are more or less uniformly distributed. The 
larger spread in December can be explained by an 
increased low pressure activity and pronounced pressure 
differences. More low pressure system paths lead through