System Nordsee 
253 
List of Figures 
Atmospheric Physics 
Fig. 2-1: NAO Index 2005. Ik: Ponta Delgada & Akureyri (Loewe and Koslowski 1998), Ipf6(lk): 
low-pass filtered (6 month), cruuea: Gibraltar & Southwest Island, cpccdb: Amplitude of NAO 
pattern from rotated principal component analysis of500 hPa height anomalies 38 
Fig. 2-2: NAO phase portrait as percent freguency distribution of monthly dynamic NAO states 
since 1879. Contours 0.5, 1, 1.5 and 2% are lines of egual relative state density (i.e. rel. #of 
states per sguare-bin, 0.6 x 0.6). The seguences of 12 yellow and 12 blue circles (1,2,..., 8, 9, 
O, N, D) show the temporal evolution in 2005 of raw (yellow) and low-pass filtered (6 month, 
blue) monthly mean states, respectively. 40 
Fig. 2-3: Sea level pressure (hPa) for the severe W-gale of Jan, 2 2005 together with grid posi 
tions of weather-typing scheme 42 
Fig. 2-4: Percent freguency distribution of daily circulation states for the period 1971 - 2000 to 
gether with classification criteria 43 
Fig. 2-5: Air circulation around high (A) and low pressure systems (C) 44 
Fig. 2-6: Seasonal freguencies of reduced weather types in 2005 along with percentiles of empir 
ical distributions for 1971 - 2000 (stacked columns); percentile range: 1 - 99, internal interval 
limits at 5,25,50 (median), 75,95% 48 
Fig. 2-7: As Fig. 2-6, except for monthly freguencies 49 
Fig. 2-8: Classified seasonal sea level pressure distributions (hPa). Left: climatology (1971 - 
2000), middle: 2005, right: anomalies; 1 = Winter = January, February, March etc. 52 
Fig. 2-9: Monthly climatology of sea level pressure (hPa), base period 1971 - 2000 53 
Fig. 2-10: Mon thly sea level pressure distributions (hPa) in 2005 55 
Fig. 2-11: Monthly SLP-anomalies (hPa) in 2005 56 
Fig. 2-12: Seasonal 50% probability ellipses for the >North Sea Wind< (1 = winter = JFM, 2 = 
spring, etc.); top: 2005, bottom: 2004 59 
Fig. 2-13: Progressive daily vectors of the >North Sea Wind< with ensemble and climatology. 
Markers indicate the first day in a month, years final points of ensemble members 61 
Fig. 2-14: Freguency of gale types G, SG,andVSG in days (stacked) in DJF win ter and win ter NAO 
index. The correlation between total gale freguency and NAO index amounts to 0.71 65 
Fig. 2-15: Total gale freguency (C+SC+ VSG) in days from October through March. Years refer to 
JFM (OND from previous year, respectively). Right panel (fGales): lowpass filtered in yr-direc- 
tion (filter length 5 yrs) 66 
Fig. 2-16: Total gale freguency in fall, winter, and from October through March. Raw series (stip 
pled) and overall linear trends (green, ±95% confidence interval) are shown along with low- 
pass filtered series for filter lengths of 5 (blue) and 18 yrs (red, Ipl8). Stars mark break points 
of piecewise linear trends fitted to Ipl8; accounted variances (R 2 ) refer to raw series 68 
Fig. 2-17: Freguency ratio of severe and very severe gale days (SC+VSC) to total gale days (G+ 
SG+VSG). Otherwise as Fig. 2-16 69 
Fig. 2-18: Seasonal cycle in 2005 of monthly averaged daily global radiation totals at Norder- 
ney together with intramonthly extremes, 1971 -2000 base period monthly means, and 
95%-band (climatology ± 1.96 standard deviations). 1 Idem 2 is eguivalent to a radiation 
flux density of 116 Wm 2 . Raw data: Deutscher Wetterdienst. 71 
Fig. 2-19: Monthly air surface temperatures at Norderney for 2005 together with 1971 - 2000 
base period means, and 95%-band (climatology ± 1.96 standard deviations) 72