Compilation of Summaries 
17 
Compilation of Summaries 
2 Atmospheric Circulation 
The atmosphere is the motor, which drives and controls the development of the 
oceanographic state of the North Sea. Atmospheric circulation often marks the 
beginning of cause-effect chains extending from oceanographic state variables 
beyond distribution patterns of pollutants and nutrients down to bio-ecological 
change. 
To characterize near-surface circulation, NCEP/NCAR reanalyses of mean sea 
level pressure were employed, evaluated on daily, monthly and seasonal time 
scales, and compared to climatological reference states. As a central diagnos 
tic tool, a weather-typing scheme after Jenkinson and Collison was applied to 
sea level pressure distributions on the same time scales. In this way, circulation 
patterns were classified in a qualitative fashion as to rotational and directional 
flow state. Beyond that, circulation strength was quantified in terms of a repre 
sentative North Sea wind and through the identification of gales. 
The significance of atmospheric circulation is exemplified through its impact on 
surface air temperature and global radiation at Norderney and mean sea sur 
face temperature of the German Bight. Anomalies always relate to the climato 
logical base period 1971-2000. By contrast, information on records and ranks 
apply to the period 1971-2013, except for Hurrel’s NAO index (1889-2013). 
Partitioned into quarterly sections, summaries of the years 2008 through 2011 
are set out below in chronological order. Here, seasons are not defined in me 
teorological terms, but equated to the quarters of a year. 
2008 (Page 32 et seq.): (JFM) A substantial number of gales were embed 
ded in a strong and persistent W(esterly) flow. Consequently, air and sea tem 
peratures in the G(erman) B(ight) were anomalously high. (AMJ) The extreme 
frequency of A(nticylconic) and E(asterly) weather types in May gave rise to 
record heights in global radiation (Norderney) and temperature (GB). (JAS). In 
unsteady, inclement weather due to a significantly increased incidence of 
C(yclonic) weather types air temperatures did not depart from climatological 
levels. (OND) Sea level pressure over the North Sea region was in good accord 
with the climatological distribution, and so were other meteorological variables. 
2009 (Page 33 et seq.): (JFM) Climatological conditions of the preceding fall 
continued into the winter; so, gale frequency, for instance, halted to normal 14 
days in comparison to the winter of 2008. (AMJ) As a consequence of omega 
blocking over Scandinavia through April and persistent high pressure over Ice 
land in June, A weather types were dominant in spring. Air temperature rose 
over climate normal by 3.1 standard deviations in April, but, in spite of con 
stantly enhanced insolation, returned to normal in northerly air flow in the 
course of June. (JAS) The cyclonic character of the atmospheric circulation in 
midsummer resulted from a strongly positive E-Atlantic pattern, which went 
along with very stable winds from WSW, later on SW. Air and sea temperatures 
were constantly 1.3 K over climatology. (OND) A deep trough over the NE-At-