System Nordsee 
23 
Compilation of Summaries 
This compilation of summaries is to make the main findings of the >North Sea Systerm 
accessible to a broader readership. As to aid following these findings, all figures and 
tables of the main sections come with English annotations and captions. 
Atmospheric Physics 
The atmosphere is the motor, which substantially drives and controls the develop 
ment of the oceanographic state of the North Sea. Characteristics and anomalies of 
the atmospheric circulation often mark the beginning of cause-effect chains extending 
from oceanographic state variables beyond distribution patterns of pollutants and nu 
trients down to bio-ecological change. The circulation state itself is derived here from 
a variety of diagnostic analyses of large-scale mean sea level pressure distributions. 
The changeover to NCEP/NCAR reanalyses as the primary database, hence, forms 
a major novelty. 
Weather types (p. 40sqs.) 
Weather types and storm events as deduced from daily atmospheric sea level pres 
sure fields were presented as annual calendars for 2006 and 2007. These calendars 
have proven useful aids in identifying and interpreting anomalous states and incidents 
in atmospheric, oceanographic and chemical variables of the North Sea System, if 
immediately or indirectly linked to atmospheric circulation. 
For robust statistical analyses the set of 27 weather types was reduced to a more 
comprehensible set of 6 states: the anti-/cyclonic rotational types A and C and di 
rectional types NE, SE, SW, and NW. Investigations of the reduced set span from 
frequency anomalies and characteristic life times to weather-type transitions in the 
framework of Markov chains. 
Frequency anomalies in 2006 and 2007 of the main weather types were determined, 
assessed, and interpreted on monthly, seasonal, and annual time scales using em 
pirical distributions pertaining to the climatological base period 1971 -2000. For in 
stance, uniformly distributed W (SW & NW) and E types in winter 2006 hint to anoma 
lously weak zonal circulation and above normal cooling rates in sea temperatures, 
while opposite implications follow from the disparity of 68 W types versus 2 E types 
from November through January 2007. Frequencies of A (15) and S types (11) in July 
2006 and C(15) and N types (10) in the succeeding month of August reveal diametri 
cally disparate temperature conditions in summer 2006. Another significant difference 
consists in the proportion of N to S types, which by increasing from 0.57 in 2006 to 
1.31 in 2007 considerably surmounted the climatological proportion of 0.75. 
Artlessly counting off the 30-year base period sequence of weather types as to num 
ber and length of weather-type episodes yields mean lengths or lifetimes that vary 
between 1.6 (NE) and 2.6 days (A). Reminiscent of radioactive decay, the exponen 
tial decline of number of episodes with increasing length points to the Geometric 
Distribution (GD) as the most simple of lifetime models. The unique property the GD 
only shares with its continuous analogue, the Exponential, is memorylessness. This 
property results from the invariance of death probability, which is the single distri 
bution parameter estimated by the inverse of mean lifetime. As a consequence, the