Nordseezustand 2003 
15 
Summary 
The 2003-report on the state of the North Sea has significantly expanded as compared 
to the pilot-issue (Loewe et al. 2003) that focussed on physical oceanography. Apart 
from various extensions as to the analysis of relevant atmospheric and oceanographic 
state variables the single most important novelty consists in a comprehensive docu 
mentation of the chemical state of the North Sea. With the joint presentation of the me 
teorological, hydrodynamical and chemical state a big step has been taken towards 
an interdisciplinary holistic assessment of observational and modelling data from the 
North Sea system. The main results are summarized in subsequent sections. 
Atmospheric Physics 
The large-scale atmospheric circulation places an important boundary condition on 
the oceanographic state of the North Sea. Its general form and intensity may be esti 
mated through an index of the North Atlantic Oscillation (NAO). In winter and fall 2003 
weak or negative NAO-states indicative of a weakened zonal circulation prevailed. 
A more comprehensive analysis of daily atmospheric circulation patterns over the 
North Sea was carried out using an objective weather-typing scheme. High-pressure 
weather at just under 30 %, or 100 days, was almost twice as frequent as in 2002. 
Long runs of 16, 17, and 12 days occurred in February, March, and August, respec 
tively. These extensive high-pressure spells were associated with abnormally low air 
temperatures in winter and mediterranean temperatures during the dog days in Au 
gust. Gale frequency was reduced from 24 (in 2002) to 16 events most of which oc 
curred in January and December. Wind force was generally much lower than in the 
preceding year, especially in winter and autumn. As in 2002, dominant wind directions 
were SW and W, with an unchanged frequency of 18 %, or 66 days. 
Physical Oceanography 
Model-based estimates of seasonal North Sea surface circulation showed markedly 
lower current intensities and directional persistence than the year before. The Atlantic 
inflow at the NW boundary of the North Sea was also considerably lower. The net-in 
flow through the Channel dropped to 0.03 Sv from 1 Sv (10 6 m 3 /s) in 2002. The strong 
outflow from the Baltic Sea along the Norwegian trench, which in fall 2002 was caused 
by unusually strong SE winds, was not observed in the year under review. 
Classification of daily residual current patterns in the German Bight again demonstrat 
ed the dominance of cyclonic patterns (150 days) over anticyclonic (50 days) and vari 
able circulation types (109 days). Annual frequencies of these main types only showed 
little departures from those in 2002 (141,42, 131 days). On a seasonal basis, how 
ever, the variable type, which at times is characterized by meso-scale eddies, experi 
enced substantial inverse changes in frequency from 13 to 34 days in winter versus 
35 to 14 days in fall 2003. 
Model-based geographical wave height distributions in all seasons show wave heights 
increasing towards the NW from where the Atlantic swell is entering the North Sea. As 
being forced by the wind, the wind sea as to direction coincides with the wind's. Sub