Local variability of surface currents based on HF-Radar measurements
F. SCHIRMER, H.-H. ESSEN, K.-W. GURGEL, T. SCHLICK, K. HESSNER
In: Sündermann, J. (Ed): Circulation and contaminant fluxes in the
North Sea, Springer, Berlin, Heidelberg, New York, pp. 271...289, 1994.
Abstract - -
Surface currents which transport oil and surface pollutants, whether
shorewards or out to sea, depend on many factors. This include winds, tides,
waves, the coastline contour and geophysical forces such as gravity and the
Coriolis force. Thus, near-surface offshore currents will be highly variable
from area to area and at different times. While the ultimate objective is to
predict these currents as a function of the driving forces, their accurate
measurement is the necessary first step in the development and testing of such
a prediction model. In fact, when near-surface currents are known, it is
theoretically possible to numerically calculate the currents and circulation
all the way down to the ocean floor.
Yet these near-surface currents are the most difficult to measure. Nearly all
available techniques are Lagrangian in nature, meaning that they measure the
trajectory of a parcel of water near the surface, thus obtaining one more
(current) streamlines vs. time. The method used in our case is a Eulerian one.
It measures surface currents at points spaced approximately 3 km from each
other in a rectangular grid.
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