High-resolution wave climate analysis in the Helgoland area - GKSS

Chapter 2
Dynamical wave modeling
2.1 Methods, data and tools
In this section the main principles and features of the spectral wave modeling are described.
In particular the K-model is discussed as the main tool for the wave simulations.
Subsequently, the HIPOCAS project, the main source of the external forcing data for the
K-model experiments, is described. Finally, the model domain in the German Bight is
specified and the details of the experiment setup are presented.
2.1.1 K-model. Description and features.
Wave models usually describe the evolution of a sea state depending on initial and
boundary conditions as well as external fields like wind, currents and bathymetry. The
sea state is defined as a number of wave trains with different wave lengths and periods
generated at or coming to a specific location at certain time. Within this concept two classes
of wave models can be distinguished (for recent overview see Ris [1997] or Cardone and
Resio [1998]). So-called ”phase-resolving models”, characterized by explicitly determined
superposition of wave trains considering their phases, belong to the first group. Such models
are advantageous in the problems where the changes in the environment occur on the scale
of wave lengths and periods or where diffraction is important. These models are often used
for specific small areas such as harbors or for short-time applications. The second class
contains ”phase-averaging” or spectral models. In these models the wave trains which form
the sea state are considered independently of their phases. With this approach the sea
surface can not be described in detail and the spatial and time resolutions of these models
are supposed to be larger than the typical wave length and wave period. These models
are used for the most of medium and large scale applications due to the computational
reasons as advantageous with respect to the phase-resolving models. They also allow the
easier and more accurate consideration of the random-phase source functions such as wind
energy input and wave dissipation. Further in this study the phase-averaging wave models
are considered. The theoretical background for this kind of models can be found in Komen