The source function describing the dissipation due to white-capping is based on the theory of Hasselmann (1974). With the introduction of Janssens (1989) description of wind input, it was realized that the dissipation source function needs to be adjusted in order to obtain a proper balance between the wind input and the dissipation at high frequencies.
For the fully spectral formulation the source function is given by
where Cds (Cdis) and d (DELTAdis) are two dispersion coefficients. The mean angular frequency, 
, and the mean wave number, 
, are calculated as follows
(6.16) 
(6.17) 
where 
and pk are mean angular frequency power and the mean wave number power. Janssen (See Komen et. al (1994)) proposed to use the following values: Cds= 4.5, d= 0.5 and 
.
To improve the the whitecapping for wave conditions with a combination of wind-sea and swell Bidlot et. al 2007 proposed a revised formulation of whitecapping. Here eq. (6.15) is still applied but the mean relative angular frequency and the mean wave number are calculated using 
and the default values for Cds and d are changed to 2.1 and 0.6, respectively.
