The soft start time interval is time over which the forcing functions are gradually increased from the reference significant wave height to 100% of the true value. The increase can either be linear or follow a sinusoidal curve.
When the Wind-sea and swell parameters (Version 1 and 2) is selected the wind-sea part is soft started using the specified reference value for the significant wave height, while the swell part always is soft started using a reference value of 0 for the significant wave height.