An automatic sea state calculator

The Sea State Code, an extension of the Beaufort Wind Scale that originated in the early 19/sup th/ century, is a written description of the sea surface with a corresponding numeric code, which is used by seamen to describe sea surface conditions for ship routing, operational safety, and weather forecasting in the absence of wind and wave measuring instrumentation. Still in use today by the WMO, the US Navy, and the marine industry, the Sea State Code relates the appearance of local wind-generated waves to both wind speed and the height of wind waves by considering such factors as the dimensions of wind waves and whitecaps, foam, and spray. The highly subjective nature of these observations and latitude for error renders them of little use for quantitative analysis. The authors describe an automatic sea state calculator based on wind and wave statistics derived from measured quantities. The primary input is the directional wave spectrum, along with associated wind speed and direction obtained from National Data Buoy Center weather buoys, commercial wave buoys, ship meteorological instruments, satellite observations, or global wave and atmospheric forecast models. This technique is written in Matlab and uses the Wave Identification and Tracking System (WITS), developed at The Johns Hopkins University Applied Physics Laboratory for wave analysis. As the sea state is generated by waves forced by local winds (wind waves as opposed to swell), the wind-wave directional spectrum is extracted from the full-wave spectrum using a wave spectral partitioning method. This method uses an inverted catchment area approach for wave peak isolation with a wave age criterion to classify the wind-wave spectral domain.