The development of ocean surface wave climatology in support of ship to ship connected transfer of cargo and personnel

The US Military´s Joint Logistics Over the Shore, (JLOTS), concept requires transferring cargo and personnel between ships that are moored and fendered together in the open ocean. A number of studies have been done that model the ship to ship motions of various combinations of vessels. The vessels range from small lighters to very large post-Panamax vessels. The smaller vessels are particularly susceptible to the wind seas with periods that are closest to the vessels natural frequencies. The larger vessels were more closely tuned to long period swells, while all but ignoring the wind seas that excite the smaller vessels. Tables of seastate probability of occurrence are readily available but not so for swell-states. The author conducted a wave climatology analysis for a potential test site. Using 35 data years of NOAA/NDBC wave buoy data, the author developed a joint probability of seas and swells, significant wave height against sea and swell modal periods. One of the biggest challenges turned out to be figuring out how to depict the joint behavior of four independent variables in a useful way. The standard method of using the properties of statistical distributions, (le Gaussian or Rayleigh), to predict the maxima into the future is limited by the assumptions that the wave parameters are not changing over time and space. The rates of change, of the seas and swells, over time and space, were captured and studied in the data. The rates of change have important implications for the validity of future modeling efforts, across a broad spectrum of ocean engineering projects.