Quantification of bias of wave measurements from lightvessels

Wave measurements are presently made by the Met Office from moored buoys and lightvessels around the UK and are used for coastal flooding prediction, marine forecasting, wave climate studies and validation of wave forecast models. However, it has long been suspected that the wave measurements from the lightvessels are less accurate than those from the buoys. This paper presents the results of a study comparing both lightvessel and buoy wave measurements for the period 2011-2014 inclusive against output from the Met Office wave model to examine whether there is a systematic deficiency in the lightvessel wave measurements. The analysis showed that moored buoys generally agreed well with the model data, but lightvessels consistently reported lower wave heights and higher wave periods than the model.