Analysis On Sea States Characteristics For Global Ship Accidents Based On Multi-source Satellite Data

Shipping industry delivers 90% of all world trade.The steady growth in seaborne trade has meant an increase in global shipping movements and tonnage.With the increasingly frequency of shipping activities,navigation safety has become a major concern.Shipping accidents,many involving spills of mineral oil or hazardous chemicals,have not only been threats on the safety of mariners and cargoes,but also been a catalyst for environment risks.Investigations into the factors of shipping accidents show that over 40% of the accidents are caused by poor weather or complex sea states.Due to these dangerous uncertainties,accidents that involve poor weather and severe sea states should be further studied for shipping safety.The data of sea states parameters are usually obtained from buoy measurement,satellite remote sensing and ocean numerical model forecast.Microwave radar technology,includes scatterometer,radiometer,altimeter,is the major way to monitor the marine dynamic parameters.In general,the data of global sea surface wind filed are usually accessed from scatterometer and radiometer.While the significant wave height can obtained from altimeter data.A ten-year(2001–2010)ship accident dataset was gathered from the Marine Casualties and Incidents Reports issued by the International Maritime Organization(IMO).A ship accident database built up according to the accidents occurred in heavy sea conditions.Hereafter,an overview on the ship incidents was conducted in terms of the spatial and temporal distributions,initial events and ship types.The satellite data(includes altimeter,scatterometer and radiometer data)and numerical model data are obtained based on the recorded time and coordinates of ship accidents that selected.Statistics and analyses are conducted towards to the sea states parameters,such as the significant wave height,the weed speed,the mean wave period and the wave steepness.Conclusions are drawn in the followings:(1)The ship accidents presented a dense distribution in the North Atlantic Ocean,the North Indian Ocean and the West Pacific Ocean,where are highly incidence areas of ship accidents.Sea state characteristics show that most of the cases occurred in a significant wave height range of 2 m ~ 4 m,a wind speed range of 10 m/s ~ 14 m/s,a mean wave period range of 6 s ~ 8 s.Regarding of wave steepness,the highest value appeared in the North Atlantic Ocean of 0.04 ~ 0.05,while the lowest value appeared in the North Indian Ocean of 0.02 ~ 0.03(2)The ship accident usually occurs when the wave periods of wind sea and swell are close to each other,meanwhile,traveling forward as an oblique angle.This is the dangerous conditions that would lead to ship wrecks.(3)Taking bulks as an example,the correlations of dead weight tonnage(DWT)and sea states parameters are discussed.Few correlations are found between DWT and the significant wave height or wave period.On the contrary,moderate positive correlations are presented between DWT and the wind speed or wave steepness.In summary,the present study is committed to the evaluation of the sea state conditions during ship accidents.Suggestions on improving maritime warning criteria and ship navigation safety are proposed.Besides,it is believed a valuable reference in the study of extreme waves.