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Investigation of ship accidents using global ERS-2 and ENVISAT wave mode

Elzbieta Bitner-Gregersen(1), Susanne Lehner(2), Johannes Schulz-Stellenfleth(2) and Thomas K├Ânig(2)

(1) DNV, Veritasveien, 1322 Hovik, Norway
(2) DLR, Oberpfaffenhofen, 82234 Wessling, Germany

Abstract

For the design of ships as well as for the investigation of ship accidents it is important to know about both two dimensional wave properties and extreme value statistics of ocean waves. Although numerical wave models have reached an impressive level of accuracy they still have weaknesses with respect to the details of the 2-D wave spectrum. Furthermore, the standard models like WAM provide estimates of the 2-D wave spectrum but lack complete information on the occurrence of extreme events.

In this study the potential advantages of utilizing global Synthetic Aperture Radar (SAR) wave mode data acquired by the European satellites ERS-2 and ENVISAT to investigate ship accidents as well as to support the ship design is discussed. These data are acquired independent of light and weather conditions on a global scale. A historic data set of ERS-2 wave mode data acquired between 1998 and 2000 is co-located with a number of marine structures' accidents which occurred during that time. ENVISAT ASAR wave mode data acquired since 2002 are considered as well. Different ocean wave parameters like significant wave height and wave periods are derived from the SAR data. The potential role of the respective wave conditions for a marine accident is discussed. This includes in particular the analysis of cross sea conditions.

The traditional design of ships is based on historical visual observations of ocean wave climate for the North Atlantic. The accuracy these visual observations, however, is questioned in the literature. It has arisen some debate whether this data base is still an appropriate one for modern ship design. In particular there is some uncertainty about the accuracy of the wave period. The potential of SAR data to improve this data basis is discussed.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry