Analysis of an Event of “Parametric Rolling” Onboard RV “Polarstern” Based on Shipborne Wave Radar and Satellite Data

摘要

During the Antarctic summer season 2008/2009 the wave radar system WaMoS II was installed onboard of the German research vessel �Polarstern.� The purpose was to collectudquasi-in situ data for the comparison with satellite-borne SARudand altimeter instruments (Envisat, TerraSAR-X, Jason). Theudexperiment was part of the German research project DeMarine-udSecurity. On 7 March 2009 in the central South AtlanticudOcean, �Polarstern� was heading towards Punta Arenas againstuda rough cross sea. In the night, a sudden event of heavy rolling,udi.e., an oscillation about its length axis, hit the vessel and lastedudfor a few minutes. Using WaMoS II data, as well as ENVISATudand wave model data, we investigate the conditions under whichudthe event occurred. It is shown that the rolling was caused by aud�parametric� resonance when the period of encounter came close to one half of the vessels�s natural rolling period. We conclude that an onboard wave radar can be helpful in diagnosing and forecasting critical conditions.