Global Analysis of a 2 Year ERS-2 Wavemode Dataset Over the Ocean

Abstract

Starting in 1991, the ERS-1 and (later) ERS-2 satellites have collected wavemode data over the global oceans whenever no image mode data acquisition was requested. Wavemode data are full resolution SAR data covering small areas of size 5km x 10km every 200km along the orbits thus forming a dataset giving information from all global oceans daily. In the scope of the WAVEATLAS ESA AO Project, ESA provided two years (Sep. 1998 – Nov. 2000) of raw ERS-2 wave mode data to DLR which were processed into more than one million single look complex images, so-called imagettes, using DLR's BSAR processor. The algorithms CWAVE and LISE were applied to estimate wind and wave parameters such as significant wave height, wind speed and sea surface elevation fields together with several single wave parameters. The paper presents global statistics with emphasis on wave parameters, namely significant wave height, single wave crest height, and wave height. Areal and seasonal distribution of high sea states is discussed and the relevance of the analysis for extreme sea state mapping is pointed out. As far as possible, the results are related to existing theoretical knowledge and compared to observational data (Hogben atlas) as well as model results. The outcome of this processing will be compiled into a new unique atlas on global waves and extreme events. It is planned to extend the atlas back to 1991 when ERS-1 was launched and forward to present times thus covering a more than 15 years period.