EOF ANALYSIS OF WATER LEVEL VARIATIONS ALONG WEST SHORELINE OF SOUTHERN YELLOW SEA

We analyzed the water level data obtained from 28 stations along the west shore of the southern Yellow Sea from January 04, 2006 to January 31, 2007, using the statistical and empirical orthogonal function (EOF) method as a tool. The average tidal range, maximum tidal range, average tidal period and phase lag of high tide were calculated. The results indicated that the study area was mainly dominated by M₂ tidal component. The EOF mode I contained 72.6% variations of water level, agreed well with the average tidal range. Both the mode Ⅰ and modeⅡclearly showed the effects of semidiurnal tidal components, e.g. M₂ and S₂. Specifically, the mode I and modeⅡ were the results of orthogonal decomposition of phase difference. The mode Ⅲ contained the information of water level variations caused by the river discharge in summer time. In addition, many of posterior modes contained the information of water level disturbances. This work indicates that EOF is a useful and efficient tool for water level analysis and has the potential to detect disturbances of water levels.