ANALYSIS OF SEASONAL CHANGE OF MEAN SEA-LEVEL IN THE CHANGJIANG ESTUARINE AREA
长江河口区平均海面季节性变化的分析

The most obvious feature of the short term sea-level variations in the Changjiang estuarine area is the seasonal cycle, which is dominated by the runoff of the Changjiang river and a variety of ocean processes as well as other factors. The monthly mean sea-level changing range is from 40 cm to 70 cm. The changing magnitudes are significant within the estuary and decrease seaward due to the expansion of the runoff and the actions of other factors; consequently, the fluctuations of sea-surface slope varies with different seasons. The highest gradient occurs during the summer and autumn, and the lowest gradient occurs in the winter. Spatial and temporal patterns of monthly mean sea-level of the Changjiang estuarine area have been calibrated by eigenfunction models identifying several distinct factors which influence on the monthly mean sea-level. The most significant factors are the variations in the runoff, atmospheric pressure and temperature, which account for about 45%, 23%, and 26% of total amount of monthly mean sea-level changes respectively, and the other two factors are abnormal change of the river runoff and the set-up resulting from moonson.