渤海表层悬浮泥沙的空间模态及其时间变化

针对整个渤海海域悬浮泥沙分布全貌研究的不足,基于2000-2004年连续5年的354个SeaWiFS反演的渤海表层悬沙浓度资料,经多年月平均得到其季节变化特征;通过经验正交函数分解,给出其空间模态及时间系数,揭示渤海表层悬浮泥沙的空间分布特征及其随时间的变化。渤海表层悬沙浓度除秦皇岛海域外近岸高,离岸低,辽东湾东岸浓度远大于西岸;冬季浓度最高,春秋次之,除河口海域外夏季浓度最低;河口海域冬夏季均为浓度高值区。经验正交分解显示第一空间模态反映渤海悬沙浓度的总体分布特征,其显著变化周期为12个月,显示渤海表层悬沙的季节变化特征。第二空间模态反映黄河入海径流对渤海表层悬沙浓度分布格局的影响, 其周期为6个月,代表黄河口海域悬沙浓度的变化周期。第三模态显示渤海不同海域悬沙浓度的增加或减小过程并不同步,存在明显的位相差异。

Spatial modes of suspended sediment concentration in surface water in Bohai Sea and their temporal variations

A five years (2000-2004) SeaWiFs satellite dataset is used to investigate the overall pattern of suspended sediments in the Bohai Sea Basin. The dataset consists of 354 charts of suspended sediment concentration (SSC) in surface water, which cannot be obtained by the conventional procedure through in-situ sampling. Results show that the 5-year mean seasonal cycle of SSC is constructed for the entire Bohai Sea Basin. The SSC exhibits a character of spatial distributions with higher values from inshore waters and lower values from offshore waters, except for those near Qinhuangdao Island. Furthermore, the SSC in the eastern part of Liaodong Bay is much higher than that of the western part. Highest concentrations occur during winter seasons and followed by spring and autumn seasons. The opposite is true during summers, except for estuary areas where the concentration remains higher during both summers and winters. The empirical orthogonal function decomposition (EOF) analysis is performed to reveal the spatial modes and the corresponding time coefficients in Bohai Sea. Results show that the first EOF mode indicates a basin-wide pattern of SSC in the Bohai Sea with an annual variation of 12-month period. The second mode reveals the influence of the Yellow River runoff on the SSC in the Bohai Sea with a dominant semi-annual (6 months) variation at the estuary of the Yellow River. The third mode indicates that there exists a clear difference in the variation of the SSC in different waters in Bohai Sea.