不同时间尺度下长江口海域表层悬浮体浓度变化

长江入海泥沙是中国东部陆架海沉积物的主要来源之一。本文基于MODIS-Aqua卫星的遥感资料并结合实测悬浮体浓度,建立了基于颗粒物后向散射系数的悬浮体浓度的反演方法,获取了2002—2017年长江口海域的表层悬浮体浓度分布,并分析其在潮周期、季节内以及年际等不同时间尺度下的变化特征。结果表明,在潮周期内,长江口122.3°E以西海域表层悬浮体浓度大潮高于小潮,落潮大于涨潮,高潮大于低潮;在季节尺度内.6—8月表层悬浮体浓度逐渐增加。而122.3°E以东海域,则出现相反的情况;长江口122.3°E以西海域的夏季平均表层悬浮体浓度年际变化明显,主要受长江入海水沙量年际变化的影响。长江口122.3°E以东海域表层悬浮体浓度的年际变化几乎不受长江入海泥沙的影响。风向对悬浮体浓度的扩散具有显著的作用,南风有利于高浓度悬浮体向外海扩散,东风则抑制扩展。

MULTIPLE TIMESCALE VARIATION IN CONCENTRATION OF SURFACE SUSPENDED SEDIMENT IN CHANGJIANG RIVER ESTUARY

Suspended sediments from the Changjiang (Yangtze) River are one of the main sources of sediments onto the shelf of the East China Sea. To analyze the multiple timescale variation in concentration of the surface suspended sediment and its relevant factors in the Changjiang River estuary during 2002-2017, we developed an algorithm between particle backscattering coefficient and suspended sediment concentration with in-situ measurements and MODIS-Aqua satellite data. The results indicate that the surface suspended sediment concentration is higher in spring, ebb, and high tide than those of neap, flood, and low tide, and the concentration of surface suspended sediment increases gradually from June to August in the west of 123°E of the estuary. The opposite situation occurs in the east of 123°E of the estuary. The concentration of surface suspended sediment varies inter-annually and significantly, due to the sediment discharge in the west of 123°E of the estuary. The inter-annual variability in concentration of surface suspended sediment shows no relationship with the sediment discharge in the east of 123°E of the estuary. In addition, wind direction has a significant effect on diffusion of suspended sediment. The southerly wind contributes to the diffusion of suspended sediment, and the easterly wind inhibits the transport of suspended sediment into the sea.