长江河口横沙小港泥沙浓度的观测及研究

用OBS－3浊度计在1998年2月12日至21日期间在长江河口横沙小港对悬浮泥沙浓度作了观测，同时也用ENDCO海流计测量了流速、流向、水温和盐度。观测数据表明不论潮还是小潮期间，在落潮过程中泥沙浓度的扰动比涨潮过程中更加频繁和强烈，存在着高频振荡。动力分析表明这是由潮扩散的不对称性造成的，即落潮期间垂向湍流扩散比涨得垂向切变不稳定增强。观测还指出泥沙浓度的变化与流速密切相关，存在着泥沙峰值滞后于流速峰值的现象。这是首次用先进的OBS浊度仪在长江口横沙小港观测在落潮期间泥沙浓度的高频扰动，并从动力成因上做出了解释。

Observation and Study of Suspended Sediment Concentration at Hengsha Channel in the Changjiang Estuary

The OBS-3 turbidity monitor was used to measure the suspended sediment concentration at the site in the Hengsha channel of the Changjiang Estuary during 12-21, February 1998. We also used the ENDCO current meters to measure the current speed and direction, water temperature and salinity simultaneously. The observation showed that the perturbations of sediment concentration in the ebb tides are much more frequency and large than the one in the food tides in both the spring and neap tides. This is caused by the tidal diffusion asymmetry in which the vertical turbulence diffusion in the ebb tides is weaker than the one in the flood tides. The much weaker tidal vertical diffusion in the ebb tides makes the vertical velocity gradient larger in the ebb tides than the one in the flood tides, thus makes the vertical stress instability increase. This is the reason why the sediment concentration is of much more perturbation during the ebb tides. In addition, the measurement also indicated that the sediment concentration variation is closely related to the current velocity, and the phenomenon that the peaks of sediment concentrations lag the one of the current speeds. This is the first time that the much more perturbation of sediment concentration during ebb tides in the Changjiang Estuary was found with the advanced OBS turbidity monitor,and is interpreted dynamically.