珠江口磨刀门水道枯季咸潮上溯与盐度输运机理分析

Analysis on salinity transport mechanism for the Modaomen waterway of Pearl River in the dry season

以珠江河口磨刀门盐度和流速观测资料为基础,采用盐度输运分解的计算方法对磨刀门盐度输运特征进行分析,对比各分解项动力成因和对盐度输运贡献的大小,分析磨刀门水道盐度分布特征和输运特征,结果表明:(1)磨刀门水道盐度输运主要由径流为主要作用的欧拉输运、潮流剪切输运和由河口密度梯度产生的垂向环流输运为主,其中欧拉输运方向向海,潮流剪切和重力环流输运向陆,两种不同方向的盐度输运在大、小潮期相对强弱的变化,导致了咸潮上溯的增强或者减弱。小潮期间,垂向环流和潮流剪切输运大于欧拉输运,净输运方向向陆导致咸潮上溯;大潮期间,垂向环流输运显著减小,净输运方向向海导致咸潮后退。(2)洪湾水道盐度输运主要以欧拉输运为主,垂向环流输运很小,与磨刀门水道盐度输运具有显著的不同。

Based on the observation data of salinity and velocity in the Modaomen waterway of Pearl River, the decomposition calculation method of salinity transport was used to analyze the characteristics of salinity transport. Comparing each decomposition term by dynamics and contribution to salinity transport to analyze the characteristics of salinity distribution and transportation in Modaomen, the result shows that： （1） Euler transport, tidal shear transport and vertical circulation transport caused by density gradients play major roles in the salinity transport in Modaomen waterway, and among these, the direction of Euler transport is seaward, and the tidal shear transport and vertical circulation transport are landward. The changes of salinity transport in two different directions at the relative strength of the spring and neap tides result in salt water intrusion increase or decrease. In neap tide, the vertical circulation transport is greater than Euler transport, so the net transport is landward which makes salt water intrusion; in spring tide, the vertical circulation transport is significantly decreased, so the net transport is seaward which makes salt water retreat. （2） In Hongwan waterway, Euler transport is the main way for the salinity transport while the vertical circulation transport is small, which is different from Modaomen waterway.