台风期间波浪和局地风对磨刀门水道盐淡水混合的影响机制

Influencing Mechanism of Wave and Local Wind on Water Mixing during Typhoon in Modaomen Waterway

珠江磨刀门水道地处亚热带季风气候区,直面南海,容易受到热带风暴的袭击。选取台风"纳沙",采用SCHISM模型建立磨刀门水道三维水流盐度数值模型,通过数值试验对比,结合势能异常分析法,探究了台风期间波浪和局地风对磨刀门水道混合与层化的影响。结果显示:由于近岸及河道内水深较浅,波高整体较小,波浪对水体层化过程影响不大,对流速分布有一定的调整作用,使其分布更为均匀,并在一定程度上加强水体掺混,利于外海高浓度盐水向河口和海岸扩散。而台风期间强劲的局地风对垂向水体状态以及势能异常变化率各项均有显著作用,影响着盐淡水的层化混合过程。

The Modaomen waterway is located in the subtropical monsoon climate zone,facing to the South China Sea,and is vulnerable to tropical storms.Taking typhoon‘Nesat’as an example,SCHISM method was applied to build three-dimensional baroclinic model for the Modaomen Waterway.This paper explored the influence of wave and local wind on water mixing and stratification based on the comparison of numerical experiments and potential energy anomaly analysis method.The results show that:due to shallow water depth in the near shore area and the river,the wave height was relatively small and wave has little influence on water stratification.It has a certain adjustment effect on the velocity distribution,making it more evenly distributed,and strengthens the water mixing to a certain extent,which is beneficial to the diffusion of high concentration salt water from the outer sea to the estuary and the coast.Besides,the strong local wind during typhoon has a significant effect on vertical water state and each term of change rate of potential energy anomaly,which affects the stratification and mixing process of salt and fresh water.