基于CART方法计算的黄河淡水水龄在渤海的分布变化特征

通过计算黄河淡水在渤海内部的水龄变化,能够进一步了解由黄河口排出的溶解性污染物在渤海中的输运时间和分布规律。利用ROMS(Regional Ocean Modeling System)数值模型,加入了基于CART(the constituent-oriented age and residence time theory)方法计算水龄的模块,用于计算黄河淡水水龄在渤海的分布以及长期变化规律。模式较好地再现了渤海物理场以及黄河淡水水龄在渤海中的分布。模拟结果显示水龄在空间分布上差异很大,莱州湾平均水龄为700天,而辽东湾则高达1760天。渤海中部与辽东湾水龄时空分布表现出季节变化,冬季辽东湾水龄西低东高,高龄水自辽东湾东侧入侵渤海中部;夏季辽东湾水龄西高东低,渤海中部低龄水占优。黄河淡水水龄在年际时间尺度上存在明显差异,1998—2003年黄河淡水水龄较高且存在上升趋势,而2003—2007年则迅速下降,此变化主要由黄河入海径流量的改变导致;径流量增大会使淡水水龄降低,反之则会使水龄升高。黄河径流量对黄河淡水水龄的影响主要是通过改变目标区域黄河淡水浓度和低龄淡水质点在水团中所占的比例来实现的。

VARIATION IN HUANGHE RIVER WATER AGE IN THE BOHAI SEA SIMULATED WITH CART METHOD

To understand the elapsed time of soluble pollutants that left from the Huanghe (Yellow) River mouth into the Bohai Sea and its distribution characteristics, the age of the river water in Bohai Sea and its long-term variation were studied by simulation in CART Method (the Constituent-orient Age and Residence Time theory) joined into the ROMS Model (Regional Ocean Modeling System). Results reveal great spatial differences in the water age:700 d in Laizhou Bay and 1760 d in Liaodong Bay, the two major parts in the western and eastern parts of the Bohai Sea, respectively. In winter, water age is high in the eastern and low in the western Liaodong Bay, and the high-age water intrudes into the central Bohai Sea from the eastern Liaodong Bay. In summer in Liaodong Bay, water age is high in the eastern and low in the western Liaodong Bay, and in the central Bohai Sea low-age water concentrated. The water age of Huanghe River presented a clear interannual variation, i.e., from 1998 to 2003, water age was greater than that from 2003 to 2007 and showed an increasing trend. However, after 2003, the water age showed a decreasing trend, which was resulted mainly from the change in the Huanghe River runoff. When the runoff increased, water age of the river water decreased, and vice versa. The river runoff affected the water age in the Bohai Sea by changing fresh water concentration and proportions of low-age water in local areas.