夏季长江冲淡水年际变化的数值研究

The modeling study of interannual variability of Changjiang River plume in summer season

基于区域海洋模式ROMS,本文对东中国海的水动力环境进行了长期(2004-2015年)模拟,分析了长江冲淡水扩展形态的年际变化特征和规律。研究发现,夏季长江冲淡水主要有三种扩展形态:东北方向、东南方向和东南-东北双向扩展,三种形态所占比例分别为37%,46%和17%。长江冲淡水的扩展面积具有显著的年际变化,近河口冲淡水(海表面盐度<28)的扩展面积主要受径流量控制,在外海(28<海表面盐度<31)则主要受南风和西南风的影响。就淡水通量而言,向东北方向最多,向东南方向次之,二者7、8月份所占比例分别为40%、60%和33%、32%。夏季长江冲淡水向东北方向的扩展主要受东风或较强东南风的影响。年际尺度上,向东北方向的淡水输运与东南方向风分量具有很好的相关性,主要受东南风驱动的Ekman输运的影响。

A ROMS model has been configured for the Changjiang River plume region and the East China Sea.A hindcast run has been conducted for the period of 2004-2015.The interannual variability of the dispersal structure of the Changjiang river plume,along with its freshwater transport are then investigated based on the long term simulation.The modeling result shows that there are generally three dispersal structures of the Changjiang river plume,i.e.,the northeastward,the southeastward,and the northeast-southeast bi-directional structure,which accounts for 37%,46%,and 17%of all summer months.The surface area of the Changjiang River plume exhibits significant interannual variations.The near field plume area(sea surface salinity<28)is dominated by the Changjiang river discharge,while the far field plume area(28<sea surface salinity<31)is mainly modulated by the southerly and southwesterly winds.In terms of freshwater transport,the main direction is northeastward,with southeastward taking the second place.The two directions accounts for about 40%and 33%of the total freshwater transport in July,and 60%and 32%in August.In summer,the northeastward dispersal of the Changjiang River plume is mainly affected by the easterly or the strong southeasterly winds.The inerannual variation of the freshwater transport towards northeast is dominated by the southeasterly winddriven Ekman transport.