长江口叶绿素分布特征和营养盐来源数值模拟研究

Study on the character of distribution of chlorophyll-a off the Changjiang River and its sources of nutrients

利用POM(Princeton Ocean Model)模型在长江口及其邻近海域建立了三维斜压动力学模式,该模式开边界处考虑了潮汐、潮流、台湾暖流、沿岸流和长江径流。模式成功地模拟了长江口及其邻近海域的潮汐特征和环流特征。此外2004年11月的实测数据分析结果表明在观测区域的水下河谷西侧位置的强表面羽状锋内,存在着高叶绿素a浓度分布。为了分析长江口外存在的高叶绿素浓度分布和长江口的营养盐输入的相关关系,进行了两次数值试验:(1)给定长江口的径流量和径流输入的营养盐,把长江口的输入作为营养盐输入的惟一源;(2)在开边界处,根据实测资料给定营养盐的输入,同时考虑径流营养盐输入。在(1)、(2)两种情况下,把硝酸盐作为保守物质,进行了平流扩散数值试验。模式的模拟结果和实测资料的对比分析表明:沿岸流、台湾暖流的营养盐输入和上升流从底部输入的营养盐是此高叶绿素浓度区营养盐的重要来源。

We succeeded in implementing baroclinic 3D ocean model POM（Princeton ocean model） in Changjiang River mouth and its adjacent area to simulate the tide,tide current,Taiwan Warm Current,and Taiwan Coastal Current.An interdisciplinary comprehensive survey was conducted in November 2004 with modern measurement instruments off the Changjiang River.The analysis of the observation data shows that there exist high chlorophyll-a（Chl-a） concentration area in the surface plume on the west side of the submerged river valley（SRV） off the Changjiang mouth.For analyzing the nutrients sources of the high Chl-a concentration area,two numerical experiments were carried on.In one experiment,the nutrient load via the Changjiang River is considered as the only one input of nutrients.On the other hand,the nutrient load via the Changjiang River and the nutrient input from the open boundaries are coupled together to simulate the nutrients distribution.In the two experiments,the nutrients were considered as conservative mass and were calculated under diffusion and advection processes by tide,tide current,Taiwan Warm Current,and coastal current.In addition,nitrate was representative of nutrients in the simulation.Based on the analysis of the field observation data off the Changjiang River mouth in November 2004 and the calculated results of the 3D numerical model experiments,it indicates that the nutrients of the high Chl-a concentration area comes from two sources.One is the input of nutrients by the upwelling on the west side of the submerged river valley off the Changjiang River mouth,which accounts for 1/2 of the total amount.The other one is the input of fishery in Shengsi and Taiwan Warm Current transport,which accounts for the same amount as the first one.