利用SOM神经网络研究长江口邻近海域海表温度特征

摘要: 长江口及邻近水域的海表面温度（SST）受到多种动力过程的共同作用，呈现出复杂的时空变化规律.本研究基于数值模拟的结果，采用SOM（Self-Organizing Map）自组织神经网络方法，对长江口及邻近海域SST的季节、大小潮和天气等不同时间尺度上的变化规律进行聚类分析.研究结果表明：长江口及邻近海域的SST在冬、夏季节比较稳定，春、秋季节随时间变化较大；长江口南部沿岸的低温带主要是由长江冲淡水冬季向南扩展造成的；近岸地区尤其是舟山群岛附近存在低温区，与浙江沿岸的上升流相关；苏北地区低温带和向东南方向延伸的低温水舌在冬季和春季最为明显.
- 长江口 /
- SOM神经网络 /
- 海表温度
Abstract: Sea surface temperature (SST) in the Changjiang Estuary and adjacent waters is affected by multiple dynamic processes, which show complex spatiotemporal variability. In this study, the SST variability was investigated by analyzing modeled results with a Self-Organizing Map (SOM) method. The SST variations were clustered on seasonal, spring-neap, and intra-tidal timescales. It was found that the SST pattern remains stable during the winter and summer seasons but highly variable during the spring and autumn seasons. A cold water band is present south of the Changjiang River mouth in the winter season, due to the southward along-shore extension of the Changjiang River plume. A cold water patch occurs near the Zhoushan Islands, caused by upwelling in the Zhejiang coastal water. In the Subei coastal water, the cold water patch and tongues were most significant during the winter and spring seasons.
- Changjiang Estuary /
- SOM neural network /
- sea surface temperature

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图 1 2016年5月(左)和7月(右)两个航次现场观测(上)和数值模拟(下)的海表温度对比

注: 黑色点代表观测位置; 温度单位℃

Fig. 1 Observed (upper panels) and modeled (lower panels) sea surface temperature in May 2016 (left panels) and July 2016 (right panels)

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图 2 2016航次观测点温度与模型温度比较

注: 直线表示由数据点线性拟合所得直线, 左上角为拟合直线表达式和相关系数的平方

Fig. 2 Comparison of sea surface temperature between observed and modeled results

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图 3 2016全年海表温度SOM 3×3的模态结果

注: 每个模态右上角的数值表示此模态出现的频率; 箭头($\to)$表示BMU时间序列指示的模态年内变化过程, 根据图 4中BMU图的每一时间段对应的模态, 把模态变化分为四季, 灰色箭头表示冬季模态跳动, 红色为春季, 绿色为夏季, 蓝色为秋季

Fig. 3 3×3 SOM patterns of sea surface temperature in 2016 with the frequency of occurrence given as a percentage

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图 4 2016全年BMU时间序列、区域风场时间序列、径流时间序列以及海气热通量时间序列

Fig. 4 BMU time series(first panel), time series of local wind(second panel), runoff(third panel), and air sea heat flux(fourth panel) in 2016

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图 5 2016夏季海表温度的SOM 2×2模态结果

注: 每个模态右上角的数值表示此模态出现的频率

Fig. 5 2×2 SOM patterns of sea surface temperature in the summer of 2016 with the frequency of occurrence given as a percentage

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图 6 2016夏季的BMU时间序列图(上)和长江口外(122.55°E, 30.95°N)的潮位时间序列(下)

Fig. 6 BMU time series(upper panel) and the water level time series (lower panel) in the Changjiang Estuary(122.55°E, 30.95°N) in the summer of 2016

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图 7 2016年7月26日到8月1日SOM 1×2海表温度模态结果

注: 每个模态右上角的数值表示此模态出现的频率

Fig. 7 1×2 SOM patterns of sea surface temperature with the frequency of occurrence given as a percentage from July 26th to August 1st, 2016

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图 8 2016年7月26日到8到1日BMU时间序列

Fig. 8 BMU time series from July 26th to August 1st, 2016

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