中国南海表层叶绿素a季节内变化特征及成因

对中国南海表层叶绿素a季节内变化的研究有助于深入认识其海洋特征,满足渔情预报等实际应用需求。利用卫星观测资料分析南海表层叶绿素a不同季节的季节内变化特征,结果表明南海表层叶绿素a季节内振荡强度冬季最高。冬季和春季的季节内振荡最强区域都位于吕宋岛西北侧海区,夏季和秋季振荡较强的区域偏向菲律宾群岛一侧。分析表明研究海区表层温度和表层叶绿素a 存在负相关,冬强夏弱,北强南弱。大部分海区海面高度和叶绿素a 相关性不显著,但南海东南边缘海区海面高度和叶绿素a在季节内存在正相关。冬季海盆尺度逆时针旋转的环流结构应是这些现象产生的原因。除南海东南边缘海区、海南岛东南海区和吕宋岛西侧海区之外,风应力大小和热通量均与叶绿素a 在季节内呈正相关。这显示非局地风场和海流等因素、海洋动力调整过程可能在吕宋海峡以西和南海东南边缘的表层叶绿素a 季节内变化中起到重要作用。

Features and Driving Mechanisms of the Intra-seasonal Variation of Sea Surface Chlorophyll a in the South China Sea

The study of intra-seasonal variation of sea surface chlorophyll a in the South China Sea (SCS) is helpful to promote the understanding of regional oceanic characteristics and the forecasting of fish activity information. Based on satellite data, this study analyzes the intra-seasonal variation in different seasons in the SCS, and finds that the magnitude of intra-seasonal variation of sea surface chlorophyll a is the highest in winter. In winter and spring, the regions with strong intra-seasonal variation are located to the northwest of the Luzon Island. In summer and fall, the regions with strong variation are shifted to the vicinity of the Philippine Islands. Correlation analysis shows that there is a tight relation between the intra-seasonal variation of sea surface temperature and the sea surface chlorophyll a, which is negative, and more significant in winter than in summer. In most regions, the correlation between the intra-seasonal variation of sea surface height and the sea surface chlorophyll a is not significant, but in the south-eastern rim of the SCS basin the correlation is positive. The above-mentioned features are likely caused by the anticlockwise basin scale circulation in winter. Analysis also shows that, except for the south-eastern rim of the SCS, the area to the south-east of the Hainan Island, and that to the west of the Luzon Island, magnitude of wind stress and sea surface heat flux are positively correlated with the sea surface chlorophyll a intra-seasonal time scale. Our study indicates that non-local factors and ocean dynamical adjustments might play an important role in the intra-seasonal variation of sea surface chlorophyll a in the region to the west of Luzon Island and in the south-eastern rim of the SCS basin.