夏季舟山上升流长期遥感观测与分析

Long-term remote sensing observation and analysis of upwelling around Zhoushan Islands in summer

舟山海域夏季常年存在上升流,且强度、范围等具有年际变化。本文利用2002—2011年7—8月份的海表温度和叶绿素a浓度数据,研究了舟山夏季上升流区域的物理特征、年际变化;此外,利用上升流区域与外海的海表温度差值以及对应的叶绿素a浓度分布范围,定义了上升流的边界。研究结果显示,舟山海域夏季海表温度明显低于外围海域,范围在29°~31°N,122°~123°E,中心平均温差在1.5℃。7月份的叶绿素a浓度均值达到6.6 mg/m^(3),且上升流区域和非上升流区域叶绿素a浓度差异大,表明上升流处于强势期。8月份的叶绿素a浓度均值达到6.4 mg/m^(3),但各年份间的差异较大,具有明显的年际变化特征。结合叶绿素a浓度分布特征和海表温度差值数据,可定义7月份的舟山上升流边界温度阈值为0.75℃,8月份阈值为0.5℃。

The upwelling exists in Zhoushan year round in summer,and its intensity and range change interannually.In this study,sea surface temperature and chlorophyll a concentration from July to August during a period from 2002 to 201l were used to study the physical characteristics and interannual changes of the Zhoushan upwelling region in summer.In addition,the upwelling boundary was defined using the difference of SST between the upwelling area and the outer waters and the corresponding distribution range of chlorophyll a concentration.The results showed that the summer sea surface temperature of Zhoushan sea area was significantly lower than that of the outer waters,ranging from 29°N to 31°N and from 122°E to 123°E,and the average temperature difference in the center was 1.5℃.The average chlorophyll a concentration in July reached 6.6 mg/m^(3),and the chlorophyll a concentration difference between the upwelling area and the non-upwelling area was large,indicating that the upwelling was in a strong period.The average chlorophyll a concentration in August reached 6.4 mg/m^(3),but the difference between the years was large,with obvious interannual variation characteristics.Combining the chlorophyll a concentration distribution characteristics and the sea surface temperature difference data,it can be defined that the Zhoushan upwelling boundary temperature threshold in July is O.75 C,and the threshold in August is O.5C.