热带东印度洋6°N断面有色可溶性有机物(CDOM)光谱吸收特性

Spectral absorption properties of colored dissolved organic matter along 6°N transect of tropical eastern Indian Ocean

有色可溶性有机物(colored dissolved organic matter,CDOM)光谱吸收特性是构建生物光学模型及水色遥感反演算法的重要基础。在2011年4月1日至5月中旬的东印度洋综合科学考察实验研究航次中,采集了6°N断面9个站位的CDOM样品并进行了测量;通过分析吸收系数aCDOM、光谱斜率值S、CDOM分子量相对大小的指示参数M值等参量,探讨了该断面处CDOM浓度与组成成分的分布及影响因素。分析结果发现,aCDOM(355)的变化范围为0.131—0.524m?1,平均值为0.272m?1;aCDOM(375)的变化范围为0.081—0.453m?1,平均值为0.242m-1,该范围小于近岸水体,高于东南太平洋海水,与南海北部18°N断面相近。叶绿素a浓度与CDOM吸收系数及光谱斜率没有表现出明显的相关性。CDOM光谱斜率的变化范围较大,其中S300—500nm的变化范围为0.008—0.019nm?1,平均值为0.012nm?1。S300—350nm与M值之间表现出正相关关系,吸收系数与光谱斜率及M值呈现出很好的负相关关系。结合该断面CTD资料发现,在30—90m水层高盐水团的影响下,M值在高盐区的平均值大于其右侧相同深度的结果,aCDOM(355)在高盐区的平均值小于其右侧相同深度的结果;在垂直方向上,受高盐水团影响区域M值没有表现出明显规律,而在其右侧则随着深度的增加M值逐渐减小,aCDOM(355)逐渐增加。

The spectral absorption properties of colored dissolved organic matter （CDOM） is important for building bio-optical model and for quantitative ocean color remote sensing. During the Eastern Indian Ocean Integrated Scientific Investigation Cruise from April 1 to mid-May, 2011, CDOM was sampled at nine stations along 6°N. Based on the dataset of 36 samples, we examined the relationship between spectral absorption coefficients and the slope of absorption curve （S）. Over the whole transect, aCDOM （355） spanned the range of 0.131？0.524 m？1 with an average value of 0.272 m？1, and aCDOM（375） varied between 0.081 and 0.453 m？1 with an average value of 0.242 m？1. The concentration of CDOM was lower than that of nearshore waters, similar to the findings along 18°N of the South China Sea. There exists low correlation between chlorophyll a and absorption coefficient of CDOM. S300-500nm varied between 0.008 and 0.019 nm？1, averaging 0.012 nm？1;S300-350nm was a good indication to M, the molecular relative weight of CDOM. Absorption coefficient and S of CDOM showed a good negative correlation, so did M and absorption coefficient. By analyzing CTD data along the 6oN section, water mass with high salinity at depth 30？90 m was found to have an impact on horizontal and vertical distribution of M and aCDOM（355）.