地球信息科学学报 ›› 2014, Vol. 16 ›› Issue (6): 989-996.doi: 10.3724/SP.J.1047.2014.00989

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太湖浮游藻类的后向散射分离及其叶绿素a浓度反演

阎福礼1(), 刘韶菲1,2, 王世新1,*(), 周艺1   

  1. 1. 中国科学院遥感与数字地球研究所,北京 100101
    2. 中国科学院研究生院,北京 100049
  • 收稿日期:2014-03-17 修回日期:2014-04-18 出版日期:2014-11-10 发布日期:2014-11-01
  • 通讯作者: 王世新 E-mail:yanfl@radi.ac.cn;wangsx@radi.ac.cn
  • 作者简介:

    作者简介:阎福礼(1973-),男,博士,副研究员,主要从事定量反演研究。E-mail:yanfl@radi.ac.cn

  • 基金资助:
    国家自然科学基金项目“富营养化水体的比辐射率测量及其红外水温遥感反演”(41371363)

Phytoplankton Backscattering Coefficients Partitioning and Its Applications in Retrieving Chlorophyll-a Concentrations in Taihu Lake

YAN Fuli1(), LIU Shaofei1,2, WANG Shixin1,*(), ZHOU Yi1   

  1. 1. Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
    2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2014-03-17 Revised:2014-04-18 Online:2014-11-10 Published:2014-11-01
  • Contact: WANG Shixin E-mail:yanfl@radi.ac.cn;wangsx@radi.ac.cn
  • About author:

    *The author: CHEN Nan, E-mail:fjcn99@163.com

摘要:

浮游藻类的后向散射是水体光谱构成的重要组成部分,作为水体辐射传输模型中的重要参数,高精度的藻类后向散射系数对水体叶绿素a浓度的遥感反演精度至关重要。本文以简化的辐射传输模型-生物光学模型为基础,尝试性分离了太湖浮游藻类的后向散射系数。通过藻类后向散射规律分析,建立了浮游藻类吸收、后向散射特征的叶绿素a反演模型,改善了叶绿素a浓度的遥感反演精度。分析表明:藻类颗粒物的后向散射系数与吸收系数之间存在反比关系,且在560 nm、700 nm附近存在明显的散射峰,与叶绿素a浓度之间相关性显著;低密度藻类水体总悬浮颗粒的后向散射以非色素颗粒为主导,适合采用经典的指数模型模拟后向散射系数,而藻类密度较高的富营养化水体,水体总悬浮颗粒的后向散射以藻类颗粒为主导,传统的指数模型已不适用;采用分离藻类后向散射系数的方法,使得叶绿素a浓度的反演值与真实值相关系数从0.66提高到0.98,相对误差从55%降低到38%,均方根误差(RMSE)也由60.95 μg/L降低至13.98 μg/L。其真实性检验表明,与经典指数模型方法相比,利用藻类颗粒后向散射分离方法反演叶绿素a浓度,能够显著改善反演精度。

关键词: 藻类颗粒, 后向散射系数, 分离, 富营养化水体

Abstract:

As key parameters in bio-optical model, the backscattering coefficients of phytoplankton plays an important role in modelling the reflectance spectra and retrieving chlorophyll-a (CHL-a) concentrations from eutrophic water. An exponential model is usually used to simulate the total backscattering coefficients by omitting the phytoplankton backscattering in inland water characterized by lower concentrations of CHL-a. However, the exponential model is not valid for inland water with high CHL-a concentrations, and high relative errors and residues may exist in retrieving the CHL-a concentrations in the algae blooming area, due to the errors made by omitting or introducing inaccurate backscattering coefficients of phytoplankton. Therefore, a precise determination of the phytoplankton backscattering coefficients is of great importance in retrieving chlorophyll-a concentrations. Based on the classical bio-optical model, we proposed a method to partition the phytoplankton backscattering coefficients. The variations of the backscattering coefficients of phytoplankton particles with wavelengths in 400~700 nm and the chlorophyll-a concentrations are illustrated and discussed in details. According to the results mentioned above, following conclusions are drawn: (a) it is appropriate to model the total backscattering coefficients by using exponential function in most Case 2 waters with lower concentrations of Chlorophyll-a, where the non-algal suspended sediments dominated the optical properties. However, it is not applicable in eutrophic waters with higher concentrations of chlorophyll-a, where the algal particles dominated the optical properties; (b) phytoplankton backscattering coefficients vary inversely to their absorption coefficients, and two backscattering peaks emerge in the wavelengths of 560nm and 700nm, which are significantly correlated with CHL-a concentrations; (c) compare to the exponential model, the accuracy of the bio-optical model using the partitioned phytoplankton backscattering coefficients has improved greatly: the correlation coefficient between the retrieved and the measured CHL-a is increased from 0.66 to 0.98, the average relative error decreases from 55% to 38% , and the RMSE decreases from 60.95 to 13.98 in estimating CHL-a concentrations.

Key words: phytoplankton, backscattering coefficients, partitioning, eutrophic water