基于MODIS数据的云南九大高原湖泊叶绿素a浓度反演

Inversion of chlorophyll-a concentration in nine plateau lakes in Yunnan based on MODIS data

叶绿素a浓度是反映水体富营养化程度的重要参数。本研究以MODIS卫星影像为数据源,结合地面实测数据,实现了对云南省九大高原湖泊的叶绿素a浓度反演。首先,以2010—2012年的叶绿素a浓度实测数据为基础,对MODIS不同波段的地表辐射率进行了组合试验,优选出九湖叶绿素a浓度的统计模型。其次,利用2013—2014年的叶绿素a浓度实测数据对反演模型进行了验证。最后,利用优选模型对九湖叶绿素a的空间分布特征和变化动态进行分析。结果表明:获取的九湖叶绿素a浓度的空间分布比较符合专业人员的判断,结果较为合理;滇池、洱海、程海、杞麓湖、星云湖、异龙湖和阳宗海的叶绿素a浓度周围高,中部低,抚仙湖和泸沽湖则为周围低,中部高;从年际变化看,2010—2014年期间,滇池、洱海、星云湖和异龙湖叶绿素a浓度年际波动幅度较大,抚仙湖、程海、杞麓湖和泸沽湖变化较为稳定,阳宗海呈减少趋势。

Chlorophyll-a concentration is an important parameter reflecting the degree of eutrophication. Based on the field data and MODIS remote sensing data,this study achieved the inversion models of chlorophyll-a concentration in nine lakes in Yunnan Province. Firstly,the optimum models of each lake in different seasons were established by the combination of the land surface radiation of different bands of MODIS with the measured chlorophyll-a concentration in2010-2012. Secondly,the inversion models of the nine lakes were validated by using the measured chlorophyll-a concentration from 2013 to 2014. Then,the spatial distributions of chlorophyll-a concentration in nine lakes were analyzed. The spatial distribution of inversed chlorophylla concentration was in accordance with the professional judgment of experts,indicating the inverse models were reasonable. The chlorophyll-a concentrations in Dianchi Lake,Erhai Lake,Chenghai Lake,Qilu Lake,Xingyun Lake,Yilong Lake and Yangzong Lake decreased from the border to the center of lake. However,the chlorophyll-a concentrations in Fuxian Lake and Lugu Lake were higher in the center than in the border of lake. During the period 2010-2014,the concentrations of chlorophyll-a of Dianchi Lake,Erhai Lake,Xingyun Lake and Yilong Lake had larger fluctuation,while those of Fuxian Lake,Chenghai Lake,Qilu Lake and Lugu Lake were relatively stable,and that of Yangzong Lake showed a decreasing trend.