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引用本文:孙凌,王晓梅,郭茂华,唐军武.MODIS水色产品在黄东海域的真实性检验.湖泊科学,2009,21(2):298-306. DOI:10.18307/2009.0220
SUN Ling,WANG Xiaomei,GUO Maohua,TANG Junwu.MODIS ocean color product validation around the Yellow Sea and East China Sea. J. Lake Sci.2009,21(2):298-306. DOI:10.18307/2009.0220
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MODIS水色产品在黄东海域的真实性检验
孙凌1, 王晓梅2, 郭茂华2, 唐军武2
1.中国气象局国家卫星气象中心, 北京 100081;2.国家海洋局国家卫星海洋应用中心, 北京 100081
摘要:
水色产品的真实性检验无论对于算法的改进还是后续应用的可靠性保障来说都是十分重要的.中国近海是世界上最为浑浊的海域之一,NASA标准MODIS水色产品在该海域的精度十分有限.然而,局限于高质量海上实测数据的获取,相关的检验工作并未得到有效开展.利用2003年春季和秋季黄东海航次的实测数据对MODISAqua标准水色产品中的归一化离水辐亮度LwN(λ)(转换成遥感反射率Rrs(λ))和叶绿素a浓度(Chl.a)进行了真实性检验分析.采用3×3像元和±3h作为时空匹配窗口,并根据空间均匀性判识准则进行了数据剔除.基于验证数据(中低混浊水体)的分析,得到初步结论:(1)MODIS的Rrs(λ)反演结果具有一定精度,但是不能满足10%的误差期盼,且412nm波段的结果明显较差.反演值与实测值之间具有良好线性相关关系,对于所有6个波段,均方根偏差约为0.0030sr-1,相对偏差绝对值的中值约为25%.MODIS反演的Rrs(λ)与实测光谱的形状基本相似,数值多数偏低,特别是在高值区,另外,412和667nm波段在低值区大多数偏低,甚至出现负值,主要是大气修正过程中近红外波段离水辐射和气溶胶类型不适当造成的.(2)MODIS的Chl.a精度很差.反演值整体偏高,且与实测值之间不具有明显的线性相关关系,两者的均方根偏差约为1.56mg/m3,相对偏差绝对值的中值约为103.25%,主要是OC3M模型(系数)的不适用性造成的.
关键词:  真实性检验  黄东海  MODIS  遥感反射率  叶绿素a浓度
DOI:10.18307/2009.0220
分类号:
基金项目:国家自然科学基金项目(40606043);国家863计划项目(2007AA12Z145);国家重点基础研究发展计划项目(2006CB40370)联合资助
MODIS ocean color product validation around the Yellow Sea and East China Sea
SUN Ling1, WANG Xiaomei2, GUO Maohua2, TANG Junwu2
1.National Satellite Meteorological Center, China Meteorological Administration, Beijing 100081, P. R. China;2.National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, P. R. China
Abstract:
Ocean color product validation is vital to improve the algorithms and to secure subsequent applications. China coastal region is one of the most highly turbid waters in the world. The precision of NASA's standard MODIS ocean color products are poor for this region. However, the validations have not been made due to the shortage of high quality in-situ data. In this paper, in-situ data collected in the Yellow Sea and the East China Sea in the spring and autumn of 2003 are used to validate the main parameters of MODIS Aqua standard ocean color product, i.e., the normalized water-leaving radiance LwN(λ) (converted to remote sensing reflectance Rrs(λ)) and chlorophyll-a concentration (Chl.a). The resolution of 3×3 pixel box and ±0.5h are used as the sampling window, and spatial homogeneity criteria are used to screen data. Based on the analysis of match-ups (in low and middle turbid waters), primary conclusions are obtained: (1) MODIS-derived Rrs(λ) can assure certain precisions but can not satisfy the expected error of 10%, and has obviously poor results in 412nm bands. There is good linear relationship between satellite images and modeled images. The overall root mean square error is 0.0030sr-1 and the median of absolute values over the relative error is about 25%, respectively. Derived Rrs(λ) is similar with in-situ ones in spectrum shape, and is mostly underestimated especially in high value region. Besides, Rrs(λ) at 412 and 667nm bands are mostly underestimated with even negative values in low value region. The reasons for this phenomenon are due to the influences of water-leaving radiance in the near-infrared bands and improper aerosol models used in the atmospheric correction process. (2) MODIS derived Chl.a is very poor. The satellite derived values are systematically overestimated. And there is no obvious linear relationship between satellite derived and in-situ Chl.a, which the root mean square error is about 1.56mg/m3, the median absolute relative error about 103.25%, and the median satellite to in-situ ratio about 2.03. The major reason for this phenomenon is the OC3M model (coefficients) unsuitability.
Key words:  Validation  Yellow & East China Sea  MOIDS  remote sensing reflectance  chlorophyll-a concentration
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