呼伦贝尔草甸草原MODIS/LAI产品验证
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摘要
以内蒙古呼伦贝尔草甸草原为研究区域,利用2013年6期地面实测数据,结合HJ-1A/B CCD高分辨率影像,经过辐射校正与模型建立,对研究区域草原生长季的MODIS/LAI产品进行验证。结果表明:在时间上,MODIS/LAI产品能够较好地反映草原的长势与物候变化。在空间上,由于MODIS/LAI产品输入数据的不确定性,MODIS/LAI产品与地面情况存在一定偏差(ΔLAI=0.59m2/m2),在呼伦贝尔草甸草原草场整个生长季都存在高估现象,平均相对误差为40%。在生长初期和末期,较大的地表异质性使MODIS/LAI产品高估现象较严重;生长中期高估现象减小,相对误差在30%以内。研究结果对了解该地区的MODIS/LAI产品精度与使用该地区MODIS/LAI产品具有重要指导意义。
Leaf area index is a crucial parameter of vegetation structure which provides key information for earth surface process simulation and climate change research on the global and regional scales.Focusing on the meadow steppe in Hulunber,Inner Mongolia,the accuracy of MODIS/LAI product in this region was analyzed.Firstly,the in situ LAI data were acquired through six field experiment in 2013,and the regression models between in situ LAI and vegetation indices were established;then,six high resolution LAI maps from corresponding HJ-1A/B CCD were obtained;finally,comparisons between MODIS/LAI products and high resolution LAI images were conducted to reflect the accuracy of MODIS/LAI products.Results showed that MODIS/LAI product can correctly indicate the grassland growth and phenology.However,because of the uncertainty of the input data,uncertainty still exists between MODIS/LAI product and ground situation with a mean absolute deviation of 0.59m2/m2.Results also showed that MODIS overestimates in situ LAI throughout the grass growing season with an average relative error of 40%.At the begin and end of the growing season,a bigger overestimation occurred of MODIS/LAI products because of the surface heterogeneity caused by the soil background,and at the middle of growing season,overestimation decreased with a relative error of 30%.The results are important to understand regional produce accuracy and further improve model predictions of Hulunber meadow steppe.
Leaf area index is a crucial parameter of vegetation structure which provides key information for earth surface process simulation and climate change research on the global and regional scales.Focusing on the meadow steppe in Hulunber,Inner Mongolia,the accuracy of MODIS/LAI product in this region was analyzed.Firstly,the in situ LAI data were acquired through six field experiment in 2013,and the regression models between in situ LAI and vegetation indices were established;then,six high resolution LAI maps from corresponding HJ-1A/B CCD were obtained;finally,comparisons between MODIS/LAI products and high resolution LAI images were conducted to reflect the accuracy of MODIS/LAI products.Results showed that MODIS/LAI product can correctly indicate the grassland growth and phenology.However,because of the uncertainty of the input data,uncertainty still exists between MODIS/LAI product and ground situation with a mean absolute deviation of 0.59m2/m2.Results also showed that MODIS overestimates in situ LAI throughout the grass growing season with an average relative error of 40%.At the begin and end of the growing season,a bigger overestimation occurred of MODIS/LAI products because of the surface heterogeneity caused by the soil background,and at the middle of growing season,overestimation decreased with a relative error of 30%.The results are important to understand regional produce accuracy and further improve model predictions of Hulunber meadow steppe.
引文
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[17]Wu Bingfang,Zeng Yuan,Huang Jinliang.Overview of LAI/FPAR Retrieval from Remotely Sensed Data[J].Advances in Earth Science,2004,19(4):585-590.[吴炳方,曾源,黄进良.遥感提取植物生理参数LAI/FPAR的研究进展与应用[J].地球科学进展,2004,19(4):585-590.]
[18]Chen J M,Pavlic G,Brown L,et al.Derivation and Validation of Canada-wide Coarse-resolution Leaf Area Index Maps Using High-resolution Satellite Imagery and Ground Measurements[J].Remote Sensing of Environment,2002,80(1):165-184.
[19]De Kauwe M G,Disney M I,Quaife T,et al.An Assessment of the MODIS Collection 5Leaf Area Index Product for a Region of Mixed Coniferous Forest[J].Remote Sensing of Environment,2011,115(2):767-780.
[20]Huang D,Yang W,Tan B,et al.The Importance of Measurement Errors for Deriving Accurate Reference Leaf Area Index Maps for Validation of Moderate-resolution Satellite LAI Products[J].IEEE Transactions on Geoscience and Remote Sensing,2006,44(7):1866-1871.
[21]Wang Y,Tian Y,Zhang Y,et al.Investigation of Product Accuracy as a Function of Input and Model Uncertainties:Case Study with SeaWiFS and MODIS LAI/FPAR Algorithm[J].Remote Sensing of Environment,2001,78(3):299-313.
[22]Tian Y,Woodcock C E,Wang Y,et al.Multiscale Analysis and Validation of the MODIS LAI Product:I.Uncertainty Assessment[J].Remote Sensing of Environment,2002,83(3):414-430.
[23]Xu Xiru,Fan Wenjie,Tao Xin.The Spatial Scaling Effect of Continuous Canopy Leaves Area Index Retrieved by Remote Sensing[J].Science in China(Series D):Earth Sciences,2009,52(3):393-401.[徐希孺,范闻捷,陶欣.遥感反演连续植被叶面积指数的空间尺度效应[J].中国科学:(D辑),2009,39(1):79-87.]
[2]Xiao Zhiqiang,Wang Jindi,Wang Zhuosen.Improvement of MODIS LAI Product in China[J].Journal of Remote Sensing,2008,12(6):993-1000.[肖志强,王锦地,王?森.中国区域MODIS LAI产品及其改进[J].遥感学报,2008,12(6):993-1000.]
[3]Zeng Yelu,Li Jing,Liu Qinhuo.Global LAI Ground Validation Dataset and Product Validation Framework[J].Advances in Earth Science,2012,27(2):165-174.[曾也鲁,李静,柳钦火.全球LAI地面验证方法及验证数据综述[J].地球科学进展,2012,27(2):165-174.]
[4]Campbell J,Burrows S,Gower S,et al.Bigfoot:Characterizing Land Cover,LAI,and NPP at the Landscape Scale for EOS/MODIS Validation.Field Manual,Version 2.1[EB/OL].http://daac.ornl.gov/LAND_VAL/BigFoot/index_bigfoot.htm,September 1999,accessed on 18 May 2013.
[5]Baret F,Weiss M,Allard D,et al.VALERI:A Network of Sites and a Methodology for the Validation of Medium Spatial Resolution Land Satellite Products[EB/OL].http://w3.avignon.inra.fr/valeri,2005,accessed on 18 May 2013.
[6]Morisette J T,Baret F,Privette J L,et al.Validation of Global Moderate-resolution LAI Products:A Framework Proposed within the CEOS Land Product Validation Subgroup[J].IEEE Transactions on Geoscience and Remote Sensing,2006,44(7):1804-1817.
[7]Li Xin,Ma Mingguo,Wang Jian,et al.Simultaneous Remote Sensing and Ground-based Experiment in the Heihe River Basin:Scientific Objectives and Experiment Design[J].Advances in Earth Science,2008,23(9):897-914.[李新,马明国,王建,等.黑河流域遥感―地面观测同步试验:科学目标与试验方案[J].地球科学进展,2008,23(9):897-914.]
[8]Sun Chenxi,Liu Liangyun,Guan Linlin.Validation of the GLASS LAI Products in Xilinhot Grass Land[J].Remote Sensing Technology and Application,2013,28(16):949-954.[孙晨羲,刘良云,关琳琳.内蒙古锡林浩特草原GLASS LAI产品的真实性检验[J].遥感技术与应用,2013,28(16):949-954.]
[9]Yang W,Tan B,Huang D,et al.MODIS Leaf Area Index Products:From Validation to Algorithm Improvement[J].IEEE Transactions on Geoscience and Remote Sensing,2006,44(7):1885-1898.
[10]Pisek J,Chen J M.Comparison and Validation of MODIS and VEGETATION Global LAI Products over Four BigFoot Sites in North America[J].Remote Sensing of Environment,2007,109(1):81-94.
[11]Gessner U,Niklaus M,Kuenzer C,et al.Intercomparison of Leaf Area Index Products for a Gradient of Sub-Humid to Arid Environments in West Africa[J].Remote Sensing,2013,5(3):1235-1257.
[12]Fang H,Wei S,Liang S.Validation of MODIS and CYCLOPES LAI Products Using Global Field Measurement Data[J].Remote Sensing of Environment,2012,119:43-54.
[13]Mccoll K,Pipunic R,Ryu D,et al.Validation of the MODIS LAI Product in the Murrumbidgee Catchment,Australia[J].19th International Congress on Modelling and Simulation.Perth,Australia.12-16December 2011:1973-1979.
[14]Liu Yibo,Ju Weimin,Zhu Gaolong,et al.Retrieval of Leaf Area Index for Different Grasslands in Inner Mongolia Prairie Using Remote Sensing Data[J].Acta Ecologica Sinica,2011,31(18):5159-5170.[柳艺博,居为民,朱高龙,等.内蒙古不同类型草地叶面积指数遥感估算[J].生态学报,2011,31(18):5159-5170.]
[15]Yang F,Yang J,Wang J,et al.Assessment and Validation of MODIS and GEOV1LAI With Ground-measured Data and an Analysis of the Effect of Residential Area in Mixed Pixel[J].IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing,2014,8(2):763-774.
[16]Sun Chenxi.Study of the Scale Effect and Validation of LAI Product[D].Beijing:University of Chinese Academy of Sciences,2013[孙晨曦.LAI产品尺度效应与真实性检验研究[D].北京:中国科学院研究生院,2013.]
[17]Wu Bingfang,Zeng Yuan,Huang Jinliang.Overview of LAI/FPAR Retrieval from Remotely Sensed Data[J].Advances in Earth Science,2004,19(4):585-590.[吴炳方,曾源,黄进良.遥感提取植物生理参数LAI/FPAR的研究进展与应用[J].地球科学进展,2004,19(4):585-590.]
[18]Chen J M,Pavlic G,Brown L,et al.Derivation and Validation of Canada-wide Coarse-resolution Leaf Area Index Maps Using High-resolution Satellite Imagery and Ground Measurements[J].Remote Sensing of Environment,2002,80(1):165-184.
[19]De Kauwe M G,Disney M I,Quaife T,et al.An Assessment of the MODIS Collection 5Leaf Area Index Product for a Region of Mixed Coniferous Forest[J].Remote Sensing of Environment,2011,115(2):767-780.
[20]Huang D,Yang W,Tan B,et al.The Importance of Measurement Errors for Deriving Accurate Reference Leaf Area Index Maps for Validation of Moderate-resolution Satellite LAI Products[J].IEEE Transactions on Geoscience and Remote Sensing,2006,44(7):1866-1871.
[21]Wang Y,Tian Y,Zhang Y,et al.Investigation of Product Accuracy as a Function of Input and Model Uncertainties:Case Study with SeaWiFS and MODIS LAI/FPAR Algorithm[J].Remote Sensing of Environment,2001,78(3):299-313.
[22]Tian Y,Woodcock C E,Wang Y,et al.Multiscale Analysis and Validation of the MODIS LAI Product:I.Uncertainty Assessment[J].Remote Sensing of Environment,2002,83(3):414-430.
[23]Xu Xiru,Fan Wenjie,Tao Xin.The Spatial Scaling Effect of Continuous Canopy Leaves Area Index Retrieved by Remote Sensing[J].Science in China(Series D):Earth Sciences,2009,52(3):393-401.[徐希孺,范闻捷,陶欣.遥感反演连续植被叶面积指数的空间尺度效应[J].中国科学:(D辑),2009,39(1):79-87.]