呼伦贝尔草甸草原MODIS/LAI产品验证

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。

Validation of MODIS/LAI Product in 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 0.59 m2/m2.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.