Assessment of the MODIS LAI Product Using Ground Measurement Data and HJ-1A/1B Imagery in the Meadow Steppe of Hulunber, China
Assessment of the MODIS LAI Product Using Ground Measurement Data and HJ-1A/1B Imagery in the Meadow Steppe of Hulunber, China
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DOI：
10.3390/rs6076242
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发表时间：
2014-07
期刊：
影响因子：
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通讯作者：
Zhenwang Li;Huanli Tang;X. Xin;B. Zhang;Dongliang Wang
中科院分区：
文献类型：
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作者：
Zhenwang Li;Huanli Tang;X. Xin;B. Zhang;Dongliang Wang
叶面积指数是反映植被结构的重要参数。它为全球和区域尺度的地球表面过程模拟和气候变化研究提供了关键信息。以内蒙古呼伦贝尔草甸草原为研究区域，对中分辨率成像光谱仪（MODIS）叶面积指数产品的精度进行了评估。首先，在2013年的生长季节进行了7次收集地面测量的实地活动，收集了252对莱什和光谱。然后，利用中国HJ-1A/1B卫星30 m CCD图像，采用回归方法得到7个场景的高分辨率叶面积指数（LAI）图。最后，比较了MODIS LAI产品和高分辨率LAI图，以确定MODIS LAI产品的精度。此外，相应的500米的MODIS叶面积指数图来自每日的MODIS表面反射率产品，以支持使用1公里HJ叶面积指数产品和地面比较的结果。结果表明，与地面数据相比，MODIS叶面积指数产品在生长季内遵循合理的季节轨迹。然而，在生长季节开始时存在异常。此外，一个轻微的高估被发现的MODIS LAI产品相比，HJ检索的LAI地图。对叶面积指数的平均高估约为0.4m2/m2，产品的相对绝对误差在10%-50%之间。生长期开始和结束时的高估
The leaf area index (LAI) is a crucial parameter of vegetation structure. It provides key information for earth surface process simulations and climate change research on the global and regional scales. Focusing on the meadow steppe in Hulunber, Inner Mongolia, China, the present study assessed the accuracy of the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI product in the study area. First, seven field campaigns collecting ground-based measurements were conducted during the growing season in 2013, and 252 pairs of LAIs and spectra were collected. Then, seven scenes of high-resolution LAI maps were obtained from the corresponding 30 m Chinese HJ-1A/1B charge-coupled diode (CCD) images by employing a regression approach. Finally, comparisons between the MODIS LAI product and the high resolution LAI maps were made to determine the accuracy of the MODIS LAI product. Moreover, the corresponding 500 m MODIS LAI maps were derived from the daily MODIS surface reflectance product to support the findings using the 1 km HJ LAI product and the ground-based comparison. The results showed that, compared to the ground data, the MODIS LAI product followed a reasonable seasonal trajectory during the growing season. However, an anomaly existed at the beginning of the growing season. Also, a slight overestimation was found for the MODIS LAI product compared to the HJ-retrieved LAI maps. The average overestimation for the LAI was approximately 0.4 m 2 /m 2 , and the relative absolute errors of the product ranged from 10%-50%. The overestimation at the beginning and end of the growing