Evaluation of earth observation based long term vegetation trends - Intercomparing NDVI time series trend analysis consistency of Sahel from AVHRR GIMMS, Terra MODIS and SPOT VGT data
Evaluation of earth observation based long term vegetation trends - Intercomparing NDVI time series trend analysis consistency of Sahel from AVHRR GIMMS, Terra MODIS and SPOT VGT data
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DOI：
10.1016/j.rse.2009.04.004
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发表时间：
2009-09-01
影响因子：
13.5
通讯作者：
Mbow, Cheikh
中科院分区：
文献类型：
--
作者：
Fensholt, Rasmus;Rasmussen, Kjeld;Mbow, Cheikh
AVHRR（高级甚高分辨率辐射计）GIMMS（全球清查、建模和绘图研究）NDVI（归一化差异植被指数）数据从1981年至今可用。全球覆盖范围8公里分辨率15天复合数据集已被用于许多地方到全球规模的植被时间序列研究在最近几年。然而，由于高级甚高分辨率辐射计传感器的设计和数据处理，有几个方面可能会在归一化差异植被指数数据集中引入噪声。从Terra中分辨率成像光谱仪和SPOT VGT数据中获得的较新的归一化差异植被指数数据集被认为是对高级甚高分辨率辐射计的改进，这些产品在理论上提供了一种可能性，可用来评价全球监测和监测系统归一化差异植被指数时间序列趋势分析在现有数据重叠期间的准确性。在这项研究中，GIMMS的NDVI时间序列趋势分析的准确性进行了评估，通过比较与1公里分辨率的Terra中分辨率成像光谱仪（MOD 13 A2）16天的复合NDVI数据，SPOT植被（VGT）10天的复合（S10）的NDVI数据和在塞内加尔Dahra的一个测试站点的原位测量。对全球监测和监测系统8年年均归一化植被指数（2000 - 2007年）的线性最小二乘回归趋势分析与Terra中分辨率成像光谱仪（1公里和8公里重采样）和SPOT VGT归一化植被指数数据1公里（2000 - 2007年）进行了比较。这三种数据产品显示的归一化差异植被指数趋势模式不同。SPOT VGT NDVI数据的特点是较高的正回归斜率在8年期间相比，Terra中分辨率成像光谱仪和AVHRR GIMMS NDVI数据，可能造成的变化通道1和2光谱响应函数从SPOT VGT 1到SPOT VGT 2在2003年。趋势分析的AVHRR GIMMS NDVI表现出更好的协议与半干旱地区的Terra MODIS NDVI的回归斜率范围。然而，GIMMS NDVI显示出更高的正回归斜率值比Terra中分辨率成像光谱仪在更潮湿的地区的趋势。2002-2007年期间，在半干旱的塞内加尔，对不同的归一化差异植被指数数据产品与连续的实地归一化差异植被指数测量结果进行了验证，结果表明，实地测量结果与所有基于卫星的归一化差异植被指数产品之间具有良好的一致性。利用Terra MODIS NDVI作为参考，得出的结论是，AVHRR GIMMS粗分辨率NDVI数据集非常适合于萨赫勒-苏丹地区的长期植被研究，接受< 1000毫米的降雨量，而在苏丹-几内亚地区的更潮湿的地区GIMMS NDVI趋势的解释应该做一定的保留。(C)2009 Elsevier Inc. All rights reserved.
AVHRR (Advanced Very High Resolution Radiometer) GIMMS (Global Inventory Modelling and Mapping Studies) NDVI (Normalized Difference vegetation Index) data is available from 1981 to present time. The global coverage 8 km resolution 15-day composite data set has been used for numerous local to global scale vegetation time series studies during recent years. Several aspects however potentially introduce noise in the NDVI data set due to the AVHRR sensor design and data processing. More recent NDVI data sets from both Terra MODIS and SPOT VGT data are considered an improvement over AVHRR and these products in theory provide a possibility to evaluate the accuracy of GIMMS NDVI time series trend analysis for the overlapping period of available data. In this study the accuracy of the GIMMS NDVI time series trend analysis is evaluated by comparison with the 1 km resolution Terra MODIS (MOD13A2) 16-day composite NDVI data, the SPOT Vegetation (VGT) 10-day composite (S10) NDVI data and in situ measurements of a test site in Dahra, Senegal. Linear least squares regression trend analysis on eight years of GIMMS annual average NDVI (20002007) has been compared to Terra MODIS (1 km and 8 km resampled) and SPOT VGT NDVI data 1 km (20002007). The three data products do not exhibit identical patterns of NDVI trends. SPOT VGT NDVI data are characterised by higher positive regression slopes over the 8-year period as compared to Terra MODIS and AVHRR GIMMS NDVI data, possibly caused by a change in channels 1 and 2 spectral response functions from SPOT VGT1 to SPOT VGT2 in 2003. Trend analysis of AVHRR GIMMS NDVI exhibits a regression slope range in better agreement with Terra MODIS NDVI for semi-arid areas. However, GIMMS NDVI shows a tendency towards higher positive regression slope values than Terra MODIS in more humid areas. Validation of the different NDVI data products against continuous in situ NDVI measurements for the period 2002-2007 in the semi-arid Senegal revealed a good agreement between in situ measurements and all satellite based NDVI products. Using Terra MODIS NDVI as a reference, it is concluded that AVHRR GIMMS coarse resolution NDVI data set is well-suited for long term vegetation studies of the Sahel-Sudanian areas receiving < 1000 mm rainfall, whereas interpretation of GIMMS NDVI trends in more humid areas of the Sudanian-Guinean zones should be done with certain reservations. (C) 2009 Elsevier Inc. All rights reserved.