Global assessment of Vegetation Index and Phenology Lab (VIP) and GlobalInventory Modeling and Mapping Studies (GIMMS) version 3 products

[摘要] Earth observation-based long-term global vegetation index products are usedby scientists from a wide range of disciplines concerned with global change.Inter-comparison studies are commonly performed to keep the user communityinformed on the consistency and accuracy of such records as they evolve. Inthis study, we compared two new records: (1) Global Inventory Modeling and Mapping Studies (GIMMS) normalized difference vegetation index version 3(NDVI3g) and (2) Vegetation Index and Phenology Lab (VIP) version 3 NDVI(NDVI3v) and enhanced vegetation index 2 (EVI3v). We evaluated the tworecords via three experiments that addressed the primary use of such recordsin global change research: (1) leaf area index (LAI), (2) vegetationclimatology, and (3) trend analysis of the magnitude and timing of vegetationproductivity. Unlike previous global studies, a unique Landsat 30 m spatialresolution and in situ LAI database for major crop types on five continents wasused to evaluate the performance of not only NDVI3g and NDVI3v but also EVI3v. The performance of NDVI3v and EVI3v was worse than NDVI3g using thein situ data, which was attributed to the fusion of GIMMS and MODIS data in the VIPrecord. EVI3v has the potential to contribute biophysical information beyondNDVI3g and NDVI3v to global change studies, but we caution its use due tothe poor performance of EVI3v in this study. Overall, the records were mostconsistent at northern latitudes during the primary growing season andsouthern latitudes and the tropics throughout much of the year, while therecords were less consistent at northern latitudes during green-up andsenescence, and in the great deserts of the world throughout much of theyear. These patterns led to general agreement (disagreement) between trendsin the magnitude (timing) of NDVI over the study period. Bias ininter-calibration of the VIP record at northernmost latitudes was suspectedto contribute most to these discrepancies.

[学科分类] 地球化学与岩石