MODIS/Terra Vegetation Indices 16-Day L3 Global 500m SIN Grid V061

The Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Vegetation Indices 16-Day (MOD13A1) Version 6.1 product provides Vegetation Index (VI) values at a per pixel basis at 500 meter (m) spatial resolution. There are two primary vegetation layers. The first is the Normalized Difference Vegetation Index (NDVI), which is referred to as the continuity index to the existing National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer (NOAA-AVHRR) derived NDVI. The second vegetation layer is the Enhanced Vegetation Index (EVI), which has improved sensitivity over high biomass regions. The algorithm for this product chooses the best available pixel value from all the acquisitions from the 16 day period. The criteria used is low clouds, low view angle, and the highest NDVI/EVI value. Provided along with the vegetation layers and two quality assurance (QA) layers are reflectance bands 1 (red), 2 (near-infrared), 3 (blue), and 7 (mid-infrared), as well as four observation layers.Terra中分辨率成像光谱仪（Moderate Resolution Imaging Spectroradiometer, MODIS）16天植被指数产品（MOD13A1）版本6.1，以单像素为基准提供500米空间分辨率的植被指数（Vegetation Index, VI）数值。该产品包含两类核心植被指数层：其一为归一化差分植被指数（Normalized Difference Vegetation Index, NDVI），可视为现有美国国家海洋和大气管理局-先进甚高分辨率辐射计（National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer, NOAA-AVHRR）衍生NDVI的连续性观测指标；其二为增强型植被指数（Enhanced Vegetation Index, EVI），在高生物量区域具备更优异的观测灵敏度。本产品的算法会从16天周期内的所有有效采集数据中选取最优像素值，选取标准为低云量、低观测角度以及最高的NDVI/EVI数值。除上述植被指数层与两个质量保证（quality assurance, QA）层外，产品还附带提供反射率波段1（红光）、2（近红外）、3（蓝光）、7（中红外），以及四个观测图层。