BELMANIP2 Network of Sites for the Global Validation and Intercomparison of Land Biophysical Products

The Benchmark Land Multisite Analysis and Intercomparison of Products (BELMANIP2) is an updated version of BELMANIP1 (Baret et al, 2006). BELMANIP2 is a globally distributed set of sites for validation and inter-comparison of biophysical products (LAI, fAPAR, fCover, albedo, etc) derived from medium resolution satellite-borne sensors. This benchmark network was designed to provide a good sampling of biomes and land surface types over the globe and brings together 420 sites extracted from several existing networks (AERONET, FLUXNET, EOS Core Sites, Bigfoot, VALERI, etc) where direct biophysical measurements are available with additional sites selected to improve the representivity of the latitudinal distribution of dominant surface types. Although ground measurements are not available for every site, the BELMANIP network is very useful to complement direct validation studies by providing a good sampling in both space and time. To be independent from ground experiment measurements and better represent the variability of vegetation types and climatological conditions at the Earth surface, BELMANIP2 was built using the GLOBCOVER vegetation land cover map derived from MERIS images in 2009. The site selection was performed for each band of latitude (10° width) by keeping the same proportion of biome types within the selected sites as within the whole band of latitude. Attention was paid so that the sites were homogeneous over a 10x10km² area, almost flat, and with a minimum proportion of urban area and permanent water bodies. The original BELMANIP2 data set included 420 sites. The updated one, BELMANIP2.1 data set complements BELMANIP2 by adding 25 sites corresponding to bare soil areas (deserts) and tropical forests.

陆地生物物理产品多站点分析与比对基准集（Benchmark Land Multisite Analysis and Intercomparison of Products，缩写为BELMANIP2）是BELMANIP1（Baret等，2006）的更新版本。BELMANIP2是一套全球分布式站点集，用于对源自中分辨率星载传感器的生物物理产品（叶面积指数LAI(Leaf Area Index)、光合有效辐射吸收比率fAPAR(Fraction of Absorbed Photosynthetically Active Radiation)、植被覆盖度fCover(Fractional Vegetation Cover)、反照率albedo等）开展验证与交叉比对。该基准网络旨在实现全球范围内生物群区与陆地表面类型的良好采样，整合了从AERONET、FLUXNET、EOS核心站点、Bigfoot、VALERI等多个现有网络中提取的420个具备直接生物物理测量数据的站点，并额外选取部分站点以优化优势地表类型的纬度分布代表性。尽管并非所有站点均具备地面实测数据，但BELMANIP基准网络仍可通过在空间与时间维度上实现优质采样，为直接验证研究提供有效补充，具备重要应用价值。为摆脱地面实验测量的依赖，同时更好地表征地球表面植被类型与气候条件的变异性，BELMANIP2采用2009年由MERIS影像生成的GLOBCOVER植被土地覆盖图完成站点遴选。站点遴选按宽度为10°的纬度带逐一开展，确保所选站点内的生物群区类型占比与对应纬度带整体的占比保持一致。遴选过程需满足以下条件：站点在10×10平方公里范围内均质性优良、地势相对平缓，且城区与永久性水体的占比需控制在最低水平。初始BELMANIP2数据集共包含420个站点，更新后的BELMANIP2.1数据集则通过新增25个对应裸土区域（荒漠）与热带森林的站点，对BELMANIP2进行了补充完善。