Global LAnd Surface Satellite (GLASS)产品集是在中国国家高新技术研究和发展项目“十一五”和“十二五”863计划及“十三五”国家重点研发计划的支持下,经十余年努力研发而生成的多种陆表特征参数的高级卫星数据产品。与国际上同类产品相比较,它们具有一系列的独特特性,正得到国内外1000 多家单位研究人员的使用,总下载量超过1.7 PB。本文概述了GLASS产品集算法的发展,产品特征,精度验证,以及这些产品的一些初步应用示例。同时还介绍了30 m 分辨率的Hi-GLASS产品集,以及将来继续完善和发展GLASS产品的一些考虑。

The Global LAnd Surface Satellite (GLASS) products suite includes a set of high-level satellite products of land surface essential variables from multiple universities and research institutes. Producing the GLASS products suite has been undertaken since 2010, and the suite spans from the initial five products to the current 16 products, which are generated mostly from the Advanced Very High Resolution Radiometer (AVHRR) and/or Moderate Resolution Imaging Spectroradiometer (MODIS) data. Some of the products have been previously introduced in the literature, and this paper provides an update on the algorithm developments, validation accuracies, and their typical applications in all 16 products. This paper also describes the Hi-GLASS products at 30-m resolution and some perspectives for further improvement and development of the GLASS products in the future. Estimating land surface variables from satellite observations is an “ill-posed” inversion problem. For each pixel, the number of multispectral bands is usually smaller than the number of environmental variables, and the values of many spectral bands are highly correlated. Some novel solutions have been proposed to solve the problem of insufficient information in generating reliable GLASS products. We can identify at least four approaches. The first is based on the temporal signature of the satellite observations. The typical example is the MODIS leaf area index (LAI) and fraction of absorbed photosynthetically active radiation (FAPAR) products that are generated using 2-year observations simultaneously. The second uses algorithm ensemble. The typical example is the evapotranspiration (ET) product that is based on integration of five estimation algorithms. The third uses multiple satellite observations. For example, the forest aboveground biomass product is based on optical, Lidar, and microwave data products. The last incorporates the physical model to generate the products, such as the gross primary production (GPP) product. The GLASS products have several unique features compared to similar products on the market, including the following. 1) Several products are unique, such as the high-resolution (1-km) broadband emissivity and time-series forest aboveground biomass products. 2) Most products have long time series, i.e., over 40 years, while most other similar global products start from approximately the year 2000, with a time span of approximately 20 years. 3) The radiation products, covering the world"s land and ocean surfaces, have a spatial resolution of 5 km, which is an order of magnitude higher than other such products in wide use, e.g., the Global Energy and Water Exchanges (GEWEX), the Clouds and the Earth"s Radiant Energy System (CERES), and the International Satellite Cloud Climatology Project (ISCCP), which have spatial resolutions coarser than 100 km. 4) Several long-time-series global products have the highest spatial resolution in the world, such as 250 m for the LAI, FAPAR, and albedo products and 5 km for snow cover extent. In addition, the all-weather LST and near-surface air temperature products have a 1-km resolution. 5) GLASS products are of high quality and accuracy. So far, over 2,000 peer-reviewed papers based on the GLASS products have been published. Their applications are distributed in many scientific disciplines and societal benefits areas. We will continue to improve the quality and accuracy of the existing GLASS products, and produce more GLASS products with higher spatial resolutions.