GEDI L4A Footprint Level Aboveground Biomass Density, Version 2.1

This dataset contains Global Ecosystem Dynamics Investigation (GEDI) Level 4A (L4A) Version 2 predictions of the aboveground biomass density (AGBD; in Mg/ha) and estimates of the prediction standard error within each sampled geolocated laser footprint. In this version, the granules are in sub-orbits. The algorithm setting group selection used for GEDI02_A Version 2 has been modified for Evergreen Broadleaf Trees in South America to reduce false positive errors resulting from the selection of waveform modes above ground elevation as the lowest mode. The footprints are located within the global latitude band observed by the International Space Station (ISS), nominally 51.6 degrees N and S and reported for the period 2019-04-18 to 2023-03-16. The GEDI instrument consists of three lasers producing a total of eight beam ground transects, which instantaneously sample eight ~25 m footprints spaced approximately every 60 m along-track. The GEDI beam transects are spaced approximately 600 m apart on the Earth's surface in the cross-track direction, for an across-track width of ~4.2 km. Footprint AGBD was derived from parametric models that relate simulated GEDI Level 2A (L2A) waveform relative height (RH) metrics to field plot estimates of AGBD. Height metrics from simulated waveforms associated with field estimates of AGBD from multiple regions and plant functional types (PFTs) were compiled to generate a calibration dataset for models representing the combinations of world regions and PFTs (i.e., deciduous broadleaf trees, evergreen broadleaf trees, evergreen needleleaf trees, deciduous needleleaf trees, and the combination of grasslands, shrubs, and woodlands). For each of the eight beams, additional data are reported with the AGBD estimates, including the associated uncertainty metrics, quality flags, model inputs, and other information about the GEDI L2A waveform for this selected algorithm setting group. Model inputs include the scaled and transformed GEDI L2A RH metrics, footprint geolocation variables and land cover input data including PFTs and the world region identifiers. Additional model outputs include the AGBD predictions for each of the six GEDI L2A algorithm setting groups with AGBD in natural and transformed units and associated prediction uncertainty for each GEDI L2A algorithm setting group. Providing these ancillary data products will allow users to evaluate and select alternative algorithm setting groups. Also provided are outputs of parameters and variables from the L4A models used to generate AGBD predictions that are required as input to the GEDI04_B algorithm to generate 1-km gridded products.

本数据集包含全球生态系统动态研究（Global Ecosystem Dynamics Investigation，简称GEDI）第四级A（Level 4A，简称L4A）版本2对地面生物量密度（Aboveground Biomass Density，简称AGBD；单位为Mg/ha）的预测以及每个采样地理激光足迹内的预测标准误差估计。在该版本中，数据粒度为子轨道。用于GEDI02_A版本2的算法设置组选择已针对南美洲的常绿阔叶树进行调整，以降低因选择地面高程波形的最低模式而导致的错误阳性误差。足迹位于国际空间站（International Space Station，简称ISS）观测的全球纬度带内，标准纬度为北纬51.6度和南纬51.6度，并报告了2019年4月18日至2023年3月16日期间的数据。GEDI仪器由三个激光器组成，总共产生八个地面横切波束，这些波束沿轨道每隔约60米即时采样八个约25米的足迹。GEDI横切波束在地球表面上的交叉轨道方向上相距约600米，对应于约4.2公里的横跨宽度。足迹AGBD是通过参数模型得出的，这些模型将模拟的GEDI第二级A（Level 2A，简称L2A）波形相对高度（Relative Height，简称RH）指标与田间地块的AGBD估计值相关联。从多个地区和植物功能型（Plant Functional Type，简称PFT）的AGBD估计值中收集与模拟波形相关的高度指标，以生成用于表示世界区域和PFT组合（例如，落叶阔叶树、常绿阔叶树、常绿针叶树、落叶针叶树以及草地、灌木和林地的组合）的模型的校准数据集。对于八个波束中的每一个，除了AGBD估计值外，还报告了与相关不确定性指标、质量标志、模型输入以及其他有关所选算法设置组的GEDI L2A波形的信息。模型输入包括缩放和转换后的GEDI L2A RH指标、足迹地理定位变量以及包括PFT和世界区域标识符在内的土地覆盖输入数据。此外，还包括每个六种GEDI L2A算法设置组的AGBD预测以及相应的自然单位和转换单位下的预测不确定性。提供这些辅助数据产品将使用户能够评估和选择替代算法设置组。此外，还提供了用于生成AGBD预测的L4A模型中参数和变量的输出，这些输出是GEDI04_B算法生成1公里格网产品所需的输入。

搜集汇总

背景与挑战

背景概述

该数据集提供GEDI L4A版本2.1的地上生物量密度（AGBD）预测，覆盖2019年至2023年全球纬度带，基于激光足迹采样和校准模型生成。其特点包括针对不同植物类型和区域的参数化建模，并附带不确定性指标和辅助数据，便于用户评估算法设置，支持生态系统研究。