Supraglacial Debris Cover

This dataset is supplementary to the article of Scherler et al. (submitted), in which the global distribution of supraglacial debris cover is mapped and analyzed. For mapping supraglacial debris cover, we combined glacier outlines from the Randolph Glacier Inventory (RGI) version 6.0 (RGI consortium, 2017) with remote sensing-based ice and snow identification. Areas that belong to glaciers but that are neither ice nor snow were classified as debris cover. This dataset contains the outlines of the mapped debris-covered glaciers areas, stored in shapefiles (.shp). For creating this dataset, we used optical satellite data from Landsat 8 (for the time period 2013-2017), and from Sentinel-2A/B (2015-2017). For the ice and snow identification, we used three different algorithms: a red to short-wavelength infrared (swir) band ratio (RATIO; Hall et al., 1988), the normalized difference snow index (NDSI; Dozier, 1989), and linear spectral unmixing-derived fractional debris cover (FDC; e.g., Keshava and Mustard, 2002). For a detailed description of the debris-cover mapping and an analysis of the data, please see Scherler et al. (2019) to which these data are supplementary material. This dataset includes debris cover outlines based on either Landsat 8 (LS8; 30-m resolution) or Sentinel 2 (S2; 10-m resolution), and the three algorithms RATIO, NDSI, FDC. In total, there exist six different zip-files that each contain 19 shapefiles. The structure of the shapefiles follows that of the RGI version 6.0 (RGI consortium, 2017), with one shapefile for each RGI region. The original RGI shapefiles provide each glacier as one entry (feature) and include a variety of ancillary information, such as area, slope, aspect (RGI Consortium 2017a, Technical Note p. 12ff). Because the debris-cover outlines are based on the RGI v6.0 glacier outlines, all fields of the original shapefiles, which refer to the glacier, are retained, and expanded with four new fields: - DC_Area: Debris-covered area in m². Note that this unit for area is different from the unit used for reporting the glacier area (km²).- DC_BgnDate: Start of the time period from which satellite imagery was used to map debris cover.- DC_EndDate: End of the time period from which satellite imagery was used to map debris cover.- DC_CTSmean: Mean number of observations (CTS = COUNTS) per pixel and glacier. This number is derived from the number of available satellite images for the respective time period, reduced by filtering pixels due to cloud and snow cover. The dataset has a global extent and covers all of the glaciers in the RGI v. 6.0, but it exhibits poor coverage in the RGI region Subantarctic and Antarctic, where the debris cover extents are based on very few observations.

本数据集为Scherler等人（已投稿）论文的补充材料，该论文对全球冰表碎屑覆盖（supraglacial debris cover）的分布完成了制图与分析工作。在冰表碎屑覆盖制图过程中，研究团队结合了伦道夫冰川目录（Randolph Glacier Inventory, RGI）6.0版（RGI联盟，2017）的冰川轮廓数据与遥感冰雪识别结果，将属于冰川范畴但既非冰也非雪的区域归类为碎屑覆盖区。

本数据集包含已制图的碎屑覆盖冰川区域的轮廓数据，存储为形状文件（shapefile, .shp）。本数据集的构建采用了2013-2017年的Landsat 8光学卫星数据，以及2015-2017年的Sentinel-2A/B卫星数据。在冰雪识别步骤中，研究团队使用了三种不同算法：红光至短波红外（short-wavelength infrared, SWIR）波段比值法（RATIO；Hall等，1988）、归一化差分积雪指数（normalized difference snow index, NDSI；Dozier，1989），以及基于线性光谱解混的碎屑覆盖分数（linear spectral unmixing-derived fractional debris cover, FDC；例如Keshava与Mustard，2002）。

如需了解碎屑覆盖制图的详细流程与数据分析细节，请参阅本数据集的补充来源论文Scherler等（2019）。本数据集包含基于Landsat 8（LS8，空间分辨率30米）或Sentinel 2（S2，空间分辨率10米）的碎屑覆盖轮廓，以及上述RATIO、NDSI、FDC三种算法的成果，总计生成6个ZIP压缩包，每个压缩包内含19个形状文件。

形状文件的命名结构遵循RGI 6.0版规范（RGI联盟，2017），每个RGI区域对应一个形状文件。原始RGI形状文件将每座冰川作为一个要素条目，并包含多种辅助信息，如面积、坡度、坡向（RGI Consortium 2017a，技术说明第12页及后续章节）。由于碎屑覆盖轮廓基于RGI v6.0的冰川轮廓生成，因此原始形状文件中所有与冰川相关的字段均被保留，并新增了4个字段：
- DC_Area：碎屑覆盖区面积，单位为平方米（m²）。需注意，该面积单位与冰川面积报告中使用的平方千米（km²）不同。
- DC_BgnDate：用于制图碎屑覆盖的卫星影像对应的时间区间起始日期。
- DC_EndDate：用于制图碎屑覆盖的卫星影像对应的时间区间结束日期。
- DC_CTSmean：每像素及每冰川的平均观测次数（CTS = COUNTS）。该数值由对应时间区间内可用卫星影像的数量计算得出，需剔除因云层与积雪覆盖而被过滤的像素。

本数据集为全球范围，覆盖RGI v6.0中的所有冰川，但在亚南极与南极RGI区域的覆盖效果较差，上述区域的碎屑覆盖范围仅依靠极少量观测数据绘制。

搜集汇总

背景与挑战

背景概述

该数据集提供了全球冰川表面碎屑覆盖的分布信息，基于Randolph Glacier Inventory (RGI) v6.0的冰川轮廓，结合Landsat 8和Sentinel-2A/B卫星数据（时间覆盖2013-2017年），使用三种遥感算法（RATIO、NDSI、FDC）识别并分类碎屑覆盖区域。数据以shapefile格式存储，包含全球范围（南极和亚南极地区覆盖有限），并扩展了碎屑覆盖面积、观测时间等新字段，适用于冰川学和遥感研究。