ISLSCP II IGBP DISCOVER AND SIB LAND COVER, 1992-1993

This data set describes the geographic distributions of 17 classes of land cover based on the International Geosphere-Biosphere DISCover land cover legend (Loveland and Belward 1997) and the 15 classes of the SiB model processed at the USGS EROS Data Center (EDC). Specifically, the resampled DISCover datasets were derived from the 1km DISCover data set compiled by the USGS. The 1km data sets for each classification scheme were aggregated to 1, 0.5 and 0.25 degree spatial resolutions for this ISLSCP II data collection. Each layer of the aggregated products corresponds to a single DISCover land cover category and the values represent the percentage of the coarse resolution cell (1 degree, etc???) occupied by that land cover category. The dominant class data show the land cover category that occupies the majority of the cell and is derived from the percentage files for each cover type.

The objective of this study was to create a land cover map derived from 1 kilometer AVHRR data using a full year of data (April 1992-March 1993). This thematic map was resampled to 0.25, 0.5 and 1.0 degree grids for the International Satellite Land Surface Climatology Project (ISLSCP) data initiative II. During this re-processing, the original EDC land cover type and fraction maps were adjusted to match the water/land fraction of the ISLSCP II land/water mask. These maps were generated for use by global modelers and others.

This data set is one of the products of the International Satellite Land-Surface Climatology Project, Initiative II (ISLSCP II) data collection which contains 50 global time series data sets for the ten-year period 1986 to 1995. Selected data sets span even longer periods. ISLSCP II is a consistent collection of data sets that were compiled from existing data sources and algorithms, and were designed to satisfy the needs of modelers and investigators of the global carbon, water and energy cycle. The data were acquired from a number of U.S. and international agencies, universities, and institutions. The global data sets were mapped at consistent spatial (1, 0.5 and 0.25 degrees) and temporal (monthly, with meteorological data at finer (e.g., 3-hour)) resolutions and reformatted into a common ASCII format. The data and documentation have undergone two peer reviews.

ISLSCP is one of several projects of Global Energy and Water Cycle Experiment (GEWEX) [http://www.gewex.org/] and has the lead role in addressing land-atmosphere interactions -- process modeling, data retrieval algorithms, field experiment design and execution, and the development of global data sets.

本数据集基于国际地圈-生物圈DISCover（International Geosphere-Biosphere DISCover）土地覆盖图例（Loveland与Belward，1997）以及美国地质调查局（United States Geological Survey，USGS）地球资源数据中心（EROS Data Center，简称EDC）处理的SiB模型（SiB model）15类分类体系，描述了17类土地覆盖类型的地理分布。具体而言，重采样后的DISCover数据集源自美国地质调查局（USGS）构建的1km分辨率DISCover数据集。本国际卫星陆面气候学计划第二阶段（ISLSCP II）数据集中，两种分类体系对应的1km分辨率数据集均被聚合至1°、0.5°与0.25°三种空间分辨率。聚合后的产品每一层对应单一DISCover土地覆盖类别，其数值代表该土地覆盖类型在粗分辨率栅格（如1°栅格等）中所占的百分比。优势类别数据展示了占据栅格绝大部分面积的土地覆盖类型，其数据源自各覆盖类型的百分比文件。

本研究的目标是利用一整年的先进甚高分辨率辐射计（Advanced Very-High-Resolution Radiometer，AVHRR）数据（1992年4月—1993年3月），构建基于1km分辨率AVHRR数据的土地覆盖图。该专题图被重采样至0.25°、0.5°与1.0°栅格，以适配国际卫星陆面气候学计划第二阶段（ISLSCP II）数据倡议。在此再处理过程中，原始EDC土地覆盖类型与占比地图被调整，以匹配ISLSCP II陆-水掩膜的水陆占比。上述地图旨在供全球建模人员及其他相关科研人员使用。

本数据集是国际卫星陆面气候学计划第二阶段（ISLSCP II）数据合集的产物之一，该合集涵盖1986年至1995年十年间的50套全球时间序列数据集，部分选定数据集的时间跨度更长。ISLSCP II是一套规范统一的数据集合集，其基于现有数据源与算法构建，旨在满足全球碳、水与能量循环研究领域的建模人员与科研人员的需求。本数据集从多家美国及国际机构、高校与科研单位获取。全球数据集采用统一的空间分辨率（1°、0.5°与0.25°）与时间分辨率（月度，气象数据采用更精细的分辨率，例如3小时），并被重格式化为通用的ASCII格式。本数据集及相关文档已通过两轮同行评审。

国际卫星陆面气候学计划（ISLSCP）是全球能量与水循环实验（Global Energy and Water Cycle Experiment，GEWEX）[http://www.gewex.org/]旗下的多个项目之一，在陆-气相互作用研究领域发挥主导作用，涵盖过程建模、数据检索算法、野外实验设计与实施，以及全球数据集开发等工作。