ISLSCP II CONTINUOUS FIELDS OF VEGETATION COVER, 1992-1993

The objective of this study was to derive continuous fields of vegetation cover from multi-temporal Advanced Very High Resolution Radiometer (AVHRR) data using all available bands and derived Normalized Difference Vegetation Index (NDVI). The continuous fields describe sub-pixel proportions of cover for tree, herbaceous, bare ground and water cover types. For tree cover, additional fields describing leaf longevity (evergreen and deciduous) and leaf morphology (broadleaf and needleleaf) were also generated. The modeling of carbon dynamics and climate require knowing tree characteristics such as these. These products were resampled and aggregated to 0.25, 0.5 and 1.0 degree grids for the International Satellite Land Surface Climatology Project (ISLSCP) data initiative II. The data set describes the geographic distributions of three fundamental vegetation characteristics: tree, herbaceous and bare ground cover, plus a water layer. For tree cover, leaf longevity and morphology layers were produced.

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.

本研究的目标为，利用所有可用波段及衍生的归一化差分植被指数（Normalized Difference Vegetation Index，NDVI），从多时间序列的先进甚高分辨率辐射计（Advanced Very High Resolution Radiometer，AVHRR）数据中提取植被覆盖连续场。该连续场描述了树木、草本、裸地及水体覆盖类型的亚像素占比。针对树木覆盖，研究还生成了描述叶片寿命（常绿与落叶）及叶片形态（阔叶与针叶）的附加场。碳循环动态与气候建模需要知晓此类树木特征参数。本数据集产品已重采样并聚合至0.25°、0.5°及1.0°分辨率的格网，以适配国际卫星陆地表面气候学计划（International Satellite Land Surface Climatology Project，ISLSCP）第二阶段数据项目。本数据集描述了三类核心植被特征的地理分布：树木覆盖、草本覆盖、裸地覆盖，以及水体图层。针对树木覆盖，研究还生成了叶片寿命与叶片形态图层。

本数据集为国际卫星陆地表面气候学计划第二阶段（ISLSCP II）数据合集的产品之一，该合集包含1986至1995年这十年间的50套全球时间序列数据集。部分数据集的时间跨度更长。ISLSCP II是一套标准化数据集合集，其整合了现有数据源与算法，旨在满足全球碳循环、水循环与能量循环的建模者及研究人员的需求。本数据集的来源包括多家美国及国际机构、高校与科研院所。全球数据集采用统一的空间分辨率（1°、0.5°及0.25°）与时间分辨率（月度，气象数据采用更高分辨率，例如3小时）进行制图，并统一格式化为ASCII标准格式。本数据集及配套文档已通过两轮同行评审。

国际卫星陆地表面气候学计划（ISLSCP）是全球能量与水循环实验（Global Energy and Water Cycle Experiment，GEWEX）旗下的多个项目之一，在陆-气相互作用研究中发挥主导作用，相关研究涵盖过程建模、数据反演算法、野外实验设计与实施，以及全球数据集开发等方向[http://www.gewex.org/]。