Humanity's Fundamental Environmental Limits -- model input files

These data constitute the spatially explicit input to our model of Earth's biophysical human carrying capacity (Binder et al 2020). They include average daily estimates of photosynthetically active radiation (PAR), light interception efficiency (EI) of crop canopy, and precipitation net of evapotranspiration (WATERFLUX); as well as land areas of each grid cell and the fractions currently farmed and irrigated. The data are made available here in a .mat (Matlab) file.<br>WATERFLUX is calculated as PRECIPITATION - PET, with negative values retained for purposes of the model. <br>PET is calculated with the Hargreaves (1985) equation using data for temperature and PAR (re-scaled by 1/0.487 to capture the full light spectrum). <br>Daily PAR for terrestrial areas are calculated from the high-frequency, instantaneous PAR values of the GLASS PAR product, using a generalized integration method developed by Holdahl (2019). For more detail, see: https://ethanholdahl.shinyapps.io/PAR_App/<br>Baseline daily interception efficiencies are calculated in two steps. First, growing periods are determined based on temperature data. All days with temperature minima in excess of 0 deg C (terrestrial) or with temperature means in excess of 10 deg C (ocean) are initially designated as eligible growing days. All eligible days that are part of a sequence of 30 or more consecutive eligible days (minimum season length) retain final designation as part of a growing period; other days are excluded. In the second step, light interception efficiencies of the crop canopy are calculated according to a quadratic equation fit to data reported in Dohleman and Long (2009). <br>AREA is calculated using the 'areaquad' function of Matlab's Mapping Toolbox. <br>FARMED is the percent of each grid cell dedicated to crop or pasture, based on data from Ramankutty et al (2008). <br>IRRIGATED is the percent of farmed land equipped for irrigation in each grid cell, based the Ramankutty data referenced above in conjunction with irrigation data from FAO's Aquastat (Siebert et al 2013). In the 1.7% of cases in which estimates of irrigated land exceed estimates of cultivated land, irrigation fractions are capped at 1. <br>UnitsPAR: MJ m-2 day-1WATERFLUX: mm m-2 day-1AREA: m2IRRIGATION, FARMED and EI are dimensionless.<br>All data have been resampled and aligned to a common 1-by-1 degree grid using Matlab's Mapping Toolbox. The upper left cell of each matrix (1, 1) corresponds to -179.5 deg E and 89.5 deg N. <br><br>For further information regarding the use and sources of these data, please consult our article, "Humanity's Fundamental Environmental Limits", in <i>Human Ecology</i>, available at:http://link.springer.com/article/10.1007/s10745-020-00140-w<br>

本数据集为我们的地球生物物理人类承载能力模型（Binder等人，2020）提供了空间显式输入数据。数据集包含光合有效辐射（photosynthetically active radiation, PAR）、作物冠层光拦截效率（light interception efficiency, EI）以及扣除蒸散后的降水量（WATERFLUX）的日均估算值；同时涵盖各网格单元的陆地面积，以及当前耕地与灌溉用地的占比。本数据集以Matlab格式的.mat文件提供。

WATERFLUX的计算方式为降水量（PRECIPITATION）减去潜在蒸散量（PET），为适配模型需求保留负值。

潜在蒸散量（PET）采用Hargreaves（1985）公式计算，输入数据为气温与光合有效辐射（PAR经1/0.487缩放以覆盖全光谱范围）。

陆地区域的日均PAR数据由GLASS PAR产品的高频瞬时PAR值，通过Holdahl（2019）提出的广义积分方法计算得到。详细信息可参考：https://ethanholdahl.shinyapps.io/PAR_App/

基准日均光拦截效率的计算分为两步：第一步，基于气温数据确定生长期：所有最低气温高于0℃（陆地）或平均气温高于10℃（海洋）的日期，初步标记为符合条件的生长期日期；仅当符合条件的日期连续达到30天及以上（最小季长）时，才最终认定为生长期内的日期，其余日期予以排除。第二步，作物冠层的光拦截效率根据Dohleman与Long（2009）报告的数据拟合的二次方程计算得到。

网格单元面积（AREA）通过Matlab地图工具箱的'areaquad'函数计算得到。

耕地占比（FARMED）指各网格单元用于作物种植或畜牧的面积百分比，数据来源于Ramankutty等人（2008）的研究。

灌溉用地占比（IRRIGATED）指各网格单元中具备灌溉条件的耕地面积百分比，结合前述Ramankutty的耕地数据与FAO Aquastat的灌溉数据（Siebert等人，2013）计算得到。当1.7%的样本出现灌溉用地估算值超过耕地估算值的情况时，将灌溉占比上限设为1。

单位说明：PAR：MJ·m⁻²·day⁻¹；WATERFLUX：mm·m⁻²·day⁻¹；AREA：m²；IRRIGATED、FARMED与EI为无量纲量。

所有数据已通过Matlab地图工具箱重采样并对齐至统一的1°×1°网格。每个矩阵的左上角单元格（1,1）对应西经179.5°、北纬89.5°。

如需了解本数据集的使用方法与来源详情，请参阅我们发表于《Human Ecology》的论文《人类的基本环境极限》，获取链接为：http://link.springer.com/article/10.1007/s10745-020-00140-w