SPEIbase v.2.10 [Dataset]

The Global 0.5° gridded SPEI dataset is made available under the Open Database License. Any rights in individual contents of the database are licensed under the Database Contents License. Users of the dataset are free to share, create and adapt under the conditions of attribution and share-alike. The Global SPEI database, SPEIbase, offers long-time, robust information on the drought conditions at the global scale, with a 0.5 degrees spatial resolution and a monthly time resolution. It has a multi-scale character, providing SPEI time-scales between 1 and 48 months. The Standardized Precipitatin-Evapotranspiration Index (SPEI) expresses, as a standardized variate (mean zero and unit variance), the deviations of the current climatic balance (precipitation minus evapotranspiration potential) with respect to the long-term balance. The reference period for the calculation, in the SPEIbase, corresponds to the whole study period. Being a standardized variate means that the SPEI condition can be compared across space and time. Calculation of the evapotranspiration potential in SPEIbase is based on the FAO-56 Penman-Monteith method. Data type: float; units: z-values (standard deviations). No land pixels are assigned a value of 1.0x10^30. In some rare cases it was not possible to achieve a good fit to the log-logistic distribution, resulting in a NAN (not a number) value in the database. Dimensions of the dataset: lon = 720; lat = 360; time = 1476. Resolution of the dataset: lon = 0.5º; lat = 0.5º; time = 1 month. Created in R using the SPEI package (http://cran.r-project.org/web/packages/SPEI).

本全球0.5°网格标准化降水蒸散指数（Standardized Precipitation-Evapotranspiration Index，SPEI）数据集采用开放数据库许可（Open Database License）进行发布。数据库中单个内容的相关权利，均依照数据库内容许可（Database Contents License）进行授权。数据集使用者可在署名及相同方式共享的许可条款下，自由对其进行分享、创作与改编。
全球SPEI数据库SPEIbase提供了长时序、稳健的全球干旱状况信息，其空间分辨率为0.5°，时间分辨率为月度。该数据集具备多尺度特性，可提供1至48个月的SPEI时间尺度序列。
标准化降水蒸散指数（Standardized Precipitation-Evapotranspiration Index，SPEI）将当前气候平衡（降水量减去潜在蒸散量）相对于长期气候平衡的偏差，转化为标准化变量（均值为0、方差为1）。在SPEIbase中，计算所用的参考时段对应于整个研究时段。作为标准化变量，SPEI数值可在不同空间与时间维度上进行对比。
SPEIbase中潜在蒸散量的计算基于FAO-56彭曼-蒙特斯（FAO-56 Penman-Monteith）方法。数据类型：浮点型；单位：z值（标准差）。无陆面像元被赋值为1.0×10^30。在极少数情况下，无法对数据进行良好的对数logistic分布拟合，此时数据库中会生成NAN（非数值，not a number）值。
数据集维度：经度（lon）=720；纬度（lat）=360；时间（time）=1476。数据集分辨率：经度分辨率0.5°；纬度分辨率0.5°；时间分辨率为1个月。本数据集基于R语言及SPEI程序包（http://cran.r-project.org/web/packages/SPEI）构建完成。

搜集汇总

背景与挑战

背景概述

SPEIbase v.2.10是一个全球0.5°网格化的标准化降水蒸散指数(SPEI)数据集，提供1至48个月时间尺度的干旱条件信息，具有0.5度的空间分辨率和月时间分辨率。该数据集基于FAO-56 Penman-Monteith方法计算潜在蒸散量，以标准化变量(z值)表示气候平衡偏差，适用于全球尺度的干旱时空比较。