WATer and global CHange (WATCH) Forcing Data (WFD) - 20th Century

New global sub-daily meteorological forcing data are provided for use with land surface and hydrological-models. The data are derived from the ERA-40 reanalysis product via sequential interpolation to half-degree resolution, elevation correction and monthly-scale adjustments based on CRU (corrected-temperature, diurnal temperature range, cloud-cover) and GPCC (precipitation) monthly observations combined with new corrections for varying atmospheric aerosol-loading and separate precipitation gauge corrections for rainfall and snowfall. The WATCH Forcing data is a twentieth century meteorological forcing dataset for land surface and hydrological models. It consists of three of 6-hourly states of the weather for global half-degree land grid points. It was generated as part of the EU FP 6 project "WATCH" (WATer and global CHange") which ran from 2007-2011. The data was generated in 2 time periods with slightly different methodology: 1901-1957 and 1958-2001, but generally the dataset can be considered as continuous. More details regarding the generation process can be found in the associated WATCH technical report and paper in J. Hydrometeorology. The data covers land points only and excludes the Antarctica.

本数据集提供一套全新的全球亚日尺度气象强迫数据，适用于陆面过程模型与水文模型。该数据集源自ERA-40再分析资料（ERA-40 reanalysis product），通过逐次插值得到0.5度分辨率，同时开展高程校正，并结合CRU（校正气温、气温日较差与云量）、GPCC（降水）的月尺度观测数据进行月尺度订正；此外还新增了针对大气气溶胶负荷变化的校正方案，以及分别针对降雨与降雪的雨量计观测校正。

WATCH强迫数据集（WATCH Forcing data）是一套面向20世纪的陆面与水文模型用气象强迫数据集，涵盖全球0.5度陆面格点的3组6小时气象状态数据。该数据集由欧盟第六框架计划（EU FP 6）项目"WATCH（水与全球变化，WATer and global CHange）"资助研发，项目执行周期为2007年至2011年。

数据集分两个时间段生成，二者采用的方法略有差异：1901年至1957年，以及1958年至2001年；但整体而言，该数据集可视为连续完整的。有关数据生成流程的更多细节，可查阅配套的WATCH技术报告以及发表于《水文气象学杂志（Journal of Hydrometeorology）》的相关论文。本数据集仅覆盖陆面格点，不包含南极地区。