IPCC Climate Change Data: 1961-1990, Vapor Pressure

From the IPCC website: The CRU Global Climate Dataset
available through the IPCC DDC consists of a multi-variate 0.5º
latitude by 0.5º longitude resolution mean monthly climatology
for global land areas, excluding Antarctica, strictly
constrained to the period 1961-1990. The mean 1961-1990
climatology comprises a suite of eleven surface variables:
precipitation (PRE) and wet-day frequency (WET); mean, maximum
and minimum temperature (TMP, TMX, TMN); diurnal temperature
range (DTR); vapour pressure (VAP;) global radiation (RAD;)
cloud cover (CLD); frost frequency (FRS); and wind speed (WND).
The mean climate surfaces have been constructed from a new
dataset of station 1961-1990 climatological normals, numbering
between 19,800 (precipitation) and 3615 (windspeed). The station
data were interpolated as a function of latitude, longitude and
elevation using thin-plate splines. The accuracy of the
interpolations are assessed using cross-validation and by
comparison with other climatologies. this data-set has been
decsribed in: New,M., Hulme,M. and Jones,P.D. (1999)
Representing twentieth century space-time climate variability.
Part 1: development of a 1961-90 mean monthly terrestrial
climatology J.Climate 12, 829-856.

本数据集源自政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）官网：气候研究单位（Climatic Research Unit, CRU）全球气候数据集，可通过IPCC数据分发中心（IPCC Data Distribution Centre, IPCC DDC）获取。该数据集为多变量数据集，空间分辨率为0.5°纬度×0.5°经度，覆盖全球陆地（不含南极洲），包含1961-1990年时段的逐月气候常态数据。
1961-1990年的气候常态包含11项地表气象变量：降水量（PRE）、降水日数频率（WET）、平均气温（TMP）、最高气温（TMX）、最低气温（TMN）、气温日较差（DTR）、水汽压（VAP）、总辐射（RAD）、云量（CLD）、霜冻日数频率（FRS）以及风速（WND）。
该平均气候场基于一套新的1961-1990年台站气候常态数据集构建，台站数量范围为19800个（降水量变量）至3615个（风速变量）。
台站数据以纬度、经度与海拔为插值协变量，采用薄板样条插值法进行空间插值。
插值结果的精度通过交叉验证以及与其他气候数据集的对比进行评估。
本数据集的详细说明参见：New、Hulme与Jones（1999）发表的论文《Representing twentieth century space-time climate variability. Part 1: development of a 1961-90 mean monthly terrestrial climatology》，刊载于《Journal of Climate》第12卷，第829-856页。