中国地面相对湿度非均一性检验及订正

利用加拿大环境部气候研究中心研发的PMTred和PMFT方法，选取均一的邻近站为参考站，使用相关系数权重平均构建参考序列，结合元数据信息，对1951-2014年中国2400多个国家级地面站月平均相对湿度进行了非均一性检验与订正，并分析了造成相对湿度序列非均一的主要原因。结果表明，中国地面相对湿度资料存在较严重的非均一问题，68%的台站存在断点，人工观测转自动观测、迁站和时次变化是造成序列非均一的主要原因。整套资料负订正量所占比例较高，订正范围主要集中在-5%～0之间，这种负订正量与人工转自动观测后相对湿度观测值偏低有密切关系。这也使得订正后中国平均相对湿度趋势与订正前存在明显差异，订正前中国平均相对湿度呈下降趋势，订正后相对湿度没有趋势性变化。

Homogenization of Surface Relative Humidity over China

Using the PMTred (penalized maximum T test) and PMFT (penalized maximum F test) developed by theEnvironment Canada, inhomogeneity test of monthly surface relative humidity of national station in China during 1951-2014 has been launched. The homogenous nearby stations with high correlation coefficients with the area averaged annual relative humidity are chosen to construct reference series by correlation coefficient weighted average method. Combined with the detailed metadata of each station, the main reasons causing the homogenization problem of the surface relative humidity in China have been analyzed. The result shows that the surface relative humidity data have serious problems of inhomogeneity, 68% stations existing break points. Automation, relocation and change of observe times are the main causes of the data discontinuity. For the whole dataset, the negative correction values have the high proportion, mainly between -5% and 0, which is linked tightly to the humidity decreasing after automation. The averaged surface humidity is decreasing in 1951-2014 before adjustment, and there is no obvious trend after adjustment.