空间分辨率对中国夏季降水时空演变特征的影响

本文使用1979—2021年国家气候中心160站(R₁₆₀)和国家级地面气象观测站2 314站(R₂₃₁₄)逐月降水观测资料,利用EOF (Empirical Orthogonal Function)分解和相关分析等方法,研究两类资料夏季降水时空变化特征及其与海气因素之间物理联系的表征水平差异,并分析了差异的可能原因。结果表明,R₁₆₀在我国西北、青藏高原等地区站点极为稀疏,导致其各EOF模态对上述地区降水的时空变化特征描述失真,中东部地区偏低的空间分辨率会使局地强降水的变化特征信号损失,造成降水的年际变率降低。而R₂₃₁₄主模态能够更为真实地反映我国降水的时空演变特征,特别是在极端降水频发的江淮地区以及降水受局地地形影响较大的山区,其EOF主模态的空间分布和时间系数演变与ENSO (El Niño-Southern Oscillation)、西太平洋副热带高压、青藏高原雪盖等气候强迫信号之间的相关性更为显著。

Effect of spatial resolution on the spatial and temporal evolution characteristics of summer precipitation in China

Based on the monthly precipitation observation data of 160 stations of National Climate Center (R₁₆₀) and 2 314 stations of national surface meteorological observatory (R₂₃₁₄) from 1979-2021, by using EOF decomposition and correlation analysis, the spatio-temporal characteristics of summer precipitation variation and its physical connection with ocean and atmosphere factors were studied respectively, meanwhile the possible reasons were discussed. Results show that the spatio-temporal characteristics of precipitation variation in northwestern China, Tibetan Plateau and other regions are distorted by the leading EOF modes due to their extremely sparse distribution of stations. In addition, its low spatial resolution would lose the signal of variation characteristics in local heavy rainfall and reduce interannual climate variability in the central and eastern China. In contrast, the leading mode of R₂₃₁₄ can reflect the spatio-temporal evolution characteristics of precipitation in China more realistically, especially in the Yangtze-Huaihe Rivers region where extreme precipitation occurs frequently and in the mountainous areas where precipitation is greatly affected by local terrain, the evolution of spatial distribution and the temporal coefficient are more different from those of R₁₆₀. Moreover, the association between abnormal variation of R₂₃₁₄ and forcing signals such as ENSO, western Pacific subtropical high and Tibetan Plateau snow cover are more significant.