西太平洋副热带高压对华北地区降水蒸发差的影响

采用小波相关和交叉小波变换等方法， 分析了西太平洋副热带高压脊线和北界位置变化对华北地区降水蒸发差的影响。结果表明， 2000年以来华北区南部的水资源短缺问题有所缓解， 但以北京为中心的华北区东北部仍处于持续缺水期； 华北地区降水蒸发差与副热带高压脊线及北界位置变化相关密切， 存在年际和年代际尺度的显著相关振荡， 与副热带高压脊线的年代际尺度相关凝聚性最强； 时域中年际尺度相关存在局部化特征， 年代际尺度相关具有阶段性。分析认为， 2000年以来副热带高压脊线和北界位置偏北并维持反气旋型环流， 有利于水汽向华北输送， 使得华北降水增多， 是近年来华北中南部降水蒸发差增大的主要原因； 而东亚季风减弱不利于西南气流的水汽输送， 以及蒙古高原显著增暖导致蒸发增大等因素， 使得华北东北部仍处于持续缺水期。

Influence of the Subtropical High over Western Pacific on the Difference between Precipitation and Evaporation in North China

The influence of the subtropical high over western Pacific (STH) on the difference between precipitation and evaporation (DPE) in North China are analyzed by the wavelet cross-correlation and cross wavelet transform as well as anomalous circulation analysis methods. The results show that the surface water resource lack is weakening in the middle and south part of North China after 2000, but continuing at the area of around Beijing in the northeast part of North China. There are significant correlation oscillations of interannual and interdecadal scales between the DPE in North China and the location of ridge line and northern limit of STH, and the coherence of interdecadal correlation between the DPE and the STH ridge line is higher then the coherence of interdecadal correlation between the DPE and the STH northern limit. The significance of interdecadal correlation is exhibited at a stage and the interannual correlations are localized in the period from 1955 to 2007. It is found that the main reason of the increasing of DPE in the middle and south part of North China since 2000 is the northward advancing of the STH ridge line and northern limit and the strengthening of the southeast current in the anticyclonic circulation leading to the water vapor transported to North China and the increase of rainfall. The continual decreasing of DPE in the northeast part of North China is due to the weakening of East Asia monsoon that prevent water vapor transported to North China and the obvious increasing of temperature in Mongolia Plateau which bring on the evaporation increasing.