本文利用NCEP/NCAR月平均再分析资料及中国160个测站月降水资料, 采用经验正交函数分解 (EOF)、相关分析、合成分析等方法, 对青藏高原夏季500 hPa纬向风近59年来的年际、 年代际变化趋势及其与我国降水的关系进行了分析。时空演变特征的分析结果表明: 自1950年以来, 青藏高原夏季500 hPa纬向风总体呈现减弱趋势, 其中在1950年代西风偏弱, 1960年代西风明显偏强, 1970年代至21世纪初西风一直处于偏弱阶段; 纬向风变化趋势的空间分布表现为高原大部分区域上空纬向风呈现减弱趋势, 其减弱趋势由东南向西北递增, 高原西北部及中部地区减弱趋势最为明显; 对高原夏季500 hPa纬向风距平时间序列作EOF分解, 得出第一特征向量的空间分布表现为整体减弱型, 其时间权重系数呈现长期正趋势; 时间系数的11年滑动平均分析表明1950年代后期到1960年代中后期纬向西风整体增强趋势比较明显, 1960年代末到21世纪初为西风减弱阶段, 且期间没有出现明显的上升或下降趋势; 时间系数的突变分析表明纬向风在1967年发生了一次较明显的减弱突变; 时间系数的小波分析表明其具有2~4年的周期, 这一周期成分在1950年代前期和1990年代末至21世纪初这两个时段比较显著。年际、 年代际尺度上高原夏季500 hPa纬向风减弱与我国降水关系的分析均表明: 高原纬向风减弱时长江中下游以北的我国部分地区降水偏少, 以东北和华北表现明显, 长江中下游以南地区降水明显偏多, 降水场与大气环流、 水汽通量散度场都有较好的配置关系。
Using the Empirical Orthogonal Function (EOF), correlation and composition analysis, the interannual and interdecadal variability of the 500-hPa zonal wind in summer in the Tibetan Plateau and its relationship to the precipitation in China are examined, based on the monthly NCAR/NCEP reanalysis data and the precipitation data from 160 stations in China. The results of spatial-temporal structure reveal that: in general, 500-hPa zonal wind in summer in the Tibetan Plateau shows a decreasing trend since 1950. And the westerly wind was weaker in the 1950s and stronger significantly in the 1960s. From the 1970s to the early 21st century the westerly wind has been in a weak phase. The spatial distribution of zonal wind trends reveals that most of the zonal wind over the plateau region show weakening trend and the trend decreases from southeast to northwest, and the most decreasing trend takes place in the northwest and the middle of the plateau. The first EOF mode of the 500-hPa zonal wind shows that the decreasing trend takes place in the whole region, and its time coefficient shows the long-term positive trend. The 11-year moving average of time coefficient shows that the increasing trend of the zonal wind taking place in the whole region was more obvious from the late 1950s to the late 60s, and from the late 1960s to the early 21st century the westerly wind has been in a weak phase and has no significant increase or decrease. Mutation analysis of the time coefficient shows that there was a pronounced weakening mutation of the zonal wind in 1967. Wavelet analysis of time coefficients indicates that it has the cycle of 2－4 years and the cycle component is more significant in the early 1950s and from the late 1990s to the early 21st century. The relationships between interannual and interdecadal weakening of the 500-hPa zonal wind in summer in the Tibetan Plateau and the precipitation in China is explored: when the zonal wind decreases, less precipitation happens in the north of the middle and lower reaches of the Yangtze River, especially in northeastern and northern China; much precipitation happens in the south of the middle and lower reaches of the Yangtze River. Meanwhile, relatively significant relationships are found between precipitation and circulation, divergence of water vapor flux.
朱丽华,范广洲,董一平,等.青藏高原夏季500hPa纬向风的时空演变特征及其与我国降水的关系.大气科学,2011,35(1):168~178 Zhu Lihua, Fan Guangzhou, Dong Yiping, et al. The Spatial-Temporal Structure of 500-hPa Zonal Wind in Summer in the Tibetan Plateau and Its Relationship to the Precipitation in China. Chinese Journal of Atmospheric Sciences (in Chinese),2011,35(1):168~178复制