摘要
使用1962-2002年逐日降水资料和NCEP／NCAR再分析资料，考察了西北地区东部春季降水及其水汽输送的低频振荡特征。通过定义并计算相对比例系数prpt，并结合统计检验，证实了春季西北地区东部、华北和长江下游地区30～60天周期的相对重要性和显著性。2002年个例分析表明，以银川站为代表的西北地区东部春季降水和水汽通量散度具有显著的20～60天振荡周期，并且在4，5月份季节转换时期显著增强；在降水处于正位相时，低频水汽主要来自东面海上的向西输送和南海北部沿高原东侧的向北输送，低频波表现为明显的向东传播。多年资料分析表明，多雨年季节内振荡较强、反之较弱；主要周期尺度有所不同，低频降水与水汽输送具有很好的对应关系，但也存在一定差异。年代际变化特征突出，表现在从20世纪70-80年代初季节内振荡特征不明显，低频降水与水汽输送之间的一致性相对较差，显示出气候异常对低频振荡的影响。
The low-frequency oscillation characteristics of the precipitation and water vapor transport in the eastern part of Northwest China （ENWC） in spring are investigated by using the daily precipitation data from NMIC and NCEP/NCAR reanalysis data from 1962 to 2002. By introducing a relative proportion coefficient （prpt） and combined with statistical test, it is verified that 20-60 day low-frequency periods are relatively important and statistically significant in the regions of ENWC, North China, and the middle- and low- reach areas of the Yangtze River during spring, which provides a theoretical basis for the latter study. The analysed results from the case of 2002 show that both the springtime precipitation and divergence of water vapor flux in ENWC have about 20-60 day low-frequency oscillation features which enhance significantly during April-May and is a primary mode of precipitation and water vapor transport on the time scale of intraseason. Simultaneously, it＇s also found that low-frequency waves clearly propagate eastward and low-frequency water vapor transport is consistent with the anomalous characteristics of the water vapor transport in rainy years. Furthermore, it follows from the multi-year analysis that with different principal periods each other, the features of intraseasonal oscillation are pronounced and their intensities are relatively strong in rainy years. We also see that there is very good corresponding and coherent relationship between the low-frequency precipitation and water vapor transport, but some differences also exist. On the other hand, the most considerable feature with regard to interdecadal variability is that the intraseasonal oscillation is week and unclear from the 1970＇s to early 1980Ps. Moreover, the correlation between low-frequency precipitation and water vapor transport is not substantial as other rainy years, which indicates the influence on low-frequency oscillation from climate anomalies.
出处
《高原气象》
CSCD
北大核心
2006年第2期285-292,共8页
Plateau Meteorology
基金
国家自然科学基金项目(40375025
40135020)资助
关键词
西北区东部
春季降水
水汽输送
低频振荡
Eastern part of Northwest China
Springtime precipitation
Water vapor transport
Low-frequency oscillation
