2010年以来华西秋季降水年代际增多原因初探
投稿时间:2019-11-25  修订日期:2019-11-30  点此下载全文
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作者单位E-mail
周波涛 南京信息工程大学 zhoubt@nuist.edu.cn 
徐曼琳   
程志刚 成都信息工程大学  
中文摘要:基于1961-2016年降水资料和NCEP/NCAR再分析数据,分析了华西秋季降水的年代际变化特征。结果表明,华西秋季降水在20世纪80年代中期经历了由多雨向少雨的年代际转折。2010年代开始,华西秋季降水又开始增多,而且,该阶段的降水量比20世纪80年代中期前还要偏多。进一步从大气环流角度,初步探讨了这种年代际变化的成因,特别是2010年代后华西降水增多与20世纪80年代中期之前的大气环流系统的异同。研究发现,与华西降水异常偏少阶段相比,在华西降水两个偏多时期,巴尔喀什湖低压槽加深、亚洲区域SLP负异常,利于高纬冷空气南下并由西路入侵华西区域;东亚低空盛行异常偏南风,利于低纬水汽向华西区域输送;东亚西风急流位置偏北,提供华西降水发生的动力抬升条件,共同造成华西秋季降水增加。不过,相比于20世纪80年代前,2010年代后欧洲高压脊和巴尔喀什湖槽更强,更利于高纬冷空气进入华西区域。同时,有来自南半球印度洋的水汽向华西区域输送。更强的冷空气活动和更多的水汽输送导致后一阶段降水更多。
中文关键词:华西秋季降水  年代际变化  大气环流  水汽输送
 
Preliminary analysis on the interdecadal increase of autumn rainfall in West China since 2010
Abstract:Based on the rainfall data and NCEP/NCAR reanalysis for the period of 1961-2016, the interdecadal change of autumn rainfall in West China (WCAR) is investigated. The results show that the WCAR shifted from the positive phase to the negative phase in the mid-1980s. After entering the 2010s, the WCAR tends to increase again, with the increasing amplitude even larger than that before the mid-1980s. The physical mechanism responsible for the interdecadal change in WCAR is further explored from the perspective of large-scale atmospheric circulations, particularly focusing on the similarity and difference of the atmospheric circulations for the increase of WCAR after the 2010s and before the mid-1980s. During these two periods, compared with the negative phase of the WCAR, the Lake Balkhash trough is deepened and the Asian sea level pressure is declined, favoring the southward outbreak of cold airs from high latitudes into West China. Meanwhile, the southerly anomalies prevail in the lower troposphere of East Asia, benefiting for the transport of water vapor from low latitudes toward West China. In addition, the East Asian jet stream shifts northward, providing a favorable dynamical condition for the occurrence of WCAR. Under such a configuration, the autumn rainfall is thus increased in West China. Furthermore, with respective to the counterparts before the mid-1980s, the blocking over Europe and the trough over Lake Balkhash are both much stronger, which may induce more cold airs from high latitudes to invade West China. Concurrently, more warm-moist airflows from the Indian Ocean in the Southern Hemisphere are transported toward West China. More cold airs and more warm-moist airflows encountering in the targeted region contribute to more rainfall after the 2010s than before the mid-1980s.
keywords:autumn rainfall in West China  interdecadal change  atmospheric circulations  water vapor transport
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