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Impact of Spring AAO on Summertime Precipitation in the North China Part: Observational Analysis
Asia-Pacific Journal of Atmospheric Sciences ( IF 2.3 ) Pub Date : 2020-01-02 , DOI: 10.1007/s13143-019-00157-2
Zhengxuan Yuan , Jun Qin , Shuanglin Li , Sijing Huang , Yassin Mbululo

By using the 160 stations monthly precipitation data and NOAA-ESRL reanalysis data, the effect of spring Antarctic Oscillation (AAO) on Summer Precipitation in North China (SPNC) is studied. The analysis results show that the positive phase of March AAO leads the easterly-southerly and ascend anomalies in the southern part of North China by affecting zonal wind, and meridional circulation in the Northern Hemisphere (NH) late summer, results in more SPNC. Key regions of Antarctic sea-ice may store preceding March AAO signal which is cross-seasonal sustained by the heat exchanging with underlying surface, and the Summer Antarctic Sea-ice Index (SSI) is defined. The upward and poleward propagations of the planetary wave are enhanced in the Southern Hemisphere (SH) high latitude, and there are significant anomalous variabilities of PSI over SH low latitude, high latitude and polar regions in the high SSI years and vice versa. The wave-current interaction weakens the descending motion over the Antarctic, strengthens the circumpolar westerlies and deepens the SH polar vortex (AAO positive phase) in the high SSI years and vice versa. The results of observation and CAM5 show that SSI is positively correlated with indices of Quasi-Biennial Oscillation (QBOI). In QBO westerly phase, the SPNC anomaly in the high SSI years shows out of phase with that in the low SSI years. In the low SSI years, Rossby wave has the characteristics of anomalous southward propagation which corresponds to the abnormal weakening of ascend motion (the decrease of precipitation) over North China. Accompanied with a significant PSI anomaly, there exists a region of weak to strong wave energy over North China which is regarded as the source region of wave energy in both high and low SSI years of QBO westerly phase. But in QBO easterly phase, SPNC anomaly is not significant. QBO may be a bridge that connecting the signals of zonal wind anomalies in the stratosphere of the SH and the NH.



中文翻译:

春季AAO对华北夏季降水的影响:观测分析

利用160个站点的月降水量数据和NOAA-ESRL再分析数据,研究了春季南极涛动(AAO)对华北夏季降水(SPNC)的影响。分析结果表明,3月AAO的正相通过影响纬向风引导华北南部异常上升,并在夏季末增加了北半球(NH)的子午环流,导致SPNC增多。南极海冰的关键区域可能会存储3月之前的AAO信号,该信号是通过与下垫面进行热交换而维持的跨季节的,并定义了夏季南极海冰指数(SSI)。在南半球(SH)高纬度,行星波的向上和向极传播得到增强,在高SSI年份中,SH低纬度,高纬度和极地地区的PSI存在明显的异常变化,反之亦然。在高SSI年中,波流相互作用减弱了南极上空的下降运动,增强了极极西风,加深了SH极涡(AAO正相),反之亦然。观测结果和CAM5结果表明,SSI与准两年一次振荡指数(QBOI)正相关。在QBO西风阶段,高SSI年的SPNC异常与低SSI年的SPNC异常不同。在低SSI年中,罗斯比波具有向南传播异常的特征,这与华北地区的上升运动异常减弱(降水减少)相对应。伴随着重大的PSI异常,华北地区存在一个由弱到强的波浪能区域,在QBO西风期的高SSI年和低SSI年均被视为波能的源区。但在QBO东风阶段,SPNC异常并不明显。QBO可能是连接SH和NH平流层纬向风异常信号的桥梁。

更新日期:2020-01-02
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