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影响秦皇岛和唐山地区夏季降水年际变化的大尺度环流和海温因子

Interannual Variability of Summer Rainfall in the Qinhuangdao–Tangshan Region of North China and the Associated Large-Scale Circulation and Sea Surface Temperature Anomalies

  • 摘要: 本文基于1981~2022年中国站点逐日降水数据,大气再分析、月平均海温资料,以及太平洋年代际振荡(PDO)、厄尔尼诺(Niño3.4)指数,采用经验正交函数、相关和合成等统计方法,揭示了秦皇岛和唐山(简称秦唐地区)夏季降水年际变化特征,探讨了对其产生影响的大尺度环流和海温因子。结果表明,秦唐地区夏季降水年际变化的主模态表现为符号一致性特征,降水量呈由北向南递减分布。蒙古气旋(MC)和日本海高压(SJH)是影响该地区夏季降水的两个关键环流系统,环流强度与降水量变化存在显著的正相关。MC和SJH偏强有利于水汽输送和冷暖空气交汇,导致该地区夏季降水极端偏多;当SJH偏弱时,水汽输送减少,该地区夏季降水极端偏少。前期冬春季的Niño3.4指数处于负(正)位相时,夏季印度洋海温偏低(高),西北太平洋海温偏高(低),SJH偏强(弱),秦唐地区降水偏多(少)。当春季PDO为正(负)位相时,夏季西北太平洋呈“北正南负(北负南正)”型海温分布,MC偏强(弱),秦唐地区夏季降水偏多(少)。因此,前期冬春季ENSO和春季PDO的位相状态对秦唐地区夏季降水的精细化季节预测具有重要的指示意义。本文的分析结果同样适用于华北地区,为提高华北夏季降水空间精细化的季节预测提供了重要的科学依据。

     

    Abstract: This study used daily observed rainfall data in China, atmospheric reanalysis, monthly sea surface temperature (SST) data, Pacific decadal oscillation (PDO) and Niño3.4 index during 1981–2022, revealed the interannual variability of summer rainfall anomaly in Qinhuangdao and Tangshan (Qin–Tang region) and the large-scale circulation regimes and SST anomalies influence on it based on the Empirical Orthogonal Function and correlation and composite analyses. Our results show that the dominant mode of summer rainfall in the Qin–Tang region exhibits consistent variation on the interannual time scale, with rainfall anomalies decreasing from north to south. The Mongolian cyclone (MC) and the Sea of Japan High (SJH) are dominant circulations, both showing a significant positive correlation with the summer rainfall anomaly in the Qin–Tang region on the interannual time scale. Stronger MC and SJH are conducive to moisture transport, enhance the interaction of warm and cold air mess, and cause extreme summer rainfall anomalies. When SJH is weak, summer rainfall in this region is extremely lower than normal due to a decrease in moisture transport. The negative (positive) phase of the Niño3.4 index observed in winter and spring is usually followed by cold (warm) and warm (cold) SST in the Indian and northwest Pacific Ocean in summer, respectively, which results in stronger (weaker) SJH and more (less) rainfall in this region. The positive phase of PDO noticed in spring is often followed by warmer (colder) SST in the north (south) of the northwest Pacific Ocean in summer, which increases MC and summer rainfall in this region or vice versa. Therefore, the phases of the PDO and Niño3.4 index observed from winter to spring possibly provide a useful signal for the accurate seasonal prediction of following summer rainfall in this region. These results are applicable to the whole of North China, which possibly benefit for the spatially accurate seasonal forecasting of summer rainfall.

     

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