平流层爆发性增温对中国天气气候的影响及其在ENSO影响中的作用

Stratospheric sudden warming impacts on the weather/climate in China and its role in the influences of ENSO

本文通过分析1957～2002年平流层爆发性增温(SSW)的环流特征,研究平流层爆发性增温可能对我国天气气候的影响.平流层爆发性增温发生后平流层高纬地区有异常的环流变化,但是这种变化并不仅局限于平流层内部,其产生的环流异常能够向下传播,并对对流层的天气和气候产生影响.研究发现,平流层出现强爆发性增温后,平流层异常温度场和位势高度场在中、高纬度形成AO型振荡并向下传播,使得对流层低层西伯利亚高压增强、阿留申低压加深,500 hPa东亚大槽加深且偏西,导致东亚冬季风增强,我国北部大部分地区气温偏低.而在爆发性增温前,强行星波扰动使得东亚大槽加深,西伯利亚高压和阿留申低压同时增强,也可能导致东亚冬季风偏强.El Nino可能激发出强行星波,有利于强SSW事件的发生.通过上述的两个过程可能造成东亚冬季风的加强,这将会对"ElNino事件通过对流层过程而引起东亚冬季风减弱"的结论有一定影响.因此,ENSO事件影响东亚冬季风及中国的天气气候存在不止一种途径,具体影响情况应该是几种途径的综合结果.

The possible influence of stratospheric sudden warming （SSW） on the weather/climate in China is investigated in this paper via the circulation property analysis of the SSW events from 1957 to 2002. The stratospheric circulation at higher latitude changes dramatically during SSW events. However, such change is not limited inside stratosphere. The resulted circulation anomalies can propagate downward and affect the weather and climate in troposphere. It is shown that, after strong SSW, the temperature and height anomalies on stratosphere can produce downward Arctic Oscillation （AO）, which may result in the stronger Siberian-High, lower Aleutian-Low and deeper, westward East-Asian trough at 500 hPa. Then, East-Asian winter monsoon （EAWM） is enhanced which makes the temperature lower than normal in most parts of North China. Furthermore, the strong planetary wave before SSW can also lead to the enhancement of East-Asian trough, Siberian-High, Aleutian-Low, and the East-Asian winter monsoon thereby. E1 Nino can excite strong planetary wave propitious to the occurrence of strong SSW event, which may enhance the EAWM via the two processes mentioned above. The results in this paper may challenge the conclusion that E1 Nino event may weaken EAWM via troposphere process. Therefore, ENSO event may affect East-Asian winter monsoon and the weather/climate in China through the integration of more than one ways.