摘要
利用1961—2012年观测、再分析资料以及全球大气环流模式数值试验,探讨了中国北方冬季平均气温对于不同类型(即东部型和中部型)ENSO事件的气候响应,并分析了不同类型ENSO对极端低温事件的可能影响,重点关注了北大西洋涛动(NAO)在其中的桥梁作用。结果表明,ENSO信号能通过调制北大西洋地区的大气环流改变欧亚中高纬度地区的纬向温度平流输送和西伯利亚高压的强度,进而影响中国北方冬季气温,由于不同类型ENSO事件海温分布的差异,这种影响具有明显的非线性特征。在两类厄尔尼诺和东部型拉尼娜事件冬季,北大西洋涛动均呈现负位相,不利于北大西洋的暖湿空气向欧亚大陆输送,西伯利亚高压偏强,因而中国北方地区较气候态偏冷。中部型厄尔尼诺和东部型拉尼娜事件冬季气温负异常的显著区域分别位于东北大范围地区、内蒙古河套附近;东部型厄尔尼诺事件冬季显著的冷异常信号仅局限于黑龙江北部与大兴安岭地区;而中部型拉尼娜事件冬季虽伴随北大西洋涛动正位相,但其空间结构向西偏移,对下游中国北方地区气温的直接影响并不显著,可能受局地信号干扰较大。数值试验再现了北大西洋涛动以及中国北方冬季气温对不同类型ENSO的响应,进一步佐证了上述结论。此外,两类厄尔尼诺事件冬季中国东北地区日平均气温容易偏低,极端低温事件的发生频次增多;而两类拉尼娜事件对极端低温的影响较弱。
The responses of surface air temperature （SAT） in northern China to the eastern Pacific （EP） and central Pacific （CP） ENSO events during boreal winter are analyzed using reanalysis and observational data as well as specific atmospheric general circulation model （AGCM） experiments. Possible influences of ENSO events on regional cold extremes are also dis- cussed. The North Atlantic Oscillation （NAO） is identified to be a bridge connecting ENSO signal and northern Eurasian tem- perature anomalies. Results show that ENSO influences northern China winter surface air temperature mainly through modula ting the atmospheric circulation over the North Atlantic region, and thus changing the zonal temperature advection over north- ern Eurasia and the intensity of Siberian High. Moreover, the ENSO effects display prominent nonlinear characteristics due to different distributions of the tropical Pacific sea surface temperature （SST） anomalies during the two types of ENSO events. Corresponding to the two types of E1 Nig-o and EP La Ni~.a winters, negative NAO-like atmospheric anomalies are evident over the North Atlantic region, which tend to inhibit the transport of warm and moist air from the Atlantic Ocean to Eurasian conti- nent and thus favor a colder than normal winter in northern China. In particular, significant negative temperature anomalies during CP E1 Nifio and EP La Nifia winters are located in northeast China and the Ordos Loop and its vicinity area, respective- ly. The significant cold signal is confined in the north of Heilongjiang Province and the Greater Khingan Range during EP La Nifia winters. In contrast, a positive NAO-like atmospheric anomaly pattern occurs over the North Atlantic region during the CP La Nifia winter, but its positive anomaly center shifts westward. As a result, significant temperature anomalies are mainly confined in Europe and few significant signals can be observed in northern China. These observed results can be realistically re- produced by AGCM experiments. In addition, daily temperature in northeastern China tends to be colder than normal during EP E1 Nigio and CP E1 Nifio winters,indicating more frequent cold extremes. However, the linkage between La Nifia events and cold extremes seems to be negligible.
出处
《气象学报》
CAS
CSCD
北大核心
2017年第4期564-580,共17页
Acta Meteorologica Sinica
基金
全球变化与海气相互作用专项(GASI-IPOVAI-03)
国家自然科学基金项目(41475086、41675073)
江苏省六大人才高峰
333高层次人才工程
优势学科建设工程(PAPD)项目
