摘要
从北大西洋中高纬度进入北极的极端气旋会引起北极异常增暖,与中高纬度极端天气事件关系密切,危害极大。利用ERA-Interim再分析资料和中国地面气象站观测资料,探讨了2015年1-2月两个极端气旋(C1,C2)影响中国天气的物理过程和机制。结果表明:当极端气旋生成并北移,附近大气低层和高层均出现异常增暖,中高纬度大气环流表现为乌拉尔阻塞形势形成,极涡断裂,低压槽加深南压,我国发生寒潮天气;且极端气旋伴随的异常增暖加强Rossby波能量频散,使中高纬度的槽和脊发展。对比发现,C1和C2的生成地和路径均存在差异,相比于C2,C1生成纬度较高且路径偏东,对应低温寒潮天气范围更大,但强度比C2略弱。这些结果均表明,极端气旋的生成和移动是中国寒潮天气发生的重要原因之一。
Extreme cyclones entering the Arctic from the mid-high latitude North Atlantic can cause anomalous warming in the Arctic region,which is closely related to extreme weather in mid-high latitudes and is very harmful.However,there are few studies on the impact of extreme cyclones upon weather and climate in China.Physical processes and mechanisms of two extreme cyclones(C1 and C2)affecting cold spells in China during January and February of 2015 are explored,ERA-Interim reanalysis data and observations from China meteorological stations are used.Results show that extreme cyclones occur on the mid-high latitude North Atlantic and meanwhile the anomalous warming appears near the extreme cyclones center in the lower and upper atmosphere.When extreme cyclones move northward,circulations in mid-high latitudes are shown as the formation and maintenance of Ural Blocking and the break-up of the polar vortex.Then the mid-high latitude trough deepens and moves southward over China,and the cold air intrudes southward into China driven by the northerly flow behind the trough,which results in cold weather occurring in China.Furthermore,the mechanism of the apparent adjustment in the polar vortex and general circulation are explored.It shows that the anomalous warming accompanied by extreme cyclones promotes the development of the mid-high latitude troughs and ridges through the energy dispersion of anomalous Rossby waves.In addition,comparison analysis in terms of their occurrence and track shows that there are significant differences between C1 and C2.Compared with C2,C1 occurs in higher latitudes and has an eastward track.Because of these differences,anomalous Rossby waves of C1 are divided into two branches which disperse energy upstream along high latitude and middle latitude,but C2 only has one branch of the anomalous Rossby wave dispersing upstream along the mid-latitude westerlies.Due to the discrepancy of anomalous Rossby waves between C1 and C2,adjustments of circulation in two events are different.Affected by these factors,C1 corresponds to a wider range of cold weather,and under effects of a little trough the duration of 5 d is longer than C2’s which only lasts for 3 d.Cold spells corresponding with C2 only affects Northeast China,but apparently its intensity is slightly stronger than C1’s.These results indicate that extreme cyclones are one of the important causes of cold spells in China.It also should be pointed out that more extreme cyclone events will be analyzed to draw more definite conclusions in future and provide a new reference for forecasting cold spells in China.
作者
张琳
吕俊梅
丁明虎
Zhang Lin;Lü Junmei;Ding Minghu(State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081)
出处
《应用气象学报》
CSCD
北大核心
2020年第3期315-327,共13页
Journal of Applied Meteorological Science
基金
国家重点研究发展计划(2018YFC1406103)
中国科学院战略性先导科技专项(XDA20100300)
中国气象科学研究院科技发展基金(2019KJ004)
中国气象科学研究院基本科研业务费(2019Z008)。
关键词
极端气旋
北极
极涡
冬季天气
寒潮
extreme cyclones
Arctic
polar vortex
winter weather
cold spells
