摘要
本文选取了对我国2021年冬季寒潮事件可能有重要影响的2021年1月北半球平流层爆发性增温(SSW)事件为例,利用观测资料、再分析资料和预报模式,探讨了2021年1月的SSW事件的特征和机制并对其进行了预报研究。此次SSW事件(简称为“事件”)发生期间,北极平流层温度几天内上升近30°C,绕极西风环流减弱甚至在此次事件中出现了三次逆转为东风环流的现象。事件发生前期,太平洋海温和巴伦支—喀拉海(BK)海冰的出现异常的降低和减少现象;使用Eliassen-Palm通量(E-P通量)研究发现,这导致更多的对流层异常行星波活动上传到平流层;海温和海冰所导致的行星波活动的异常增多可能是导致此次SSW事件的主要因素。除此之外还发现,事件期间平流层位势高度正异常下传到对流层,与2021年1月中旬亚欧大陆出现的极端低温事件,存在显著的联系。最后,本文使用基于WACCM6模式和DART同化工具建立的平流层预报模型对此次事件进行了回报研究。该模型成功的预报了2021年1月发生的这次SSW事件,预报的温度大小和纬向风强度基本和观测结果一致。对回报试验的进一步研究发现,同化平流层温度、臭氧和水汽,减少预报初始场中平流层环流和温度误差,对准确预报这次SSW事件有重要的作用。初始场中没有同化平流层温度、臭氧和水汽的预报试验结果,与观测结果之间存在很大差异,甚至结果完全相反。
Taking the Northern Hemisphere stratospheric sudden warming(SSW)event in January 2021 as an example,which may considerably impact the winter cold wave event in China,this study discusses the characteristics and mechanism of the SSW in January 2021 using observation data,reanalysis data,and a prediction model.During this SSW event(hereinafter referred to as“event”),the Arctic stratospheric temperature increased by approximately 30 K in a few days,and westerly winds weakened over the Arctic and even reversed to the easterly winds thrice.In the early stage of the event,the Pacific sea surface temperature(SST)and Barents–Kara sea ice decreased abnormally.By examining the anomalies of an Eliassen–Palm flux,it is observed that these decreases result in more tropospheric planetary waves being propagated into the stratosphere;moreover,the increase in planetary wave activity in the stratosphere caused by a decrease in SST and sea ice may be the main factor responsible for the SSW event.Additionally,it is observed that during the event,the positive anomaly of the stratospheric geopotential height propagated downward into the troposphere,which is considerably related to the extreme cold event on the Eurasian continent in mid-January 2021.Finally,the stratospheric prediction model based on the WACCM6(Whole Atmosphere Community Climate Model 6)and the DART(Data Assimilation Research TestBed)assimilation tool is used to study this event.The model successfully predicted the SSW event in January 2021.The predicted temperature and zonal wind intensity are essentially consistent with the observation results.Furthermore,the simulation results show that the assimilation of stratospheric temperature,ozone,and water vapor is crucial for accurately predicting the SSW event by reducing the errors of stratospheric circulation and temperature in the initial prediction field.However,when not assimilating stratospheric temperature,ozone,and water vapor in the initial field,the simulation results are considerably different from the o
作者
吴少华
牛迎丽
谢飞
WU Shaohua;NIU Yingli;XIE Fei(College of Global Change and Earth System Science,Beijing Normal University,Beijing 100875)
出处
《大气科学》
CSCD
北大核心
2024年第3期1012-1026,共15页
Chinese Journal of Atmospheric Sciences
基金
国家自然科学基金项目42122037、41975047。
