2022年5月欧亚大陆中高纬度地区“三极子”型异常气温的特点和成因

Characteristics and Causes of the"Tripole"Pattern of Temperature Anomaly in the Mid-High Latitude of Eurasia in May,2022

2022年5月,欧亚大陆中高纬度地区出现了“三极子”型的异常表面气温(Surface air temperature,SAT),东欧和东北亚偏冷,欧亚大陆中北部偏暖,是2000年以来5月最明显的一次气温异常。基于多种资料和方法,本文探讨了此次“三极子”型异常气温的特点和成因。结果表明:“三极子”型异常SAT在5月15—27日期间最显著,与“三极子”型的异常大气环流密切相关,偏暖(冷)处受到了异常高(低)压和异常偏南(北)风的影响,欧亚大陆中北部(东欧)还受到了异常下沉(上升)运动和净热通量正(负)异常的影响,东北亚较弱的异常环流可能是该处SAT异常较弱的原因。比较不同物理过程对三极子各区域SAT异常的贡献,发现异常温度平流(异常经向风对气候态温度的平流)在“三极子”型异常SAT的形成中贡献最大,贡献率分别为40.5%、18.7%和17.7%。“三极子”型异常环流与两支波列有关。里海以北和中纬度北大西洋东部分别在5月9—10日和15—17日期间有与低层辐合异常和高层辐散异常相关的异常上升运动,导致降水异常偏多。线性斜压模式结果证明,降水导致的潜热释放在对流层形成的异常热源可以激发出欧亚大陆上的“三极子”型环流。

In May,2022,a"tripole"pattern of anomalous surface air temperature(SAT)appeared in the mid-high latitude of Eurasia,characterized by colder eastern Europe and Northeast Asia,and warmer central and northern Eurasia,which is the most significant occurrence in May since 2000.Based on various data and methods,this paper explores the characteristics and causes of the"tripole"pattern of anomalous temperature.Results show that the tripole of SAT anomaly is most significant during May 15—27,closely related to the tripole of atmospheric circulation anomaly.The warmer(colder)region is affected by anomalous high(low)pressure and southerly(northerly).The central and northern Eurasia(eastern Europe)is also affected by anomalous downward(upward)motion and positive(negative)net heat flux.The weak anomalous circulation in Northeast Asia may lead to the weak temperature anomaly here.Comparing the contributions of different physical processes to the tripole of SAT anomaly,it is found that the tripole of anomalous temperature advection(advection of anomalous meridional wind on mean temperature)contributes the most to the tripole of SAT anomaly,with rates of 40.5%,18.7%,and 17.7%,respectively.The tripole of circulation anomaly is related to two wave trains.During May 9—10 and 15—17,anomalous upward motion related to lower convergence and upper divergence anomaly occurred in the north side of the Caspian Sea and eastern mid latitude of North Atlantic,respectively,resulting in positive precipitation anomaly.The release of latent heat results in anomalous heat sources in the troposphere.The linear baroclinic model proves that the anomalous heat source formed by the release of latent heat caused by precipitation in the troposphere can stimulate the tripole of circulation in Eurasia.