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...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。展开更多
The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional win...The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.展开更多
文摘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。
基金jointly supported by the National Key Research and Development Program of China[grant number 2016YFA0600601]the National Natural Science Foundation of China[grant numbers 42030601 and 41875087]。
文摘The interannual variability of cross-equatorial flows(CEFs)over the Asian–Australian monsoon(AAM)region during boreal summer was analyzed by applying the empirical orthogonal function(EOF)method to the meridional wind at 925 h Pa.The first mode(EOF1)exhibits an in-phase relationship among different CEF channels over the AAM region,which has received much attention owing to its tight linkage with ENSO.By contrast,the second mode(EOF2)possesses an out-of-phase relationship between the Bay of Bengal(BOB)CEF(90°E)and Australian CEF,among which the New Guinea CEF near 150°E shows the most significant opposite correlation with the BOB CEF.Observational and numerical model results suggest that the equatorially asymmetric heat source(sink)over the western(eastern)Maritime Continent,closely associated with the in-situ sea surface temperature anomaly,can induce cross-equatorial northerly(southerly)flow into the heating hemisphere,which dominates the out-of-phase relationship between the BOB and New Guinea CEFs.Furthermore,an equatorially symmetric heating over the central Pacific may indirectly change the CEFs by modulating the zonal atmospheric circulation near the Maritime Continent.
