在对逐日气象资料进行纬向谐波分析的基础上,对比和讨论了2007/2008年冬季强极涡期间和2008/2009冬季弱极涡期间平流层和对流层不同波数的行星波的变化特征,特别关注强极涡或弱极涡发生之后,500 h Pa沿60°N和30°N行星波1波和...在对逐日气象资料进行纬向谐波分析的基础上,对比和讨论了2007/2008年冬季强极涡期间和2008/2009冬季弱极涡期间平流层和对流层不同波数的行星波的变化特征,特别关注强极涡或弱极涡发生之后,500 h Pa沿60°N和30°N行星波1波和2波振幅和位相的差异,以及相应的500 h Pa位势场的差异,进而讨论为什么不同的平流层极涡异常会对东亚有不同的影响,特别讨论为什么同一种极涡异常,对我国南北方近地面气温的影响会不同。结果表明:平流层极涡发生异常时,平流层行星波活动有明显的异常。随着极涡异常的下传,对流层行星波的振幅和位相也有明显的变化,而且,对于不同的纬度带,其变化又有不同,表现为:2008年1月强极涡发生之后,500 h Pa行星波1波和2波的扰动都向南伸,而2009年1月的弱极涡(SSW)期间和之后,1波和2波的扰动都偏北;在对流层,强极涡和弱极涡发生之后不但行星波1波和2波的振幅有所差异,其位相也有明显的不同。特别是,其位相的差异还随纬度而变化。就同一年(或者说对于同是强极涡或者同是弱极涡)而言,无论是1波还是2波,在60°N和30°N附近的扰动相比,几乎反位相。这样就使得它们的500 h Pa位势场也有明显不同:在东半球,主要表现为乌拉尔高压和东亚大槽的强度和位置不同。2008年1月强极涡发生之后,乌拉尔高压和东亚大槽东移,不利于冷空气向欧亚大陆北部(包括我国北方)的输送,使这些地区的温度偏高;而2009年1月弱极涡之后,东亚大槽西退,利于冷空气向欧亚大陆北部输送,导致这些地区较冷。对于同一种极涡异常(如2008强极涡或者2009弱极涡)由于南方和北方行星波扰动的位相不同,对南方和北方冷暖空气的输送也就不一样。所以同一种极涡异常对(我国)南北地区的温度影响是不同的。展开更多
In this study,the reversal of monthly East Asian winter air temperature(EAWT) in 2020/21 and its predictability were investigated.The reversal of monthly EAWT in 2020/21 was characterized by colder temperatures in ear...In this study,the reversal of monthly East Asian winter air temperature(EAWT) in 2020/21 and its predictability were investigated.The reversal of monthly EAWT in 2020/21 was characterized by colder temperatures in early winter(December 2020 to mid-January 2021) and warmer temperatures in late winter(mid-January to February 2021).Results show that the reversal in the intensity of the Siberian high(SH) also occurred between early and late winter in 2020/21.In early winter,as the Barents-Laptev sea ice in the previous September(i.e., in2020) reached a minimum for the period 1981-2020,the SH was strengthaned via a reduction of the meridional gradient between the Arctic and East Asia.In late winter,as a sudden stratospheric warming occurred on 5 January 2021,the stratospheric polar vortex weakened,with the weakest center shifting to North America in January.Subsequently,the negative Arctic Oscillation-like structure shifted towards North America in the middle and lower troposphere,which weakened the SH in late winter.Furthermore,the predictability of the reversal in EAWT in 2020/21 was validated based on monthly and daily predictions from NCEP-CFSv2(National Centers for Environment Prediction-Climate Forecast System,version 2).The results showed that the model was unable to reproduce the monthly reversal of EAWT.However,it was able to forecast the reversal date(18 January 2021)of EAWT at lead times of 1-20 days on the daily scale.展开更多
Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar...Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar region.After the onset of a December WPV event,the dynamic processes influencing Eurasian temperature can be split into two separate periods.Period I(lag of 0-25 days)is referred to as the stratosphere-troposphere interactions period,as it is mainly characterized by stratospheric signals propagating downwards.In Period I,a stratospheric negative Northern Annular Mode(NAM)pattern associated with the WPV propagates downwards,inducing a negative NAM in the troposphere.The anomalous low centers over the Mediterranean and North Pacific bring cold advection to northern Eurasia,resulting in a north-cold-south-warm dipole pattern over Eurasia.The zero line between negative and positive temperature anomalies moves southwards during days 5-20.Stratospheric cold anomalies at midlatitudes propagate downwards to high latitudes in the troposphere and contribute to the dipole structure.During PeriodⅡ(lag of 25-40 days),as downward signals from the stratosphere have vanished,the dynamic processes mainly take place within the troposphere.Specifically,a wave train is initiated from the North Atlantic region to northern Europe.The propagation of wave activity flux intensifies a cyclonic anomaly over northern Europe,which brings cold advection to Scandinavia and warm advection to central Asia.Therefore,a northwest-cold-southeast-warm dipole structure occupies Eurasia and migrates southeastwards during this period.展开更多
To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linea...To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linear trend in the zonal wind at these latitudes are analyzed and removed, and the QBO signal is retrieved from the monthly zonal wind for the period 1979-2014. The zonal wind has a strong decreasing trend in winter, with a maximum decrease （less than -0.35 m s-1 yr-1） occurring within 70-100°E. The zonal wind has an in-phase response of 1.6 m s-1 to the solar cycle, with a maximum within 100-140°E. A clear QBO signal is detected in the zonal wind during the period 1979-2014, with an amplitude of 2.5 m s-1 and a period of 30 months. The latitudinal distribution of the QBO signal is inhomogeneous, with a maximum within 120-180°E and a minimum within 25-45°E.展开更多
文摘在对逐日气象资料进行纬向谐波分析的基础上,对比和讨论了2007/2008年冬季强极涡期间和2008/2009冬季弱极涡期间平流层和对流层不同波数的行星波的变化特征,特别关注强极涡或弱极涡发生之后,500 h Pa沿60°N和30°N行星波1波和2波振幅和位相的差异,以及相应的500 h Pa位势场的差异,进而讨论为什么不同的平流层极涡异常会对东亚有不同的影响,特别讨论为什么同一种极涡异常,对我国南北方近地面气温的影响会不同。结果表明:平流层极涡发生异常时,平流层行星波活动有明显的异常。随着极涡异常的下传,对流层行星波的振幅和位相也有明显的变化,而且,对于不同的纬度带,其变化又有不同,表现为:2008年1月强极涡发生之后,500 h Pa行星波1波和2波的扰动都向南伸,而2009年1月的弱极涡(SSW)期间和之后,1波和2波的扰动都偏北;在对流层,强极涡和弱极涡发生之后不但行星波1波和2波的振幅有所差异,其位相也有明显的不同。特别是,其位相的差异还随纬度而变化。就同一年(或者说对于同是强极涡或者同是弱极涡)而言,无论是1波还是2波,在60°N和30°N附近的扰动相比,几乎反位相。这样就使得它们的500 h Pa位势场也有明显不同:在东半球,主要表现为乌拉尔高压和东亚大槽的强度和位置不同。2008年1月强极涡发生之后,乌拉尔高压和东亚大槽东移,不利于冷空气向欧亚大陆北部(包括我国北方)的输送,使这些地区的温度偏高;而2009年1月弱极涡之后,东亚大槽西退,利于冷空气向欧亚大陆北部输送,导致这些地区较冷。对于同一种极涡异常(如2008强极涡或者2009弱极涡)由于南方和北方行星波扰动的位相不同,对南方和北方冷暖空气的输送也就不一样。所以同一种极涡异常对(我国)南北地区的温度影响是不同的。
基金funded by the National Key Research and Development Program of China[grant number 2022YFE0106800]the National Natural Science Foundation of China[grant number 41730964]the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)[grant number 311021001].
基金jointly supported by the National Natural Science Foundation of China [grant numbers 42088101 and 41730964]the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) [grant number 311021001]。
文摘In this study,the reversal of monthly East Asian winter air temperature(EAWT) in 2020/21 and its predictability were investigated.The reversal of monthly EAWT in 2020/21 was characterized by colder temperatures in early winter(December 2020 to mid-January 2021) and warmer temperatures in late winter(mid-January to February 2021).Results show that the reversal in the intensity of the Siberian high(SH) also occurred between early and late winter in 2020/21.In early winter,as the Barents-Laptev sea ice in the previous September(i.e., in2020) reached a minimum for the period 1981-2020,the SH was strengthaned via a reduction of the meridional gradient between the Arctic and East Asia.In late winter,as a sudden stratospheric warming occurred on 5 January 2021,the stratospheric polar vortex weakened,with the weakest center shifting to North America in January.Subsequently,the negative Arctic Oscillation-like structure shifted towards North America in the middle and lower troposphere,which weakened the SH in late winter.Furthermore,the predictability of the reversal in EAWT in 2020/21 was validated based on monthly and daily predictions from NCEP-CFSv2(National Centers for Environment Prediction-Climate Forecast System,version 2).The results showed that the model was unable to reproduce the monthly reversal of EAWT.However,it was able to forecast the reversal date(18 January 2021)of EAWT at lead times of 1-20 days on the daily scale.
基金supported by the National Natural Science Foundation of China [grant numbers 41730964,41575079,and 41421004]
文摘Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar region.After the onset of a December WPV event,the dynamic processes influencing Eurasian temperature can be split into two separate periods.Period I(lag of 0-25 days)is referred to as the stratosphere-troposphere interactions period,as it is mainly characterized by stratospheric signals propagating downwards.In Period I,a stratospheric negative Northern Annular Mode(NAM)pattern associated with the WPV propagates downwards,inducing a negative NAM in the troposphere.The anomalous low centers over the Mediterranean and North Pacific bring cold advection to northern Eurasia,resulting in a north-cold-south-warm dipole pattern over Eurasia.The zero line between negative and positive temperature anomalies moves southwards during days 5-20.Stratospheric cold anomalies at midlatitudes propagate downwards to high latitudes in the troposphere and contribute to the dipole structure.During PeriodⅡ(lag of 25-40 days),as downward signals from the stratosphere have vanished,the dynamic processes mainly take place within the troposphere.Specifically,a wave train is initiated from the North Atlantic region to northern Europe.The propagation of wave activity flux intensifies a cyclonic anomaly over northern Europe,which brings cold advection to Scandinavia and warm advection to central Asia.Therefore,a northwest-cold-southeast-warm dipole structure occupies Eurasia and migrates southeastwards during this period.
基金supported by the Special Fund for Meteorological Research in the Public Interest[grant number GYHY201206041]the projects entitled‘Comprehensive Evaluation of Polar Areas in Global and Regional Climate Changes’[grant number CHINARE2015–2019]‘Polar Environment Comprehensive Investigation and Assessment’[grant number CHINARE2015–2019]
文摘To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linear trend in the zonal wind at these latitudes are analyzed and removed, and the QBO signal is retrieved from the monthly zonal wind for the period 1979-2014. The zonal wind has a strong decreasing trend in winter, with a maximum decrease （less than -0.35 m s-1 yr-1） occurring within 70-100°E. The zonal wind has an in-phase response of 1.6 m s-1 to the solar cycle, with a maximum within 100-140°E. A clear QBO signal is detected in the zonal wind during the period 1979-2014, with an amplitude of 2.5 m s-1 and a period of 30 months. The latitudinal distribution of the QBO signal is inhomogeneous, with a maximum within 120-180°E and a minimum within 25-45°E.
