大气环流及北大西洋海温对我国南方冬季寒潮频次异常的可能影响

The Possible Influence of Atmospheric Circulation and North Atlantic Sea Surface Temperature Anomaly on the Winter Cold Wave Frequency in the Southern China

利用国家气象信息中心提供的1980-2022年日最低温度站点资料、NCEP/NCAR逐月再分析资料和NOAA逐月海表温度(Sea Surface Temperature,SST)资料,采用了EOF、一元线性回归和T-N波作用通量等方法,分析了南方冬季寒潮频次的主要异常时空特征及大气环流异常和冬季大西洋海温异常(Sea Surface Temperature Anomaly,SSTA)对其影响机制。结果表明:(1)冬季寒潮频次大值区主要位于南方东部及中部地区,大致呈“逆C”型分布。寒潮频次主要有全区一致型、南北反位相型和三极型三类主要异常模态,其中全区一致型能很好反映南方寒潮频次的总体异常时空特征。(2)负位相的北大西洋涛动(North Atlantic Oscillation,NAO)、强的里海-青藏高原脊和偏东偏北的东亚大槽、北弱南强的西伯利亚高压、强的温带急流和弱的副热带急流是影响南方冬季寒潮频次的关键环流系统,冷空气堆位于西西伯利亚地区,高低层环流系统配合,使得冷空气自西西伯利亚南下到里海附近,再沿着青藏高原北侧向东输送,在青藏高原东侧南下进入南方地区,造成南方冬季寒潮频次全区一致型增加。(3)冬季北大西洋“+”“-”“+”三极型SSTA可通过海气间热通量交换激发出-NAO型环流异常及Rossby波能量异常。Rossby波能量沿南、北两条路径自北大西洋向东亚传播,并激发出相应的异常波列,增强了影响南方寒潮的南、北方关键环流系统,致南方寒潮频发。当春季北大西洋SSTA呈现逆“C”型异常,且夏、秋季有发展为+”“-”“+”三极型的态势,可预测南方寒潮频次偏多。

Based on the daily minimum temperature station data provided by the National Meteorological Information Centre from 1980 to 2022,the month-by-month reanalysis data of the NCEP/NCAR,and the monthly Sea Surface Temperature(SST)data from the NOAA,by using EOF,simple linear regression and T-N wave flux methods,the main anomalous spatial and temporal characteristics of winter cold wave frequency in the southern China are studied,and the influence mechanisms of atmospheric circulation and winter Atlantic Sea Surface Temperature Anomaly(SSTA)on it are also analyzed.The results show that:(1)The large value areas of winter cold wave frequency are mainly located in the eastern and central of the southern China,with an approximately"inverse C"distribution.There are three main frequency anomalous modes,namely,regionally consistent anomaly,north-south antiphase anomaly and tripole anomaly patterns according to the EOF analysis,among which the regionally consistent anomaly reflects the overall anomalous spatial and temporal characteristics of the winter cold wave frequency in the southern China.(2)The negative phase of the North Atlantic Oscillation(NAO),the strong Caspian Sea-Tibetan Plateau ridge and the East Asian Trough located to the north and to the east,the weak in the north and strong in the south of the Siberian High,the strong temperate jet and the weak subtropical jet are the key circulation systems affect the winter cold wave frequency in the southern China.The cold air pool is located in the Western Siberia.The high and low level circulation systems cooperate together to make the cold air from Western Siberia move southward to the vicinity of the Caspian Sea,and then transport eastward along the northern side of the Tibetan Plateau,then move southward into the southern China along the eastern side of the Tibetan Plateau,resulting in the increase of the winter cold wave frequency in the whole southern China.(3)In winter,the“+”“-”“+”tripolar SSTA in the North Atlantic can stimulate the-NAO atmospheric circulation anomalies through the exchange of heat fluxes between air and sea and the Rossby wave energy anomalies.The Rossby wave energy propagates from the North Atlantic to East Asia along the south and north two paths,and stimulates the corresponding anomalous waves,which enhance the key circulation systems in the north and south affecting the cold wave frequency in the southern China.When the North Atlantic SSTA exhibits an inverse"C"anomaly in spring,and there is a trend of developing into a“+”“-”“+”tripolar pattern in summer and autumn,the winter cold wave frequency in the southern China can be predicted to more.