Mechanistic Analysis Of The Intraseasonal Effects Of Scandinavian Teleconnection-type Events On Temperature In Eastern My Country In Winter

The teleconnection pattern reflects the atmospheric characteristics of large spatial scale and long duration.Previous studies have studied the influence and maintenance mechanism of the teleconnection pattern based on the monthly or seasonally mean data sets.Based on the daily Japanese 55-year Reanalysis dataset from 1958 to 2020,this study reveals that positive-phase Scandinavian(SCA)teleconnection events can cause significant negative surface air temperature(SAT)anomaly over the whole eastern China from 6 to 12 days after the peak day of SCA events,which is obviously different from the significant influence of other teleconnection events on SAT over eastern China only within one week after the peak day.In fact,the timing of this significant impact exceeds the e-folding timescale of approximately 6days of SCA events by approximately one week.Through the combination of potential vorticity inversion dynamic method and linear baroclinic model,the mechanism of SCA events affecting the SAT over eastern China is further revealed.The main conclusions are summarized as follows:Due to the fact that the typical wave-train anomalies disappear in the upper troposphere after day 6,the period from day 0 to day 12 is further divided into two stages,i.e.,the first stage from day 0 to day 6 and the second stage from day 7 to day 12.During the first stage,the vertical coupling between the upper and lower tropospheric circulation anomalies over Eurasian continent facilitates the accumulation of cold air masses from the higher latitude to the north of the Tibetan Plateau,which becomes a precursory signal of persistent negative SAT anomaly affecting eastern China.During the second stage,the diabatic heating anomaly caused by precipitation anomaly becomes an important factor in the persistence of the negative SAT anomaly over eastern China.Firstly,the persistent negative diabatic heating anomaly near Lake Baikal before day 12 is conducive to the maintenance of anomalously enhanced Siberian High over eastern China.Secondly,corresponding to the gradually southward movement of the positive precipitation anomaly over East Asia,significant negative diabatic heating anomaly gradually substitutes the positive diabatic heating anomaly over East Asia,which is also favorable for the maintenance of the local anticyclonic anomaly.Eventually,the sustained anticyclonic anomaly can induce the persistent negative SAT anomaly over eastern China.We use the monthly average data and further find that there is a significant negative correlation coefficient between the SCA index and the SAT anomaly over eastern China on the same period,in particular,the SCA index in January can continuously affect the SAT anomaly over eastern China in February.In addition,this correlation is significantly enhanced after 2000,and it shows obvious interdecadal variation characteristics.