The Influence Of Planetary Wave Anomalies On Persistent Cold Events In Southern China Under Positive NAO And Negative WP Modes

Using NCEP/NCAR and European Center reanalysis data,combined with multiple linear regression,composite analysis,harmonic analysis,plumb wave activity and other methods,this paper studies the effects of different configurations of Western Pacific teleconnection(WP)and North Atlantic Oscillation(NAO)on winter temperatures in southern China.The main conclusions are as follows:(1)In the fourth configuration,WP is negative phase NAO is positive phase,both of which have synchronous cooling effect on southern China,and southern China shows significant cold anomaly.WP affects the temperature in southern China through its local effect.Although NAO teleconnection type is mainly located in the North Atlantic,it can regulate and control the North-South trough system through the North-South two wave trains respectively,and affect the temperature in southern China cooperatively.(2)Abnormal planetary wave activity in the flat troposphere under WP negative phase NAO positive phase leads to the occurrence of persistent cold events in the south.Through analysis and discussion of 1984 and 1995,it is found that planetary wave activity shows different characteristics in different years.In 1984,the cooling period was dominated by one wave and ended in the later period due to two waves of abnormal activity.In 1995,the cooling period was dominated by two waves,and ended with one wave and three waves being extremely active in the later period.Due to different dominant wave numbers,the cooling time in 1984 was about 9 days longer than that in 1995.Due to the standing wave of wave 1and its north-south meridional structure in 1984,the north-south blockage in East Asia was established and maintained,and the generation of transverse trough caused continuous cooling.In 1995,the ridge system affected by two waves was prone to alternation,so the duration of the ridge system in Asia was short,making the cooling duration in 1995 shorter than that in 1984.(3)3 wave is of great significance in cold anomaly events.During the end of the two cooling processes,the average vertical wave energy evolution in the latitudinal circle has an abnormal development of 3 waves.3 wave will interact with the 1 wave and 2 wave on the planetary scale,causing the evolution of the ridge system,causing the horizontal trough to turn vertical and accelerating the cold air to erupt southward.In a sense,the abnormal activity of 3 waves can cause cold air to invade lower latitudes,resulting in cold wave weather.