| In this paper,the daily average data of NCEP global reanalysis from 1960 to 2015 and the data of winter precipitation at 2426 stations in China are used to analyze the climate state of the East Asian Subtropical Westerly Jet Stream(EASJ)during the rainy season and the abnormal rainy year.The characteristics of space-time distribution;Morlet wavelet analysis method is used to discuss the narrow-band signal of EASJ and its corresponding relationship with the typical rainy season in eastern China;The wave-packet propagation diagnosis(WPD)system is used to study the average summer climate in East Asia.The characteristics of the subtropical westerly jet and its high-frequency baroclinic wave packets are discussed.Based on this analysis,the EASJ and the high-frequency baroclinic wave packets of the typical anomaly EASJ and its high-frequency baroclinic wave packages are analyzed.The influence of the distribution of high-frequency baroclinic wave packets on the abnormal Meiyu;finally,the role of EASJ wave flux and its relationship with Meiyu anomalies were initially discussed.The results show:(1)In the Meiyu rainy season,the spatial distribution of EASJ is different from that of the whole summer background field.It mainly shows the features of location southerly,strong intensity,and wide coverage;the EASJ position's meridional shift and intensity change are abnormal for the Meiyu year relative to the climate state.(2)The narrow-band signals of summer EASJ and its corresponding relationship with the typical rainy season in eastern China show that the 3-7d and 10-15 d narrow-band signals are the characteristics of the narrow band signals of EASJ.The 3-7d high-frequency narrow-band signals cover the 2-4d and 6-8d high-frequency narrow-band signals of rainstorms in South China during the flood season of 2-4d and 5-7d,during the Meiyu season of the Yangtze and Huaihe Rivers,and between July and August.It reflects the gradual changes of the narrow-band signal of summer EASJ and its corresponding relationship with the typical rainy season in eastern China.(3)The 3-7d high-frequency baroclinic wave packets corresponding to the East Asian subtropical westerly jet are quasi-zonal distribution,which represents the strong disturbance area,the dynamic instability zone of the strong west wind shears;the low-value region of the wave packet corresponds to the high pressure in South Asia,which represents the weak perturbation region,the weak wind pressure stability zone.The distribution characteristics of wave packets during the Meiyu season shows that the two 5-7d high-frequency baroclinic wave-band and high value zones,respectively,in the mid latitude and high latitude,have a good correspondence with the high energy values of the baroclinic energy dispersive waveguides and the critical areas influencing the precipitation of the Yangtze River and the Meiyu season.The 3-7d high-frequency baroclinic wave band,located at 40°N-55°N,which is corresponding to the subtropical westerly jet,has the regularity of meridional displacement and intensity changes,the meridional displacement shows that it falls on the South and rises on the North and then fluctuates,The intensity of the performance gradually weakens and then strengthens.The latitudinal evolution of the zonal winds is divided into two stages,which is characterized by significant differences in the distribution of the wave packets.The first stage has two large wave areas,the Black Sea to the Caspian Sea region and the northeast of China to the island of Japan;the second stage has three large wave areas,the Black Sea to the Caspian Sea,the west side of the Balkhash Lake and the northeastern region of Japan,in which the disturbance of 3-7d high frequency baroclinic wave on the west side of the Balkhash Lake has an important contribution to the precipitation in eastern China.(4)Through the further study of the typical anomalous Meiyu EASJ and its high-frequency baroclinic wave packages,intensity changes,and morphological characteristics,it was found that the high-frequency baroclinic wave packet intensity of the Meiyu rain year is stronger than the climatic state.In the heavy and light Meiyu years,the large-scale value zone of wave packets with rapids is located in the vicinity of the Mediterranean Sea and the Black Sea,and there is a large difference in the downstream from the east of Baikal to the Japan Sea,in the area the EASJ wave package in heavy Meiyu years is relatively westward and weaker than that of light Meiyu years.The characteristics of the high-frequency baroclinic wave packages with average zonal winds and main rain belts are similar during the 3-7d of the Meiyu years,and the location of the heavy rains is located on the south side of the rapids axis.In the Meiyu rainy season,the entire plum rainy season wave values are located north of the rapids zone,that is the north side of the jet belt is active.In addition,the perturbations on the north side of the jet stream before the Meiyu and after the Meiyu season are more northward than the central axis of the jet stream.(5)In the Northern Hemisphere,the E-P flux in the climatic phase of the Meiyu season has a clear convergence and divergence zone,which corresponds to the large ridge formed by the topography.Rossby waves originate in the eastern Mediterranean-near the Black Sea.They travel eastward along the jet stream and gradually weaken near the Ural Mountains.The jet exit zone is near 140°E-160°E and has a weak wave flux convergence center.The central location of strong divergence in heavy Meiyu years is stronger than that in the east of climate.The north of China and the Bohai Sea are strong convergence areas.Japan and the North Pacific Ocean are strong divergence areas;the distribution characteristics of the light Meiyu years are the opposite... |
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