Relationships Between Perturbation Kinetic Energy Anomaly Along East Asian Westerly Jet and Subtropical High in Summer

In summer, upper level subtropical westerly jet stream along 40°N over East Asia is one of the most important large-scale circulation systems which influence weather and climate change over east China. At the same time, it is also a wave-guide along Rossby wave activity.Thus, it is necessary to define an objective and quantitive perturbation kinetic energy (E_k) index along East Asian westerly jet (EAWJ), and E_k annual variation and anomalies are investigated.Moreover, the relationships between E_k and EAWJ intensity and EAWJ position are examined, lastly the configuration and connection processes between E_k variability along EAWJ and South Asia high (SAH) and western pacific subtropical high (WPSH) in summer are confirmed by NCEP/NCAR reanalysis dataset from 1979 to 2003.u basic and v basic are defined by wave number k < 3 based on wind u and v in 200 hPa calculated by Fourier expressions, the perturbation kinetic energy of Rossby wave along EAWJ is defined by k≥3 wave activity, and Rossby wave perturbation (u′, v′)=(u, v)-(u_b v_b), E_k=(u′·u′+v′·v′)/2 which is averaged in the area of latitude with maxima zonal wind shifted±5°and in 100°—140°E, so normal E_k is defined as Rossby wave activity index along EAWJ which also includes meridional displacement variability of EAWJ.EAWJPI (East Asian westerly jet position index) is defined by the difference of zonal wind in 200 hPa between 35°—40°N, 100°—140°E and 40°—45°N, 100°—140°E, and EAWJII (East Asian westerly jet intensity index) is defined by the summation of zonal wind in 200 hPa averaged by 35°—45°N, 100°—140°E.The results show that EAWJ is southward (northward) than the normal and its intensity becomes stronger (weaker) while E_k strengthened (weakened). Not only E_k variations are associated with EAWJ intensity and steady Rossby wave perturbation along westerly jet in summer, but also south—north wave train anomaly in East Asia. Height anomaly in Asia mid-latitude area is most remarkable.When E_k appears stronger (weaker) than normal, center position of circumglobal wave train wave in mid-latitude zone moves to southern (northern). The correlation coefficient is 0.56 between E_k and SAH intensity, 0.66 between E_k and SAH eastward ridge point position, and-0.52 between E_k and WPSH ridge line position during 1979—2003 summer respectively, all are over 99% level.While E_k appears stronger (weaker) than normal, SAH moves to eastward (westward) and stronger (weaker) than the normal.At the same time, WPSH is southward (northward) than the normal.It is found that the response of WPSH to E_k anomaly is going with the change of divergence-convergence over East Asia in 200 hPa and vertical motion in tropic and subtropical zone from surface to upper air.