夏季东亚西风急流扰动异常与副热带高压关系研究
Relationships Between Perturbation Kinetic Energy Anomaly Along East Asian Westerly Jet and Subtropical High in Summer
-
摘要: 利用1979—2003年NCEP/NCAR月平均再分析资料, 探讨夏季 (6—8月) 200 hPa东亚西风急流扰动异常与南亚高压和西太平洋副热带高压的关系。研究指出:夏季200 hPa东亚西风急流扰动动能加强 (减弱), 东亚西风急流位置偏南 (偏北)、强度偏强 (偏弱); 东亚西风急流扰动动能强弱不仅与北半球西风急流强弱和沿急流的定常扰动有关, 而且还与东亚地区高、中、低纬南北向的扰动波列有关, 亚洲地区是北半球中纬度环球带状波列异常最大的区域。夏季200 hPa东亚西风急流扰动动能加强 (减弱), 南亚高压的特征为位置偏东 (偏西)、强度加强 (减弱); 西太平洋副热带高压的特征为位置偏南 (偏北)。东亚环流特别是500 hPa西太平洋副热带高压对东亚西风带扰动异常的响应由高空东亚西风急流南侧的散度场及其对流层中下层热带和副热带地区的垂直速度距平场变化完成。Abstract: 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 (Ek) index along East Asian westerly jet (EAWJ), and Ek annual variation and anomalies are investigated.Moreover, the relationships between Ek and EAWJ intensity and EAWJ position are examined, lastly the configuration and connection processes between Ek 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)-(ub vb), Ek=(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 Ek 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 Ek strengthened (weakened). Not only Ek 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 Ek 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 Ek and SAH intensity, 0.66 between Ek and SAH eastward ridge point position, and-0.52 between Ek and WPSH ridge line position during 1979—2003 summer respectively, all are over 99% level.While Ek 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 Ek 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.
-
图 8 夏季垂直速度距平合成经向-高度剖面图 (110°~130°E平均)
(单位: Pa·s-1, ω>0表示下沉运动, ω<0表示上升运动) (a) 扰动强年, (b) 扰动弱年
Fig. 8 Meridian-height cross section (averaged over 110°—130°E) of anomalous vertical velocity in summer of the strong Ek(a) and weak Ek(b) years
(unit : Pa/s, ω>0 indicates subsidence, ω<0 indicates ascending)
-
[1] Lau K M, Kim K M, Yang S.Dynamical and boundary forcing characteristics of regional components of the Asian summer monsoon. J Climate, 2000, 13: 2461-2482. doi: 10.1175/1520-0442(2000)013<2461:DABFCO>2.0.CO;2 [2] 陶诗言, 赵煜佳, 陈小敏.东亚的梅雨与亚洲上空大气环流季节变化的关系.气象学报, 1958, 29(2):119-134. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB195802006.htm [3] Tao S Y, Chen L X.A Review of Recent Research of the East Summer Monsoon in China∥Chang C P, Krishinamurti T N.Monsoon Meteorology.Cambridge :Oxford University Press, 1987: 60-90. [4] 李崇银, 王作台, 林士哲, 等.东亚夏季风活动与东亚高空西风急流位置北跳关系的研究.大气科学, 2004, 28(5):641-658. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK200405000.htm [5] 廖清海, 高守亭, 王会军, 等.北半球夏季副热带西风急流变异及其对东亚夏季风气候异常的影响.地球物理学报, 2004, 47(1): 10-18. http://www.cnki.com.cn/Article/CJFDTOTAL-DQWX200401002.htm [6] Lu Riyu.Associations among the components of the East Asian summer monsoon system in the meridional direction.J Meteor Soc Japan, 2004, 82(1):155-165. doi: 10.2151/jmsj.82.155 [7] Lin Zhongda, Lu Riyu.Interannual meridional displacement of the East Asian upper-tropospheric jet stream in summer.Adv Atmos Sci, 2005, 22(2) :199-211. doi: 10.1007/BF02918509 [8] 吴国雄, 丑纪范, 刘屹岷, 等. 副热带高压形成和变异的动力学问题∥国家自然科学基金研究专著地球科学系列. 北京: 科学出版社, 2002. [9] Ambrizzi T, Hoskins B J, Hsu H H.Rossby wave propagation and teleconnection patterns in the Austral winter.J Atmos Sci, 1995, 52: 3661-3672. doi: 10.1175/1520-0469(1995)052<3661:RWPATP>2.0.CO;2 [10] Terao T.Barotropic disturbances on intraseasonal time scales observed in the midlatitudes over the Eurasian continent during the northern summer.J Meteor Soc Japan, 1998, 76: 419-436. https://www.researchgate.net/publication/294217661_Barotropic_disturbances_on_intraseasonal_time_scales_observed_in_the_midlatitudes_over_the_Eurasian_continent_during_the_northern_summer [11] Terao T.The zonal wavelength of the quasi-stationary Rossby waves trapped in the westerly jet.J Meteor Soc Japan, 1999, 77: 687-699. https://www.researchgate.net/publication/294399197_The_zonal_wavelength_of_the_quasi-stationary_Rossby_waves_trapped_in_the_westerly_jet [12] Takeshi Enomoto, Hoskins B J, Matsuda Yoshihisa.The formation mechanism of the Bonin high in August.Quart J Roy Meteor Soc, 2003, 587: 157-178. [13] Lu R Y, Oh J H, Kim B J.A teleconnection pattern in upperlevel meridional wind over the North African and Eurasian continent in summer.Tellus, 2002, 54A:44-55. https://www.researchgate.net/publication/229672949_A_teleconnection_pattern_in_upper-level_meridional_wind_over_the_North_African_and_Eurasian_continent_in_summer [14] Ding Qinghua, Wang Bin. Circumglobal teleconnection in the Northern Hemisphere summer.J Climate, 2005, 18: 3483-3505. doi: 10.1175/JCLI3473.1 [15] 黄荣辉, 孙凤英.热带西太平洋暖池的热状态及其上空的对流活动对东亚夏季气候异常的影响.大气科学, 1994, 18(2): 141-151. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK199402001.htm