夏季东亚西风急流扰动异常与副热带高压关系研究

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杨莲梅, 张庆云. 夏季东亚西风急流扰动异常与副热带高压关系研究[J]. 应用气象学报, 2007, 18(4): 452-459. 复制到剪切板

Yang Lianmei, Zhang Qingyun. Relationships Between Perturbation Kinetic Energy Anomaly Along East Asian Westerly Jet and Subtropical High in Summer[J]. Journal of Applied Meteorological Science, 2007, 18(4): 452-459 复制到剪切板

夏季东亚西风急流扰动异常与副热带高压关系研究

杨莲梅^1,2,3, 张庆云¹

1. 中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室, 北京 100029;
2. 中国气象局乌鲁木齐沙漠气象研究所, 乌鲁木齐 830002;
3. 中国科学院研究生院, 北京 100039

2006-03-03 收到, 2007-01-09 收到修改稿.

资助项目: 中国科学院知识创新工程重要方向项目 (编号KZCX3-SW-221)、新疆维吾尔自治区自然科学基金 (200421102)、新疆维吾尔自治区气象局课题 (200609) 共同资助

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。

关键词: 东亚西风急流扰动异常副热带高压

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

Yang Lianmei^1,2,3, Zhang Qingyun¹

1. State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;
2. Institute of Desert Meteorology, China Meteorological Administration, Urumqi 830002;
3. Graduate University, Chinese Academy of Sciences, Beijing 100039

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 (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.

Key words: East Asian westerly jet stream perturbation kinetic energy subtropical high

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图 1. 1958—2003年夏季 (6—8月) 200 hPa纬向风的标准差分布 (单位: m/s; 阴影区表示置信度大于95%) Fig 1. The climatology standard deviation of 200 hPa zonal wind in summer (JJA) averaged over 1958—2003 (unit : m/s; shaded areas denote exceeding the test of 95% level)


图 2. 1979—2003年6—8月东亚 (100°~140°E) 急流扰动动能E_K标准化序列 Fig 2. The interannual variations of normalized Rossby wave perturbation kinetic energy E_k along 100°—140°E westerly jet in summers during 1958—2003


图 3. 夏季东亚200 hPa纬向风EOF方差最大的前二个特征模态 (a) 第一模态, (b) 第二模态 Fig 3. The patterns of the eigenvectors of the first two gravest EOF modes of 200 hPa over East Asia in summer (a) the first mode, (b) the second mode


图 4. 夏季200 hPa高度距平场 (单位: gpm; 阴影区表示纬向风速大于25 m/s) (a) 扰动强年, (b) 扰动弱年 Fig 4. Geopotential height anomalies at 200 hPa in summer of the strong E_k(a) and weak E_k(b) years (unit: gpm; shade areas indicate zonal winds larger than 25 m/s)


图 5. 夏季15°~30°N位势高度纬向-高度剖面图 (单位: gpm)(a) 扰动强年, (b) 扰动弱年 Fig 5. Zone-height cross section (averaged over 15°—30°N) of geopotential height in summer of the strong E_k(a) and weak E_k(b) years (unit : gpm)


图 6. 夏季500 hPa高度距平场 (单位: gpm)(a) 扰动强年, (b) 扰动弱年 Fig 6. Geopotential height anomalies at 500 hPa in summer of the strong E_k(a) and weak E_k(b) years (unit : gpm)


图 7. 夏季200 hPa散度场 (单位: 10^-6s^-1) (a) 气候平均场, (b) 扰动强年距平场, (c) 扰动弱年距平场 Fig 7. Divergence at 200 hPa in summer (unit : 10^-6s^-1) (a) climate mean, (b) anomalies for strong E_k yeas, (c) anomalies for weak E_k years


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