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《Chinese Journal of Atmospheric Sciences》 2006-01
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Influence of Anomalous East Asian Winter Monsoon on Zonal Wind Anomalies over the Equatorial Western Pacific

PU Ye~(1),PEI Shun-Qiang~(1),LI Chong-Yin~(1),and CHEN Yue-Juan~(2)1 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 1000292 Department of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026  
Zonal wind anomaly over the equatorial western Pacific plays an important role in the occurrence of ENSO.The results of data analysis and theoretical studies show that the strong East Asian winter monsoon(the strong East Asian upper trough activity) will stimulate the anomalous west wind and the strong convective activity(strong intra-seasonal oscillation) over the equatorial western Pacific,and will further stimulate El Nio by airsea interaction.Based on the NCEP/NCAR reanalysis data(2.5°×2.5°) for 19581998 and NOAA OLR data,this paper analyzes the dynamic impact of East Asian winter monsoon on the formation of zonal western(eastern) wind anomalies over the equatorial western Pacific and a cyclonic(an anticyclonic) circulation over the east of Philippines.The physical process that East Asian winter monsoon stimulates zonal wind anomalies over the equatorial western Pacific and ENSO are further discussed.The paper reveals the relationship between zonal western(eastern) wind anomalies over the equator and a cyclonic(an anticyclonic) circulation over the east of Philippines and anomalous strong(weak) the East Asian winter monsoon,especially the formation mechanism of this relationship.The main results are as follows: (1) Both zonal western(eastern) wind anomalies over the equatorial western Pacific and a cyclonic(an anticyclonic) circulation over the east of Philippines,which are closely related to the occurrence of El Nio(La Nia),are related to strong(weak) East Asian winter monsoon anomalies in the earlier period.Before the occurrence of El Nio(La Nia) event,west(east) wind anomalies occur over the equatorial western Pacific,while a cyclonic(an anticyclonic) circulation occurs over the east of Philippines.However,before these anomalies occur,north(south) wind anomalies,i.e.anomalous strong(weak) East Asian winter monsoon,have already occurred over the northwestern Pacific and the East Asian coastal area.(2) There is the opposite anomalous pressure situation over the western Pacific and Southeast Asia,in accordance with strong(weak) East Asian winter monsoon.Continuous strong(weak) East Asian winter monsoon dynamic impact is favorable for forming anomalous west(east) wind over the equatorial western Pacific and a cyclonic(an anticyclonic) circulation over the east of Philippines.(3) Strong or weak East Asian winter monsoon has the important dynamic impact on different pressure gradient and meridional wind anomalies over the northwestern Pacific and East Asian coast.It causes the formation of anomalous west(east) wind over the equatorial western Pacific and a cyclonic(an anticyclonic) circulation over the east of Philippines.
【Fund】: 国家自然科学基金资助项目40233033;; 中国科学院创新项目ZKCX2-SW-210
【CateGory Index】: P732.1
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