夏季低空越赤道气流与ENSO及中国夏季降水关系的研究
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摘要
利用1948～2002年NCEP／NCAR再分析风场、高度场和海温资料，1951～2000年中国160站降水资料，分析了东半球夏季低空各支越赤道气流与ENSO循环及中国夏季降水的关系及其年代际变化。结果表明：
东半球夏季低空有5个主要的越赤道气流通道，分别位于45°E、90°E、105°E、125°E和150°E附近。
东半球夏季低空越赤道气流强度的年际变化和ENSO循环密切相关，ElNif(?)o年夏季马斯克林高压减弱，导致索马里越赤道气流变弱，而澳大利亚高压加强，105°E及其以东的越赤道气流明显加强，La Ni(?)a年则相反。夏季低空索马里越赤道气流较弱、105°E及其以东的越赤道气流较强时，有利于赤道西太平洋异常西风的形成，异常西风向东传播，有利于El Ni(?)o事件在赤道中东太平洋发生。
夏季越赤道气流与ENSO的年际关系具有年代际变化特征，索马里越赤道气流与ENSO的关系在二十世纪七十年代末变弱，而105°E及其以东的越赤道气流与ENSO的关系在二十世纪七十年代末增强。赤道太平洋西风异常及Walker环流上升支的东移使得夏季越赤道气流与ENSO的关系产生了明显的年代际变化。
夏季低空90°E附近越赤道气流与中国长江中下游及东北地区夏季降水有着密切的关系。夏季低空90°E附近越赤道气流较强时，东亚夏季风较强，西太平洋副热带高压位置偏北，EPA(东亚太平洋美洲)波列伸展纬度偏北，造成长江中下游夏季降水偏少，东北地区夏季降水偏多；夏季低空90°E附近越赤道气流较弱时，情况则相反。
夏季低空90°E附近越赤道气流与中国夏季降水的关系同样具有年代际变化特征，在二十世纪七十年代末以后，夏季低空90°E附近越赤道气流与中国长江中下游及东北地区夏季降水关系增强。夏季低空90°E附近越赤道气流与东亚地区夏季500hPa高度的相关在1978年以后明显增强，使得夏季低空90°E附近越赤道气流与中国夏季降水的关系在1978年以后变得更为密切。
The features of interannual relationships and the decadal variabilities of interannual relationships between summer 850hPa cross equator flows of eastern hemisphere and ENSO and China summer rainfall are analyzed by using NCEP/NCAR reanalysis data, sea surface temperatures data of Hadley Center and rainfall data of 160 stations of China. Results show that:
There are 5 cross equator flows channels in the eastern hemisphere. They are 45 E,90 E,105 E, 125 Eand 150 E.
Mascarene High is weaker(stronger) and Australia High is stronger(weaker) than normal in the El Nino(La Nina) years, which cause summer 850hPa Somali jet weaker(stronger) and the cross equator flows of 90 E, 105 E, 125 E and 150 E are stronger(weaker) than normal in the El Nifio(La Nina) years. The strong cross equator flows of 90 E, 105 E, 125 E and 150 E and weak Somali jet will cause the western wind anomolis breaking out in the western equator Pacific, which will be in favor of the arising of ENSO events.
The interannual relationship between Somali jet and ENSO has broken down in the late 1970s while the interannual relationships between the cross equator flows of 105 E, 125 E and 150 E and ENSO have strengthened in the late 1960s. The eastward shift in the Walker circulation and western wind anomolis are the possible reasons of the change of relationships between summer cross equator flows and ENSO.
East Asia summer monsoon is stronger when the cross equator flow of 90 E is stronger than normal. The East Asia summer monsoon anomoly can affect the atmosphere circulation and climate in the East Asia and Pacific Ocean regions through the western Pacific subtropical anticyclone and the EPA wavetrain. In the
strong cross equator flow of 90 E years, there has more precipitation in the middle and lower reaches of Yangtze river valley regions while there has less precipitation in the northeast China regions. Vice versa.
The interannual relationship between summer low level cross equator flow of 90 E and the precipitation of China has strenthened in the late 1970s. The possible reason is the relationship between the summer low level cross flow of 90 E and 500hPa height has strenthened in the late 1970s.
东半球夏季低空有5个主要的越赤道气流通道，分别位于45°E、90°E、105°E、125°E和150°E附近。
东半球夏季低空越赤道气流强度的年际变化和ENSO循环密切相关，ElNif(?)o年夏季马斯克林高压减弱，导致索马里越赤道气流变弱，而澳大利亚高压加强，105°E及其以东的越赤道气流明显加强，La Ni(?)a年则相反。夏季低空索马里越赤道气流较弱、105°E及其以东的越赤道气流较强时，有利于赤道西太平洋异常西风的形成，异常西风向东传播，有利于El Ni(?)o事件在赤道中东太平洋发生。
夏季越赤道气流与ENSO的年际关系具有年代际变化特征，索马里越赤道气流与ENSO的关系在二十世纪七十年代末变弱，而105°E及其以东的越赤道气流与ENSO的关系在二十世纪七十年代末增强。赤道太平洋西风异常及Walker环流上升支的东移使得夏季越赤道气流与ENSO的关系产生了明显的年代际变化。
夏季低空90°E附近越赤道气流与中国长江中下游及东北地区夏季降水有着密切的关系。夏季低空90°E附近越赤道气流较强时，东亚夏季风较强，西太平洋副热带高压位置偏北，EPA(东亚太平洋美洲)波列伸展纬度偏北，造成长江中下游夏季降水偏少，东北地区夏季降水偏多；夏季低空90°E附近越赤道气流较弱时，情况则相反。
夏季低空90°E附近越赤道气流与中国夏季降水的关系同样具有年代际变化特征，在二十世纪七十年代末以后，夏季低空90°E附近越赤道气流与中国长江中下游及东北地区夏季降水关系增强。夏季低空90°E附近越赤道气流与东亚地区夏季500hPa高度的相关在1978年以后明显增强，使得夏季低空90°E附近越赤道气流与中国夏季降水的关系在1978年以后变得更为密切。
The features of interannual relationships and the decadal variabilities of interannual relationships between summer 850hPa cross equator flows of eastern hemisphere and ENSO and China summer rainfall are analyzed by using NCEP/NCAR reanalysis data, sea surface temperatures data of Hadley Center and rainfall data of 160 stations of China. Results show that:
There are 5 cross equator flows channels in the eastern hemisphere. They are 45 E,90 E,105 E, 125 Eand 150 E.
Mascarene High is weaker(stronger) and Australia High is stronger(weaker) than normal in the El Nino(La Nina) years, which cause summer 850hPa Somali jet weaker(stronger) and the cross equator flows of 90 E, 105 E, 125 E and 150 E are stronger(weaker) than normal in the El Nifio(La Nina) years. The strong cross equator flows of 90 E, 105 E, 125 E and 150 E and weak Somali jet will cause the western wind anomolis breaking out in the western equator Pacific, which will be in favor of the arising of ENSO events.
The interannual relationship between Somali jet and ENSO has broken down in the late 1970s while the interannual relationships between the cross equator flows of 105 E, 125 E and 150 E and ENSO have strengthened in the late 1960s. The eastward shift in the Walker circulation and western wind anomolis are the possible reasons of the change of relationships between summer cross equator flows and ENSO.
East Asia summer monsoon is stronger when the cross equator flow of 90 E is stronger than normal. The East Asia summer monsoon anomoly can affect the atmosphere circulation and climate in the East Asia and Pacific Ocean regions through the western Pacific subtropical anticyclone and the EPA wavetrain. In the
strong cross equator flow of 90 E years, there has more precipitation in the middle and lower reaches of Yangtze river valley regions while there has less precipitation in the northeast China regions. Vice versa.
The interannual relationship between summer low level cross equator flow of 90 E and the precipitation of China has strenthened in the late 1970s. The possible reason is the relationship between the summer low level cross flow of 90 E and 500hPa height has strenthened in the late 1970s.
引文
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[3] Krishnamurti T N , Numerical simulation of the Somali Jet. J. Atmos.Sci.,1976,33:2350—2362.
[4] Bannon P R, On the dynamics of the East African jet, Ⅰ: Simulation of mean conditions for July. J. Atmos.Sci.,1979,36:2139—2152.
[5] 中国科学院大气物理研究所热带气象研究组，南半球气流对南海和北太平洋西边地区热带环流的影响．大气科学，1979，(2)：1—18．
[6] 陈于湘，夏季西太平洋越赤道气流的谱分析．大气科学，1980，4(4)：363—368．
[7] 王兴东、陶诗言，西太平洋越赤道气流的初步研究．海洋学报，1984，6(2)：160—173．
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[10] 汤明敏、黄士松、周德佩．全球越赤道气流的时空变化[J]．热带气象，1985，1(4)：287—296．
[11] 彭维耿．越赤道气流与全球中低纬大气环流．全国季风与暴雨科学讨论会论文集，2000，42—44．
[12] Krishnamurti T N and Bhalme H N, Oscillation of a monsoon system, Part Ⅰ, Observational aspects, J.A.S.,1976,33,1937-1954.
[13] 陈隆勋、朱乾根、罗会邦，东亚季风，1991，气象出版社，北京．
[14] 曾庆存、张邦林，论大气环流的季节划分和季风．大气科学，1992，22：805—813．
[15] Xue Feng, Zeng Qingcun, Diagnostic study on seasonality and interannual variability of wind field. Adv. Atmoas. Sci., 1999,16:567—575.
[16] 李崇银、屈昕，伴随南海夏季风爆发的大尺度大气环流演变．大气科学，2000，
24(1)：1—14．
[17] 李崇银、吴静波，索马里越赤道气流对南海夏季风爆发的重要作用．大气科学，2002，26(2)：185—192．
[18] Saha K R, Bavadekar S N, Water vapour budget and precipitation over the Arabian Sea during the northern summer. Quart.J.Roy. Meteor.Soc., 1973,99,273—278.
[19] 王会军、薛峰，索马里急流的年际变化及其对半球间水汽输送和东亚夏季降水的影响．地球物理学报，2003，46(1)：18—25．
[20] 王继志、李麦村，源于澳洲过赤道气流与中国季风环流和降水．大气科学，1982，6(1)：1—10．
[21] 李曾中、钱传海、孙除荣，1991年江淮暴雨与越赤道气流关系初步分析．气象学报，2000，58(5)：628—635．
[22] 谢安等，南海季风爆发期间的水汽输送气候特征．全国季风与暴雨科学讨论会论文集，2000，13—15．
[23] 黄士松、汤明敏，夏季东半球海上越赤道气流与赤道西风、台风及副热带高压活动的联系．南京大学学报(气象学专辑)，1982，1—15．
[24] 李曾中．越赤道气流与中国天气关系的初步统计分析．气象，1986，12(4)：11—14．
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