【作者】 谭桂容；

【导师】 孙照渤；

【作者基本信息】 南京信息工程大学 ， 气象学， 2007， 博士

【摘要】 利用观测资料、NCEP／NCAR再分析逐日资料、月海温资料和CCM3.6气候模式，分析了亚洲中纬度大陆高压的地理分布和时间变化特征，重点以20世纪70年代末气候突变以来异常频繁发生的贝加尔湖南侧地区大陆高压为例，分析了大陆高压异常的时空演变特征，利用诊断分析和数值试验，从内部动力学和外部强迫两个方面探讨了大陆高压维持及其异常频发的原因，然后在此基础上讨论了大陆高压异常对我国夏季气候的影响。结果表明：1．大陆高压存在两种类型，与两类大陆高压相联系的大尺度环流场特征基本相反。1979年以来，贝加尔湖南侧(35-55°N；90-105°E)区域的大陆高压活动异常增加，特别在7、8月份。大陆高压以维持日数在3天以上的占多数，其中具有闭合中心的大陆高压占少数。2．大陆高压维持的波能传播路径主要有三条，北太平洋西部和北大西洋东部近欧亚大陆海域为大陆高压异常维持的海洋热强迫涡动源区。扰动能量在大气中传播通过涡流相互作用引起的动量和热量输送，在贝加尔湖附近有利于扰动从基流中获得能量而发展，是贝加尔湖南侧大陆高压维持的重要大气内原因。3．北大西洋东部和北太平洋西部近大陆海域海温异常增暖是贝加尔湖南侧大陆高压异常频发的重要原因。夏季北半球海温(Mode1和Mode2)和环流(AMode1和AMode2)主要存在两种异常分布型，AMode1除受热带海温影响外，还反映了北大西洋东部和北太平洋西部近大陆海域的海温异常对大气环流的影响。AMode2对应热带地区海温异常，北半球热带外地区的海温异常为对大气异常的响应。Mode1对应的关键区域海温变化趋势与贝加尔湖南侧大陆高压的变化趋势一致，为大陆高压频发的主要原因。热带海温异常(特别是太平洋)的不同分布，分别对应不同类型大陆高压的发生。4．大陆高压发生时，中国东部盛行偏北风异常，夏季风减弱。不同环流背景下大陆高压异常对我国气候的影响不同，大陆高压的作用表现为对背景环流场影响的调节。对应大陆高压的年代际异常，华北降水分布及其耦合环流的年际关系发生了改变。当大陆高压活动异常频繁时，华北夏季降水主要与西风带系统有关；反之，华北夏季降水则主要与西太平洋副高的变化有关。更多还原

【Abstract】 Land high at mid-latitudes over Asian is investigated in terms of observed data;NCEP/NCAR daily reanalysis data, monthly SST data and CCM3.6 model, including geographydistribution and time variation. Then land high around Baikal is examined as a case, which occursmost frequently since the climate chop at the end of 1970s. Later, the causes of the abnormaloccurrence are studied by diagnosis and numerical test, involving in inner dynamics and exteriorforcing. Finally, the influence of the land high on China summer climate is discussed. The resultssuggest:There are two types of land highs (DG+ & DG-) with related large scale circulations beingopposed. Since 1979, the land highs over (35-55°N; 90-105°E) area increase greatly, especially inJuly and August. Land highs maintaining over 3 days are the majority, among which the landhighs with closed center are the minority.There are mainly three paths for wave energy propagating during the maintaining of landhigh. And the sea area near Eurasia both in Atlantic and Pacific may be wave resource. The waveenergy propagates along the main paths with ridge south to Baikal obtaining energy from thezonal flows by the momentum and heat transportation of wave. Thereby the land high is able tomaintain.The warmer SSTs near coastal sea of Atlantic and Pacific are one of the dominant factors forthe more frequently occurring land high near Baikal. There exist two principal patterns for SST(Model& Mode2) and atmosphere (Amodel& Amode2) of Northern Hemisphere. Amodel isinfluenced mainly by SSTA and the other is principally the influencing-factor of the SSTA at midlatitudes. SSTs in key areas of Model are warming greatly since 1979 consisted with variation ofthe land high, being important factor for the more frequently occurring land high near Baikal.Different SSTA in tropical (especially in Pacific) is corresponding to the two land highsrespectively.The land high will weaken Asian summer monsoon with northerly wind departure over east China. However, the influence on climate of the two type land high pattems is different on theirlarge-scale settings. Related to the decadal variation of the land high, the annual relationshipbetween rainfall of North China and related circulation are changed. The Subtropical high of westPacific is unable to arrive at the North China during more frequently occurring land high time,and rainfall over North China is closely related to western weather system at mid-high latitudes.Otherwise, opposite circumstance will happen with the rainfall principally influenced by theSubtropical high.更多还原