【作者】 肖天贵；

【导师】 孙照渤；

【作者基本信息】 南京信息工程大学 ， 气象学， 2011， 博士

【摘要】 东亚季风变化及其影响是中国气候最主要的特征之一,尤其是东亚夏季风是影响中国夏季降水分布的最重要因子。东亚夏季风的年代际变化异常不仅影响中国气候的年际和年代际变化,而且对世纪时间尺度的中国降水也有明显影响,因此,加强东亚夏季风年代际变化规律及其影响的研究具有重大意义。本文基于广泛使用的NCEP/NCAR再分析资料,利用波包传播诊断方法(WPD)及相关的统计方法,诊断分析和讨论了东亚夏季风年代际变化特征、环流异常与扰动波能分布及波能传播特征,并从波能传播的角度研究了其变化机制。(1)多尺度扰动波包气候平均表明,全球扰动波包基本都呈纬向带状分布,在由冬到夏季节转变过程中,赤道地区波包大值区加强北推可达10°N；热带和中纬度西风带扰动频繁区域往往表现为强的波包大值中心,而副热带高压控制下的主体区域往往表现为强的波包小值中心。(2)1950～2008年间的东亚夏季风呈现出显著的年代际强弱变化特征,可划分为三个年代际变化时期：1950～1965年为东亚夏季风偏强时期,1975～2008年为东亚夏季风偏弱时期,1966～1974年为东亚夏季风由偏强向偏弱发生年代际强弱转变的转换时期。合成分析表明,东亚夏季风偏强(弱)时期,北半球高、中、低层大气环流的主要特征为在亚洲北部地区、北非大陆为负(正)距平中心,太平洋北部地区为弱的正(负)距平,呈现出强(弱)东亚夏季风期间,亚洲、北非两地低压系统偏强(弱),副高系统较强(弱)相反的环流变化特征。同时,还显示了强夏季风时期,低层(海平面气压、850hPa)亚洲中纬地区包括东亚季风区及北非地区是全球两个最强扰动能量中心,其次是亚洲南部的阿拉伯海、印度半岛、孟加拉湾、中南半岛到澳大利亚以北地区,印度洋北部地区、赤道太平洋地区为扰动能量较强区域。(3)东亚夏季风与大范围的扰动能量呈显著的正相关关系。扰动波包影响东亚夏季风变化的关键区,海平面和850hPa低层有东亚中纬地区(30～50°N,80～120°E)、北非地区(0-～0°N,0～40°E)和北澳越赤地区(15°S～15°N,90～120°E)；500hPa中层有东亚中纬地区(30～50°N,80～120°E)和北澳越赤地区(15°S～15°N,90～120°E)。各关键区区域平均波包往往先于东亚夏季风出现强弱位相的转换。低层(海平面气压、850hPa)东亚中纬地区、北非地区关键区均较东亚季风主体区域波包突变变化早；中层(500hPa)则热带北澳越赤关键区、东亚中纬关键区均较东亚季风主体区域波包突变早。并且关键区区域平均波包具有年代际的周期振荡变化。(4)扰动能量经、纬向传播特征显示,强东亚夏季风时期,中低层(500hPa、850hPa、海平面气压)东亚季风区扰动能量主要受来自高纬(40°～60°N)南传累积及南半球低纬的苏门答腊以南区域向北传播累积的影响,没有明显的纬向传播影响。弱东亚夏季风时期,中低层东亚中纬地区(20°～40°N)扰动能量向更低纬地区传播并减弱,期间低层东亚地区(海平面气压、850hPa)中纬(30°N)受源自西太平洋扰动能量自东向东西传播的影响,低纬0°～20°N范围内受来自北非地区扰动能量传播影响,中层(500hPa)没有表现出明显的纬向传播特征。(5)东亚夏季风年代际变化的波包传播与亚洲-太平洋流型、海温及华北、长江流域的降水分布都有显著的相关性。更多还原

【Abstract】 The change and effect of East Asian monsoon is one of the main features of China’s climate, especially East Asian summer monsoon, which has the most effect on distribution of rainfall in summer in China. Abnormal interdecadal change of the East Asian summer monsoon not only affects interannual and interdecadal change of China’s climate but also affects China’s rainfall on century time scale. Thus, it is full of meaning to research rules and effects of interdecadal changes of the East Asian summer monsoon. Based on NCEP/NCAR reanalysis materials, this paper analyzes and discusses interdecadal change features, abnormal circulation, perturbation wave energy distribution and propagation features of East Asian summer monsoon as well as its change system from the point of wave energy propagation by wave-packet propagation diagnosis (WPD) and relevant statistics data.(1) According to multi-scale perturbation wave-packet climate, the global perturbation wave-packet is basically distributed in zonal belt shape. In the transition from winter to summer, high value areas of wave packet in equator area move northwards to 10°N. Strong large wave-packet value centers appear in west wind perturbation areas in torrid and middle-latitude zones while major areas under control of subtropical high pressure suffer small wave-packet value centers.(2) East Asian summer monsoon during 1950 and 2008 showed obvious interdecadal change features and it can be divided into three interdecadal change periods, namely relatively strong summer monsoon period from 1950 to 1965, relatively weak summer monsoon period from 1975 to 2008 and interdecadal transition period from relatively strong to relatively weak summer monsoon from 1966 to 1974. According to the comprehensive analysis, in relatively strong (weak) summer monsoon period, the major circulation features of high, middle and low aerosphere of northern hemisphere are as follows:north of Asia and North Africa continent are negative (positive) anomaly centers, north of the Pacific Ocean is weak negative (positive) anomaly, and during strong (weak) summer monsoon period low pressure system is relatively strong (weak) in Asia and North Africa and sub-tropical high pressure system is relatively strong (weak). Meanwhile, in strong summer monsoon period, low aerosphere (aerosphere at sea level is 850hPa) in middle latitude areas of Asia including East Asian monsoon area and North Africa area are the strongest perturbation energy centers in the world, followed by Arabian Sea, Indian Subcontinent, Bay of Bengal and Asian Indo-China Peninsula and north of Australia, north of Indian Ocean, Equatorial Pacific region.(3) East Asian summer monsoon has positive correlation relationship with large-scale perturbation energy. Perturbation wave-packet affects key areas of change of East Asian summer monsoon. The sea level and 850hPa low atmosphere include middle latitude areas of East Asia (30～50°N,80～120°E), North Africa (0～20°N,0～40°E) and North Australia areas (15°S～15°N,90～120°E).500hPa middle atmosphere includes middle latitude areas of East Asia (30～50°N,80～120°E) and North Australia areas (15°S～15°N,90～120°E). Average wave-packet of each key area suffers transition of strong and weak phase before that of East Asian summer monsoon. Low aerosphere (aerosphere at sea level is 850hPa) in middle latitude areas of East Asia and North Africa areas suffer change of wave-packet before major areas of East Asian summer monsoon, and so do the middle atmosphere (500hPa) tropical North Australia areas and middle latitude areas of East Asia. Besides, average wave-packet of key areas has interdecadal rectilinear oscillation change.(4) According to meridional and zonal propagation features of perturbation energy, in strong summer monsoon period, perturbation energy in middle and low aerosphere (aerosphere at sea level is 500hPa and 850hPa) in East Asian monsoon area mainly comes from high latitude (40o～60°N) and south of Suvara Dvipa in low latitude areas of southern hemisphere, without obvious zonal propagation effects. In weak summer monsoon period, perturbation energy in middle and low aerosphere (20°～40°N) is propagated to lower latitude areas and is weakened and during that period low aerosphere (aerosphere at sea level is 850hPa) in middle latitude (30°N) areas of East Asia is affected by propagation of perturbation energy from West Pacific from east to west, low latitude (0°～20°N) areas are affected by propagation of perturbation energy from North Africa, and middle aerosphere shows no obvious zonal propagation features.(5) Wave-packet propagation of interdecadal changes of the East Asian summer monsoon is obviously related with Asia-Pacific flow pattern, sea temperature, North China, Southwest of China and rainfall in the Yangtze River drainage area.更多还原