【作者】 俞亚勋；

【导师】 王式功； 钱正安；

【作者基本信息】 兰州大学 ， 气象学， 2011， 博士

【摘要】 本文利用美国NCEP/NCAR再分析资料和全国743个气象站逐日降水观测资料,以及大气环流特征量等多种资料,针对显著影响我国天气气候变化的东亚夏季风及其主要成员—西太平洋副热带高压不同时间尺度活动特征开展研究,目的在于进一步揭示和了解掌握每年主导我国汛期雨带进退和降水异常的关键因子的活动规律,以期为提高我国汛期气候预测水平提供科学思路和方法。另外,对江苏区域气候变化开展研究和评估将有助于丰富和完善国家气候变化评估的内容,为政府和公众科学应对气候变化提供参考依据。得出的主要结论如下：1)西太副高西脊点侯平均位置作为表征副高活动的一个指标,与东亚夏季风气候雨带位置对应非常一致。西太副高北推东缩期(5月1日—9月5日)北进缓慢,东缩明显,阶段性清楚,有3次相对稳定期(5月中—6月中,6月中—7月上旬及7月中—9月初)；南撤西伸期(9月5日—11月10日)南撤迅速,有两次明显的西伸期(9月11日—25日和10月6日—20日)。2)西太副高北进时出现的三个相对稳定期正好对应着东亚夏季风向北推进时的三个阶段。平均说来,当西太副高西脊点急剧东缩到菲律宾东北近海并相对稳定时(5月中—6月中),华南区粤、桂、闽、台及海南五省进入前汛期；当西脊点稳定在台湾海峡时(6月中—7月上旬),江淮流域及西北区东南部进入梅雨期；当西脊点再次急剧东缩并稳定在日本四国岛南部近海时,华北、东北及西北区东部(张掖以东)进入北方多雨期；而副高南撤期的两次明显西伸时段(9月1日—15日及10月6日—20日)分别引起西北区东南部及华西的秋雨。3)本文根据候平均雨量相对系数≥1.5及持续性等标准,初步划分了各地的雨季。东部的雨季常由几段相邻的季风雨期及地方性雨期组成,其长短、降水强度、成因及相对重要性各不相同。西北区东部的雨季常由梅雨、北方雨期及秋雨三段组成,降水强度弱,中间常间有伏旱段。关中和陕南以梅雨降水为主,兰州及银川等以北方雨期为主,而天水等三段雨期同样重要。新疆天山北麓和南疆西部虽然春、夏雨量相对多于其它时段,但不够雨季标准。4)副高强度指数与西脊点位置的年代际变化特征十分一致：近30多年副高有强度增强和西脊点向西偏移的趋势；1978年前副高强度偏弱,西脊点偏东,但距平值较小,1978年后则相反；二者都有18—-20年以上和6—8年振荡周期。近30多年我国北干南湿及西北区秋雨减少格局主要与西太副高位置逐年渐次偏西,强度逐渐增强,东亚夏季风渐次减弱等年代际变化有关。5)近50年来江苏省年平均气温明显升高,且苏南年平均气温增暖的幅度高于江淮和淮北,其中全省均有冬、春季增暖显著的特点。全省年降水量常年平均值变化相对平稳,其中江淮之间和苏南地区在90年代变化幅度相对较大,近些年变化比较平稳,而淮北地区变化幅度始终相对较大,特别是近十几年来,降水量有增多的趋势。江苏省近年来极端强降水、强对流、高温热浪、干旱、寒潮、大雾、雨雪冰冻等极端天气气候事件增多趋强,历史极值记录屡被突破,由极端天气气候事件引发的气象及其衍生灾害呈突发、多发、强度增强、影响加重的特点。6)未来三种情景(A2、A1B、B1)下江苏区域年平均气温均呈增加趋势,B1情景升温趋势最大,A1B情景次之,A2情景升温趋势最弱。三种情景下的年降水存在较大差异,其中,A1B情景年降水量为北部增加南部减少,B1情景年降水量为全省大部分地区减少,而A2情景则是全省大部分地区呈增加趋势。另外,三种情景下均是春季和夏季降水变化比较显著,而秋季和冬季降水则无明显变化。总之,本文以东亚夏季风活动影响中国汛期降水异常为出发点,着重以西太平洋副热带高压西脊点逐侯平均位置作为表征西太副高活动性的指标,揭示了东亚夏季风季节变化三阶段雨带进退和西太副高西脊点位置的密切关系,强调了西太副高西伸东缩活动的重要性,侧重分析了受东亚夏季风影响最为直接的江淮流域季风活动中心区和受夏季风间接影响的我国西北区东南部季风边缘区域的降水变化特征,通过对我国各地雨季划分和雨季降水特征的异同分析,初步摸清了夏季风对我国大陆地区的影响范围和程度。通过分析西太副高位置、强度和夏季风指数以及我国夏季降水的年代际变化特征,发现正是近30多年来西太副高渐次南移,才造成东亚夏季风上世纪70年代后期以来逐渐减弱,导致我国近30年来“北旱南湿”的降水分布格局。最后以东亚夏季风影响重点区域江苏为例,重点探讨了江苏区域的气候变化特征,指出近50年来苏南增暖更加明显,淮北及苏南降水波动更大、春秋季干旱程度呈加重的变化趋势。并针对未来20—30年三种气候变化排放情景下,利用区域气候模式对江苏地区作出了未来仍将增暖、降水增加的气候变化趋势预估。论文研究结果具有一定的学术意义和应用价值。更多还原

【Abstract】 In this paper, The activity characters of the East Asian summer monsoon which have significant effects to weather and climate in China and the different time scales change of West Pacific subtropical high which is the one of main members consist of the East Asian summer monsoon system were researched using the NCEP/NCAR Reanalysis data, the daily precipitation data in 743 meteorological stations over China since the station established and atmospheric circulation data,The objective was to further reveal and understand the activity rhythm of the key factors influenced the retreat of rain belt in flood season and precipitation anomalies. These rhythms can be used to provide the scientific ideas and methods and improve the climate prediction level in flood season in China. In addition, the research of the regional climate change and its impact and assessment in Jiangsu area not only will help to enrich and improve the content of national climate change assessment but also provide scientific reference to government and public about how to deal with climate change. The main results obtained are as follows:1) The pentad-averaged west ridge point of West Pacific subtropical high which is considered an index describing the activities of subtropical high which position is very consistent with the climate rain belt of East Asian summer monsoon. The West Pacific subtropical high shows slowly northward advancing and obvious contraction in the period of northward advancing and eastward shrink (May.1-Sep.5) and the characteristics of stage is distinct,which have 3 relatively stable stages include the stage from the mid-May to the mid-Jun,the stage from the mid-Jun to the early Jul and the stage from mid-Jul to the early Sep; the period of southward retreat and westward movement shows the character of fast southward retreat and have 2 westward period:the period from Sep.11 to Seq.25 and the period from Oct.6 to Oct 20.2) The three stable stages of West Pacific subtropical high northward advancing are correspond to the three stages of East Asian summer monsoon northward.On average, when the west ridge point of West Pacific subtropical high sharp shrink to the Philippines northeast offshore and maintain relative stability, the five provinces include Guangdong, Guangxi, Fujian and Taiwan and Hainan in south China enter the pre-flooding season; when the west ridge point maintain in the Taiwan Strait, the Yangtze River and Huaihe River valleys and southeastern part of the northwest China enter rainy season, when the west ridge point again sharp shrink and stabilize to the southern island offshore in Japan, the north, northeast and northwest China into north rainy period; the two obvious west stretch time in the period of subtropical high southward retreat(from Seq,l to Seq,15 and Oct,6 to Oct,20) respectively led to the autumn rainy season in southeastern part of northwest and west China3) The monsoonal rainy seasons are divided according to criterion of the pentad-average precipitation relative coefficient greater than 1.5 and the precipitation duration and so on, the eastern rainy seasons consist of several adjacent monsoon rains period and local rain which length, rainfall intensity, the causes and relative importance are different. The eastern part of Northwest China’s rainy season usually include Meiyu rainy season, northern rainy season and autumn rainy season, but these three sections of the composition of precipitation intensity is weak, with the drought period in summer in the rainy seasons. The rainy rainfall give priority to the total rainfall in the central and south of Shanxi and the rainfall bases on the northern rainy rainfall in Lanzhou and Yinchuan,while all these there rainy periods have equally important contribution in Tianshui, while the other three sections of Tianshui rain period is equally important. The rainfall is more relatively in spring and summer but which does not come to the monsoon standard in north piedmont of Tianshan Mountain in Xingjiang and west region in southern Xingjiang.4) The interdecadal variation of the intensity index of West Pacific subtropical high at 500hPa is very consistent with that of the west ridge point position of West Pacific subtropical high. The subtropical high has an obvious trend of strengthening and moving westward in recent 30 years. Before 1978, the intensity index of subtropical high was weaker and its position of west ridge point located east to the normal with small anormaly value, but the situation was contrary after 1978. Both of the period intensity index of subtropical high exhibits oscillation periods of 6-8 years and 18-20 years. The distribution of dry in Northern China while wet in Southern China and autumn rainfall in Northwest China decreased in recent 30 years are related to the interdecadal variation which the intensity of West Pacific subtropical high is strenthened and its position is westerly advancement together with the weakening East Asian summer monsoon.5) The average temperature of Jiangsu shows the increasing tendency in recent 50 years, and the southern average increasing rate of warming is higher than the jianghuai region and southern Huai River, where the whole province’s temperature shows significant warming in spring and winter in whole province.The changes of average annual precipitation is relatively stable in which the amplitude of variation in jianghuai basin and southern Jiangsu is relatively large in 90’s but steady in recent years, while the amplitude of variation in huaibei region is relatively large from beginning to end especially in recent decades, the precipitation shows the trend of increasing.6) In recent years, the disastrous weather days such as extreme heavy precipitation, strong convection, heat wave and cold wave, fog, freezing rain become more and stronger, The history records have been repeatedly broken, the incidence of extreme weather events arise increasingly, the meteorological disasters and its derivative disasters triggered by extreme weather shows the features of out-burst, multiple, intensity and disastrous influence.7) The future (2010-2039 year) climate changes in Jiangsu for three emission scenarios (SRES A2, A1B, B1) are projected by RegCM3 nested within the NCAR_CCSM3 AGCM. The results show that, the annual averaged temperature will rise mostly in the whole area for all three emission scenarios, in which temperature rising will be most distinct for B1 scenario, then less for A1B, and the least for A2. But for precipitation appear obviously different changes among three emission scenarios, in which precipitation will have an increasing tendency in northern area while a decreasing tendency in southern area for A1B, a decreasing tendency in most part of area for B1 scenario and an increasing tendency in most part of area for A2 scenario. Furthermore, the precipitation displays conspicuous variations in spring and summer for all three emission scenarios, but the changes are not evident in autumn and winter.更多还原