广西秋季干旱成因分析 硕士学位论文.doc

中山大学硕士学位论文广 西 秋 季 干 旱 成 因 分 析学位申请人： 导师姓名及职称： 专业名称： 气象学答辩委员会成员（签名）：主席：成员：中山大学大气科学系二八年十二月三日学位论文原创性声明本人郑重声明：所呈交的学位论文，是本人在导师的指导下，独立进行研究工作所取得的成果。除文中已经注明引用的内容外，本论文不包含任何其他个人或集体已经发表或撰写过的作品成果。对本文的研究作出重要贡献的个人和集体，均已在文中以明确方式标明。本人完全意识到本声明的法律结果由本人承担。 学位论文作者签名： 日期：2008年10月9日学位论文使用授权声明本人完全了解中山大学有关保留、使用学位论文的规定，即：学校有权保留学位论文并向国家主管部门或其指定机构送交论文的电子版和纸质版，有权将学位论文用于非赢利目的的少量复制并允许论文进入学校图书馆、院系资料室被查阅，有权将学位论文的内容编入有关数据库进行检索，可以采用复印、缩印或其他方法保存学位论文。学位论文作者签名： 导师签名：日期： 年 月 日 日期： 年 月 日论文题目：广西秋季干旱成因分析 摘 要本工作利用均匀分布在广西境内的89个气象观测台站19612006年逐日降水资料、NCEP/NCAR全球月平均要素场再分析资料、NOAA/NCEP/CPC ONI指数资料、月平均ERSST.v2海温资料、WHOI全球海气通量分析资料（OAFlux）、以及比利时SIDC月度太阳黑子活动数据，运用客观定量化的小波分析、趋势（突变）分析、合成偏差分析、相关分析、水汽通量分析计算等多种方法，对广西区域秋季异常干旱（降水）事件的时空异常分布和变化特征、年际年代际变化的相关因子、天气气候背景以及可能的影响因子、成因机制等方面内容进行了综合分析，揭示出一些新的观测事实，得到以下结果：广西秋季的降水具有南多北少的特征，境内秋旱出现频繁：全区各地的秋旱频率多在30%40，其中桂东南是广西秋旱发生最为频繁、也是近年来旱情趋于严重的地区。广西秋季降水变化以全区一致旱涝的分布型占主要地位；此外，广西秋季降水还具有东西差异型、南北差异型以及自桂西北到桂东南呈“”（或“”）的波状分布型式等其它三种典型的分布型式。广西秋季降水存在着年代际变化和年际变化两个显著的振荡特征；二者对广西秋季降水具有同等重要的影响；近二十年来广西秋季降水有逐渐减少的趋势，且从2003年开始可能出现了趋于明显减少的气候突变。以ENSO事件为典型特征的赤道太平洋地区热力振荡与广西秋季降水的年际变化密切关联；而太阳活动的周期性变化则是年代际变化的重要影响因子，由此造成的广西秋季严重干旱持续现象值得关注。中纬度东太平洋海温变化与广西秋季降水呈显著负相关、而中低纬中西部太平洋则为显著的正相关区；另外，在印尼西部沿岸的东印度洋区域，海洋热力变化与广西秋季降水也有较为显著的负相关关系，显示出印度洋海洋热力状况对广西秋季降水也有相当程度的复杂影响。秋季热带气旋是广西秋季降水最重要的天气系统，直接影响广西的秋季热带气旋数目在很大程度上决定了广西秋季降水的多寡以及旱情的严重程度。降水偏少年影响广西的热带气旋的平均强度和生存周期明显偏小、登陆地点也明显偏南。海气相互作用的分析表明，广西秋季降水的多寡与南海、孟加拉湾以及赤道以南印尼澳洲沿岸的大片东印度洋海区的海气通量输送均呈显著的负相关关系；而与赤道中东太平洋以及南太平洋大片海区的海气通量输送呈显著的正相关关系。其中，我国南海等西太平洋区域的海气通量异常变化可能是受东亚大陆高压异常变化影响、导致相关区域全风速异常变化而引起的。另外，从孟加拉湾到印尼西部沿海到澳洲西部沿岸的东印度洋的大片海区，其海气通量异常所激发的大气异常型与广西秋季干旱状况有着密切的关联。广西秋季旱涝的大致环流背景是：当中纬度亚欧大陆东亚西太平洋沿岸日本海以东太平洋地区大气环流的两脊一槽“高低高”波状分布形势不易被破坏、且两脊区均偏高偏强时，广西秋季降水偏少、旱象加重；而当这种“两脊一槽”形势破坏、出现只有大陆高压脊偏高、东亚大槽和太平洋高压脊均偏低的“西高东低”形势的环流调整时，广西秋季降水增多、严重旱情不容易出现。就广西秋季干旱成因分析而言，常用的海温和环流分析方法对辨别中高纬度的影响系统是有帮助的，但对低纬度影响系统的分析能力有限；而进行海气相互作用分析，则可以弥补上述不足，发现更多的有价值的低纬度影响因子信息。 2004年是广西秋旱极端严重的一年，分析显示：该年秋季影响广西降水的海洋热力异常主要以太平洋海域的热力异常为主，其中中纬度东太平洋和赤道中、东太平洋海域是异常变化最明显的两个区域；而日本列岛周边海域的海气交换通量变化幅度也异常明显；该年秋季自南海北部北部湾区域到台湾海峡一带的广阔海域上空还出现了历年同期罕见的大片水汽输送负偏差区；这些结果表明，太平洋区域海洋热力和环流异常变化可能是造成2004年秋季广西异常严重旱情发生的主要原因。关键词：秋旱，副高，海气交换通量，太阳黑子，突变，成因Title：Cause Analysis of the Autumn Drought in GuangxiMajor: MeteorologyName: Li YuzhongSupervisor: Prof. Li WeibiaoAbstractBased on the precipitations from 89 stations in Guangxi offered by Guangxi meteorological observatory, NCEP/NCAR global monthly mean reanalyses, NOAA/NCEP/CPC ONI index data, ERSST.v2 SST data, WHOI OAFlux data,and Belgium SIDC sunspot activities data, using objective and quantitative analysis such as wavelet analysis, trend analysis, composition analysis, correlation analysis, moisture channel analysis, the text analyzes the space-time abnormal distributing characteristic and transformation characteristic, synoptic and climate background, conceivable infection genes and cause of formation for the exceptional drought event at autumn in Guangxi area, then open out same new observation and reality, the results show that:The autumn precipitation in Guangxi has the character that the rainfall at the southern part is more than that at the northern part, and the drought event has a high frequency. Using the precipitation anomaly percent index to analyze the frequency of the drought event, we find that the autumn drought frequency in each area of Guangxi is between 30% and 40%, and the southeastern of Guangxi is the area that the autumn drought happen most and the ravages of a drought is going to serious at the recent year.The autumn precipitation in Guangxi has two notable oscillation characteristics which are decadal change (which cycle is 1012years) and interannual change (which cycle is 46years), and both of them have important effect to the autumn precipitation in Guangxi. At the near 20 years, The autumn precipitation in Guangxi is going to be reduce and maybe has a climate break that the rainfall is reducing obviously since 2003.At the years that the autumn precipitation in Guangxi is less, both of the Pacific subtropical high and Asia and Europe continent high are stronger, while the departure field at Asia and pacific area in middle latitude distribute as “+”,and the meridionality of the season average circulation is being smaller. The cold air activity is more northern so it affects the south China less. On the effect of the strong Continent High, the moisture from the Pacific and the South Sea can not go to the inland of South China which leads to the moisture transportation of the area being low, and the autumn drought is more serious.The analysis of air-sea interaction shows: there is a negative correlation between the autumn precipitation of Guangxi province and the air-sea transportation in South China Sea, Bay of Bengal And east of Indian ocean; positive correlation with the air-sea transportation in middle-east pacific ocean. It is found that subtropical high may affect the changing of wind speed in South China and west Pacific ocean, which will lead to the abnormal of air-sea flux transportation. What's more, the air-sea interaction in Bay of Bengal And east of Indian ocean can also affect the abnormal circulation in autumn then lead to autumn draught in Guangxi province. At the year that the autumn precipitation in Guangxi is more, the departure field at Asia and Pacific area in middle latitude distribute as east high and west low. On the one hand, it leads to the East trough deepening and the meridionality of general circulation become bigger which steering the cold air effect the South China more continually. On the other hand, the Pacific subtropical high move southernly and westernly leads to the Continent High and the West Pacific subtropical high connect and the South China is affected by the east air current on the south side of the subtropical high, which make the moisture easier transport to the inland of South China. The cold air activity and the favorable water condition make the autumn precipitation in Guangxi more and the serious drought event hard to happen.The thermal condition of the Pacific is correlated nearly with circulation pattern change of the autumn precipitation in Guangxi. The ENSO interannual oscillation has good relation with the autumn precipitation in Guangxi, which indicate that the thermal oscillation of the Pacific such as ENSO maybe the most important factor of the autumn precipitation interannual change of Guangxi; and the interannual change of sunspot has obviously relationship with the autumn precipitation interannual oscillation of Guangxi which explain that the seasonal change of sun maybe the pivotal effect factor for the autumn precipitation decadal change of Guangxi. It's deadly serious drought in 2004 in Guangxi.The analysis shows that the abnormal thermal condition of the Pacific is the most important effect factor to this year.Key Words: Autumn Drought; Subtropical High; Air-Sea Heat Fluxes； Sunspot; Abrupt Change；Cause 目 录原创性声明 ·············································································································( I )使用授权声明 ········································································································()中文摘要 ················································································································(III)ABSTRACT ············································································································()目 录 ····················································································································()第 1 章 前言 ······································································································· (1)1.1 有关干旱的描述和对干旱特征的研究···················································(2)1.2 有关干旱成因的研究···············································································(3)1.3 有关广西干旱的研究···············································································(4)1.4 存在的问题以及本论文的研究内容·······················································(5)第 2 章 资料和分析方法 ··················································································· (7)2.1 资料来源 ·································································································(7)2.2 主要概念定义和研究方法简介 ·····························································(7)第 3 章 广西秋季干旱的气候特征及近期极端干旱个例介绍·························(13)3.1 广西秋季气候概况··················································································(13)3.2 广西秋季降水的时空变化特征······························································(14)3.3 广西秋季干旱的分布和变化特征··························································(20)3.4 广西近期秋季极端干旱个例介绍··························································(22)3.5 小结 ········································································································(24)第 4 章 广西秋季干旱（降水）年际、年代际变化的相关因子特征分析··········(25)4.1 广西秋季干旱（降水）与同期海洋热力变化的相互关系··················(25)4.2 广西秋季干旱（降水）与热带气旋系统的相互关系··························(25)4.3 广西秋季干旱（降水）与海-气交换通量变化的相互关系················(29)4.4 广西秋季干旱（降水）与ENSO的联系············································(36)4.5 广西秋季干旱（降水）与太阳黑子活动的联系 ································(37)4.6 小结··········································································································(38)第 5 章 广西秋季干旱的环流特征分析·····························································(40)5.1 广西秋季中低层位势高度场的变化特征分析······································(40)5.2 广西秋季近地面层流场的变化特征分析··············································(45)5.3 广西秋季海平面气压场和温度场的变化特征分析······························(46)5.4 广西秋季水汽输送通量特征分析··························································(46)5.5 广西秋季干旱的成因分析······································································(50)5.6 小结··········································································································(51)第 6 章 2004年广西秋季异常干旱个例分析····················································(53)6.1 2004年秋季广西降水和旱情概况·························································(53)6.2 2004年秋季环流形势场特征分析·························································(54)6.3 2004年秋季海洋热力变化特征分析·····················································(60)6.3 2004年秋季西太平洋热带气旋系统的活动状况·································(61)6.5 2004年秋季海气潜热和感热输送通量的变化特征·························(61)6.6 2004年秋季水汽输送通量场的变化特征·············································(64)6.7 小结··········································································································(65)第 7 章 结论与讨论 ···························································································(66)7.1 总结 ········································································································(66)7.2 结果讨论与研究展望 ············································································(67)参考文献 ·················································································································(68)致 谢 ·················································································································(72)第1章 前 言干旱不仅是全球范围内的一种对社会经济和人民生活影响最大、造成损失最为严重的气象灾害1，2，也是在我国发生得最频繁、对社会生活和农业生产影响最大的自然灾害。近十五年的统计表明，我国常年的干旱受灾面积占农作物总受灾面积的一半以上，严重干旱年份比例甚至高达75%以上，因此造成的社会经济损失远远超过了其它气象灾害（图1-1）3，4。随着社会经济的迅速发展以及人口的不断膨胀，一方面，大量草场林地被开垦成农田或开辟为城乡生活用地，工农业生产和城乡生活用水急剧增加，加之水资源环境恶化，使得可用水的供应日趋紧张；另一方面，人类活动还引起气候变暖等全球气候变化因素，使得蒸发量不断增大、而降水量的分布又日益不均匀，这些都导致干旱灾害有进一步频繁化和严重化的趋势。图1-1 19892005年我国各类气象灾害受灾面积占农作物总受灾面积的百分比4干旱通常是指较大范围内的因水分收支（供求）不平衡而引起的持续性的土壤水分缺乏现象(WMO，1992；AMS，1997)5，6，7；其核心内容是水分匮乏，并且有一定的时空尺度和规模程度；一般来说，降水量不足是导致干旱的最主要的原因。按发生的季节，干旱可划分为春旱、夏旱、秋旱和冬旱；其中，春秋干旱对广西农业生产的影响最大8，9。长期以来，学者们从各种角度对春季以及汛期降水（干旱）的分析研究很多，而针对秋冬季节降水特征规律等方面的探讨还不多见。事实上，近年来随着社会经济的发展、人口的不断膨胀，加之农村产业结构的调整，秋冬季降水异常偏少所造成的社会经济损失也在逐年加重。以广西区域为例，尽管秋冬季常年降水量还不足全年总降水量的三成，但近年秋季发生的几次严重干旱事件都对人们群众的生产生活造成了严重影响、引起了地方政府和社会各界的高度关注。尤其是自2003年以来，该区域出现了近五十年来罕见的连续四年秋季降水异常偏少、严重秋旱的事件；特别是在2004年秋季，降水量比常年同期偏少近9成、且10月份几乎滴雨未下，造成全区88个县(市)发生不同程度的干旱，且重旱比例达7成以上10。严重的秋旱使得农业生产几乎陷于停顿状态，数百万计人畜饮水困难、森林火灾频繁；由于境内各大江河水位持续下降，水力发电、内河航运和以漓江为代表的旅游业均受到严重影响；而远在千里之外的珠江三角洲一带，因上游来水严重不足，珠江口河道出现数十年来最严重的咸潮等现象11，造成了非常严重的社会经济损失。上述情况表明，秋冬季降水的重要性已经不容忽视。广西区域秋冬季历年来都有不同程度的旱情发生、其中出现全区性重旱的情况也不算少数8,9,12。在这些普遍的现象当中是否隐藏着某种规律性的特征？它们的成因、机理又是什么？有针对性地研究、探讨这些课题，不仅可以加深人们对广西秋季异常干旱过程细节的认识和理解，有重要的科学价值；而且对我们提高相关事件的预测预报水平，指导有关部门及早做出防范部署，减轻异常干旱事件对社会经济造成的损失，也有着非常重大的社会意义。1.1 关于干旱的描述和对干旱特征的研究干旱的形成与很多因素有关,包括气象（降水、蒸发、气温等）、水文、地质地貌、土壤底墒、灌溉条件、种植作物、作物的生育期以及工业和城乡生活用水状况等等。因此，就不同学科、或针对不同的研究目的，对干旱的定义和分类均有所不同。目前国内学术界普遍参照采用的是美国气象学会（AMS，1997）的4类干旱标准6，即：气象干旱（因蒸发和降水不平衡导致的水分缺乏）、农业干旱（土壤含水量小于农作物的需水量）、水文干旱（河流水位或含水层水位低于常年值）和社会经济干旱（人类社会生活中因可用水分缺乏而严重影响社会经济活动的现象）。上述四类干旱中，气象干旱是基础和先导，其它干旱是具体的表现形式；鉴于本文研究的主要是气象干旱方面的内容，在后续讨论中如无特别说明，所使用的“干旱”定义均指“气象干旱”。由于涉及到多个不同学科，干旱研究有其复杂性。首先，为了客观定量地反映干旱的程度，为旱灾的监测和评估提供必要的理论基础，一般使用各种干旱指标（指数）来对干旱现象进行描述。早期的干旱定量监测标准一般是“连续少雨日数”等指标，最早在20世纪初期的美国开始使用（Munger13，1916；Kincer14，1919）；我国气象业务部门目前常用降水距平百分率、降水量标准差等与气象降水要素直接相关的统计数据作为干旱指标15；美国等西方国家自上世纪60年代以来广泛采用相对复杂的、综合考虑了与干旱发生的气象、土壤、蒸散等各方面因素的“机理性干旱指标”，如著名的PDSI （Palmer16，1965）、作物水分指标CMI（Palmer17， 1968）以及它们的各种改进指标18,19等；俄罗斯（前苏联）等国习惯使用布德科辐射指数来作为干旱的衡量标准20；在意大利，Le Houorou等21用“可靠降水指标”（Dependable rains ，1993）来研究非洲大陆的干旱状况，以弥补Palmer指标的不足；而南半球的澳大利亚干旱监测中心22则使用“持续少雨月数”指标来作为干旱等级划分的标准（Wilhite and Glantz，1985)。另外，由于复杂的机理性干旱指标往往还存在着实时资料获取难、受地域限制大、不利于不同地区相互间的分析比较等缺点，美欧等国在近年来的研究中也有使用相对简单实用的降水距平百分率（Willeke，1994）23、标准化降水指数SPI( McKee,1993）24，25等干旱指标的趋势；John Keyantash等26通过对各种气象干旱指标的普适性（能否广泛适用于各种自然环境）、实用性（资料是否易于获取、计算是否有效可行）、理论性（是否包含明确的物理机制）等关键特性进行综合分析、评估后也认为，在众多干旱指数中，降水成数仍是最有价值的干旱衡量标准。进入21世纪以来，在发达国家的干旱监测业务中还有将多种指标综合在一起、通过一定权重组合成一个相对客观的复合干旱指标投入实际应用的趋势27。由于目前各国、各地区在业务科研中应用的干旱指标还很不统一，每种评定方法既有其优点、又有其不足之处；当立足于不同的研究着眼点、选用不同指标进行分析时，对同一干旱事件可能会得出不同的干旱期或干旱强度等级划分结果，这往往会对相关学术研究造成一些困扰。 其次，由于干旱与其它短期突发性气象灾害不同，具有多发性、渐进性、持续性、累积性、滞后性等特点3,23，旱情的开始、发展和结束以及其严重程度、对农业生产和社会经济造成的影响等往往得不到及时准确的判断和评估；加之各种干旱指标均无法合理地反映干旱过程中非气象因素（如区域农业系统结构、人口和社会经济结构、人类的抗灾减灾行为等）的响应和反馈作用，这也造成了干旱分析难以客观定量化、无法满足监测预报的时效要求、各种干旱研究成果也难以相互比对借鉴等许多现实的困难。 最后，鉴于干旱是气候系统、外源强迫以及人类活动等几方面因素的非线性相互作用结果3,4，28；除了不同气候基本态之间的转换以及外源强迫（太阳辐射）的循环演变会对干旱的形成有重要影响外，人类的生产生活也会在相当程度上影响和改变干旱的时空分布和进程2931。基于历史气候监测数据和灾情统计资料研究得出的干旱演变规律，往往因为受到人类大规模砍伐、耕作以及灌溉等行为的持续影响，已不能作为现今干旱监测和预测预报的依据。因此，及时根据客观形势发展对干旱评估标准进行更新调整，并结合遥感监测、区域社会经济结构分析等其它手段来综合分析区域干旱的最新格局，才会有更现实的意义32。1.2 关于干旱成因的研究关于干旱的成因研究，一般分为两大部分。一是针对区域性常年降水偏少的“干旱区”或“干旱气候”的成因研究，另一方面是针对气候异常导致的某个时期或时段内出现干旱现象的研究。对于“干旱区”的形成，一般解释为：或受因副热带Hadley环流的下沉运动（副热带高压）影响；或因山脉地形背风坡下沉运动影响；或因远离海洋、水汽难以达到所致；或受海洋（海温）直接影响以及类似青藏高原等大地形的影响等3341。而对于气候异常引起的区域性干旱事件的成因，研究热点多集中于作为水汽输送主要载体的季风环流活动异常、导致大尺度水汽的输送和辐合过程出现明显的改变，进而引起局地旱涝灾害发生的情况：大尺度环流型的异常、夏季风载体的建立和迟早强弱变化、海洋等水汽源地的特点等都是相关研究关注的焦点由于广西区域发生的干旱就