【作者】 杨宇星；

【导师】 王斌；

【作者基本信息】 中国海洋大学 ， 气象学， 2010， 博士

【摘要】 本文利用美国联合预警中心(Joint Typhoon Warning Center, JTWC)和美国海洋大气局的国际飓风中心(the National Hurricane Center, NHC)的最佳路径资料,美国国家环境预报中心和美国国家大气科学研究中心(the National Centers Environmental Prediction and the National Center for Atmospheric Research, NCEP/NCAR)大气环流场资料,美国海洋大气局(the National Oceanic Atmospheric Administration, NOAA)的扩展海温资料(ERSST)以及政府间气候变化专门委员会(IPCC)模式试验中GFDL CM2.0模式结果,应用季节联合主成分分析(Season-reliant Empirical Orthogonal Function, SEOF),季节联合奇异值分解(Season-reliant Singular Value Decomposition, SSVD)等统计方法,对热带气旋(TC)活动与大尺度环流场的关系进行了三方面的研究。首先,文章研究了全球TC活动的变化特征及其与全球海温(SST)的关系；第二方面的探讨是基于TC活动最为活跃的西北太平洋海域进行的,分析了该海域内TC活动频发区TC出现频率变化特征和可能影响这些区域TC活动背景场因素；最后一方面,文章利用IPCC第四次评估中GFDL CM2.0模式结果分析了由Emanuel和Nolan定义的表征TC潜在生成的指数(GPI)在CO2加倍过程中和加倍过程后TC生成的变化趋势,并探讨了引起TC趋势变化的可能环流因素。下面是本文的具有创新性的研究成果：1、应用SEOF的方法分析全球热带气旋的变化特征,找到了独立、显著的第一主模态,也就是热带气旋的全球模。并指出这一模态的主要影响因子是ENSO和PDO,而不是ENSO和NAO(Elsner和Kocher,2000; Frank和Young,2007),其中ENSO的作用要更大一些。本文所定义的热带气旋的全球模是指：以TC年(自当年的6月份至下一年的5月份为一个TC年)为基础,TC在全球尺度上变化特征的第一显著模态。其空间分布为：TC出现频率在太平洋上变化态势一致,北大西洋的主体变化趋势与太平洋相反,仅在其东北部分表现出与太平洋一致的变化特征。南半球上,南太平洋海域TC出现频率呈南北变化趋势相反的经向分布态,南印度洋和北印度洋区域主体变化趋势一致,与太平洋同向。研究表明此模态的主要影响因子为ENSO和PDO,其时间序列的相关系数达：0.83和0.56,与NAO的相关系数却很小,仅为0.06。2、通过SSVD的分析方法探讨了全球TC出现频率和全球热带、副热带海温的关系。除发现对于热带气旋全球模的主导影响因子是ENSO和PDO外,还给出了全球TC出现频率伴随全球变暖信号所表现出的变化趋势的空间分布。伴随全球海温的增暖,TC出现频率在西北太平洋上的中国南海和西北太平洋东部地区均呈现出下降趋势,但是在东亚地区TC出现频率增高；在东北太平洋上以显著的下降趋势为主,而在大西洋则为全海盆一致的增高现象,南半球海洋澳大利亚东、西两侧分别显示出了下降和上升两种趋势,北印度洋区域则是显著的下降趋势。由于本文的研究对象,TC出现频率,不仅受到TC生成频次的影响同时受到TC生命周期作用,其研究意义还体现了部分TC强度变化特征,所以本文指出大西洋TC出现频率存在显著的上升趋势,是TC生成频次、TC生命周期和部分TC强度综合作用的结果。本文同时发现印太暖池区域(17.5°S-10°N,70°E-140°E)TC出现频率存在上升趋势。尽管全球热带地区存在0.5～1.0℃的升温现象,却不足以令TC出现频率在全球范围内出现增大趋势,仅在部分海域存在趋势变化。3、揭示了西北太平洋副热带高压不同时间尺度上的变化导致了西北太平洋不同区域的热带气旋活动表现出不同时间尺度的变化。研究表明：西北太平洋副热带高压存在显著的西伸和南压的趋势变化特征,这种长期趋势变化对中国南海区域(S区)的TC经过个数有显著影响,使得经过此区域TC个数呈现下降趋势；而西北太平洋副热带高压的年代际变化特征则主要影响了经过菲律宾海附近区域(P区)TC路径条数；其年际变化特征正是经过中国东海区域(E区)的TC个数产生3-4年显著振荡的主要影响因子。本文同时指出对于热带气旋频发区S区不仅经过该区域的TC个数存在显著的下降趋势,而其本身区域内TC生成个数也表现出显著的递减趋势,进而导致了此区域的TC出现频率同样表现出通过95%置信度检验的线性下降趋势。而影响S区TC生成趋势变化的主要环流因子为700hPa相对湿度和500hPa纬向风的经向切变。4、利用热带气旋潜在生成指数对CO2加倍过程中和加倍后热带气旋的生成能力进行预测。其中CO2加倍过程中的研究结果体现了人类活动影响下未来50～100年TC生成的趋势变化,而CO2加倍后的变化趋势则为未来100～150年TC生成的气候变化特征。研究发现无论是CO2加倍过程中还是加倍后,未来热带气旋生成在北太平洋上存在北移增强的特点,在大西洋上则表现为墨西哥湾以东海域TC生成能力减弱,以北、以南区域生成能力增强的特点。其中,在未来100～150年间增强幅度更大。进一步研究表明：由于CO2增加而造成的热带海洋和大陆、海域和海域间增暖的不一致性使得未来环流条件发生不一致的变化特征,而最终引起TC生成表现出上述变化特征。其主要是通过改变垂直风切变和相对湿度这两个因子实现的。更多还原

【Abstract】 Based on the 44-yr (1965-2008) tropical cyclone (TC) data of the Joint Typhoon Warning Center (JTWC) and the National Hurricane Center (NHC), the data of Atmosphere circulation field from the National Centers Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR), the ERSST from the National Oceanic Atmospheric Administration (NOAA) and the results of GFDL CM2.0 model, some statistic methods, such as Season-reliant Empirical Orthogonal Function (SEOF), Season-reliant Singular Value Decomposition (SSVD), have been used to do the following analysis:the first one is to study the global mode of the TCs and to analyze the relationship between this mode and the SST; the second is to discuss the variation of the TC in the High frequency of occurrence regions (HFOR) in the western north Pacific (WNP) and associated general circulation; the last one is about the climate prediction of TCs using Genesis potential Index defined by Emanuel and Nolan. Some useful results have been got.1. It is the first time to using the SEOF to analysis the global TCs and getting a dominant dependent mode, the global mode of TCs. The analysis also shows that it is influenced by El Nino-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), the ENSO more important.In this paper, the global mode of TCs is the first dominant mode of the SEOF of global TC based on TC year. Its spatial pattern displays an east-west contrast between enhanced activity in the North Pacific and reduced activity in the North Atlantic and a north-south contrast in the Southern Pacific oceans between active tropics and inactive subtropics, which are coupled with the El Nino and a positive phase of the PDO. The correlation coefficient between the PC1 and the index of ENSO and that between the PC1 and PDO reach 0.83 and 0.56, while the one between the PC1 and North Atlantic Oscillation (NAO) is only 0.06.2. Using the SSVD, the relationship between the global TCs and the SST is discussed. The two leading mode are got, the first one display the relationship between the global mode of TCs and ENSO and PDO, and the second suggests the variation of the global TC with global warming.The second mode reveals regional upward trends over the North Atlantic and the Indo-Pacific warm pool (17.5°S-10°N,70°E-140°E) coupled with the global warming. However, the global total number of frequency of occurrence shows no trend and only an unexpected large amplitude fluctuation driven by ENSO and PDO. The rising temperature of about 0.5～1.0℃in the tropics so far has not yet affected the frequency of occurrence of the global TC, while it only leads to upward or downward trend in some regions in some basins.3. The variation of Western North Pacific Subtropical High (WNPSH) in different time scale can affect the variation of the frequency of occurrence (FOC) of TCs in HFOR in the WNP.The variation of TCs in peak season (JASO) in three HFORs (the region E, region S and region P) is different. In the region S, whatever the FOC, the track number (TN) and the genesis number (GN) all show significant downward trends. In the P region, the FOC, TN and GN all show about 8-11-year decadal variation. Otherwise, in the region E, the significant 3-4 years oscillation appears in the FOC and TN.For the three regions, the TN’s variability that influenced by the variation of the WNPSH is the main reason of the variation of the FOC. For the long term trend of the TN of the region S, compare the period 1987 to 2008 with period 1965 to 1986, the WNPSH displays westward and southward, and strengthened. It even expands to the region S. This change of the WNPSH will reduce the number of the tracks which go through the region S. On the decade scale, an anomaly anticyclone appearing in the’ northwest of the region P makes the WNPSH stretch northward and westward, and this is suitable for TCs reaching the region P in the larger FOC year of the region P. The interannual variation of the WNPSH results in the interannual variation of the TN of the region E.Otherwise, for the region S, the decreasing trend of the GN of the region S and the region (140°～160°E,5°～20°N) where the TC generating may go through the region S is another reason of the downward trend of the FOC of the region S. The reduced relative humidity and increased meridianal shear of zonal wind may be lead to the trend of the GN in the two regions.4. The GPI is used to predict the change of the genesis of the TCs in JASO when the CO2 is doubling and doubled in the GFDL2.0 mode.The results show that whatever in the doubling of CO2 or doubled, the genesis of TCs in the north Pacific may shift northward (the GPI is positive on the north of 10°N, while negative on the south of 10°N); in the Atlantic, the property of genesis of TCs will decrease on the east of the Gulf of Mexico (GPI, negative), increasing on the south and north the Gulf of Mexico (GPI, positive). The possible reason of these changes may be the change of vertical shear of zonal wind and the relative humidity caused by the inconsistency of the increasing of SST.更多还原