西北太平洋生成热带气旋的年代际变化

为了分析热带气旋年代际变化的特征和造成这种变化的原因,利用西北太平洋编号台风资料对1949～2003年55 a的西北太平洋热带气旋特点进行分析,发现西北太平洋生成的热带气旋不管是频数还是生成位置都存在明显的年代际变化,根据热带气旋频数的年代际变化,把研究的55 a分成低频时期(LFP)和高频时期(HFP)分别加以考察.结果发现:热带气旋生成的高低频时期海气条件存在明显的差异,HFP的海温、对流、涡散度和切变条件都有利于西北太平洋热带气旋的生成,而LFP则明显存在物理量场的相反异常.这表示HFP的海气环境相比LFP更有利于热带气旋生成,说明了变化的海气条件是引起热带气旋频数和生成位置年代际变化的主要原因.     

太平洋海域海平面变化的灰色系统分析

应用灰色系统理论，对太平洋海域４８个长期验潮站的月均海平面分别建立了ＧＭ（１，１）模型，ＧＭ（１，１）模型能较好地反映太平洋海域的海平面变化的趋势，它除了能给出连续的海平面变化速率外，同时能方便地给海平面变化的加速率，模拟结果表明，在太平洋地壳均衡假设下，太平洋海域的月均海平面以平均速率０．１７ｃｍ／ａ上升。在太平洋海以的４８个长期验潮站中，有４０个站在加速上升，全部站的平均加速度为０．０００２９     

热带太平洋海平面高度季节内振荡的空间分布特征

根据三年卫星高度计（ＴＯＰＥＸ／ＰＯＳＥＩＤＯＮ）资料和涡分辨率的海洋环流（ＰＯＰ）模式模拟计算的海平面高度资料，利用功率谱和最大熵谱的方法，揭示了热带太平洋平面高度季节内振荡的空间分布特征。     

近十年我国海平面变化研究进展

系统地回顾了2006—2015年我国在海平面变化规律、机制及影响领域的最新研究进展。分析了全球及区域海平面以及比容海平面在不同时间尺度上的变化规律;探讨了海平面的变化机制,海表热通量、淡水通量、环流、风应力以及Rossby波对不同区域海平面变化的动力及热力影响;采用统计方法和数值模拟等手段,对21世纪海平面变化进行了预测;同时海平面变化会影响海洋的动力过程(如潮波系统的变化),并进而对近海和海岸带环境产生重要影响(如海岸侵蚀、海水入侵和土地盐渍化、河口咸潮入侵、近岸低地淹没、红树林衰退等)。     

登陆中国热带气旋路径的年代际变化

利用1951~2002年热带气旋年鉴资料,将52年分成ID1(1951~1979年)和ID2(1980~2002年)两个年代际时段,研究西北太平洋7~9月登陆中国热带气旋路径的年代际变化.结果表明,登陆中国热带气旋存在明显的月际、年际和年代际变化,从ID1到ID2,热带气旋路径频数在东海和菲律宾海明显下降,而在南海略微有所上升.东海和南海热带气旋路径频数的时间序列进一步揭示了20世纪70年代末期热带气旋路径频数位置的变化.     

热带下平流层重力波的季节和年际变化特征

利用位于热带太平洋中的Truk岛（7.4°N，151.8°E）长达7年的（1998—2004年）高垂直分辨率探空观测资料分析了热带地区下平流层（18—25km）重力波活动的气候特征.分析结果显示，在该高度范围内，重力波活动表现出明显的季节变化，总能量在一月份达到最大，6月份最小；这种变化与北半球西风带向南扩张从而加强当地对流活动的气候特征是一致的.研究结果还表明，重力波活动还有显著的与赤道QBO周期一致的年际变化.赤道QBO的东风位相向西风位相转变的时段，重力波能量总是达到异常的最大，此地区重力波活动的年际变化与QBO密切相关.此外还介绍了重力波的其他参数，如固有频率，垂直波长和传播方向.     

ENSO影响热带大气季节内振荡的年代际变化特征

为了研究厄尔尼诺和南方涛动(ENSO)现象影响热带大气季节内振荡(ISO)的年代际变化特征,利用奇异值分解(SVD)、小波分析和经验正交函数分析(EOF)等方法对热带大气ISO强度指数、赤道中东太平洋海温及热带大气环流场进行了分析。计算结果显示,20世纪70年代中期以前,ENSO对热带大气ISO的影响较弱;70年代中期以后,ENSO对热带大气ISO的影响加强。造成上述年代际变化的原因与热带大气环流的年代际变化有关,因此,ENSO对热带大气ISO的影响也存在年代际变化。     

西北太平洋热带气旋气候特征及其变化研究的若干进展

为了对我国气象工作者全面了解和参与热带气旋的研究有所帮助,在大量阅读和调研的基础上,介绍了近20年西北太平洋热带气旋活动在季节、年际和年代际尺度上研究的若干主要成果.重点阐述了EN-SO与热带气旋的关系,温室效应热带气旋的数值模拟和观测研究等的最新动态.     

北太平洋海气系统主要模态的年代际变化

结合北太平洋各种指数、海表温度和高度场,分析了北太平洋海气系统的突变特征及其与时间尺度分量的联系.研究结果表明:各种指数、海表温度和高度场在20世纪60年代、70年代和90年代末期均存在显著突变;海表温度60年代的突变主要分布于北太平洋北部,70年代的突变主要分布于北太平洋北部、中部和东南部,90年代突变则主要分布于北太平洋东南部和西南部;高度场突变主要分布于北太平洋北部、西北部和东南部,且突变范围从高层向低层递减.各种指数中60年代突变1～8a尺度分量的贡献较大,70年代突变是20～30a尺度分量的贡献较大,90年代的突变则是1～8a尺度和20～30a尺度分量作用相当.在3个突变时期中,海表温度和高度场的空间分布及相关性分析验证了这种联系的可能性.     

热带印度洋海温与海表面高度相关关系分析

为了研究热带印度洋偶极子(IOD)与海平面异常之间的相关性,采用经验正交函数分析方法(EOF)及Hilbert-Huang变换等统计方法,分析热带印度洋的海表面温度(SST)与海平面高度异常(SLA)的相关关系。通过对热带印度洋偶极子指数(DMI)与南方涛动指数(SOI)和SLA的相关性分析,得出IOD与El Nio-Southern Oscillation(ENSO)之间可能存在一定相关关系,此外,IOD与海平面变化有很好的相关性。通过对IOD爆发年的DMI以及海平面变化的分析,证实IOD具有季节锁相的重要特征,并探讨了该季节变化与海平面变化的相关关系。结果表明,IOD事件与海平面的变化这两者之间存在很强的一致性。     

热带印度洋海面温度与高度的相关性分析

基于海面温度与海面高度异常的月均数据,采用EOF、SVD和功率谱分析等方法,对热带印度洋海面温度与海面高度进行特征分析,研究两者在时空结构上的相关性。利用EOF方法分析出海面温度第二模态与海面高度第一模态的空间结构类似,呈现偶极型。相关分析与功率谱表明,两模态的时间序列存在滞后相关和类似的周期结构。SVD结果显示,第一耦合模态的相关系数达0.7左右,且左右场的空间形态呈现东西反相。这表明,海面高度偶极型与海面温度的单极型和偶极型存在着相关。同时,海面高度指数也表现与偶极子指数类似的结构特征。针对上述诊断分析事实特征,对海面温度和海面高度偶极子形成的物理机制进行了初步分析,总结了前人所做的一些工作,指出其中可能的影响因素。     

基于多卫星融合数据的海平面特征分析

利用1993—2008年法国空间局的AVISO多卫星融合高度计资料,采用随机动态、EOF等方法分析全球海平面变化的长期趋势、变化幅度以及季节变化的空间分布特征.结果表明:(a)1993—2008年间太平洋海平面呈西升东降的形态,印度洋绝大部分海区海平面呈上升趋势,大西洋除湾流流域外的其他海区海平面的长期趋势以上升为主;(b)全球海平面变化存在显著的年变化和半年变化等季节信号,无论是半球平均还是洋盆平均,北半球海平面季节变化的振幅明显大于南半球,中纬度海区季节变化的振幅最大;(c)北印度洋海平面季节变化的振幅高于同纬度带的北太平洋和北大西洋;(d)太平洋、印度洋、大西洋三大洋受西边界流、赤道流系等强流影响的海域海平面变化幅度大于周围海域;(e)赤道海域各大洋东、西边界和大洋内区海平面变化不同步,可能受赤道海洋波动的影响较大;(f)厄尔尼诺年,西太平洋暖池和赤道太平洋中部海平面明显降低,赤道东太平洋海域海平面明显升高,赤道印度洋海域东、西边界的海平面变化与其相反.     

Circulation in the western tropical Pacific Ocean and its seasonal variation

An assimilation data set based on the GFDL MOM3 model and the NODC XBT data set is used to examine the circulation in the western tropical Pacific and its seasonal variations. The assimilated and observed velocities and transports of the mean circulation agree well. Transports of the North Equatorial Current (NEC), Mindanao Current (MC), North Equatorial Countercurrent (NECC) west of 140°E and Kuroshio origin estimated with the assimilation data display the seasonal cycles, roughly strong in boreal spring and weak in autumn, with a little phase difference.The NECC transport also has a semi-annual fluctuation resuiting from the phase lag between seasonal cycles of two tropical gyres' recirculations. Strong in summer during the southeast monsoon period, the seasonal cycle of the Indonesian throughfiow (ITF) is somewhat different from those of its upstreams, the MC and New Guinea Coastal Current (NGCC), implying the monsoon's impact on it.     

Premonitory phenomenon of El Ni(n)o event reflected in the observations of LOD and sea level

Data sets of the changes of the length of day, the sea surface temperature in the eastern Pacific and of the sea level in Hong Long from tide gauge observations are used to analyze and reveal the reflections in the observations of the length of day and the sea level changes concerned with the premonitory phenomenon of next El Ni(n)o event. The results from this study indicate that a new El Ni(n)o event has been brewing with the ending of the strong La Nina event that started in early summer of 1998. The estimated formation period of the new El Ni(n)o event will begin before the end of 2000, and the peak period may be reached at around the end of 2001.     

Connection between interannual variability of the western Pacific and eastern Indian Oceans in the 1997 - 1998 El Nino event

In this paper, the sea surface height and the heat content of the upper ocean are analyzed to retrieve the relationship of interannual variabilities between the tropical western Pacific and eastern Indian Oceans during the 1997 - 1998 El Nino event. In the prophase of this El Nino, the negative sea level anomalies (SLA) occurred in the tropical western Pacific (TWP) firstly, and then appeared in the tropical eastern Indian Ocean (TEI). The negative heat content anomalies (HCA) emerged in the TWP before this El Nino burst while the SLA signals developed over there. During the mature stage of this El Nino, two kinds of signals in the TWP and TEI turned to be the maximum negative sequently. Due to the connected interannual adjustment between the TEI and TWP, we adopted a method to estimate the Indonesian Throughflow (ITF) transport by calculating the HCA budget in the TEI. The indirect estimation of the ITF was comparable to the observation values. Therefore, the anomalies in the TEI had been proved as adv     

Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

Relationship between the tropical cyclone genesis over the Northwest Pacific and the sea surface temperature anomalies

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.     

Interdecadal variability in the tropical Indian Ocean and its dynamic explanation

Interdecadal variability in the tropical Indian Ocean has been analyzed based on the long-term climatic observational data. Case study showed that strong interannual signals formed at the surface can penetrate the depth of seasonal thermocline, where the anomalies last a couple of years. Artificial time series based on damping with exponential decay of selected strong events agree well with the detected interdecadal variability in the tropical Indian Ocean. A possible dynamic explanation for interdecadal variability in the tropical Indian Ocean was proposed that irregular interannual signals can lead to a slowly evolving climatic background with the interdecadal time scale through damping of the memory about anomalies in the seasonal thermocline.     

The pathway of the interdecadal variability in the Pacific Ocean

Cases of the interdecadal variability in the Pacific Ocean and their evolution were examined in the paper with the statistic methods (CEOF and composite analysis) over the period of 1950–1993. Observations of oceanic temperatures in the upper 400 m revealed an obvious region of the interdecadal signals in the central North Pacific. Such signals propagated southwestward, then subducted to the subtropics. The hypothesized link for interdecadal oceanic variability between the subtropics and the tropics, especially with the western tropical Pacific was unraveled in order to detect the cause of decadal signals in the tropics. The thermal anomalies subducted in the central North Pacific east to the dateline only reach 18°N. There has been no further southward propagation since then due to a certain barrier. The origin of the interdecadal signals in the western tropical Pacific was traced to the southern tropical Pacific. There is a meridional pathway around the dateline where the signals were loaded. These variabilities were in the nature of the thermocline circulation.