固体地球-海洋-大气耦合的一个简单线性模式及其试验结果

选取实际的海陆边界,建立了一个固体地球-海洋-大气耦合的简单线性模式,模式中包含了地气角动量守恒的关系,地转变速摩擦力对大气的作用,风吹流改变海温异常,海温异常又改变大气的质量分布。在无外源作用于地球系统的情况下,地球系统内部的各个部分(纬向风、海温和地转速度)都存在着准两年振荡(QBO),由此可见,QBO是地球系统内部的一种固有振荡。     

ENSO循环的数值模拟(Ⅱ)──变化性及时间尺度选择机制

利用热带太平洋海气耦合异常模式的３０ａ模拟结果，对模式ＥＮＳＯ的变化性及多重时间尺度过程进行了细致分析，建立了一ＥＮＳＯ循环多重时间尺度过程相互作用的非线性相似（Ａｎａｌｏｇ）模型，并提出了ＥＮＳＯ循环主周期形成的一种可能机制。指出：和观测事实类似，模式ＥＮＳＯ过程确实涉及到三种时间尺度，即３—４ａ主周期振荡（ＬＦ）、准两年振荡（ＱＢ）和年循环（ＡＣ）；其中，ＱＢ过程是线性海气耦合系统的本征模态，年循环（ＡＣ）对其形成没有本质的影响；３—４ａ主周期振荡（ＬＦ）是一非线性系统的自激振荡现象，其形成是线性系统的本征模即ＱＢ过程通过非线性机制尤其是通过大气辐合反馈加热的“单向性”过程在ＱＢ的暖态产生的减频增幅所致；平均年循环（ＡＣ）虽然不能对ＥＮＳＯ循环形成有本质影响，但它可明显影响ＥＮＳＯ循环的具体振幅和位相，使得ＥＮＳＯ循环具有明显的不规则性并对季节循环具有明显的“锁相”特征；ＥＮＳＯ变化性确是ＬＦ、ＱＢ以及ＡＣ多重时间尺度相互作用形成的。本文提出的ＥＮＳＯ循环时间尺度选择机制不仅解释了主周期振荡的形成过程，而且也较好地解释了ＥＮＳＯ变化的谱，因此，这一机制更接近于观测事实。     

印度洋-太平洋海温长期变化的周期性及其年代际变化

运用小波分析方法对近百年来印度洋－太平洋海温的周期变化特征进行了详细讨论,并且结合以前的工作,运用方差分析的方法对近半个世纪以来各周期振荡水平分布的年代际变化进行了综合分析。研究表明：近百年中,赤道东太平洋海温的长期变化不仅具有准两年（ＱＢＯ）和３－７年（ＬＦＯ）的年际振荡,而且具有１０－１２年、１８－２０年和３０－４０年的年代际振荡。各振荡分量的振幅和周期具有显著的年代际变化特征。近半个世纪各振     

CISK、蒸发-风反馈机制和热带大气30-60天振荡

建立一个包含ＣＩＳＫ机制和蒸发－风反馈机制（Ｅｖａｐｏｒａｔｉｏｎ－ＷｉｎｄＦｅｅｄｂａｃｋＭｅｃｈａｎｉｓｍ，简写为：ＥＷＦＭ）的热带大气运动的无耗散、线性斜压半地转模式，引入反映ＣＩＳＫ的无量纲凝结潜热参数η和反映ＥＷＦＭ的无量纲参数α，并求得模式系统的解析解。动力学分析和模式大气的计算结果进一步说明了ＣＩＳＫ和ＥＷＦＭ的共同作用是激发和驱动热带大气低频振荡的重要物理过程。     

季风异常,ENSO事件和地气角动量交换

季风异常和ＥＮＳＯ事件是发生在低纬地区的年际大气和海洋异常现象。本文把近年来这方面的分散研究集中到固体地球，全球海气相互作用的地球系统中来，揭示出季风异常和ＥＮＳＯ事件以及其它的大气和海洋事件的固海气相互作用的反映。这一分析具体得到下列认识：（１）南方涛动（ＳＯ）是太平洋东西部海温异常与山脉地形共同作用在海平面气压场上的反映；（２）在地球系统的年际变化中，除了大气对海洋的动力作用和海洋对大气的热力     

海温对热带低频振荡系统影响的动力学研究

根据热带地区蒸发、辐合上升运动剧烈以及海温异常的特点，构造了一个斜压模式方程组，讨论了海表温度（海温加热和海温异常变化）对热带低频波动的影响。分析表明，对天气尺度波动（Lx～Ly～10^6m），采用完全非地转模式，在海温异常作用下，频率明显发生变化，并容易产生波动的不稳定：海温较低时，波稳定，并随海温的增高，频率变低，波速变慢；海温较高时，会引起波动不稳定，且周期随海温的增高而变小。对超长波系统（Lx～10^7m,L,～10^6m），可以采用半地转模式，海温作用可以激发向东传播的低频Kelvin波以及向西传播的低频Rossby波，热带超常波的波动周期随海温升高和异常增大而变长，且在海温异常作用下，波动会产生不稳定。     

赤道东太平洋海温异常增暖对低频振荡影响的数值试验

为研究海温的异常增暖对３０－６０天低频振荡的影响，利用ＯＳＵ两层大气环流模式作了两组试验：一组使用气候平均海温，另一组包括两个试验，它们分别设正的海温距平（ΔＳＳＴ）中心位于赤道东太平洋的东部（１００°Ｗ）和中部（１４５°Ｗ）。结果表明：赤道东太平洋冬半年的海温异常增暖可改变低频振荡方差贡献的地理分布，其中当正的ΔＳＳＴ中心位于赤道东太平洋的东部时，热带印度洋和西太平洋地区的低频振荡的方差贡献较为显著，而热带东太平洋的低频振荡较为不活跃；当正的ΔＳＳＴ中心位于赤道东太平洋的中部时，情形则相反，即热带东太平洋的低频振荡的方差贡献较显著，而西太平洋地区的则不活跃。在赤道东太平洋海温异常增暖过程中，低频振荡的传播特性对ΔＳＳＴ中心位置的响应是敏感的，即当正的ΔＳＳＴ中心位置偏于该海区的东部或中部时，低频振荡的传播方向和传播速度有明显的差异     

7月份降雨分布型的预报方法

综述了我国７月份雨型的划分方法，各种雨型的多雨特点及环流特征，总结了各类雨型的预报判据，着眼于赤道东太平洋海温（ＳＳＴ），冬季（１－３月）５００ｈＰａ环流，春季（３－５月）西太平洋副热带高压，夏季（６－８月）赤道平流层纬向风准两年振荡（ＱＢＯ）等方面，分析了与７月雨型的关联。该方法对业务预报有很好的指导意义。     

60～70oS臭氧总量的QBO和ENSO信号

本文利用Ｎｉｍｂｕｓ－７上搭载的臭氧总量观测光谱仪（ＴＯＭＳ）得到的６０～７０ｏＳ纬圈中臭氧总量资料,分析研究了该地区臭氧总量准两年振荡（ＱＢＯ）和ＥＮＳＯ信号的纬向分布,指出在该纬圈臭氧总量的长期变化中包含着的ＱＢＯ和ＥＮＳＯ信号。同时,本文还分析研究了沿纬圈分布的大气臭氧总量季节变化和长期变化趋势,指出在该纬圈各个季节中臭氧总量呈下降趋势,以６０～１００ｏＷ十月份的下降最大,达到－９．３ＤＵ／ａ。研究同时表明：臭氧总量季节变化、长期变化趋势、以及ＱＢＯ信号的纬向分布都在西南极上空出现异常。本文对此进行了讨论,认为这是西南极海陆分布调整大气环流及大气波动造成对臭氧总量分布和变化的影响     

广东省森林火险等级的评价模式

利用美国ＮＯＡＡ－ＣＡＣ、夏威夷大学、中国气象局提供的热带太平洋海温，水位及风场资料和“ＴＯＧＡ－ＣＯＡＲＥ”（１９９２年１１月－１９９３年２月）提供的赤道西太平洋深层海温资料，对１９９３年全球大气及热带海洋异常状况作了诊断分析，认为１９９３年世界气象灾害频频发生的原因是：（１）大气环流的异常变化对１９９３年东传型ＥＮＳＯ事件的响应几乎同步。（２）１９９１、１９９３年两次东传型ＥＮＳＯ事件在短期内     

外强迫对热带季节内振荡影响的模拟研究

应用经过修改的NCAR CCM3模式和CAM2模式进行的数值实验结果以及NCEP的GFS模式的输出结果讨论了海温等外强迫作用对热带季节内振荡的影响.结果表明,热带季节内振荡是热带大气固有的内部变率.它是由大气内部过程的相互作用决定的.但外强迫对热带季节内振荡的强度、传播方向等有明显的影响.当外强迫没有变化时,模式可以模拟出与观测近似的低频振荡.当作为外强迫的海温和太阳辐射有年内季节变化时,模式模拟的季节内振荡则明显减弱.当海温与辐射不仅有季节变化而且有年际变化时,模式模拟的季节内振荡会进一步减弱.具有长周期的外强迫还会削弱季节内振荡中东移波动的能量而增加静止波的强度.在与海洋模式耦合的状态下,模式不受来自海洋的外强迫影响,而是与海洋构成一个耦合系统,可以产生最强的季节内振荡.     

中国东部夏季降水准两年振荡的主振荡型分析

利用中国160个测站月降水资料和NCEP/NCAR再分析月平均资料,选取中国东部夏季降水准两年振荡(TBO)分量做主振荡型分析(POP)和伴随相关分析(ACP)。结果表明:第一个POP对占东部夏季降水TBO总方差的18.2%,循环周期约为4年。实部为过渡型,振幅在1950年代中期和1980年代初期明显增大,在1980年代中后期到1990年代中期振幅的TBO特征异常显著。虚部为峰值型,在华南东部—长江流域—江淮流域有大范围的正值中心,高值中心位于长江—江淮流域,华南中西部为一负中心。虚部型振幅,1990年代中后期虚部型的振幅有明显加强。海温的伴随相关说明东部夏季降水TBO过渡型与西太平洋海温异常相对应,峰值型与赤道中东太平洋海温异常相对应。850 hPa风场异常、赤道纬向风异常和经向垂直环流异常的伴随相关显示,当POP对处于过渡型(负过渡型)时西太平洋对流旺盛(弱),南海上空有反气旋(气旋)生成。当POP对处于峰值型(负峰值型)时,赤道上Walker环流减弱(加强),经向上Hardly环流位置偏南(北),强度加强(减弱)。总之,中东太平洋海温异常与东部夏季降水TBO的传播有着密切联系,并通过海气相互作用和低纬与中高纬的相互作用来影响中国东部夏季降水TBO的传播,南北半球环流的相互作用也需要进一步探讨。     

Interdecadal variability over the North Pacific in a multi-century climate simulation

Interdecadal variability in the North Pacific region is investigated in a 500-y control integration of the Hamburg ECHAM+LSG coupled ocean-atmosphere general circulation model. The spectrum is predominantly red, but a significant peak with a period of about 18 y is detected in the spectrum of sea surface temperature (SST). This peak is shown to be associated with an irregular oscillation that involves both the model ocean and atmosphere. The SST, sea-level pressure, and geopotential height at 500 hPa all undergo a primarily standing oscillation with an extensive monopole structure centered near the date line. The surface anticyclone is situated to the northeast of the warm SST anomaly, and there is a small westward tilt with height; temporal changes are approximately in phase. The anomalous surface heat flux accompanying the warm phase of SST is primarily out of the ocean, but is compensated by anomalous warm advection by surface currents, allowing the SST anomaly to persist. Oceanic thermocline anomalies propagate northward in the western Pacific, and lag the atmosphere indicating a disequilibrium with the atmosphere; sub-surface thermal advection appears to play an important role. A comparison is made between the model's 18-y oscillation and oscillatory components identified in an analysis of the GISST observational SST dataset, which have periods of approximately 6 and roughly 30 y.     

FEATURES AND COMPARISONS OF THE QUASI-BIENNIAL VARIATIONS IN THE ASIA-PACIFIC MONSOON SUBSYSTEMS

The National Centers for Environmental Prediction (NCEP) reanalysis data, Climate Diagnostics Center Merged Analysis of Precipitation (CMAP) results, and NOAA Extended Reconstructed Sea Surface Temperature (SST), have been utilized in this paper to study the quasi-biennial variations in Asia-Pacific monsoon subsystems and associated SST anomalies (SSTA) and wind anomalies. Four monsoon indices are computed from NCEP/ National Center for Atmospheric Research (NCAR) reanalysis to represent the South Asian monsoon (SAM), South China Sea summer monsoon (SCSSM), Western North Pacific monsoon (WNPM) and East Asian monsoon (EAM), respectively. The quasi-biennial periods are very significant in Asia-Pacific monsoons (as discovered by power spectrum analysis), and for SAM and EAM---with moderate effects by El Ni?o-Southern Oscillation (ENSO)---the quasi-biennial periods are the most important factor. For SCSSM and WNPM (once again due to the effects of ENSO), the quasi-biennial periods are of secondary durations. There are obvious interdecadal variations in the quasi-biennial modes of the Asia-Pacific monsoon, so in the negative phase the biennial modes will not be significant or outstanding. The wind anomalies and SSTA associated with the biennial modes are very different in the SAM, WNPM and EAM regions. Since the WNPM and SCSSM are very similar in the biennial modes, they can be combined into one subsystem, called SCS/WNPM.     

The propagation characteristics of interannual low-frequency oscillations in the tropical air-sea system

The time series of sea surface temperature (SST), sea level pressure (SLP), zonal wind (U) and total cloudiness (CA), for the period of 1950-1979, over a 8o×8o grid-point latitudinal belt between 32oS and 32oN are made from COADS (Comprehensive Ocean-Atmosphere Data Set). The time harmonic analysis and power spectra analysis show that there exist quasi-biennial oscillation (QBO), three and half years oscillation (SO), five and half years oscillation (FYO) and eleven years oscillation (EYO) in these time series. The main propagation characteristics of these interannual low-frequency oscillations are as follows:(1) The variance analysis of SST shows that there is an active region of QBO and SO (with maximum variance), coming from the southwestern part of the subtropical Pacific, stretching eastward up to the west coast of South America, and then northward to the eastern equatorial Pacific. The QBO and SO disturbances of SST follow the same route and cause the anomaly of SST (El Nino and period of cold water) in the eastern equatorial Pacific.(2) Either the QBO or SO of SST can cause El Nino events, although it is easier when they are situated in the same phase of warm water at the eastern equatorial Pacific. The FYO of SST seems to be a standing oscillation. It plays an important role on the formation of strong El Nino events or strong cold water events.(3) The QBO and SO of U propagate eastward along the equator. The origin of QBO and SO may at least be traced as far as the western Indian Ocean. While they propagate along the equator, it strengthens two times at 90oE and the western Pacific, respectively. Like SST, the FYO of U is somehow a standing oscillation.(4) The Oscillations of U have a good coupling relationship with those of SST, while they propagate. When the QBO and SO of SST move to the east side of the eastern equatorial Pacific, it is the time for the QBO and SO of U to enter into the east part of the western Pacific.It is clear that, when we do research work on the formation of El Nino events, our consideration would not be confined to the tropics, it should cover the subtropical region in the southern Pacific. The features of the circulation and other oceanic states in this area are very important to the El Nino events.     

近百年全球平均气温年际变率中的QBO长期变化特征

应用奇异谱分析(SSA)方法和奇异交叉谱分析(SCSA)方法，对全球及南北半球近100多年(1856～1997年)逐月地面气温距平序列中的准两年周期振荡(QBO)的长期演变特征进行诊断分析。结果表明:全球平均气温序列蕴含显著的QBO分量，它们与全球气候系统中其他各个子系统所隐含的QBO信号具有各种耦合对应关系，尤其突出地表现在Nino区海温和以SLP序列为代表的全球大气环流系统中QBO信号的耦合对应关系上。而平均气温的QBO的年代际特征及其变率的阶段性，不但表现在振幅上，而且其位相亦很明显。上述特征在全球、两半球具有明显的差异。     

A NUMERICAL STUDY OF SHORT-RANGE CLIMATIC OSCILLATION WITH VARIOUS TIME SCALES FORCED BY EL NINO DURING THE NORTHERN SUMMER

The normal mode method is adopted to decompose the differences between simulations with SST(seasurface temperature)anomahes over centra-eastern Pacific and normal SST by use of a nine-layer global spec-tral model in order to investigate short-range climatic oscillation with various time scales forced by ElNino during the northern summer.Investigation shows that El Nino may have the following influence onatmosphere on various space-time scales.Extra-long wave components of Rossby mode forced by convectiveanomaly over equatorial western Pacific resulting from El Nino produce climatic oscillation on monthly(sea-sonal)time scale in middle-high latitudes of Southern and Northern Hemispheres;extra-long wave componentsof Kelvin mode forced by SST anomalies propagate along the equator,resulting in 30—60 day oscillation oftropical and subtropical atmosphere;and its long waves move eastward with westerly,resulting in quasi-biweekoscillation.     

加利福尼亚附近的海温强迫及其与北太平洋年代际振荡的可能联系

本文利用1958～2018年期间海表面温度（SST）异常和湍流热通量异常变化的关系,探讨了其与北太平洋年代际振荡（PDO）相关的年际和年代际时间尺度上在不同海域的海气相互作用特征。结果表明:在年际尺度上,黑潮—亲潮延伸区（KOE）表现为显著大气强迫海洋,赤道中东太平洋表现为显著海洋强迫大气;在年代际尺度上,PDO北中心表现为大气强迫海洋,加利福尼亚附近则表现为显著海洋强迫大气。进一步分析表明:加利福尼亚附近区域是北太平洋准12年振荡的关键区域之一,与PDO准十年的周期类似,加利福尼亚附近的冷（暖）海温对应其上有反气旋（气旋）型环流,赤道中太平洋海水上翻和北太平洋东部副热带区域经向风应力的变化是北太平洋准12年振荡的另外两个重要环节。     

Isolating mesoscale coupled ocean–atmosphere interactions in the Kuroshio Extension region

The Kuroshio Extension region is characterized by energetic oceanic mesoscale and frontal variability that alters the air–sea fluxes that can influence large-scale climate variability in the North Pacific. We investigate this mesoscale air-sea coupling using a regional eddy-resolving coupled ocean–atmosphere (OA) model that downscales the observed large-scale climate variability from 2001 to 2007. The model simulates many aspects of the observed seasonal cycle of OA coupling strength for both momentum and turbulent heat fluxes. We introduce a new modeling approach to study the scale-dependence of two well-known mechanisms for the surface wind response to mesoscale sea surface temperatures (SSTs), namely, the ‘vertical mixing mechanism’ (VMM) and the ‘pressure adjustment mechanism’ (PAM). We compare the fully coupled model to the same model with an online, 2-D spatial smoother applied to remove the mesoscale SST field felt by the atmosphere. Both VMM and PAM are found to be active during the strong wintertime peak seen in the coupling strength in both the model and observations. For VMM, large-scale SST gradients surprisingly generate coupling between downwind SST gradient and wind stress divergence that is often stronger than the coupling on the mesoscale, indicating their joint importance in OA interaction in this region. In contrast, VMM coupling between crosswind SST gradient and wind stress curl occurs only on the mesoscale, and not over large-scale SST gradients, indicating the essential role of the ocean mesocale. For PAM, the model results indicate that coupling between the Laplacian of sea level pressure and surface wind convergence occurs for both mesoscale and large-scale processes, but inclusion of the mesoscale roughly doubles the coupling strength. Coupling between latent heat flux and SST is found to be significant throughout the entire seasonal cycle in both fully coupled mode and large-scale coupled mode, with peak coupling during winter months. The atmospheric response to the oceanic mesoscale SST is also studied by comparing the fully coupled run to an uncoupled atmospheric model forced with smoothed SST prescribed from the coupled run. Precipitation anomalies are found to be forced by surface wind convergence patterns that are driven by mesoscale SST gradients, indicating the importance of the ocean forcing the atmosphere at this scale.