Perturbed solution of sea-air oscillator for the El Niño/La Niña-Southern Oscillation mechanism

A class of coupled system of the El Niño/La Niña-Southern Oscillation (ENSO) mechanism is studied. Using the perturbed theory, the asymptotic expansions of the solution for ENSO model are obtained and the asymptotic behavior of solution for corresponding problem is considered.     

两类厄尔尼诺事件对金华气候的影响

利用金华本站历史观测资料,分别就两类厄尔尼诺事件次年降水量、梅雨、高温日数、日照时数和台风等情况逐一进行分析探讨。结果表明:两类厄尔尼诺事件对金华气候的影响存在显著的差别,第1类影响年金华年降水量偏多,是涝年。入梅偏早,出梅偏晚,梅期偏长,降水量比常年偏多。日照时数比常年偏少,出现高温天数少,高温天气不严重。第2类影响年正好相反,金华年降水偏少,是旱年,入梅容易偏晚,出梅偏早,梅期偏短,梅雨量偏少,日照比常年偏多,高温出现也多,是高温天气比较严重的年份。     

西风爆发事件对暖池厄尔尼诺和冷舌厄尔尼诺的作用——一个概念模型得到的结果

本文通过1个概念模型讨论了西风爆发事件对暖池厄尔尼诺与冷舌厄尔尼诺两种事件的作用,并讨论了它们对应的物理机制。结果表明,由西风爆发所诱导的纬向平流异常和海洋波动对厄尔尼诺的多样性有着至关重要的作用。由于模型包含了最基本的海-洋与大气物理变量及其相互作用机制,本结果可为解释西风爆发事件对厄尔尼诺多样性影响研究提供最基本的框架。     

利用卫星测高技术监测厄尔尼诺和拉尼娜现象

利用美国宇航局和法国空间局联合公布的T／P数据（1993-2000年）和Jason-1数据（2002—2006年），由共线法计算了热带太平洋地区海平面高度的变化。根据T／P和Jason-1数据计算的海面月变化异常图，分别研究了和分析了1997-1998年的厄尔尼诺和拉尼娜现象、2002-2003年厄尔尼诺现象的变化发展过程。     

1997∽1998年厄尔尼诺事件的特征、成因及对气候的影响

1997年爆发了20世纪以来最强的一次厄尔尼诺事件。此次ElNin～o事件的发生,与赤道中、西太平洋地区大气季节内振荡(ISO)在1996年冬到1997年春的异常增强有重要关系。西太平洋暖池次表层海温(SOT)正距平沿温跃层东传到赤道东太平洋并向海洋表层扩展是ElNin～o事件爆发的直接原因。1997～1998年的ElNin～o事件爆发后,引起全球大气环流和世界许多地区的气候异常,导致一些国家和地区多雨洪涝,另外一些国家和地区高温少雨和严重干旱。     

El Niño/Southern Oscillation (ENSO) Related Variations in Particulate Export Fluxes in the Western and Central Equatorial Pacific

Time-series data from sediment trap moorings intermittently deployed during 1991–1999 show that the fluxes of biogenic material (carbonate, opal and organic matter, including amino acids) and other related parameters are temporally and spatially distinct across the Western Pacific Warm Pool (WPWP). These variations resulted from the El Niño and La Niña conditions, which alternately prevailed over the equatorial Pacific Ocean during the mooring deployments. The westernmost WPWP (a hemipelagic region) recorded relatively high average total mass and amino acid fluxes during the El Niño event. This was in sharp contrast to the eastern part of the WPWP (oligotrophic and weak upwelling regions) which recorded higher flux values during the La Niña event. Settling particulate organic matter was rich in labile components (amino acids) during La Niña throughout the study area. Relative molar ratios of aspartic acid to β-alanine together with relative molar content of non-protein amino acids β-alanine and γ-aminobutyric acid) suggested that organic matter degradation was more intense during La Niña relative to that during El Niño in the WPWP. This study clearly shows that during an El Niño event the well documented decrease in export flux in the easternmost equatorial Pacific is accompanied by a significant increase in export flux in the westernmost equatorial Pacific Ocean.     

2011/2012年我国冷冬与中部型La Ni(n)a事件的联系

应用中国气象局国家气候中心提供的160个站逐月气温观测资料以及74项环流特征量中西太平洋副热带高压资料、TAO实测资料以及美国国家海洋和大气局提供的OLSST海表温度资料和NCEP-NCAR再分析资料,采用合成分析、相关分析等统计诊断方法,对2011/2012年我国冬季的天气状况,以及大气环流异常及其对我国气候产生影响的可能机理进行了分析,为我国气候变化预测提供参考.结果表明,2011/2012年我国冬季(DJF)出现异常寒冷的天气状况可能与2011/2012年赤道太平洋海表温度冷异常最大值出现在中部太平洋的La Ni(n)a事件(简称中部型La Ni(n)a事件)的爆发存在一定联系.赤道太平洋海表温度的异常分布对北半球大气环流形势产生重要影响,它直接影响着赤道地区Walker环流和Hadley环流的异常,导致西太平洋副热带高压的异常偏弱、偏东.由于西太平洋副热带高压偏弱、偏东,对冬季的经向环流产生重要影响,最终导致我国2011/2012年冬季出现冷冬现象.     

地球系统模式FIO-ESM对2016-2017年La Ni(n)a事件及其对中国近海地区影响的预测

最近的观测表明赤道太平洋中部及东部的水温略低于拉尼娜事件的阈值,但大气与海洋的状态还不足以完全支持转为弱拉尼娜现象.本研究基于地球系统模式FIO-ESM和集合调整卡尔曼滤波同化方案建立的短期气候同化和预测系统,进行了1992-01-01-2016-10-31的模式同化,结果表明同化系统能够为预测提供较好的初始场.随后对2016-2017年拉尼娜事件的状态以及中国近海地区气温和降水异常进行了未来6个月的预测,结果表明赤道太平洋会在2016年年底继续降温,Ni(n)o3.4区海温异常将持续略低于拉尼娜事件的阈值-0.5 ℃,说明2016-2017年为弱拉尼娜事件,2017年春季东太平洋继续降温,表明此次拉尼娜事件可能会持续较长时间.预测结果同时也表明2016年冬季至2017年春季中国近海地区存在着北高南低的气温异常分布,中国南部地区降水存在负异常.拉尼娜带来的极端天气与气候异常会对中国沿岸地区带来巨大影响,但总体来说2016-2017年拉尼娜事件对中国的影响相对较弱.     

厄尔尼诺/拉尼娜信号循环回路及其传播特性研究

基于1992～2001年卫星高度计资料分析了海面高度距平在厄尔尼诺/拉尼娜(El Niño/La Niña)现象中的演变过程,发现:(1)在El Niño过程中,海面高度正距平信号从西太平洋沿赤道海域向东传播至东海岸,然后分成南北两支,北支在10°N附近从东太平洋传回西太平洋的信号最强,到达西太沿岸海域再传回赤道,表明El Niño信号传播在北半球存在一明显循环回路.赤道以南循环圈不及赤道以北环路清晰.东太平洋的季节变化信号主要通过6°N,10°N和8°S附近的3个通道向西太平洋传播.La Niña信号主要从5°N和7°S向西传播;(2)在大洋海盆尺度快速传播信号背景下,存在波长700～800km的慢速传播信号,两类信号将信息在太平洋内传送.传播速度分析表明,慢速传播信号的相速与Rossby波相速相符,而快速传播信号应该是海洋对大气变异的响应.     

Hydrography, nutrients and chlorophyll during El Niño and La Niña 1997–99 winters in the Gulf of the Farallones, California

Nutrient and chlorophyll concentrations were measured in January 1997, 1998 and 1999 in the Gulf of the Farallones, CA at locations stretching north/south from Point Reyes to Half Moon Bay, and seaward from the Golden Gate to the Farallon Islands. The cruises were all carried out during periods of high river flow, but under different climatological conditions with 1997 conditions described as relatively typical or ‘neutral/normal’, compared to the El Niño warmer water temperatures in 1998, and the cooler La Niña conditions in 1999. Near-shore sea-surface temperatures ranged from cold (9.5–10.5°C) during La Niña 1999, to average (11–13°C) during 1997 to warm (13.5–15°C) during El Niño 1998. Nutrients are supplied to the Gulf of the Farallones both from San Francisco Bay (SFB) and from oceanic sources, e.g. coastal upwelling near Point Reyes. Nutrient supplies are strongly influenced by the seasonal cycle of fall calms, with storms (commencing in January), and the spring transition to high pressure and northerly upwelling favorable winds. The major effect of El Niño and La Niña climatic conditions was to modulate the relative contribution of SFB to nutrient concentrations in the coastal waters of the Gulf of the Farallones; this was intensified during the El Niño winter and reduced during La Niña. During January 1998 (El Niño) the oceanic water was warm and had low or undetectable nitrate, that did not reach the coast. Instead, SFB dominated the supply of nutrients to the coastal waters. Additionally, these data indicate that silicate may be a good tracker of SFB water. In January, delta outflow into SFB produces low salinity, high silicate, high nitrate water that exits the bay at the Golden Gate and is advected northward along the coast. This occurred in both 1997 and 1998. However during January 1999, a La Niña, this SFB feature was reduced and the near-shore water was more characteristic of high salinity oceanic water penetrated all the way to the coast and was cold (10°C) and nutrient rich (16 μM NO₃, 30 μM Si(OH)₄). January chlorophyll concentrations ranged from 1–1.5 μg l⁻¹ in all years with the highest values measured in 1999 (2.5–3 μg l⁻¹) as a result of elevated nutrients in the area. The impact of climatic conditions on chlorophyll concentrations was not as pronounced as might be expected from the high temperatures and low nutrient concentrations measured offshore during El Niño due to the sustained supply of nutrients from the Bay supporting continued primary production.     

解Schr(o)dinger方程的一种修正的Runge-Kutta方法

在经典的四阶Runge-Kutta(简记为RK)方法的基础上,得到一种新的解Schr(o)dinger方程的修正的RK方法,并证明这个方法的代数阶为4.这个方法的稳定性和相性质分析也在本文中给出,新方法的相误差阶为6,耗散误差阶为5,并且通过数值试验证明了新方法的高效性.     

两类强度厄尔尼诺和拉尼娜事件对中国近海鲐鱼栖息地的影响

鲐鱼是中上层鱼类,具有较高经济价值,其种群受到气候和海洋环境的显著影响。本文根据2006-2015年7-9月中国远洋渔业数据中心提供的中国近海鲐鱼捕捞和海表温度以及海面高度两个关键环境因子的数据,构建了基于捕捞努力量的鲐鱼综合栖息地指数模型,分析研究了在不同强度厄尔尼诺和拉尼娜条件下鲐鱼栖息地适宜性的变动规律。通过计算和交叉验证,结果发现,基于算术平均法的栖息地模型能够较好地预测鲐鱼渔场栖息地适宜性指数。空间相关性结果表明,鲐鱼渔场主要作业海域范围内海表温度异常与栖息地指数值呈显著正相关关系,而海表面高度异常与栖息地指数值呈显著负相关关系。不同强度厄尔尼诺和拉尼娜事件对鲐鱼种群影响不同,具体表现为:相对于中强度厄尔尼诺事件（或中强度拉尼娜事件）,超强厄尔尼诺事件（或强拉尼娜事件）驱动鲐鱼主要作业海域内温度下降（或上升）,海面高度上升（或降低）,鲐鱼渔场适宜栖息地面积显著减小（或增大）,导致鲐鱼单位捕捞努力量渔获量骤减（或显著增加）。研究表明,中国近海鲐鱼栖息地适宜性与厄尔尼诺和拉尼娜事件显著相关,且随着异常气候事件强度的不同而发生变化。     

具有高阶奇点的2n+1次系统

研究1类具有2个零特征根和1个4n2 2n 1阶奇点的2n 1次系统,并给出了极限环存在与否的条件。     

Distribution of whitemouth croaker (Micropogonias furnieri, Desmarest 1823) larvae in the Río de la Plata estuarine front

Whitemouth croaker (Micropogonias furnieri) larvae obtained and hydrographic data collected in the Rio de la Plata estuary (35°S–56°W) between 1987 and 2000 were used to explore the early life stages spatial and temporal distribution patterns and their relation to oceanographic features. The spatial distribution, restricted to a band in the inner part of the estuary, coincided with the bottom salinity front and the maximum turbidity zone (MTZ, turbidity front). Larvae were present during the warmest months (October through May) within a range of 14–24.5 °C temperature and 0.9–33 salinity. A vertically stratified sampling performed in the region where the largest abundance was found (December 2005 and March 2006) was used to test the hypothesis that larvae retention occurs in the bottom salinity front.The vertically stratified sampling showed larvae throughout the water column with high predominance in the river–estuary transition zone. A positive correlation between abundance and the bottom salinity horizontal gradient was found. The size analysis showed that the largest individuals (>10 mm SL), probably undergoing the settlement process, inhabited near the bottom and that the smallest (<10 mm SL) were present in the whole water column. Length distribution along the front showed no trend.Results support the estuarine retention hypothesis of previous studies on whitemouth croaker gravid females, eggs distribution and outcomes from a numerical simulation model. Retention in the salinity front/MTZ would allow larvae to benefit from food accumulation in the region, the high turbidity level provide shelter against predators and retention in the estuary secure closeness to the main nursery ground.     

基于GM(1,1)模型的海区大风灰色理论预测

根据灰色理论方法对影响东海某海区大风建立了GM(1,1)模型,并利用海区8~10月观测资料进行了对比分析,研究发现,该模型物理概念清晰,对9~10月海区大风预测效果较好,对海区灾害性大风长期预报具有一定的指导意义。     

A novel decomposition of the quadratic transfer function (QTF) for the time-domain simulation of non-linear wave forces on floating bodies

In the present study, a novel method is proposed for the separation of the second-order sum- and difference-frequency wave forces—that is, quadratic transfer functions (QTFs)—on a floating body into three components due to wave–wave, wave–motion, and motion–motion action. By applying the new QTF components, the second-order wave forces on a floating body can be strictly computed in the time domain. In this work, the boundary value problems (BVPs) corresponding to the three kinds of QTF components were derived, and non-homogeneous boundary conditions on the free surface and the body surface were obtained. The second-order diffraction potentials were determined using the boundary integral equation method. In the solution procedure, the highly oscillatory and slowly converging integral on the free surface was evaluated in an accurate and effective manner. Furthermore, the application of the QTF components in the time domain was demonstrated. The second-order exciting forces in the time domain were divided into three parts. Each part of these forces was computed via a two-term Volterra series model based on the incident waves, the first-order motion response, and the QTF components. This method was applied to several numerical examples. The results demonstrated that this decomposition yields satisfactory results.     

Emergence Patterns of Small Subtidal Arthropods in Relation to Day/Night, Tidal, and Surface/Bottom Factors: Investigations in the Boreal Sea, Japan (Akkeshi, Hokkaido)

The emergence of small arthropods was studied in the boreal sea, Japan (Akkeshi, Hokkaido). In the shallow subtidal zone, two impeller pumps were set in the surface and bottom waters. The pumps ran continuously for 25 days (22 August-16 September, 1998), and invertebrates were sampled using a nylon net (300 to 500 m in mesh size). The small arthropods collected with the net belonged to 16 orders comprising about 60 taxa. In the dominant 23 taxa, a two-way ANOVA was applied to determine whether there was any significant difference in abundance between day and night and between surface and bottom. While emergence of 15 taxa (65%) was significantly different with regard to the day/night factor, that of the other 8 taxa (35%) was not. As to the difference between the two depths, the distribution of 15 taxa (65%) was significantly different. Furthermore, in 25 taxa for which over 100 specimens were collected in each of the two depths of water, emergence patterns were examined with regard to the synchrony with day/night and tidal cycles. There were various nocturnal patterns, and the strength of the synchrony with the day/night cycle was different for each species or group. Within the same taxa, nocturnal patterns were more clearly manifested in the surface water than in the bottom water. A tidal rhythm of emergence was only seen in zoeas of shrimp. Variations of the emergence patterns of benthic crustaceans are accounted for by a hypothesis that the frequency of swimming during day versus at night is different in each species. On the other hand, the emergence patterns of some zooplankton reflect by the daily rhythm of vertical migration or dispersal in the water column.