Effects of adjusting vertical resolution on the eastern equatorial Pacific cold tongue

The vertical resolution of LICOM1.0 (LASG/IAP Climate System Ocean Model, version 1.0) is adjusted by increasing the level amount within the upper 150 m while keeping the total of levels. It is found that the eastern equatorial Pacific cold tongue is sensitive to the adjustment. Compared with the simulation of the original level scheme, the adjusting yields a more realistic structure of cold tongue extending from the coast of Peru to the equator, as well as a temperature minimum at Costa Rica coast, north of the cold tongue. In the original scheme experiment, the sharp heating by net surface heat flux at the beginning of spin-up leads to a great warm- ing in the eastern equatorial Pacific Ocean. The weak vertical advection due to a too thick mixed layer in the coarse vertical structure also accounts for the warm bias. The fact that most significant improvements of the upper 50 m temperature appear at the region of the thinnest mixed layer indicates the necessity of fine vertical resolution for the eastern equatorial Pacific Ocean. However, the westward extension of equatorial cold tongue, a defect in the original scheme, gets even more serious in the adjusting scheme due to the intensi- fied vertical velocity and hence vertical advection in the central-eastern equatorial Pacific Ocean.

Eastern equatorial Pacific SST seasonal cycle in global climate models: from CMIP5 to CMIP6

The sea surface temperature(SST)seasonal cycle in the eastern equatorial Pacific(EEP)plays an important role in the El Nino–Southern Oscillation(ENSO)phenomenon.However,the reasonable simulation of SST seasonal cycle in the EEP is still a challenge for climate models.In this paper,we evaluated the performance of 17 CMIP6 climate models in simulating the seasonal cycle in the EEP and compared them with 43 CMIP5 climate models.In general,only CESM2 and SAM0-UNICON are able to successfully capture the annual mean SST characteristics,and the results showed that CMIP6 models have no fundamental improvement in the model annual mean bias.For the seasonal cycle,14 out of 17 climate models are able to represent the major characteristics of the observed SST annual evolution.In spring,12 models capture the 1–2 months leading the eastern equatorial Pacific region 1(EP1;5°S–5°N,110°–85°W)against the eastern equatorial Pacific region 2(EP2;5°S–5°N,140°–110°W).In autumn,only two models,GISS-E2-G and SAM0-UNICON,correctly show that the EP1 and EP2 SSTs vary in phase.For the CMIP6 MME SST simulation in EP1,both the cold bias along the equator in the warm phase and the warm bias in the cold phase lead to a weaker annual SST cycle in the CGCMs,which is similar to the CMIP5 results.However,both the seasonal cold bias and warm bias are considerably decreased for CMIP6,which leads the annual SST cycle to more closely reflect the observation.For the CMIP6 MME SST simulation in EP2,the amplitude is similar to the observed value due to the quasi-constant cold bias throughout the year,although the cold bias is clearly improved after August compared with CMIP5 models.Overall,although SAM0-UNICON successfully captured the seasonal cycle characteristics in the EEP and the improvement from CMIP5 to CMIP6 in simulating EEP SST is clear,the fundamental climate models simulated biases still exist.

Correlations between Sea Surface Temperature in Eastern Equatorial Pacific and Rain Days over China in Summer

Sea-surface temperature (SST) in the eastern, equatorial Pacific and rain days over China in summer are analysed using correlation moments that is proposed by author and principal component analysis(PCA). Occurrences of the strong rain-day anomalies over China are associated with extreme SSTs in some years. Areas significantly affected by the phenomena include North and Northeast China.

Simulating Tropical Instability Waves in the Equatorial Eastern Pacific with a Coupled General Circulation Model

Satellite observations of SSTs have revealed the existence of unstable waves in the equatorial eastern Pacific and Atlantic oceans. These waves have a 20-40-day periodicity with westward phase speeds of 0.4-0.6 m s^-1 and wavelengths of 1000-2000 km during boreal summer and fall. They are generally called tropical instability waves （TIWs）. This study investigates TIWs simulated by a high-resolution coupled atmosphere-ocean general circulation model （AOGCM）. The horizontal resolution of the model is 120 km in the atmosphere, and 30 km longitude by 20 km latitude in the ocean. Model simulations show good agreement with the observed main features associated with TIWs. The results of energetics analysis reveal that barotropic energy conversion is responsible for providing the main energy source for TIWs by extracting energy from the meridional shear of the climatological-mean equatorial currents in the mixed layer. This deeper and northward-extended wave activity appears to gain its energy through baroclinic conversion via buoyancy work, which further contributes to the asymmetric distribution of TIWs. It is estimated that the strong cooling effect induced by equatorial upwelling is partially （-30%-40%） offset by the equatorward heat flux due to TIWs in the eastern tropical Pacific during the seasons when TIWs are active. The atmospheric mixed layer just above the sea surface responds to the waves with enhanced or reduced vertical mixing. Furthermore, the changes in turbulent mixing feed back to sea surface evaporation, favoring the westward propagation of TIWs. The atmosphere to the south of the Equator also responds to TIWs in a similar way, although TIWs are much weaker south of the Equator.

Response of global subtropical highs to the equatorial eastern Pacific SST anomaly

Based on the reanalysis data of global 500hPa geopotential height (NCEP NCAR CDAS-1) and tropical Pacific SSTs, the characteristics of global subtropical highs and their response to tropical eastern Pacific SST are investigated. Results show that global subtropical highs respond to SST consistently. Subtropical high intensity correlates to the 3 months leading SST maximally. The relationship between SST and 500hPa height stands out in low latitudes. The time for 500hPa height reaching maximuxn correlation to SST is 2 months later in latitude of 10 degree and 9 months in latitude of 30 degree than equatorial zone. And the response of atmospheric circulation over extratropic performs as wave train, and the response is more significant in the condition of warmer SST. Persistence of SSTs and subtropical highs changes obviously from season to season. Minimum persistence of subtropical highs in September and October may relate to the low persistence of SSTs in August and September.

The low frequency oscillations of the sea surface temperature in the Equatorial Eastern Pacific and El Nino formation

-In this paper the variations of the sea surface temperature anomalies (SSTA) in the Equatorial Eastern Pacific are analysed. The results show that there are two peaks in the spectrum. One is the low frequency oscillation with a period of 3 - 5 years, and the other is the quasi-biennial oscillation. The former shows a westward migration in the warm episode of SSTA and the latter has the opposite trend. The El Nino events will be formed while the two frquency bands are in phase in the warming stage of SSTA in the Equatorial Eastern Pacific

Examination of seasonal variation of the equatorial undercurrent termination in the Eastern Pacifi c diagnosed by ECCO2

Seasonal variations of the equatorial undercurrent(EUC) termination in the Eastern Pacific,and their mechanism were examined using the Estimating the Circulation and Climate of the Ocean,PhaseⅡ(ECCO2).The ECCO2 reproduced a weak and shallow eastward EUC east of the Galapagos Islands,with annual mean transport of half of EUC to the west of the Islands.The diagnosis of zonal momentum equation suggests that the zonal advection(nonlinear terms) drives the EUC beyond the Islands rather than the pressure gradient force.The EUC in the Far Eastern Pacific has the large st core velocity in boreal spring and the smallest one in boreal summer,and its volume transport exhibits two maxima in boreal spring and autumn.The seasonal variability of the EUC in the Eastern Pacific is dominated by the Kelvin and Rossby waves excited by the zonal winds anomalies in the central and Eastern Pacific that are associated with the seasonal relaxation or intensification of the trade wind.In the Far Eastern Pacific to the east of 120°W,the eastward propagation Kelvin waves play a dominate role in the seasonal cycle of the EUC,results in a semiannual fluctuation with double peaks in boreal spring and autumn.A construction of water mass budget suggests that approximately 24.1% of the EUC water east of 100°W has upwelled to the mixed layer by0.35 m/d.The estimated upwelling is stronge st during boreal autumn and weake st during boreal winter.It is also found that approximately 42.6% of the EUC turns westward to feed the south equatorial current(SEC),13.2% flows north of the equator,and 20.1% flows south of the equator,mainly contributing to Peru-Chile undercurrent.

基于海表温度遥感资料重构的热带不稳定波特征分析

[目的]研究赤道东太平洋热带不稳定波(tropical instability waves,TIWs)的时空分布特征及其驱动机制.[方法]利用数据插值经验正交函数方法对MODIS卫星2003-2018年赤道东太平洋海表面温度(sea surface temperature,SST)数据进行重构,进而提取TIWs的波长和速度,并分析其时空分布特征以及与赤道风场和流场的关系.[结果]研究发现:TIWs在纬向上呈正负相位交替分布,在经向上则表现为双峰结构.季节性方面,TIWs在3-5月强度最弱,而在8-10月强度最强.纬向风场通过影响赤道纬向流场,特别是南赤道流(South Equatorial Current,SEC)的北分支(SEC-N)和北赤道逆流(North Equatorial Countercurrent,NECC)的剪切调控TIWs的生成;经向风场则通过调制“冷舌”边缘的SST梯度影响TIWs的生成.在年际尺度上,TIWs在厄尔尼诺(El Nino)年受到抑制,在拉尼娜(La Nina)年得到加强.纬向风场、纬向流场和TIWs三者的异常均超前于厄尔尼诺-南方涛动(El Nino-Southern Oscillation,ENSO)指数所刻画的赤道东太平洋SST异常,这表明纬向风场影响下的纬向流场剪切同样驱动TIWs的年际变化.NECC上空纬向风异常较弱,而SEC-N上空纬向风异常较强,这使得SEC-N年际变化主导流场剪切的强度,对TIWs的年际特征有重要作用.[结论]这一发现强调了大气风场和海洋动力过程共同驱动TIWs的季节性特征和年际变化.

Impacts of the SSTs over Equatorial Central–Eastern Pacific and Southeastern Indian Ocean on the Cold and Rainy/Snowy/Icy Weather in Southern China

Low temperature together with snow/freezing rain is disastrous in winter over southern China.Previous studies suggest that this is related to the sea surface temperature(SST)anomalies,especially La Nina conditions,over the equatorial central–eastern Pacific Ocean(EP).In reality,however,La Nina episodes are not always accompanied by rainy/snowy/icy(CRSI)days in southern China,such as the case in winter 2020/2021.Is there any other factor that works jointly with the EP SST to affect the winter CRSI weather in southern China?To address this question,CRSI days are defined and calculated based on station observation data,and the related SST anomalies and atmospheric circulations are examined based on the Hadley Centre SST data and the NCEP/NCAR reanalysis data for winters of1978/1979–2017/2018.The results indicate that the CRSI weather with more CRSI days is featured with both decreased temperature and increased winter precipitation over southern China.The SSTs over both the EP and the southeastern Indian Ocean(SIO)are closely related to the CRSI days in southern China with correlation coefficients of-0.29 and 0.39,significant at the 90%and 95%confidence levels,respectively.The SST over EP affects significantly air temperature,as revealed by previous studies,with cooler EP closely related to the deepened East Asian trough,which benefits stronger East Asian winter monsoon(EAWM)and lower air temperature in southern China.Nevertheless,this paper discovers that the SST over SIO affects precipitation of southern China,with a correlation coefficient of 0.42,significant at the 99%confidence level,with warmer SIO correlated with deepened southern branch trough(SBT)and strengthened western North Pacific anomalous anticyclone(WNPAC),favoring more water vapor convergence and enhanced precipitation in southern China.Given presence of La Ni?a in both winters,compared to the winter of 2020/2021,the winter of 2021/2022 witnessed more CRSI days,perhaps due to the warmer SIO.

Response of Sea Surface Temperature to Chlorophyll-a Concentration in the Tropical Pacific:Annual Mean,Seasonal Cycle,and Interannual Variability

The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model.The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific.The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation.Equatorial upwelling dominates the heat budget in that region.Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model.After introducing the seasonal cycle of chlorophyll-a concentration,the peak of the power spectrum becomes broad,and longer periods（3 years） are found.These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves,which are caused by the shallow mean thermocline in the northeastern Pacific.

Study of relationship between wave transport and sea surface temperature anomaly(SSTA) in the tropical Pacific

Large-scale water transport is one of the key factors that affect sea surface temperature anomaly（SSTA） in the eastern equatorial Pacific（EEP）.The relationship between the wave transport in the tropical Pacific and the SSTA in the EEP is examined by different methods,including band-pass filtering,period analysis,correlation analysis,significant analysis,and empirical orthogonal function（EOF） analysis.We have found that the eastward shift of the wave transport anomaly in the tropical Pacific,with a period of 2 a and enhancing the transport of warm waters from the western Pacific warm pool,precedes the increase of sea surface temperature（SST） in the EEP.The wave transport and the SSTA in the EEP have a maximum correlation of 0.65 with a time-lag of 6 months（transport variation precedes the temperature）.The major periods（3.7 a and 2.45 a） of the wave transport variability,as revealed by the EOF analysis,appear to be consistent with the SSTA oscillation cycle in the EEP.Based on the first occurrence of a significant SSTA in the Ni？o 3 region（5°S–5°N,90°–150°W）,two types of warm events are defined.The wave transport anomalies in two types present predominantly the west anomaly in the tropical Pacific,it is that the wave transport continues transport warm water from west to east before the onset of the warm event.The impact of wave-induced water transport on the SSTA in the EEP is confirmed by the heat flux of the wave transport.The wave transport exerts significant effect on the SSTA variability in the EEP and thus is not neglectable in the further studies.

东太平洋赤道海域茎柔鱼角质颚形态差异

海洋生物的表型与其栖息环境密切相关,了解其与资源利用相关的表型特征有助于理解其资源利用方式及生态位特征。茎柔鱼广泛分布于东太平洋,是该海域生态系统的关键种,其个体形态受环境影响变化明显。为探究不同环境条件是否会对茎柔鱼的重要摄食器官角质颚的形态产生影响,本研究对东太平洋赤道海域加拉帕戈斯群岛东、西部两个群体共244尾茎柔鱼的角质颚进行了形态学分析。采用传统形态方法测量了角质颚的12项外部形态参数,并利用几何形态测量方法对其上、下角质颚图像分别设置20个地标点并进行数字化分析。结果显示,不同群体的茎柔鱼角质颚的11项外部形态参数均存在显著差异,但差异系数均小于1.28。几何形态分析显示,不同群体茎柔鱼角质颚的整体大小及形状均差异显著,并具有不同的异速生长模式,形状差异主要体现在上颚的喙部与侧壁、下颚的喙部与翼部。不同群体的上、下角质颚均具有较高的判别成功率,平均判别正确率分别为89.61%和85.88%。加拉帕戈斯群岛以东海域的茎柔鱼具有较小的角质颚、较弯曲和尖锐的喙部、较大的侧壁及较短较宽的翼部,可能与该栖息地的环境及食物类型有关。这些与资源利用相关的表型可塑性反映了茎柔鱼对于不同栖息环境的适应,有利于提高其生存能力。

东赤道太平洋高生产力和热液活动叠加沉积环境铁组分特征及其古海洋意义

沉积物Fe组分是研究不同地质历史时期古海洋氧化还原环境的重要指标,而现代海洋不同沉积环境下的Fe组分变化特征则是限定这一指标适用范围的基础。东赤道太平洋巴拿马海盆作为高生产力和热液活动的叠加作用沉积区,代表了地质历史上大陆边缘海的一类典型沉积环境,但前人对这类沉积环境的Fe组分研究较为缺乏。本次研究分析了巴拿马海盆氧化底水下ODP 677钻孔(1°12.138′N, 83°44.220′W, 3461 m)约300 m长的岩心柱有机C、Fe组分及氧化还原敏感元素(U、Mo)含量的变化。结果表明, ODP 677钻孔Fe/Al值大约为0.78±0.14(n=35,σ),明显高于上部陆壳的平均值0.44,而Al/Ti值与上部陆壳接近且保持稳定在22.4±1.3(n=35,σ),可以推测,相当一部分Fe应来源于活跃热液活动和高生产力背景下有机碳颗粒对水柱中Fe氢氧化物微粒的吸附或Fe的自聚集/沉淀。高活性Fe与总Fe的比值(FeHR/FeT)大约为0.30±0.10(n=35,σ),远低于活性Fe加入通量的预期,表明一部分活性Fe可能在高生产力背景下转化为活性较差的组分。同时,部分活性Fe发生了黄铁矿化,黄铁矿Fe与高活性Fe比值(Fepy/FeHR)大约为0.39±0.14(n=35,σ),最高可达0.7左右。ODP677钻孔在1.5~2.2Ma(钻孔深度90m处)记录到强烈的有机碳通量增高现象,有机C含量可达4.61%,其高Mo和U通量指示了该时期早期成岩中孔隙水可能处于高硫化环境,但钻孔中黄铁矿埋藏通量或Fepy/FeHR的高值则出现在钻孔更深的位置,表明孔隙水中部分还原态硫和铁可能发生迁移并在更深处沉淀。与目前已发表的氧化性底水环境下沉积物的Fe组分相比,ODP677钻孔部分样品具有较高程度的Fepy/FeHR和FeHR/FeT值同时升高的现象,与典型的“铁化海洋”沉积特征吻合。本次研究进一步证实在利用Fe组分解释古深水的氧化还原环境时,需可靠分析沉积环境并排除高生产力和热液活动叠加作用的潜在影响。

Interannual variation of North China rainfall in rainy season and SSTs in the equatorial eastern Pacific

The rainfall in North China during rainy sea-son (July and August (JA)) exhibits a strong interannual variability. In this study, the atmospheric circulation and SST anomalies associated with the interannual variation of JA North China rainfall are examined. It is found that on the interannual timescale, the JA North China rainfall is associ-ated with significant SST anomalies in the equatorial eastern Pacific, and the North China rainfall and SST anomaly in the equatorial eastern Pacific correspond to the similar variation of the upper-level westerly jet stream over East Asia. A pos-sible mechanism is proposed for the influence of the SST anomalies in the equatorial eastern Pacific on the North China rainfall.

Eastern Equatorial Pacific cold tongue evolution since the late Miocene linked to extratropical climate

With support of the National Natural Science Foundation of China,the research team directed by Prof.Tian Jun(田军)at the State Key Laboratory of Marine Geology,Tongji University,and Associate Prof.Liu ZhongHui(柳中晖)at the Department of Earth Sciences,The University of Hong Kong,recently reported that Eastern Equatorial Pacific cold tongue(CT)was only weakly developed to non-existent Figure EEP cold tongue development compared with other representative surface and subsurface records.before^4.3million years ago,which was published in Science Advances(2019,5:eaau6060).

2008年初云南低温雨雪冰冻天气的气候成因分析

2008年1月下旬～3月上旬云南出现了一次持续性的低温雨雪冰冻天气,给交通、电力、通讯以及人民的生产、生活带来了极大危害。本文首先对云南高低层大气的异常状况及大尺度环流背景场特征对这次天气过程的影响进行诊断分析,然后进一步探讨了赤道东太平洋海温异常对东亚冬季风活动和云南天气气候异常的影响。结果表明,这次低温冷害过程主要发生在冷空气由北至南逐渐加强南压,南支西风波动配合,以及西太平洋副热带高压减弱东退的大尺度环流背景之下。同时,云南区域的大气异常状态表现出了明显的高湿、强上升运动以及对流层中高层温度升高而低层温度降低。另外,本文分析还进一步表明了2008年赤道东太平洋地区的冷海水异常对这次云南低温冷害天气过程的重要作用。

3个不同海区鸢乌贼渔业生物学的初步比较

根据2005年4～5月、2014年4～6月以及2014年2—6月我国渔船分别在印度洋海域、中东太平洋赤道海域和中西太平洋海域采集的鸢乌贼（Sthenoteuthisoualaniensis）样本，对其胴长、体质量、性成熟度组成和初次性成熟胴长等基础生物学进行比较研究。结果表明，印度洋海域雌性个体优势胴长及所占的比例为380～560mm和83．50％；中东太平洋赤道海域为160—240mm和81．86％；中西太平洋海域雌性为140—180mm和77．78％，雄性为140～160mm和93．14％。印度洋海域雌性个体优势体质量及所占比例分别为1500～4500g和85．00％；中东太平洋赤道海域为200—500g和78．43％；中西太平洋海域雌性为100～280g和88．89％，雄性为160—220g和88．24％。印度洋海域个体生长指数小于3，其它地区均大于3。印度洋海域的性成熟个体占总体的46．5％，在胴长为320mm已经开始出现性成熟个体；中东太平洋赤道海域性成熟个体占总体的63．24％，在胴长为200mm时已经出现了性成熟个体；中西太平洋海域雌性性成熟个体占总体的10．1％，胴长160mm已经有性成熟个体，雄性为65．68％。印度洋海域雌性个体初次性成熟胴长为392．74mm；中东太平洋赤道海域为196．40mm；中西太平洋雌性个体为213．80mm，雄性个体为146．95mm。本研究结果显示，3个海域的鸢乌贼均为混合群体，印度洋海域主要为大型群，中东太平洋赤道海域和中西太平洋海域主要为中型群，也有一定量的小型群存在。

南北半球副热带高压对赤道东太平洋海温变化的响应

本文利用１９７４年１月到１９９６年１２月重分析（ＮＯＡＡＮＣＥＰ－ＮＣＡＲＣＤＡＳ－１）全球５００ｈＰａ位势高度场资料，及同期赤道太平洋各海区ＳＳＴ资料，研究了南北半球副热带高压的变化特征及其对赤道东太平洋ＳＳＴ变化的响应。结果表明，全球副热带高压的变化及对ＳＳＴ的响应，在南北两个半球有很好的一致性。全球副热带高压强度的变化与超前３个月ＳＳＴ的正相关最为显著。对ＳＳＴ响应最强烈的区域主要在南北纬３０°之间的低纬，低纬地区局地ＳＳＴ对副热带高压也有强烈的影响。从１０°到３０°纬度，对ＳＳＴ的响应分别落后于赤道２～９个月．在中、高纬大气环流的响应表现为波列特征，对暖ＳＳＴ及冷ＳＳＴ的响应波列基本相反，但对暖ＳＳＴ的响应更为显著。海温和副热带高压的月际持续性有明显的季节变化，副热带高压９－１０月的相关障碍可能与ＮｉｎｏＣ区ＳＳＴ８－９月的相关障碍低点有关。

海南岛秋季降水异常对应的热带大尺度环流和海温

海南岛的地理环境特殊,具有独特的降水变化特征。作者利用海南岛7个站的月降水资料、NCEP再分析资料及NOAA的海温资料,研究了近45年海南岛降水的变化规律,并给出了产生降水异常的一个可能的物理机制。结果表明,海南岛降水具有明显的季节变化,一年中秋季的9、10月份降水最大,而且这两个月降水的年际方差占全年降水总方差的47.1%。秋季降水的年际异常对应的环流形式主要表现为对流层中下层存在的两个异常的气旋和反气旋中心。当降水偏多时,有两支异常的气流分别从热带太平洋和印度洋吹向海南岛附近地区,为该地区提供了更多的水汽,有利于岛上降水。而当降水偏少时,两支异常的气流变为从大陆吹向海洋,使海南岛上空水汽偏少,不利于岛上降水。另一方面,这种与秋季降水异常对应的环流异常是由赤道中东太平洋海表温度异常造成的,异常的海温将使热带地区的沃克环流发生异常,并最终使海南岛附近环流发生异常,导致降水异常。

北极海冰与赤道东太平洋海温的相互影响及其与El Nino的联系

对北极海冰面积与赤道东太平洋海温作了交叉相关分析，揭示了北极海冰与赤道东太平洋海温间相互影响的关系及其时空特点，并讨论了ＥｌＮｉｎｏ与北极海冰间的联系。结果表明，北极Ⅴ－Ⅵ区冬季海冰面积能够对以后各季的赤道东太平洋海温产生持续的影响，而北极Ⅶ区夏秋季的海冰面积能够影响来年夏秋季的海温；赤道东太平洋海温对海冰的影响表现为前期海温能够影响北极Ⅰ区春季海冰的消融。此外，前期北极海冰状况对ＥｌＮｉｎｏ的发生有明显的指示意义。冬季北极Ⅴ－Ⅵ区海冰对赤道东太平洋海温的持续影响可能与极涡异常、东亚冷空气活动有关，而赤道东太平洋海温对Ⅰ区海冰的影响则可能与大气对海温响应的ＰＮＡ结构有关。