西风爆发、次表层暖水东移与厄尔尼诺现象

利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用.     

Localised intermittent upwelling intensity has increased along South Africa’s south coast due to El Niño–Southern Oscillation phase state

The El Niño–Southern Oscillation (ENSO) phase state is reported to drive interannual variability in sea temperatures along South Africa’s south coast through its influence on wind-induced upwelling processes. Whether ENSO drives the intensity of localised, abrupt, intermittent upwelling is less well known. To explore this relationship, we used an index of localised, extreme (>2 °C anomaly), intermittent upwelling intensity, derived from in situ sea temperature data within the Tsitsikamma National Park Marine Protected Area, and quantified the relationship between annual cumulative upwelling intensities (1991–2013) with an annual ENSO index, namely the Southern Oscillation Index. We found that ENSO phase state modulates the cumulative intensity of extreme intermittent upwelling events during an annual period, with more and greater events during La Niña phases compared with El Niño phases. Furthermore, these extreme upwelling events have increased with time along South Africa’s south coast as ENSO phase state becomes more intense and variable. Our findings support the emerging notion that the biological effects of climate change may be manifested through increased environmental variability rather than long-term mean environmental changes as ENSO is predicted to remain the dominant driver of local climate patterns in the future.     

Construction of synthetic ocean wave series along the Colombian Caribbean Coast: A wave climate analysis

In this paper a methodology is applied to generate synthetic wave series during mean and extreme conditions. An analysis is carried out that describes mean and extreme wave behavior for several climatic conditions along the Colombian Caribbean Coast. During mean conditions, the most energetic ocean waves are observed during the DJF season for both ENSO phases (El Niño and La Niña) for most of the Caribbean Sea. During the Niño years, there is a reduction in the speed of the north-east trade winds and their associated waves, but only in the DJF and MAM seasons. However, during the JJA season, this situation is reversed with the highest values occurring during El Niño and low values appearing during La Niña. Toward the east around the Guajira region, this general pattern is shown to change significantly. For extreme conditions, the results show a significant influence of extreme events toward the northwest, around La Guajira and the insular zones of San Andres and Providence when compared with other regions along the coast. All of these results (including the synthetic wave series) provide a design and management tool for the successful implementation of any coastal project (scientific or consulting) in Colombia.     

Variations of eddy kinetic energy in the South China Sea

Fifteen years of merged altimetric data were used to acquire the seasonal to interanual variations of eddy kinetic energy (EKE) in the South China Sea (SCS). The results show that climatological mean EKE in the SCS ranges from 50 cm²/s² to 1,400 cm²/s², with high values in the regions southeast of Vietnam and southwest of Taiwan Island. The amplitude of the annual harmonic of the EKE is characterized by high values to the southeast of Vietnam where the maximum exceeds 800 cm²/s². The EKE in the northern SCS reaches its maximum in August-February, while it peaks in September–December in the southern SCS. Besides the seasonal variation, the EKE also shows strong interannual variation, which has a negative (positive) anomaly in boreal winter during El Niño (La Niña) events. The interannual variation of local wind stress curl associated with El Niño-Southern Oscillation events may be the cause of the interannual variation of the EKE in the SCS.     

Oceanic Rossby waves induced by the meridional shift of the ITCZ in association with ENSO events

This study investigated the eastern Pacific Intertropical Convergence Zone (ITCZ) as an atmospheric forcing to the ocean by using various observed and reanalysis data sets over 29 years. Climatologically, a zonal band of positive wind stress curl (WSC) with a 10° meridional width was exhibited along the ITCZ. A southward shift of the positive WSC band during the El Niño phase induced a negative (positive) WSC anomaly along the northern (southern) portion of the ITCZ, and vice versa during the La Niña phase. This meridional dipole accounted for more than 25 % of interannual variances of the WSC anomalies (WSCAs), based on analysis of the period 1993–2008. The negative (positive) WSCA in the northern portion of the ITCZ during the El Niño (La Niña) phase was collocated with a positive (negative) sea surface height anomaly (SSHA) that propagated westward as a Rossby wave all the way to the western North Pacific. This finding indicates that this off-equatorial Rossby wave is induced by the WSCA around the ITCZ. Our analysis of a 1.5-layer reduced gravity model revealed that the Rossby waves are mostly explained by wind stress forcing, rather than by reflection of an equatorial Kelvin wave on the eastern coastal boundary. The off-equatorial Rossby wave had the same SSHA polarity as the equatorial Kelvin wave, and generation of a phase-preserving Rossby wave without the Kelvin wave reflection was explained by meridional movement of the ITCZ. Thus, the ITCZ acts as an atmospheric bridge that connects the equatorial and off-equatorial oceanic waves.     

ENSO事件下赤道中东太平洋海温场非对称性特征

利用1950—2020年冬季HadISST逐月海面温度（sea surface temperature,SST）资料、SODAv2.2.4逐月SST和三维海洋流速同化资料以及NCEP/NCAR 2 m高度上的逐月气温（surface air temperature,SAT）资料,使用非对称合成差分析方法、海洋混合层热量收支诊断方法等,探究El Niño事件和La Niña事件下造成赤道东太平洋（E区：110°W~80°W,10°S~10°N）、赤道中太平洋（C区：160°E~170°W,10°S~10°N）SST异常场显著不同非对称性特征的可能海洋动力过程,分析ENSO事件非对称强迫下2 m高度上SAT异常场的非对称空间响应。结果表明：E区El Niño事件的强度显著强于La Niña事件,C区则相反。非线性动力学加热作用对E区和C区El Niño年和La Niña 年SST异常场的非对称分量都起到了正反馈作用,是造成这两个区域SST异常场产生正、负非对称分量的主导动力因子。埃克曼输送作用不利于E区SST异常场正非对称分量的形成,但有利于C区SST异常场负非对称分量的形成。平均流、纬向平流和温跃层的非对称正反馈作用阻碍了C区SST异常场负非对称分量的形成。2 m高度上SAT异常场的非对称分布与SST异常场的非对称分布较为一致,但SAT异常场正、负非对称分量的显著范围明显减小,部分区域的非对称结果不显著。     

ENSO对华东地区春季降水影响的不对称性

利用1958—2019年的观测和再分析数据集,对冷、暖两类厄尔尼诺-南方涛动（El Niño-Southern Oscillation,ENSO）事件与后期华东地区春季降水之间的关系进行了分析。结果表明：（1）在暖ENSO事件中,华东春季降水量与前冬季ENSO海面温度异常存在较强的正相关关系。在冷ENSO事件中,这种强正相关向内陆地区西移,主要集中在江西和湖南。（2）暖ENSO事件通常会导致浙江、江苏和福建等沿海省份春季降水量过剩,而冷ENSO事件往往导致江西和湖南降水偏少。这归因于ENSO对大气环流的非线性影响。（3）与暖ENSO事件相比,冷ENSO事件引起的海面温度异常中心明显西移,造成异常低层大气环流的西移,最终导致华东降水的西移效应。（4）通过分析和发现,强调了华东春季降水对ENSO的非线性响应,这对华东地区的季节性气候预测具有重要意义。     

Modeling the long-term variability of phytoplankton functional groups and primary productivity in the South China Sea

Primary productivity (PP) and phytoplankton structure play an important role in regulating oceanic carbon cycle. The unique seasonal circulation and upwelling pattern of the South China Sea (SCS) provide an ideal natural laboratory to study the response of nutrients and phytoplankton dynamics to climate variation. In this study, we used a three-dimensional (3D) physical–biogeochemical coupled model to simulate nutrients, phytoplankton biomass, PP, and functional groups in the SCS from 1958 to 2009. The modeled results showed that the annual mean carbon composition of small phytoplankton, diatoms, and coccolithophores was 33.7, 52.7, and 13.6 %, respectively. Diatoms showed a higher seasonal variability than small phytoplankton and coccolithophores. Diatoms were abundant during winter in most areas of the SCS except for the offshore of southeastern Vietnam, where diatom blooms occurred in both summer and winter. Higher values of small phytoplankton and coccolithophores occurred mostly in summer. Our modeled results indicated that the seasonal variability of PP was driven by the East Asian Monsoon. The northeast winter monsoon results in more nutrients in the offshore area of the northwestern Luzon Island and the Sunda Shelf, while the southwest summer monsoon drives coastal upwelling to bring sufficient nutrients to the offshore area of southeastern Vietnam. The modeled PP was correlated with El Niño/Southern Oscillation (ENSO) at the interannual scale. The positive phase of ENSO (El Niño conditions) corresponded to lower PP and the negative phase of ENSO (La Niña conditions) corresponded to higher PP.     

热带太平洋第二类El Nio事件及其对中国气候的影响

基于热带太平洋次表层海温资料,分析了热带太平洋第二类El Nio事件海温异常的分布特征及其形成机制,讨论了与经典El Nio事件、El Nio Modoki、WP(西太平洋暖池)及CT(冷舌)El Nio事件之间的关系,揭示了第二类El Nio事件对中国降水的影响,得到以下结论。(1)第二类El Nio事件表征为热带太平洋次表层海温异常第三模态,占总方差贡献的4.7%。在海洋表面层,第二类El Nio事件暖期赤道东太平洋为沿赤道西伸的冷舌,热带中西太平洋为环绕冷舌的马蹄型大范围暖区。该型具11a和30~40a年代际振荡及3~4a年际变率,峰值多出现在春季。第二类El Nio事件是热带太平洋异常海面风应力场和赤道两侧的风应力旋度共同作用的结果,在赤道东印度洋-中西太平洋与赤道东太平洋-南美洲上空出现以反号垂直运动为特征的异常Walker环流。(2)El Nio Modoki与第二类El Nio事件有密切关系,它实质上是第二类El Nio事件次表层海温与近海面大气相互作用的结果,捕捉了第二类El Nio事件的主要信息。(3)第二类El Nio事件对中国春季及夏初降水有一定影响。在事件暖期,东海地区存在一个显著的异常反气旋性环流,其南侧的中国南方地区盛行异常东北气流,水汽来源减少,导致该地区少雨,其西侧的异常偏南气流北上直达华北地区,异常多水汽向北输送,并与北方的偏北流场相遇,导致该地区降水偏多。在第二类El Nio事件冷期相反。本文结果还指出,WP与CT El Nio事件是由经典El Nio事件第一模态与El Nio Modoki事件组合而成,它们不是独立的El Nio类型。此外,还讨论了夏半年El Nio事件对大气环流影响的物理过程。     

Long-term trends in pelagic environments of the east sea ecosystem

Physical and biological environmental variations in the East Sea were investigated by analysing time-series of oceanographic data and meteorological indices. From 1971 to 2000, dominant periodicity in water temperature variations had two apparent periods of 3 to 4 years and of decades, especially in the southwestern part of the East Sea affected by the influence of inflowing Tsushima warm current. Fluctuating water temperature within a certain period appears to respond to El Niño events with a time lag. It was found that there was a strong correlation between water temperature and El Niño events with a time lag of 1.5 and 5.5 years for periods of 3 to 6 years and of decades, respectively. Corresponding with El Niño events, water temperature variability also showed strong correlation with shift and/or changes in biological and chemical environments of nutrient concentrations, zooplankton biomass, and fisheries. However, there also occurred a short-term periodicity of water temperature variations. Within a period of 1 to 4 years, a relatively short-term cycle of water temperature variation had strong correlation with other climate indices such as Pacific Decadal Oscillation and monsoon index. After comparing coherence and phase spectrum between water temperature and different climate indices, we found that there was a shift of coherent periods to another climate index during the years when climate regime shift was reported.     

ENSO indices from sea surface salinity observed by Aquarius and Argo

Analysis of the first 26 months of data from the Aquarius satellite confirms the existence of a sharp sea surface salinity (SSS) front along the equator in the western equatorial Pacific. Following several earlier studies, we use the longitudinal location of the 34.8-psu isohaline as an index, termed Niño-S34.8, to measure the zonal displacement of the SSS front and consequently the eastern edge of the western Pacific warm pool. The on-going collection of the Array for Real-time Geostrophic Oceanography (ARGO) program data shows high correlations between Niño-S34.8 and the existing indices of El Niño, suggesting its potential important role in ENSO evolution. Further analysis of the ARGO data reveals that SSS variability in the southeastern tropical Pacific is crucial to identify the type of El Niño. A new SSS index, termed the southeastern Pacific SSS index (SEPSI), is defined based on the SSS variability in the region (0°–10°S, 150°–90°W). The SEPSI is highly correlated with the El Niño Modoki index, as well as the Trans-Niño index, introduced by previous studies. It has large positive anomalies during central Pacific El Niño or El Niño Modoki events, as a result of enhanced zonal sea surface temperature gradients between the central and eastern tropical Pacific, and can be used to characterize the type of El Niño. The processes that possibly control these SSS indices are also discussed.     

Observations of the North Equatorial Current,Mindanao Current,and Kuroshio current system during the 2006/07 El Niño and 2007/08 La Niña

Two onboard observation campaigns were carried out in the western boundary region of the Philippine Sea in December 2006 and January 2008 during the 2006/07 El Niño and the 2007/08 La Niña to observe the North Equatorial Current (NEC), Mindanao Current (MC), and Kuroshio current system. The NEC and MC measured in late 2006 under El Niño conditions were stronger than those measured during early 2008 under La Niña conditions. The opposite was true for the current speed of the Kuroshio, which was stronger in early 2008 than in late 2006. The increase in dynamic height around 8°N, 130°E from December 2006 to January 2008 resulted in a weakening of the NEC and MC. Local wind variability in this region did not appear to contribute to changes in the current system.     

Cause chain of an El Niño event in the eastern equatorial pacific and feedback and decrease-increase effects

Physical factors affecting El Niño events are subdivided into two categories. The first category includes those physical factors that have been demonstrated by modern science to have an effect on El Niño events. The second category comprises those physical factors that are only a hypothesis based on correlations that have yet to be corroborated to have affected El Niño events. This paper proposes the concept of a cause chain for an El Niño, pointing out that physical factors are linked and interdependent. The feedback effect and decrease-increase effect upon physical factors within the cause chain provide results superior to any single theory. We can only further explore the feedback effect and decrease-increase effect together with comprehensive analysis on the contributive ratio of these physical factors so as to improve the forecast accuracy of El Niño events. This represents a new way of thinking in the explanation of the cause of El Niño events.     

Specific features of the 2010 summer heat formation in the European territory of Russia in the context of general climate changes and climate anomalies

Specific features of the extreme summer heat of 2010 in the European part of Russia are analyzed against the background of global and regional climate changes taking into account antropogenic influences and natural anomalies related, in particular, to the El Niño/La Niña phenomena. The tendencies of the characteristics of the activity of blocking anticyclones (blockings) responsible for the formation of drought regimes and the increase in the fire hazard at midlatitudes are estimated in connection with climate changes.     

太平洋褶柔鱼冬生群资源丰度变动对ENSO事件的响应研究

太平洋褶柔鱼为大洋性经济鱼种,具有一年生命周期,其资源变动受气候和海洋环境条件的显著影响。本研究根据日本提供的2003-2012年太平洋褶柔鱼冬生群体的渔业统计数据,结合产卵场环境数据以及尼诺指数ONI（定义为Niño 3.4区海表温度距平值）,分析不同气候条件下（厄尔尼诺和拉尼娜）太平洋褶柔鱼冬生群体产卵场海表温度（SST）、叶绿素a（Chl-a）浓度以及适宜产卵面积（SSA）的变动情况及对其资源丰度（CPUE）的影响。结果表明,太平洋褶柔鱼冬生群体产卵场SST、Chl-a浓度和SSA具有明显的季节性变化。相关分析表明,各年CPUE与Chl-a浓度以及SSA具有显著的正相关关系（p<0.05）,但与SST相关性不显著（p>0.05）。此外,厄尔尼诺和拉尼娜事件通过驱动太平洋褶柔鱼冬生群体产卵场SSA和关键海域（25°-29°N,122.5°-130.5°E）内的Chl-a空间分布和大小变化,从而改变其资源丰度,但影响作用随各异常事件的强度不同而变化,具体表现为：发生弱强度厄尔尼诺事件时,产卵场SSA较高,Chl-a浓度处于较低水平,导致资源补充量处于较低水平,CPUE降低;发生中等强度厄尔尼诺事件时,产卵场SSA较低,但Chl-a浓度处于较高水平,导致资源补充量增加,CPUE处于上升水平;发生中等强度拉尼娜事件时,产卵场SSA和Chl-a浓度均处于较高水平,资源补充量显著增加,CPUE显著升高。研究表明,厄尔尼诺和拉尼娜事件对太平洋褶柔鱼冬生群体产卵场摄食孵化环境和资源丰度变动具有显著影响。     

Upwelling variability along the southern coast of Bali and in Nusa Tenggara waters

Spatial and temporal variation of upwelling along the southern coast of Bali and in the Nusa Tenggara waters — Indonesia was studied by using satellite image data of sea surface temperatures and chlorophyll-a from September 1997 to December 2008. This study clearly reveals annual upwelling in the regions from June to October, associated with the southeast monsoon cycle, with the sea surface temperature (chlorophyll-a concentration) being colder (higher) than that during the northwest monsoon. In addition, this study also shows that the upwelling strength is controlled remotely by ENSO and IOD climate phenomena. During El Niño/positive IOD (La Niña/negative IOD) periods, the Bali — Nusa Tenggara upwelling strength increases (decreases).     

Variability in upper-ocean water properties in the NE Pacific Ocean

A review of oceanographic properties in the vicinity of Ocean Station Papa (OSP) is presented, using data collected over the past 42 years. Average annual signals at OSP and seasonal characteristics along Line P represent variability on a large scale in the Gulf of Alaska. Between winter and summer, the upper ocean mixed layer varies between 120 and 40 m, monthly average winds decrease from 12 m/s in winter to 7 m/s in July, seawater temperatures warm from lows of 6°C to highs >12°C, waters freshen slightly in summer, and macronutrients are partially depleted by phytoplankton growth (removal of 7.8 μM NO₃ in 1970s and 6.5 μM NO₃ in 1990s). El Niño events influence this area by transporting heat northward. During the prolonged El Niño of the early 1990s, warming persisted at OSP through 1994, resulting in a reduced macronutrient supply during winter mixing. Changes in water properties over the four decades of observations are evident. There are trends towards warmer and less saline surface waters, lower winter nitrate and silicate levels, and less macronutrient utilisation in the 1990s compared to the 1970s. We speculate that these changes must be reducing the productivity of NE subarctic Pacific waters.     

Impact of quasi-decadal variability in the tropical Pacific on ENSO modulations

The impact of quasi-decadal (QD: 8 to 18 years) variability in the tropical Pacific on ENSO events is investigated. It is found that there is a significant difference in the behavior of ENSO events between the phases of positive and negative anomalies of the QD Niño-3.4 index. During the period of negative QD-scale Niño-3.4 index, ENSO events, especially La Niña events, occur more frequently, and larger amplitudes of thermal anomalies related to El Niño events appear over the central to eastern equatorial Pacific. Furthermore, propagations of upper ocean heat content anomaly and a phase relationship between upper ocean heat content and Niño-3 index in the equatorial Pacific, which have been pointed out by previous studies, are clearly detected during the period of negative QD Niño-3.4 index.     

137°经向断面温、盐度的年际变异

系统地分析了137°E断面温、盐度的多年变化,主要结果为:(1)137°E断面100m层温度,在低纬度海域于某些年份出现异常低温,此现象可能与厄尔尼诺事件有关;指出棉兰老冷涡的存在是造成该断面于6°～8°N附近出现低温的主要原因。(2)厄尔尼诺期间,冬季137°E断面上28℃等温线所在纬度小于其多年平均值。(3)冬季137°E断面上次表层高盐水可划分为强型、次强型、中等型和弱型4种类型。     

Adaptation of fisheries and mariculture management to extreme oceanic environmental changes and climate variability in Taiwan

This study presents the response of fisheries management to the extreme climatic events that affect marine capture fisheries and mariculture in Taiwan. Two regional approaches that can be applied universally to help capture fisheries and mariculture adapt to extreme weather events are also proposed. In the winter of 2008, an anomalously strong and continuous northeasterly wind caused by a La Niña event drove the cold China Coastal Current southward to penetrate the southern Taiwan Strait, and a portion of this current intruded eastward to the southern Penghu Archipelago. The cold current intrusion appreciably damaged marine aquaculture and the wild fish population, causing the death of more than 73 t of wild fish and 80% of cage aquaculture fish at the Penghu Islands. This extremely cold seawater event occurred between late January and the beginning of February 2008. To recover fishery resources around the waters of Penghu, fishery-related agencies adapted recovery measures over 3 years starting in April 2008 that included hatchery juvenile release, environmental monitoring, fishery subsidies, and ecological field investigations. This study suggests that responding to extreme climatic influences on fisheries and mariculture should include (1) establishing an early warning system by connecting fisheries agencies and marine research institutions to assist decision makers in performing time-adaptive measures, (2) temporarily suspending fishing activities after the occurrence of a natural disaster to help recover fishery resources and ecosystems, (3) altering the governance of farming fishing right so that fish farmers can temporarily transfer their aquaculture cages from high-risk areas to waters outside the influence of extreme weather events, and (4) continually filing surveys to understand the recovery status of marine ecosystems.