ENSO对南海北部初级生产力的影响

利用2002年7月至2014年12月的卫星遥感数据,研究ENSO期间我国南海北部的海表温度(SST)、风场等环境场变化特征,并探讨其对南海北部初级生产力的影响。结果表明,El Ni?o/La Ni?a期间南海北部初级生产力较正常年份变化显著,很大程度上受到ENSO的调控,其变化与风场、SST等的分布变化密切相关。具体趋势:厄尔尼诺年的冬季风期间,南海北部海域风场强度减小,沿岸海域SST升高,初级生产力降低,南海东北部海域SST降低,初级生产力升高,整个海域的总初级生产力与MEI指数呈负相关关系;拉尼娜年的冬季风期间,相应海域的风场、SST和初级生产力的变化则与厄尔尼诺期间的相反,整个海域的总初级生产力与MEI指数呈正相关关系。     

20世纪80年代初以来北太平洋海温变化特征

应用1979.1-2006.12北太平洋海表温度（SST）资料,采用一元线性回归、功率谱等统计方法对该区SST的变化特征进行分析,结果表明：（1）北太平洋SST年际变化较为显著,尤其在靠近亚洲大陆一带洋面、北太平洋中部中纬度海域及赤道中、东太平洋;（2）北太平洋西部和中部SST1-12月均呈上升趋势,靠近亚洲大陆的日本海一带和我国大陆以东洋面升温最快。除我国以东洋面升温中心在冬季外,其余海域升温均在夏秋季更迅速,20世纪90年代初以来尤为明显;北美海岸山脉以西及赤道中、东太平洋SST则呈弱的下降趋势;（3）赤道中、东太平洋春夏季存在显著5a和3.5a左右的年际变化;北太平洋中部30°N一带冬春季存在5-6a左右的年际变化和约14a的年代际变化;（4）除北太平洋中部（西风漂流区）外,各个海域大部分月份SST高值年和低值年分别与厄尔尼诺年和拉尼娜年对应,西风漂流区SST高值年均出现在20世纪末21世纪初,低值年与厄尔尼诺年对应。     

基于时序栅格的海洋异常事件提取方法

海洋异常事件（Marine Abnormal Event,MAE）可为区域海气相互作用和全球气候变化研究提供重要的时空特征参考,具有重要的科学意义。鉴此,本文基于长时间序列的栅格数据集,提出了一种海洋异常事件时空提取算法（Marine Abnormal Event Spatio-Temporal Extraction Method,MAESTEM）。MAESTEM的核心步骤包括事件的时间维度提取、事件的空间维度提取和事件追踪。在时间维度提取方面,将每一个栅格像元作为一维时间序列,计算其平均值和标准差作为判断每个时刻是否异常的标准,并根据异常持续发生的时间长短来提取时间维度的海洋异常事件（Temporal MAE,TMAE）。在空间维度提取方面,利用空间邻域统计方法,统计栅格像元的空间邻域中属于TMAE的个数,并通过空间维度异常判断规则获取空间维度的海洋异常事件（Spatial MAE,SMAE）。利用时刻状态的SMAE的空间拓扑关系,根据事件前后时刻覆盖的空间区域是否重叠以及事件持续的时间长短,实现异常事件的追踪。最后,通过提取太平洋海域1993年1月至2012年12月的月均海面高度异常（Sea Level Anomaly,SLA）事件,验证了该算法的有效性和实用性。     

中国近海浮游植物叶绿素、初级生产力时空变化及其影响机制研究进展

综合分析中国近海不同海域浮游植物的时空分布和季节变化特征研究,概述该海域浮游植物叶绿素和初级生产力研究。受复杂的物理环境场、生物地球化学作用等综合影响,不同海域Chl-a和初级生产力具有显著的时空变化特征:空间上,叶绿素浓度表现为近岸高离岸低、离岸海域随纬度增加呈升高趋势;时间上,大体呈现明显的季节变化特征,北部季节特征尤为明显,其中叶绿素浓度及生产力的季节最大值在南海出现在冬季,而在中国北部海域逐渐变化为春季。影响浮游植物生长的主要因素有营养盐、温度、光照、陆源输入、季风、环流、涡旋等,不同海域、不同季节浮游植物生长的限制因子有差异。另外,由于遥感数据的精度以及现场观测航次的频率较低和站位布置较为稀疏影响了上述机制的探讨,因而浮游植物生长的主要调控机制仍待进一步研究。     

川渝冬季降水的年际变化及其与海温异常的关系

为了认识川渝冬季降水与海温之间的关系,利用川渝地区44个站点降水资料和海表温度资料并借助EOF分解、小波分析和相关分析等方法,讨论了川渝冬季年际降水变化特征及其与前期海温异常之间的关系。结果表明：川渝冬季年际降水空间分布主要有3个类型,EOFl型为川渝冬季降水的一致偏多（偏少）,EOF2型为川渝西南部、东部降水偏少（偏多）,而川渝地区西北部、中部降水偏多（偏少）;EOF3型为川渝西南部降水偏多（偏少）,而东北部降水偏少（偏多）;EOF1型和EOF2型降水与前期海温的相关明显小于EOF3型并较为分散,EOF3型降水与前期夏季、秋季海温在热带中、东太平洋和印度洋中、北部呈现非常显著的正相关,对应ENSO特征非常明显。     

四川省山洪灾害时空分布规律及其影响因素研究

山洪灾害时空分布规律及其影响因素,是灾害时空数据挖掘领域所关注的重点问题。本研究采用1950-2015年四川省历史山洪灾害事件数据,结合地统计、地理探测器、空间分析等方法,系统地分析了四川省1950-2015年历史山洪灾害的时空分布规律及其影响因素。结果表明：① 1950-2015年四川省山洪灾害数量整体呈先稳定后增长的趋势;山洪灾害主要集中在5-9月,7月覆盖率100%。② 县域灾害频次在南-北方向呈递减分布趋势;平均降雨量（历史山洪灾害过程降雨的平均值）在东-西方向呈指数型增长趋势,南-北方向由中部向南北递减。③ 1950s-2010s和5-9月历史累计山洪灾害重心及各标准差椭圆中心集中在四川中部地区,向东北方向移动,累计灾害点空间分布呈西南—东北格局。④ 县域山洪灾害数量及平均降雨量呈空间正自相关。⑤ 地理探测器分析表明自然因素、降雨、人类活动等因素对山洪灾害时空分布影响较大,其中不同降雨指标、高程标准差、坡度是山洪灾害时空分布规律的主要驱动因素。研究结果对查清四川省山洪灾害时空分布特征及小流域山洪监测预警、风险评价、防治区划等提供坚实的理论基础和科技支撑。     

中国大陆强震前的电离层异常特征

利用中国地壳运动观测网络的GPS观测数据,获取2000~2019年中国大陆63次强震（MS≥6.0）前的电离层垂直总电子含量VTEC的时空分布。通过分析震前20 d内的电离层日-日变化,发现有58次地震在震前10 d内于震中附近出现明显的电离层异常。通过分析这些电离层异常期间的日-地空间环境,并结合电离层异常的时空分布特征,认为其中的44次地震前的电离层异常可能是由地震孕育活动引起的,这些异常可视为地震的短临前兆。     

南海区域渔船活动时空特征分析

近年来海洋资源的不断开发利用,使得海洋空间规划变得尤为重要,其中以渔业资源占主要比重。为了对渔业资源监测与规划提供辅助决策信息,本文通过对南海及周边国家2018年船舶自动识别系统（AIS）数据进行预处理,采用数理统计和GIS空间分析方法,实现了南海区域渔船活动强度时空特征分析。结果显示： ① 2018年南海及周边国家渔船以区域性分布为主,集中在中国和越南沿海岸100 km以内区域,在秋季11月捕捞活动频繁,全年渔船平均活动强度白天大于夜晚,16:00 PM 时达到最大渔船活动强度; ② 中国在广东省、广西省和海南省各主要港口渔船活动强度呈现聚集性点状分布,渔船活动强度多大于100,部分港口附近海域呈条带状分布,西沙群岛相较南海其他群岛渔船活动强度较大,除越南外其他周边国家靠近南海附近海域部分海湾和港口有聚集式分布,渔船活动强度都小于2; ③ 越南渔船区域性分布明显,在胡志明港口呈现稳定的块状聚集性分布,且一年四季活动强度变化趋势不大,近岸渔船活动强度保持在50~100,越南渔船在中国南海禁渔线内靠近海南省西南部有两处活动较强的块状分布区域,2018年全年在此区域活动频率占采样天数的87.71%,且平均每小时有7~10艘渔船在该海域活动,休渔期内平均每小时渔船数量大于5,给中国南海海域渔业资源造成巨大威胁。本文通过AIS数据研究分析渔船活动可为海洋空间规划与政府相关部门提供数据支撑。     

面向不同用户群体的社交媒体台风舆情演化分析及对比研究

社交媒体数据可以为台风灾害追踪、灾时救援和灾情评估提供及时有效的信息。现有研究常采用主题建模和情感分析等技术对台风期间社交媒体平台（如新浪微博等）舆论话题和情感变化进行研究。在省域范围内以小时为时间粒度的多维度有效性论证尚有欠缺,且在舆情分析时未能区分用户群体差异。本文以台风“利奇马”为例,在浙江省域范围内,以新浪微博数据为研究对象,首先从词频分析、台风关注度时空变化以及特定灾害事件响应3个角度探讨了微博数据对台风灾情响应的有效性;其次采用隐含狄利克雷分布（Latent Dirichlet Allocation,LDA）主题模型技术挖掘微博文本主题信息,并根据Louvain算法对主题社团进行划分;然后开发了一种基于自定义情感词典的情感分析方法用于情感指数计算,与SnowNLP相比情感倾向性预测精度得到了提高;最后分析了台风期间官方和民众在新浪微博平台上的话题关注以及情感演变差异。结果表明：① 在省级范围内,微博数据能有效反映台风动态和灾害时空分布;② 台风事件微博文本的主题变化反映了灾情不同阶段舆论关注点的动态变化;③ 官方微博文本比民众微博文本具有更明确的主题社团结构;④ 台风事件相关微博文本中的消极情绪在台风登陆后显著增加,其中民众微博文本对台风灾害的情绪响应更及时,官方微博文本中的情感表达始终相对积极。     

2020年全球鱿钓捕捞的时空特征分析

了解全球鱿钓捕捞的时空特征可为鱿鱼资源的评估与管理提供参考。本文选取2020年全球鱿钓船AIS轨迹数据与VIIRS夜间灯光影像,以FAO major Fishing Areas的19个海洋主要捕鱼区为捕捞分区依据,结合GIS空间分析方法开展了全球鱿钓捕捞的时空特征分析。结果表明：(1)鱿钓捕捞主要分布在西南大西洋阿根廷专属经济区周边、西北太平洋日本东北部远海、东南太平洋秘鲁西部远海、西北印度洋阿拉伯海以及中西太平洋阿拉弗拉海,集中在中、低纬度离陆地100 km以内和400～700 km范围内,呈现以条带式为主的分布模式;(2)全球鱿钓捕捞的时间规律表现出“两峰两谷”的变化态势,分别于1—4月、6—8月呈上升趋势,而在4—6月、8—12月呈下降趋势。中纬度的鱿钓捕捞于夏秋呈上升趋势,而在冬春呈下降趋势;低纬度的鱿钓捕捞在秋冬季节呈增加态势,而在春季呈减少态势;(3)鱿钓捕捞的时空特征受洋流、鱿鱼繁殖特性及各国远洋鱿钓政策影响,其空间分布走向与主要洋流流向一致,捕捞强度在鱿鱼产卵高峰期、休渔期时减弱;(4) AIS轨迹密度与夜间灯光亮度在鱿钓捕捞信号上有良好的时空相关性,AIS轨迹密度与夜...     

Intraseasonal variability of the equatorial Pacific Ocean and its relationship with ENSO based on Self-Organizing Maps analysis

We investigated the intraseasonal variability of equatorial Pacific subsurface temperature and its relationship with El Nino-Southern Oscillation(ENSO) using Self-Organizing Maps(SOM) analysis.Variation in intraseasonal subsurface temperature is mainly found along the thermocline.The SOM patterns concentrate in basin-wide seesaw or sandwich structures along an east-west axis.Both the seesaw and sandwich SOM patterns oscillate with periods of 55 to 90 days,with the sequence of them showing features of equatorial intraseasonal Kelvin wave,and have marked interannual variations in their occurrence frequencies.Further examination shows that the interannual variability of the SOM patterns is closely related to ENSO;and maxima in composite interannual variability of the SOM patterns are located in the central Pacific during CP El Nino and in the eastern Pacific during EP El Nino.The se results imply that some of the ENSO forcing is manife sted through changes in the occurrence frequency of intraseasonal patterns,in which the change of the intraseasonal Kelvin wave plays an important role.     

Zonal displacement of western Pacific warm pool and zonal wind anomaly over the Pacific Ocean

The thermal condition anomaly of the western Pacific warm pool and its zonal displacement have very important influences on climate change in East Asia and even the whole world. However, the impact of the zonal wind anomaly over the Pacific Ocean on zonal displacement of the warm pool has not yet been analyzed based on long-term record. Therefore, it is important to study the zonal displacement of the warm pool and its response to the zonal wind anomaly over the equatorial Pacific Ocean. Based on the NCDC monthly averaged SST (sea surface temperature) data in 2°×2° grid in the Pacific Ocean from 1950 to 2000, and the NCEP/NCAR global monthly averaged 850 hPa zonal wind data from 1949 to 2000, the relationships between zonal displacements of the western Pacific warm pool and zonal wind anomalies over the tropical Pacific Ocean are analyzed in this paper. The results show that the zonal displacements are closely related to the zonal wind anomalies over the western, central and eastern equatorial Pacific Ocean. Composite analysis indicates that during ENSO events, the warm pool displacement was trigged by the zonal wind anomalies over the western equatorial Pacific Ocean in early stage and the process proceeded under the zonal wind anomalies over the central and eastern equatorial Pacific Ocean unless the wind direction changes. Therefore, in addition to the zonal wind anomaly over the western Pacific, the zonal wind anomalies over the central and eastern Pacific Ocean should be considered also in investigation the dynamical mechanisms of the zonal displacement of the warm pool.     

An ENSO-like oscillation system

INTRODUCTIONElNi no SouthernOscillation (ENSO)istheinterannualinteractionofocean atmosphereinthetropical (especiallyequatorial)Pacific,andisconsideredtobethedominantmechanismoftheearth’sinterannualclimatechange.ThereareseveralparadigmsproposedforinterpretingENSO .Bjerknes’ (1 966,1 969)pio neeringworkvisualizedacloseassociationbetweenoceanandatmosphereandexplainedhowthedis turbancecoulddevelopthroughtheocean atmosphereinteraction .Heproposedapositivefeedbackmechanism .ButENSOisan…     

Relationships of interannual variability between the equatorial pacific and tropical Indian Ocean in 17 CMIP5 models

Seventeen coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are employed to assess the relationships of interannual variations of sea surface temperature (SST) between the tropical Pacific (TP) and tropical Indian Ocean (TIO). The eastern/central equatorial Pacific features the strongest SST interannual variability in the models except for the model CSIRO-Mk3-6-0, and the simulated maximum and minimum are produced by models GFDL-ESM2M and GISS-E2-H respectively. However, It remains a challenge for these models to simulate the correct climate mean SST with the warm pool-cold tongue structure in the equatorial Pacific. Almost all models reproduce El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole mode (IOD) and Indian Ocean Basin-wide mode (IOB) together with their seasonal phase lock features being simulated; but the relationship between the ENSO and IOD is different for different models. Consistent with the observation, an Indian Ocean basin-wide warming (cooling) takes place over the tropical Indian Ocean in the spring following an El Niño (La Niña) in almost all the models. In some models (e.g., GFDL-ESM2G and MIROC5), positive ENSO and IOB events are stronger than the negative events as shown in the observation. However, this asymmetry is reversed in some other models (e.g., HadGEM2-CC and HadGEM2-ES).     

Distribution of the tropical Pacific surface zonal wind anomaly and its relation with two types of El Niño

El Nio events with an eastern Pacific pattern(EP) and central Pacific pattern(CP) were first separated using rotated empirical orthogonal functions(REOF).Lead/lag regression and rotated singular value decomposition(RSVD) analyses were then carried out to study the relation between the surface zonal wind(SZW) anomalies and sea surface temperature(SST) anomalies in the tropical Pacific.A possible physical process for the CP El Ni o was proposed.For the EP El Ni o,strong westerly anomalies that spread eastward continuously produce an anomalous ocean zonal convergence zone(ZCZ) centered on about 165°W.This SZW anomaly pattern favors poleward and eastward Sverdrup transport at the equator.For the CP El Nio,westerly anomalies and the ZCZ are mainly confined to the western Pacific,and easterly anomalies blow in the eastern Pacific.This SZW anomaly pattern restrains poleward and eastward Sverdrup transport at the equator;however,there is an eastward Sverdrup transport at about 5°N,which favors the warming of the north-eastern tropical Pacific.It is found that the slowness of eastward propagation of subsurface warm water(partly from the downwelling caused by Ekman convergence and the ZCZ) is due to the slowdown of the undercurrent in the central basin,and vertical advection in the central Pacific may be important in the formation and disappearance of the CP El Nio.     

Spatial-temporal variations of dominant drought/flood modes and the associated atmospheric circulation and ocean events in rainy season over the east of China

By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Nino-Southern Oscillation (ENSO) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Nino, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a ’Southern Flood and Northern Drought’ pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode (IOBM) warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a ’Northern Flood and Southern Drought’ pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over the east of China. The third mode is positively correlated with the tropical SSTA in the Indian Ocean from the spring of preceding year(-1) to the winter of following year(+1), but not related to the ENSO events. The positive SSTA in the South China Sea and the Philippine Sea persists from spring to autumn, leading to weak north-south and land-sea thermal contrasts, which may weaken the intensity of the East Asia summer monsoon. The weakened rainfall over the northern Indian monsoon region may link to the third spatial mode through the ’Silk Road’ teleconnection or a part of circumglobal teleconnection (CGT). The physical mechanisms that reveal these linkages remain elusive and invite further investigation.     

Tropical pacific decadal variability in subsurface temperature

The nature decadal variability of the equatorial Pacific subsurface temperature is examined in the control simulation with the Geophysical Fluid Dynamics Laboratory coupled model CM2.1.The dominant mode of the subsurface temperature variations in the equator Pacific features a 20-40 year period and is North-South asymmetric about the equator.Decadal variations of the thermocline are most pronounced in the southwest of the Tropical Pacific.Decadal variation of the north-south asymmetric Sea Surface wind in the tropical Pacific,especially in the South Pacific Convergence,is the dominant mechanism of the nature decadal variation of the subsurface temperature in the equatorial Pacific.     

Wind-forced equatorial wave dynamics of the Pacific Ocean during 2014/2015 and 2015/2016 E1 Ni?o events

The equatorial wave dynamics of interannual sea level variations between 2014/2015 and2015/2016 El Nino events are compared using the Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics Climate Ocean Model(LICOM) forced by the National Centers for Environmental Prediction(NCEP) reanalysis I wind stre s s and heat flux during 2000-2015.In addition,the LICOM can reproduce the interannual variability of sea surface temperature anomalies(SSTA) and sea level anomalies(SLA) along the equator over the Pacific Ocean in comparison with the Hadley center and altimetric data well.We extracted the equatorial wave coefficients of LICOM simulation to get the contribution to SLA by multiplying the meridional wave structure.During 2014/2015 El Nino event,upwelling equatorial Kelvin waves from the western boundary in April2014 reach the eastern Pacific Ocean,which weakened SLA in the eastern Pacific Ocean.However,no upwelling equatorial Kelvin waves from the western boundary of the Pacific Ocean could reach the eastern boundary during the 2015/2016 El Nino event.Linear wave model results also demonstrate that upwelling equatorial Kelvin waves in both 2014/2015 and 2015/2016 from the western boundary can reach the eastern boundary.However,the contribution from stronger westerly anomalies forced downwelling equatorial Kelvin waves overwhelmed that from the upwelling equatorial Kelvin waves from the western boundary in 2015.Therefore,the western boundary reflection and weak westerly wind burst inhibited the growth of the 2014/2015 El Nino event.The disclosed equatorial wave dynamics are important to the simulation and prediction of ENSO events in future studies.     

The increased storage of suspended particulate matter in the upper water of the tropical Western Pacific during the 2015/2016 super El Ni?o event

The climate variability induced by the El Ni?o-Southern Oscillation(ENSO) cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cycle.During 2015-2016,a super El Ni?o event occurred in the equatorial Pacific.Suspended particulate matter(SPM) data and related environmental observations in the tropical Western Pacific were obtained during two cruses in Dec.2014 and 2015,which coincided with the early and peak stages of this super El Ni?o event.Compared with the marine environments in the tropical Western Pacific in Dec.2014,an obviously enhanced upwelling occurred in the Mindanao Dome region;the nitrate concentration in the euphotic zone almo st tripled;and the size,mass concentration,and volume concentration of SPM obviously increased in Dec.2015.The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths,even into the euphotic zone,which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone.The se results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Ni?o events.In the context of the ENSO cycle,if predicted changes in biogenic particles occur,the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%,ultimately affecting the regional and possibly even global carbon cycle.This paper highlights the prospect for long-term prediction of the impact of a super El Ni?o event on the global carbon cycle and has profound implications for understanding El Ni?o events.     

Modulation of tropical cyclogenesis over the South China Sea by ENSO Modoki during boreal summer

This study examines the modulation of tropical cyclogenesis over the South China Sea(SCS) by the El Nio-Southern Oscillation(ENSO) Modoki during the boreal summer. Results reveal that there were more tropical cyclones(TCs) formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors(including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity) contribute to this influence is investigated, using a genesis potential(GP) index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modoki-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC frequency over the SCS by the ENSO Modoki during the boreal summer.