南极海冰涛动对北半球夏季大气环流的影响

南极海冰首要模态呈现偶极子型异常,正负异常中心分别位于别林斯高晋海/阿蒙森海和威德尔海。过去研究表明冬春季节南极海冰涛动异常对后期南极涛动（Antarctic Oscillation,AAO）型大气环流有显著影响,而AAO可以通过经向遥相关等机制影响北半球大气环流和东亚气候。本文中我们利用观测分析发现南极海冰涛动从5～7月（May–July,MJJ）到8～10月（August–October, ASO）有很好的持续性,并进一步分析其对北半球夏季大气环流的可能影响及其物理过程。结果表明,MJJ南极海冰涛动首先通过冰气相互作用在南半球激发持续性的AAO型大气环流异常,使得南半球中纬度和极地及热带之间的气压梯度加大,在MJJ至JAS,纬向平均纬向风呈现显著的正负相间的从南极到北极的经向遥相关型分布。对流层中层位势高度场上,在澳大利亚北部到海洋性大陆区域,出现显著的负异常,在东亚沿岸从低纬到高纬呈现南北走向的“? + ?”太平洋—日本（Pacific–Japan,PJ）遥相关波列,其对应赤道中部太平洋及赤道印度洋存在显著的降水和海温负异常,西北太平洋至我国东部沿海地区存在显著降水正异常和温度负异常;低纬度北美洲到大西洋一带存在的负位势高度异常和北大西洋附近存在的正位势高度异常中心,构成一个类似于西大西洋型遥相关（Western Atlantic,WA）的结构,对应赤道南大西洋降水增加和南撒哈拉地区降水减少。从物理过程来看,南极海冰涛动首先通过局地效应影响Ferrel环流,进而通过经圈环流调整使得海洋性大陆区域和热带大西洋上方的Hadley环流上升支得到增强,海洋性大陆区域特别是菲律宾附近的热带对流活动偏强,激发类似于负位相的PJ波列,影响东亚北太平洋地区的大气环流,而热带大西洋对流增强和北传特征,则通过激发WA遥相关影响大西洋和欧洲地区的大气环流。以上两种通道将持续性MJJ至ASO南极海冰涛动强迫的大气环流信号从南半球中高纬度经热带地区传递到北半球中高纬地区,从而对热带和北半球夏季大气环流产生显著影响。     

Low-latitude control of interhemispheric sea-surface temperature contrast in the tropical Atlantic over the past 21 kyears: the possible role of SE trade winds

To stimulate a discussion on the role of tropical atmospheric circulation versus thermohaline circulation changes for tropical Atlantic sea-surface temperature (SST) variations, we present a record of the SST contrast (SST) between the tropical northwest and southeast Atlantic from the Last Glacial Maximum to the Late Holocene. The SST was calculated from two alkenone-derived SST records; one from the Caribbean Sea and the other from the Angola Basin. Changes in the cross-equatorial SST were then compared with an abundance record of Florisphaera profunda from the equatorial Atlantic, which is indicative of SE trade-wind induced variations in thermocline depth in the equatorial divergence zone. This comparison implies that the Last Glacial Maximum, the Younger Dryas, and the Mid to Late Holocene were periods of strong SE trade winds, which led to an intense upwelling-related cooling in the southeast Atlantic and concurrently enhanced advection of warm tropical South Atlantic waters into the western tropical Atlantic. Accordingly, a coupled ocean-atmospheric process has probably created a dipole-like SST distribution pattern in the tropical Atlantic during these three distinct climatic periods. In contrast, Heinrich Event 1, the Bølling-Allerød, and the Early Holocene were intervals of weakened SE trade winds, causing a warming in the southeast Atlantic. However, synchronous warming in both regions during Heinrich Event 1 can be partially attributed to a weakening of thermohaline overturning which caused a reduced northward heat transport from the low-latitude to the high-latitude North Atlantic.     

The North Atlantic Oscillation and oceanic precipitation variability

Global North Atlantic Oscillation (NAO) oceanic precipitation features in the latter half of the twentieth century are documented based on the intercomparison of multiple state-of-the-art precipitation datasets and the analysis of the NAO atmospheric circulation and SST anomalies. Most prominent precipitation anomalies occur over the ocean in the North Atlantic, where in winter a “quadrupole-like” pattern is found with centers in the western tropical Atlantic, sub-tropical Atlantic, high-latitude eastern Atlantic and over the Labrador Sea. The extent of the sub-tropical and high-latitude center and the amount of explained variance (over 50%) are quite remarkable. However, the tropical Atlantic center is probably the most intriguing feature of this pattern apparently linking the NAO with ITCZ variability. In summer, the pattern is “tripole-like” with centers in the eastern Mediterranean Sea, the North Sea/Baltic Sea and in the sub-polar Atlantic. In the eastern Indian Ocean, the correlation is positive in winter and negative in summer, with some link to ENSO variability. The sensitivity of these patterns to the choice of the NAO index is minor in winter while quite important in summer. Interannual NAO precipitation anomalies have driven similar fresh water variations in these “key” regions. In the sub-tropical and high-latitude Atlantic in winter precipitation anomalies have been roughly 15 and 10% of climatology per unit change of the NAO, respectively. Decadal changes of the NAO during the last 50 years have also influenced precipitation and fresh water flux at these time-scales, with values lower (higher) than usual in the high-latitude eastern North Atlantic (Labrador Sea) in the 1960s and the late 1970s, and an opposite situation since the early 1980s; in summer the North Sea/Baltic region has been drier than usual during the period 1965–1975 when the NAO was generally positive.     

Response of the Asian summer monsoon to weakening of Atlantic thermohaline circulation

Various paleoclimate records have shown that the Asian monsoon was punctuated by numerous suborbital time-scale events, and these events were coeval with those that happened in the North Atlantic. This study investigates the Asian summer monsoon responses to the Atlantic Ocean forcing by applying an additional freshwater flux into the North Atlantic. The simulated results indicate that the cold North Atlantic and warm South Atlantic induced by the weakened Atlantic thermohaline circulation （THC） due to the freshwater flux lead to significantly suppressed Asian summer monsoon. The authors analyzed the detailed processes of the Atlantic Ocean forcing on the Asian summer monsoon, and found that the atmospheric teleconnection in the eastern and central North Pacific and the atmosphere-ocean interaction in the tropical North Pacific play the most crucial role. Enhanced precipitation in the subtropical North Pacific extends the effects of Atlantic Ocean forcing from the eastern Pacific into the western Pacific, and the atmosphere-ocean interaction in the tropical Pacific and Indian Ocean intensifies the circulation and precipitation anomalies in the Pacific and East Asia.     

Multidecadal-to-centennial SST variability in the MPI-ESM simulation ensemble for the last millennium

We assess the responses of North Atlantic, North Pacific, and tropical Indian Ocean Sea Surface Temperatures (SSTs) to natural forcing and their linkage to simulated global surface temperature (GST) variability in the MPI-Earth System Model simulation ensemble for the last millennium. In the simulations, North Atlantic and tropical Indian Ocean SSTs show a strong sensitivity to external forcing and a strong connection to GST. The leading mode of extra-tropical North Pacific SSTs is, on the other hand, rather resilient to natural external perturbations. Strong tropical volcanic eruptions and, to a lesser extent, variability in solar activity emerge as potentially relevant sources for multidecadal SST modes’ phase modulations, possibly through induced changes in the atmospheric teleconnection between North Atlantic and North Pacific that can persist over decadal and multidecadal timescales. Linkages among low-frequency regional modes of SST variability, and among them and GST, can remarkably vary over the integration time. No coherent or constant phasing is found between North Pacific and North Atlantic SST modes over time and among the ensemble members. Based on our assessments of how multidecadal transitions in simulated North Atlantic SSTs compare to reconstructions and of how they contribute characterizing simulated multidecadal regional climate anomalies, past regional climate multidecadal fluctuations seem to be reproducible as simulated ensemble-mean responses only for temporal intervals dominated by major external forcings.     

2020年夏季海洋天气评述

2020年夏季（6—8月）,北半球极涡呈现明显的单极型分布,极涡主体位于北极圈内,中心偏向东半球,中高纬环流呈现4波型分布。6—7月,西太平洋副热带高压较常年平均偏强,且位置偏西偏南,不利于热带气旋活动。2020年夏季共有8个热带气旋在西北太平洋和南海生成,其中7月没有热带气旋生成。除西北太平洋和南海之外,其他热带洋面另有20个热带气旋生成,其中北大西洋11个,东太平洋8个,北印度洋1个。受偏南暖湿气流的影响,我国北方海域多海雾天气。同时受入海气旋活动影响,多海上大风过程。夏季近海海域共出现了7次比较明显的海雾过程,其中6月3次,7月1次,8月3次。大风过程出现了10次, 2次由热带气旋影响,7次与入海气旋活动有关。发生2 m以上的大浪过程12次,6—8月分别出现了4次、5次和3次。     

Projected future changes in tropical cyclone-related wave climate in the North Atlantic

Tropical cyclones are a major hazard for numerous countries surrounding the tropical-to-subtropical North Atlantic sub-basin including the Caribbean Sea and Gulf of Mexico. Their intense winds, which can exceed 300 km h⁻¹, can cause serious damage, particularly along coastlines where the combined action of waves, currents and low atmospheric pressure leads to storm surge and coastal flooding. This work presents future projections of North Atlantic tropical cyclone-related wave climate. A new configuration of the ARPEGE-Climat global atmospheric model on a stretched grid reaching ~ 14 km resolution to the north-east of the eastern Caribbean is able to reproduce the distribution of tropical cyclone winds, including Category 5 hurricanes. Historical (1984–2013, 5 members) and future (2051–2080, 5 members) simulations with the IPCC RCP8.5 scenario are used to drive the MFWAM (Météo-France Wave Action Model) spectral wave model over the Atlantic basin during the hurricane season. An intermediate 50-km resolution grid is used to propagate mid-latitude swells into a higher 10-km resolution grid over the tropical cyclone main development region. Wave model performance is evaluated over the historical period with the ERA5 reanalysis and satellite altimetry data. Future projections exhibit a modest but widespread reduction in seasonal mean wave heights in response to weakening subtropical anticyclone, yet marked increases in tropical cyclone-related wind sea and extreme wave heights within a large region extending from the African coasts to the North American continent.

     

North Atlantic decadal regimes in a coupled GCM simulation

 The non-stationarity of the North Atlantic atmosphere-ocean coupling is investigated utilizing a long time integration of a coupled atmosphere-ocean general circulation model (GCM) and a consistent atmospheric experiment forced by the climatological sea surface temperature (SST) of the coupled GCM. The temporal behavior of the North Atlantic Oscillation (NAO) is non-stationary with two different decadal regimes being identified: (a) phases with enhanced (active) low-frequency variability of the NAO index are characterized by regional modes with a baroclinic Pacific-North America (PNA) and a dominant barotropic North Atlantic pattern; (b) in phases with reduced (passive) low-frequency variability a global mode connects tropics and midlatitudes. The characteristic space scales are similar in the coupled and the consistent atmospheric experiment; the time scales of the atmospheric eigenmodes are modified by ocean dynamics. In the active (passive) phase the corresponding atmospheric mode is reinforced by the North Atlantic (tropical Pacific) SST. Received: 15 September 2000 / Accepted: 30 March 2001     

Large-scale environmental controls on the seasonal statistics of rapidly intensifying North Atlantic tropical cyclones

This study is concerned with the connections between the large-scale environment and the seasonal occurrence of rapid intensification (RI) of North Atlantic tropical cyclones. Physically-motivated statistical analysis using observations and reanalysis products suggests that for tropical cyclones over the open tropical North Atlantic, the interannual variability of the probability of storms undergoing RI is influenced by seasonal large-scale atmospheric and oceanic variables, but not so for storms over the Gulf of Mexico and western Caribbean Sea. We suggest that this differentiated response is due to the former region exhibiting a strong negative correlation between the seasonal anomalies of vertical wind shear and potential intensity. Differences in the mean climatology and subseasonal variations of the large-scale environment in these regions appear to play an insignificant role in the distinctive seasonal environmental controls on RI. We suggest that the interannual correlation of vertical wind shear and potential intensity is an indicator of seasonal predictability of tropical cyclone activity (including RI) across the tropics .     

2019年夏季海洋天气评述

2019年夏季（6—8月）大气环流特征为：北半球极涡呈偶极型分布,中高纬度西风带呈4波型分布,欧亚大陆为“两槽一脊”的环流型。6月,我国北方海域多入海气旋和海雾,7—8月副热带高压位置较常年偏东、偏南,不利于热带气旋生成。我国近海有10次8级以上大风过程,其中热带气旋过程大风有6次,2次由入海温带气旋造成,另外2次过程主要由雷暴大风引起;出现了14次明显的海雾过程,其中6月出现7次,7月出现4次,8月出现3次;发生13次2 m以上的大浪过程,6月出现4次,7月出现5次,8月出现4次。西北太平洋和南海共有10个热带气旋命名,比常年平均偏少1个;其他各大洋共有14个命名热带气旋生成,分别为：北大西洋4个、东太平洋9个、北印度洋1个。     

Effects of Amazon basin deforestation on regional atmospheric circulation and water vapor transport towards tropical South America

The water cycle over the Amazon basin is a regulatory mechanism for regional and global climate. The atmospheric moisture evaporated from this basin represents an important source of humidity for itself and for other remote regions. The deforestation rates that this basin has experienced in the past decades have implications for regional atmospheric circulation and water vapor transport. In this study, we analyzed the changes in atmospheric moisture transport towards tropical South America during the period 1961–2010, according to two deforestation scenarios of the Amazon defined by Alves et al. (Theor Appl Climatol 100(3-4):337–350, 2017). These scenarios consider deforested areas of approximately 28% and 38% of the Amazon basin, respectively. The Dynamic Recycling Model is used to track the transport of water vapor from different sources in tropical South America and the surrounding oceans. Our results indicate that under deforestation scenarios in the Amazon basin, continental sources reduce their contributions to northern South America at an annual scale by an average of between 40 and 43% with respect to the baseline state. Our analyses suggest that these changes may be related to alterations in the regional Hadley and Walker cells. Amazon deforestation also induces a strengthening of the cross-equatorial flow that transports atmospheric moisture from the Tropical North Atlantic and the Caribbean Sea to tropical South America during the austral summer. A weakening of the cross-equatorial flow is observed during the boreal summer, reducing moisture transport from the Amazon to latitudes further north. These changes alter the patterns of precipitable water contributions to tropical South America from both continental and oceanic sources. Finally, we observed that deforestation over the Amazon basin increases the frequency of occurrence of longer dry seasons in the central-southern Amazon (by between 29 and 57%), depending on the deforestation scenario considered, as previous studies suggest.     

北大西洋多年代际振荡（AMO）对南海夏季风撤退年代际变率的影响及可能机理

基于美国国家海洋和大气管理局（NOAA）物理科学实验室（PSL）和科罗拉多大学环境科学研究所（CIRES）重建的NOAA-CIRES 20th再分析数据和国际综合海洋大气数据集（ICOADS）的全球月海表温度数据（ERSST）,并结合数值试验分析了南海夏季风撤退的年代际变率特征及北大西洋多年代际振荡（AMO）对其产生的影响。结果表明,南海夏季风撤退时间具有明显的年代际变率,南海夏季风撤退偏晚（早）年代中国南海及其附近区域上空有显著的气旋性（反气旋性）环流异常,降水偏多（少）。进一步研究发现,AMO与南海夏季风撤退年代际变率呈显著正相关,即AMO为正位相时,南海夏季风撤退偏晚;AMO为负位相时,南海夏季风撤退偏早。北大西洋海温升高（即AMO位于正位相）,从海洋释放更多的热通量到大气,导致北大西洋上空对流层的对流活动明显增强,通过海-气相互作用激发北大西洋上空的波活动异常,进而影响与东北亚关键区域大气环流变化密切相关的中纬度欧亚遥相关波列的形成和传播,引起东北亚关键区的正位势高度异常和明显的下沉运动,并在其对流层低层产生辐散运动,能量伴随着偏北的辐散风气流传播至中国南海及邻近区域辐合上升,进一步加强了南海区域的气旋性环流异常,使得南海夏季风撤退偏晚。AMO负位相时,异常情况与之大致相反,使得南海夏季风撤退偏早。      

Intraseasonal and submonthly variability over the Eastern Amazon and Northeast Brazil during the autumn rainy season

Summary The precipitation variability over the eastern Amazon (EAM) and northeast Brazil (NEB) during the autumn rainy season (March to May) is diagnosed using raingauge-based weekly data from 1982 to 2001. Since precipitation in this region is remarkably modulated by the combined effects of the Pacific and Atlantic Sea Surface Temperature (SST) anomalies, two extreme and contrasting large-scale climatic scenarios are considered in this study. The unfavorable (UNFAV) scenario, defined by the simultaneous occurrences of the El Niño and northward SST gradient in the intertropical Atlantic and the favorable (FAV) scenario, by the simultaneous occurrence of the La Niña and southward SST gradient in the intertropical Atlantic. UNFAV (FAV) composites with unfiltered data show remarkable changes in both the Walker and the Hadley cells associated with the Atlantic Intertropical Convergence Zone (ITCZ) anomalously weakened (enhanced) thus with deficient (abundant) seasonal rainfall in most of the EAM/NEB. Precipitation variability is identified objectively through EOF analyses performed on the (30–70 day) intraseasonal and submonthly (蠄21 day) filtered weekly precipitation anomalies for 18 autumn seasons (1983 to 2000). The principal components (PC) of the first mode of each analysis show strong oscillations. In particular, the oscillations of the PC series during UNFAV and FAV years reveal that events with anomalously deficient and abundant precipitation over the EAM/NEB occur alternately, even under extreme climatic conditions in the tropical Pacific and Atlantic. Composites based on events with anomalously increased precipitation (objectively selected from the PC series) on intraseasonal and submonthly scales are analyzed separately for the UNFAV and FAV years. These analyses show that for both scenarios the more important rainfall-producing atmospheric mechanism over the EAM/NEB on intraseasonal time scales consists of the establishment of deep convective bands trigged by South Atlantic Convergence Zone events or persistent frontal systems over northeast Brazil. Such a regional pattern is embedded in a large-scale dynamic environment related to the propagation of the Madden-Julian Oscillation over tropical South America. On the other hand, the main rainfall-producing atmospheric mechanism over the EAM/NEB on submonthly time scales is the Atlantic ITCZ during FAV years, whilst weakened Atlantic ITCZ activity may be forced by meridionally elongated mid-latitude wave trains in the upper troposphere during UNFAV years.     

南海登陆热带气旋对长江三角洲地区降水的影响

利用热带气旋年鉴资料统计了1949~2000年南海热带气旋影响期间我国长三角地区的最大降水量，计算有南海热带气旋影响时最大降水量大于50 mm的条件概率为60%。并把历年引起长三角地区50 mm以上降水的南海气旋频数序列作小波变换，发现其具有周期性振荡的特点，并且振荡周期在频率的分布上也有一定的规律。把南海热带气旋频数序列与夏季3个月副高面积指数之和的序列做交叉谱分析，发现两者具有准2年和准5年的耦合周期，气旋频数序列在位相上超前约半年。最后用1951~1999年的500 hPa月平均高度资料统计频数异常年的500 hPa高度场的距平和t统计量，发现在西太平洋、大西洋和极地都有显著的异常。     

春季北大西洋三极型海温异常变化及其与NAO和ENSO的联系

利用1951—2016年HadISST逐月海表温度(Sea Surface Temperature,SST)资料,NCEP/NCAR再分析资料以及1958—2016年美国伍兹霍尔海洋研究所(Woods Hole Oceanographic Institution,WHOI)提供的OAFlux数据集,运用经验正交函数分解(Empirical Orthogonal Function,EOF)和偏相关分析等统计方法,研究了春季北大西洋海温异常的主要特征及其与春季NAO和前期冬季ENSO联系。结果表明:春季北大西洋海温异常EOF的第一模态是自北而南出现的三极结构的海温距平型,其方差贡献率为35.7%。春季北大西洋三极型海温异常的形成主要受到春季NAO主导作用,还受到前期冬季热带中东太平洋海温异常的影响。消除前期冬季Niňo3.4的影响后,春季北大西洋三极型海温异常指数与同期北大西洋涛动(North Atlantic Oscillation,NAO)指数的偏相关系数分别为0.50,通过了99%置信度水平的显著性检验。消除春季NAO的影响后,春季北大西洋三极型海温异常指数与前期冬季Niňo3.4指数的偏相关系数为-0.26,通过了95%信度水平的显著性检验。春季NAO正(负)位相引起的海表风场和海表湍流热通量的异常,进而激发出正(负)位相的北大西洋三极型海温异常。前期冬季ENSO事件可以引起春季大气环流异常和热带外海温异常,进而调制春季NAO对北大西洋三极型海温异常的影响。     

Holocene climate variability as derived from alkenone sea surface temperature and coupled ocean-atmosphere model experiments

Holocene climate modes are identified by the statistical analysis of reconstructed sea surface temperatures (SSTs) from the tropical and North Atlantic regions. The leading mode of Holocene SST variability in the tropical region indicates a rapid warming from the early to mid Holocene followed by a relatively weak warming during the late Holocene. The dominant mode of the North Atlantic region SST captures the transition from relatively warm (cold) conditions in the eastern North Atlantic and the western Mediterranean Sea (the northern Red Sea) to relatively cold (warm) conditions in these regions from the early to late Holocene. This pattern of Holocene SST variability resembles the signature of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). The second mode of both tropical and North Atlantic regions captures a warming towards the mid Holocene and a subsequent cooling. The dominant modes of Holocene SST variability emphasize enhanced variability around 2300 and 1000 years. The leading mode of the coupled tropical-North Atlantic Holocene SST variability shows that an increase of tropical SST is accompanied by a decrease of SST in the eastern North Atlantic. An analogy with the instrumental period as well as the analysis of a long-term integration of a coupled ocean-atmosphere general circulation model suggest that the AO/NAO is one dominant mode of climate variability at millennial time scales.     

2017年夏季海洋天气评述

2017年夏季（6—8月）大气环流特征为：北半球极涡仍呈单极型位于北极上空,但强度较春季明显减弱。6月,我国近海北部有弱冷空气活动。7—8月,中高纬度槽脊活动进一步减弱,副热带高压西伸北抬,热带气旋活动频繁。我国近海海域主要有15次8级以上大风过程,其中热带气旋大风过程有8次,入海温带气旋过程有5次,强对流导致雷暴大风过程2次。有11次范围较大的2 m以上的大浪过程。仅出现1次范围较大的海雾过程。西北太平洋和南海共生成15个台风,其他各大洋共有热带气旋18个,分别为：大西洋7个、东太平洋11个。海表温度整体呈上升趋势。     

The North Atlantic thermohaline circulation simulated by the GISS climate model during 1970–99

Abstract

Evidence based on numerical simulations is presented for a strong correlation between the North Atlantic Oscillation (NAO) and the North Atlantic overturning circulation. Using an ensemble of numerical experiments with a coupled ocean‐atmosphere model including both natural and anthropogenic forcings, it is shown that the weakening of the thermohaline circulation (THC) could be delayed in response to a sustained upward trend in the NAO, which was observed over the last three decades of the twentieth century, 1970–99. Overall warming and enhanced horizontal transports of heat from the tropics to the subpolar North Atlantic overwhelm the NAO‐induced cooling of the upper ocean layers due to enhanced fluxes of latent and sensible heat, so that the net effect of warmed surface ocean temperatures acts to increase the vertical stability of the ocean column. However, the strong westerly winds cause increased evaporation from the ocean surface, which leads to a reduced fresh water flux over the western part of the North Atlantic. Horizontal poleward transport of salinity anomalies from the tropical Atlantic is the major contributor to the increasing salinities in the sinking regions of the North Atlantic. The effect of positive salinity anomalies on surface ocean density overrides the opposing effect of enhanced warming of the ocean surface, which causes an increase in surface density in the Labrador Sea and in the ocean area south of Greenland. The increased density of the upper ocean layer leads to deeper convection in the Labrador Sea and in the western North Atlantic. With a lag of four years, the meridional overturning circulation of the North Atlantic shows strengthening as it adjusts to positive density anomalies and enhanced vertical mixing. During the positive NAO trend, the salinity‐driven density instability in the upper ocean, due to both increased northward ocean transports of salinity and decreased atmospheric freshwater fluxes, results in a strengthening overturning circulation in the North Atlantic when the surface atmospheric temperature increases by 0.3°C and the ocean surface temperature warms by 0.5° to 1°C.     

热带北大西洋海温异常对南海夏季风的影响及其机理

利用HadiSST资料、CMAP降水资料和NCEP/NCAR再分析资料,分析了热带北大西洋(Northern Tropical Atlantic,NTA)海表温度异常(Sea Surface Temperature Anomaly,SSTA)与南海夏季风(South China Sea Summer Monsoon,SCSSM)的联系及可能机制。观测分析表明,夏季NTA海温异常与SCSSM存在显著的负相关关系;NTA海温正异常时,北半球副热带东太平洋至大西洋区域存在气旋式环流异常,有利于热带大西洋(热带中太平洋)地区产生异常上升(下沉)运动,使得西北太平洋地区出现反气旋环流异常,该反气旋环流异常西侧的南风异常使得SCSSM增强。利用春季NTA指数、东南印度洋海温异常指数、北太平洋海温异常指数、南太平洋经向模(South Pacific Ocean Meridional Dipole,SPOMD)及Niňo3.4指数构建了SCSSM季节预测模型,预测模型后报与观测的SCSSM指数的相关系数为0.81,表明该模型可较好预测SCSSM。     

2017年春季海洋天气评述

2017年春季（3—5月）大气环流特征为：北半球极涡呈单极型分布,主体位于北冰洋上空,中高纬西风带呈5波型分布。3月,地面冷高压偏强,冷空气活动频繁。4月,环流由纬向型向经向型逐渐调整,冷空气势力减弱。5月,东北气旋明显加强,冷暖势力相当,入海气旋增多。春季,我国近海海域主要有16次8级以上大风过程,其中冷空气大风过程有7次,冷空气和温带气旋共同影响的大风过程有1次,入海温带气旋过程有4次,东北冷涡影响大风过程有3次,强对流导致雷暴大风过程1次;且有8次明显的浪高在2 m以上的大浪过程。春季共有6次比较明显的海雾过程,分别为3月1次、4月2次、5月3次。西北太平洋和南海共生成1个台风“梅花”和1个热带低压,其他各大洋共有热带气旋15个,分别为大西洋1个、东太平洋1个、南太平洋5个、南印度洋6个、北印度洋2个。