Numerical simulation of Eurasian teleconnection pattern in atmospheric circulation during the Northern Hemisphere winter

In this paper, the anomaly of disturbance height field over Northern Hemisphere due to SST anomaly in the tropical Atlantic Ocean is simulated by using the general circulation model of IAP. A quasi-geostrophic, 34-level spherical coordinate model is also used to compute the distribution of atmospheric circulation anomaly when there is an anomaly of heat source over the tropical Atlantic. The computed results show that, owing to the heat source anomaly over the tropical Atlantic, the EU-pattern anomaly in the winter circulation may be caused. Namely, a ridge will be enhanced over the northwest Europe, a trough will be deepened over Siberia, but a positive anomaly of disturbance height field will be formed over the northeast China, Japan and other areas of East Asia. Moreover, the numerically simulated results show that the above-mentioned EU-pattern anomalies of circulation are due to the propagations of planetary wave train. About 15 days after an anomaly of the heat source over the tropical Atlantic is injected, the EU-pattern anomaly of atmospheric circulation is formed. This is in good agreement with the results analysed theoretically. On the leave from Geophysical Institute, Faculty of Science in Tokyo University, Japan.     

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。     

冬季低纬度热源异常在北半球对流层大气环流异常中的作用

本文首先从理论上讨论了北半球冬季低纬度强迫源与中纬度强迫源强迫所产生的准定常行星波在实际基本气流中传播路径及其振幅分布的差异,指出冬季低纬度热源异常将对北半球中、高纬度对流层大气环流的异常起很大影响,而中纬度热源异常将对平流层环流异常起很大作用。 本文应用一个包括Rayleigh摩擦、Newton冷却及水平涡旋热力扩散准地转34层球坐标模式分别计算了冬季低纬度热源异常与中纬度热源异常所造成北半球扰动系统的异常情况,计算结果表明了冬季低纬度热源异常将对中、高纬度对流层大气环流异常起很大作用,热带太平洋上空热源异常将产生PNA型环流异常。     

Numerical Simulation of the Effect of the SST Anomalies in the Tropical Western Pacific on the Blocking Highs over the Northeastern Asia

The effects of the sea surface temperature (SST) anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are simulated by the IAP-GCM with an observed and idealized distributions of the SST anomalies in the tropical western Pacific,respectively.Firstly,the atmospheric circulation anomalies during July and August,1980 are simulated by three anomalous experiments including the global SST anomaly experiment,the tropical SST anomaly experiment and the extratropical SST anomaly experiment,using the observed SST anomalies in 1980.It is shown that the SST anomalies in the tropical ocean greatly influence the formation and maintenance of the blocking high over the northeastern Asia,and may play a more important role than the SST anomalies in the extratropical ocean in the influence on the atmospheric circulation anomalies.Secondly,the effects of the SST anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are also simulated w     

SRES A2 情景下中国区域性高温热浪事件变化特征

随全球变暖,应对高温热浪事件是未来现代化城市面临的难题之一。本文利用全球模式-HadAM3p提供的3组不同边界场和初始场驱动区域气候模式系统PRECIS的输出结果,模拟未来情景下中国区域性高温热浪事件发生频率、强度及持续时间的变化趋势。结果表明：全球PRECIS对基准时段（1961-1990年）的高温热浪事件的发生的频率、强度和持续时间及对应的大气环流特征具有较强的模拟能力。相对于基准时段,未来情景下未来时段（2071-2100年）中国各地区的高温热浪的强度增加,发生频率增幅超过了100 %,且持续时间增加30 %以上。此外,观测资料和模拟结果均表明武汉和哈尔滨地区的高温热浪与500 hPa高度场的正距平密切相关。而未来情景下,武汉和哈尔滨地区500 hPa高度场的正距平呈增加趋势,表明这些地区未来可能面临危害更严重的高温热浪事件。     

青藏高原大气热源年际变率及其驱动因子

青藏高原（以下简称高原）大气热源对亚洲夏季风爆发、演变、推进,乃至全球气候系统都有重要影响,因此近年来高原大气热源变异机理也日益受到关注。本文在回顾已有关于不同季节高原热源变异原因的研究基础上,利用1980～2018年日本气象厅再分析数据JRA55（Japanese 55-year Reanalysis）,对逐月高原大气总热源的年际变率进行分类,并进一步探究了影响不同类别高原大气总热源的异常大尺度环流系统及海温驱动因子。除了传统上受关注的“冬季型”和“夏季型”以外,本文还提出了“早春型”和“过渡型”两种高原大气热源变率模态。总体而言,高原大气总热源年际变率以降水引起的凝结潜热异常为主,其中“冬季型”及“早春型”高原大气热源异常中心位于高原西部,主要受到中高纬遥相关波列的影响。此外,“冬季型”还受到厄尔尼诺—南方涛动（El Ni?o-Southern Oscillation, ENSO）及印度洋偶极子（Indian Ocean Dipole, IOD）的影响。“夏季型”高原大气热源呈东西偶极型反相变化,最大异常中心位于高原东南部,主要受北大西洋涛动（North Atlantic Oscillation, NAO）的影响;“过渡型”高原大气热源呈南北偶极型反相变化,受热带太平洋—印度洋海表温度异常的共同影响。因此,不同背景环流下高原热源年际变率的驱动因子存在明显差异。     

热带西太平洋海温异常对东北亚阻塞形势影响的数值模拟

本文利用ＩＡＰ－ＡＧＣＭ模拟研究了实测海温异常和热带西太平洋假想海温异常对夏季东亚地区环流异常的影响,并与观测结果进行了比较,籍此间接地研究了海温异常对东北亚阻塞形势的影响。首先,利用１９８０年实测海温异常,分三种试验（全球海温异常试验、热带海温异常试验、热带外海温异常试验）模拟了该年７月和８月的大气环流异常,指出海温异常是致使东北亚阻塞形势得以形成和维持的一个重要原因,同时也表明在对东亚大气环流异常型的影响方面,热带海温异常比热带经温异常更为重要。此外,我们还模拟研究了热带西太平洋的假想海温异常对东亚大气环流异常的影响,表明了热带西太平浃海温负异常对东北亚阻塞形势形成和维持有着重要作用     

A statistical�Cdynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables

The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500?hPa geopotential height and 1,000?hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50?years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our findings are encouraging for the prospects of basin-scale ocean dynamical downscaling using a weather-typing approach to reconstruct forcing fields for high resolution ocean models (Part II) from coarse resolution climate models.     

中国东部夏季分区降水对海温异常响应特征的研究

用刘征宇最新发展的广义平衡反馈方法结合经验正交分析和旋转经验正交分析法,研究中国东部6个分区夏季降水异常对各海盆海温异常(SSTA)模态的响应特征,探讨了东北区降水异常对SSTA的响应机制。结果表明:各分区降水异常对SSTA的响应特征有明显差异。东北区降水异常对热带太平洋SSTA的回应显著,当SSTA表现为类似El Niño模时,该区夏季降水增加;江淮区降水异常同时受到中纬度以及热带SSTA的强迫,对热带太平洋SSTA的类似La Niña Modoki模、北大西洋SSTA三极型模等回应显著;西南地区的降水异常主要与中纬度SSTA有密切关联。对流层高度场对热带太平洋SSTA类似El Niño模的直接回应在热带太平洋上空为显著正异常。通过东亚—太平洋型遥相关波列使东北地区上空高度场出现负异常,并在其西侧形成负异常中心,对流层低层为气旋性环流异常。这一环流回应与东北地区夏季降水偏多时的环流特征相近。     

Winter AO/NAO modifies summer ocean heat content and monsoonal circulation over the western Indian Ocean

This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation (AO/ NAO) on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation. The strong interannual co-variation between winter 1000-hPa geopotential height in the Northern Hemisphere and summer ocean heat content in the uppermost 120 m over the tropical Indian Ocean was investigated by a singular decomposition analysis for the period 1979–2014. The second paired-modes explain 23.8% of the squared covariance, and reveal an AO/NAO pattern over the North Atlantic and a warming upper ocean in the western tropical Indian Ocean. The positive upper ocean heat content enhances evaporation and convection, and results in an anomalous meridional circulation with ascending motion over 5°S–5°N and descending over 15°–25°N. Correspondingly, in the lower troposphere, significantly anomalous northerly winds appear over the western Indian Ocean north of the equator, implying a weaker summer monsoon circulation. The off-equator oceanic Rossby wave plays a key role in linking the AO/NAO and the summer heat content anomalies. In boreal winter, a positive AO/NAO triggers a down-welling Rossby wave in the central tropical Indian Ocean through the atmospheric teleconnection. As the Rossby wave arrives in the western Indian Ocean in summer, it results in anomalous upper ocean heating near the equator mainly through the meridional advection. The AO/NAO-forced Rossby wave and the resultant upper ocean warming are well reproduced by an ocean circulation model. The winter AO/NAO could be a potential season-lead driver of the summer atmospheric circulation over the northwestern Indian Ocean.     

北半球500hPa 3—5年周期的初步研究

本文用带通时间滤波器，对北半球500hPa高度距平（从1951年1月—1986年12月共432个连续月）的每个格点的时间序列进行滤波计算，初步结果如下:1．北半球500 hPa普遍存在3—5年周期，该周期的相对方差都在30%以上。35°N以南相对方差可达50%以上，在太平洋、大西洋、欧亚低纬地区最大相对方差高于70%。2．3—5年周期的水平结构要比Wallace的遥相关型更具有波列结构，通过波列的射线路径可以把能量从低纬度频散到高纬度。3．从分析1982/1983 El Nino年个例可以看到，赤道东太平洋海水异常增暖对大气的影响，除了一般公认的通过PNA型影响北美外，可能还存在另一条路径。     

The numerical simulation of the three-dimensional teleconnections in the summer circulation over the Northern Hemisphere

In this paper, a quasi-geostrophic, 34-level spherical coordinate model with Rayleigh friction, New-tonian cooling and the horizontal eddy thermal diffusivity is used to simulate the three-dimensional teleconnection in the summer circulation over the Northern Hemisphere.The computed results show that the change of the heat source over the Tibetan Plateau may cause the change of the atmospheric circulation over the middle and high latitudes in the Northern Hemisphere. When the heat source over the Tibetan Plateau is enhanced, it may cause the Tibetan high to enhance over South Asia and cause the change of the atmospheric circulation over East Asia and North America, i. e. Northeast China and North Japan will be controlled by a trough, which brings about a cold summer in this area. In the same way, an anticyclone will be enhanced over the Okhotsk sea. Moreover, another trough will be formed over Alaska, while another ridge will develop to the northeast of North America. Besides, the Pacific subtropical high will be weakened. These results are in good agreement with those obtained from the observed data.     

The relationship between South Atlantic SST and SACZ intensity and positioning

This study explores the ocean–atmosphere interaction in the formation and dynamics of the South Atlantic Convergence Zone (SACZ), through the analysis of the heat sources estimated through the outgoing longwave radiation. The results obtained with this study show that the coupled variability between SACZ and the South Atlantic Ocean indicates that in northern positioned SACZ cases (over Southeastern Brazil), westerly anomalies are verified in the low level continental tropical circulation, consistent with the active phase of the South America Monsoon System (SAMS). In these cases, cold anomalies in the subtropical Atlantic Ocean cause an increase in the continent–ocean temperature gradient, favoring an easterly flow in this region, and blocking the SACZ at a northerly position. Easterly anomalies in the tropical continent were verified in the low level circulation in southern positioned cases (over Southern Brazil), consistent with the SAMS break phase. The SST anomaly patterns indicate cold anomalies in the tropics and warm anomalies in the subtropics, which do not favor the development of an easterly flow at low levels over the western tropical Atlantic. In these cases, two situations may occur: the strengthening of the Low Level Jet (LLJ), which prevails in the eastern subtropical South America and convergence with the South Atlantic Subtropical High at its southern position; or the atmospheric unstable conditions caused by ocean warm SST anomalies (in this case the LLJ may be weaker than its climatological intensity).     

Twentieth century North Atlantic climate change. Part II: Understanding the effect of Indian Ocean warming

Ensembles of atmospheric general circulation model (AGCM) experiments are used in an effort to understand the boreal winter Northern Hemisphere (NH) extratropical climate response to the observed warming of tropical sea surface temperatures (SSTs) over the last half of the twentieth Century. Specifically, we inquire about the origins of unusual, if not unprecedented, changes in the wintertime North Atlantic and European climate that are well described by a linear trend in most indices of the North Atlantic Oscillation (NAO). The simulated NH atmospheric response to the linear trend component of tropic-wide SST change since 1950 projects strongly onto the positive polarity of the NAO and is a hemispheric pattern distinguished by decreased (increased) Arctic (middle latitude) sea level pressure. Progressive warming of the Indian Ocean is the principal contributor to this wintertime extratropical response, as shown through additional AGCM ensembles forced with only the SST trend in that sector. The Indian Ocean influence is further established through the reproducibility of results across three different models forced with identical, idealized patterns of the observed warming. Examination of the transient atmospheric adjustment to a sudden “switch-on” of an Indian Ocean SST anomaly reveals that the North Atlantic response is not consistent with linear theory and most likely involves synoptic eddy feedbacks associated with changes in the North Atlantic storm track. The tropical SST control exerted over twentieth century regional climate underlies the importance of determining the future course of tropical SST for regional climate change and its uncertainty. Better understanding of the extratropical responses to different, plausible trajectories of the tropical oceans is key to such efforts.     

Local and remote impacts of a tropical Atlantic salinity anomaly

The climatic impacts of an enhanced evaporation prescribed during 50 years in the tropical Atlantic are investigated in a coupled ocean–atmosphere general circulation model. Locally, the salinity increase leads to a rapid deepening and cooling of the surface mixed layer. This induces a deepening of the equatorial undercurrent and an intensification of the south equatorial current. A remote atmospheric response to the tropical Atlantic perturbation is detected in the North Atlantic sector after ten years. It has the form of a robust wave-like tropospheric perturbation seemingly excited by the weakening of atmospheric deep convection over the Amazonian basin. Meanwhile, the salt anomaly is carried northward by the mean oceanic circulation. It is traced up to the convection sites and then on its return path at depth towards lower latitudes. Consistent with the density increase, deep convection is enhanced after the arrival of the salt anomaly and the Atlantic meridional overturning circulation (AMOC) intensifies about 20 years after the beginning of the perturbation. The adjustment of the tropical Atlantic to the AMOC intensification then modifies its initial response to the freshwater forcing, leading to a weaker cooling in the northern tropical Atlantic than in the southern tropical Atlantic, a slight northward shift of the tropical Atlantic precipitation pattern and an intensification of the North Brazil current. On the other hand, no significant anomalous precipitations are found in the Pacific. The initial remote atmospheric response is also modulated, by an NAO-like response to the AMOC intensification.     

On the linear response of tropical African climate to SST changes deduced from regional climate model simulations

Summary Previous studies have highlighted the crucial role of sea surface temperature (SST) anomalies in the tropical Atlantic region in forcing the summer monsoon rainfall over subsaharan West Africa. Understanding the physical processes, relating SST variations to changes in the amount and distribution of African rainfall, is a key factor in improving weather and climate forecasts in this highly vulnerable region. Here, we present sensitivity experiments from a regional climate model with prescribed warmer tropical SSTs, according to enhanced greenhouse conditions at the end of the 21st century. This dynamical downscaling approach provides information about the nonlinear response of the atmosphere to oceanic heating. It has been suggested that the response is at least partly accounted for by the linear theory of tropical dynamics, involving a Kelvin and Rossby wave response to a tropical heat source. We compute the major modes of the linear Matsuno-Gill model for geopotential height and horizontal wind components and project the simulated response patterns onto these linear modes, in order to evaluate to which extent the simple linear theory may explain the SST-induced climate anomalies over Africa. A multivariate Hotelling T² test is used to evaluate whether these anomalies are statistically significant. Forcing the regional climate model by warmer SSTs leads to substantial climate anomalies over tropical Africa: Rainfall is increases over the Guinea Coast region (GCR) and tropical East Africa, but decreases over the Congo Basin and the Sahel Zone (SHZ). At the 850 hPa level, a trough develops over southern West Africa and the Gulf of Guinea, and is associated with stronger surface wind convergence over the GCR. These changes in the atmospheric dynamics strongly project onto the leading modes of the linear Matsuno-Gill model at various zonal wave numbers. The corresponding atmospheric heating pattern is highly reminiscent of the simulated nonlinear model reponse. The T² test statistics reveal that the SST forcing induces a statistically significant climate anomaly over tropical Africa if the climate state vector is reduced by projecting the simulated data onto the leading 10 linear modes. It is also shown that the linear response prevails in a long-term simulation with more realistic lower and lateral boundary conditions. Thus, linear tropical dynamics are assumed to be a major physical process on the ground of the prominent SST-African rainfall relationship.     

春季中国东海黑潮区大气热源异常对中国东部降水的影响

采用ERA-interim逐日再分析数据集与中国东部389个站逐日降水资料,通过相关和合成分析讨论了不同时间尺度上,春季中国东海黑潮区上空大气热源异常对东亚大气环流和中国东部降水的影响。观测分析表明,春季中国东海黑潮区上空为一显著的大气热源,大气对该热源的响应在不同时间尺度上表现出不同的形式。在较长时间的季节和年际尺度上,春季中国东海黑潮区大气热源增强时,可在大气对流层低层强迫出偏南气流,同期春季及后期夏季西太平洋副热带高压增强并西伸,相比于热源低值年西北太平洋副热带地区为一反气旋式异常环流所控制,中国长江中下游以南地区降水增多;反之亦然。与年际和季节时间尺度不同,在较短的天气时间尺度上,中国东海黑潮区上空大气热源增强可在其下方强迫出气旋式异常环流。大气热源的增强与中国东部对流层低层气旋式异常环流的东移有关,相应地在中国东部地区出现了显著的降水增多。     

The Role of Warm North Atlantic SST in the Formation of Positive Height Anomalies over the Ural Mountains during January 2008

The most severe snowstorm and freezing-rain event in the past 50 years hit central and southern China in January 2008. One of the main reasons for the anomalous climate event was the occurrence of atmospheric circulation anomalies over middle and high latitudes, particularly the persistent blocking that occurred over the Ural Mountains. Along with atmospheric anomalies, a strong La Nia event in the Pacific and warm sea surface temperature anomalies (SSTAs) in the North Atlantic were the most significant in the lower boundary. Since a brief analysis suggests that La Nia exerts no significant impact on the Urals, the key point of focus in this study is on the role of the warmer SSTAs in the North Atlantic. Based on an observational composite, North Atlantic SSTAs pattern when the height anomaly over the Urals is strongly positive is found similar to that in January 2008, but no significant SSTAs occurred elsewhere, such as the Pacific. Using an atmospheric general circulation model, ECHAM5, the impact of North Atlantic SSTAs on the extratropical atmosphere circulation in the event was investigated. The results show that the warm SSTAs strengthened the blocking high over the Urals, through anomalous transient eddies. The consistency between the study model and the observational composite indicates that the warm SSTAs in the North Atlantic were indeed an important factor in the formation of the snowstorm disaster of January 2008.     

On the change of the tropical cyclone structure during its passage over islands

The impact is studied of small land areas on the configuration and structure of the tropical cyclone as well as on the variations of different characteristics of hurricanes (wind field, kinetic energy, and vorticity) during their passage over islands. The results of computations based on the regional numerical atmospheric ETA model for the hurricanes of the Caribbean Sea and typhoons of the Northwestern Pacific revealed that the disturbance of the symmetric circulation in the vortex accompanied by significant kinetic energy losses takes place when crossing the archipelagos or separate islands. It is demonstrated that the vortex intensity depends not on the energy loss due to the underlying surface roughness only but on the heat flux from it as well. The kinetic energy generation in the hurricane sharply decreases as a result of the decrease in the pressure gradient over the land that is caused, in turn, by the tropical cyclone moving away from the oceanic heat source. At the recurring appearance of the cyclone over the warm ocean waters, its deepening and intensification recommence.     

我国南方盛夏气温主模态特征及其与海温异常的联系

利用NCEP/NCAR大气环流资料、HadISST海温数据以及中国160站气温数据等,通过EOF分解、线性相关等统计方法,分析了我国南方盛夏气温异常的主导模态及其所对应的关键环流系统和可能的海洋外强迫信号。结果表明:我国南方盛夏气温偏高有两种不同的分布模态,一是以江淮地区为中心的江淮型高温,二是以江南和华南为中心的江南型高温,导致这两种高温型发生的环流影响系统和海温外强迫因子均有显著差异。影响江淮型高温的关键环流系统是高低空正压结构的高度场正距平和偏弱的东亚副热带西风急流。而影响这两个关键环流系统的海洋外强迫因子包括热带印度洋至东太平洋的"-+-"海温异常分布型及北大西洋中纬度的暖海温异常。2016年盛夏江淮型高温的大气环流和海温异常均表现出典型江淮型高温年的特征,更好的证明了统计分析的结论。而江南型高温的关键环流系统主要是加强西伸的西太平洋副热带高压。其海洋外强迫因子包括前冬赤道中东太平洋的暖海温异常和春季-盛夏热带印度洋全区一致型暖海温异常,其中热带印度洋海温的影响更为持续和显著。