An intercomparison between the surface heat flux feedback in five coupled models,COADS and the NCEP reanalysis

The surface heat flux feedback is estimated in the Atlantic and the extra-tropical Indo-Pacific, using monthly heat flux and sea surface temperature anomaly data from control simulations with five global climate models, and it is compared to estimates derived from COADS and the NCEP reanalysis. In all data sets, the heat flux feedback is negative nearly everywhere and damps the sea surface temperature anomalies. At extra-tropical latitudes, it is strongly dominated by the turbulent fluxes. The radiative feedback can be positive or negative, depending on location and season, but it remains small, except in some models in the tropical Atlantic. The negative heat flux feedback is strong in the mid-latitude storm tracks, exceeding 40 W m^–2 K^–1 at place, but in the Northern Hemisphere it is substantially underestimated in several models. The negative feedback weakens at high latitudes, although the models do not reproduce the weak positive feedback found in NCEP in the northern North Atlantic. The main differences are found in the tropical Atlantic where the heat flux feedback is weakly negative in some models , as in the observations, and strongly negative in others where it can exceed 30 W m^–2 K^–1 at large scales, in part because of a strong contribution of the radiative fluxes, in particular during spring. A comparison between models with similar atmospheric or oceanic components suggests that the atmospheric model is primarily responsible for the heat flux feedback differences at extra-tropical latitudes. In the tropical Atlantic, the ocean behavior plays an equal role. The differences in heat flux feedback in the tropical Atlantic are reflected in the sea surface temperature anomaly persistence, which is too small in models where the heat flux damping is large. A good representation of the heat flux feedback is thus required to simulate climate variability realistically.     

The surface heat flux feedback. Part I: estimates from observations in the Atlantic and the North Pacific

The surface heat flux feedback is estimated in the Atlantic and the North Pacific, using monthly heat flux and sea surface temperature (SST) anomaly data from COADS and the NCEP reanalysis. In the Atlantic, the heat flux feedback is dominated by the turbulent flux. It is negative, mostly ranging between 10 and 35 W m^-2 K^-1, but larger in the western subtropical gyre and part of the subpolar gyre, and weaker in the tropics. The radiative feedback is generally weak. In the North Pacific, the heat flux feedback is also dominated by the turbulent flux and is negative nearly everywhere, peaking in the subtropics. In both oceans, the turbulent heat flux feedback remains primarily negative in each season, and is stronger in fall and winter; patches of positive feedback can be seen, but often with limited correspondence between COADS and NCEP. The radiative feedback remains weak, and is positive in spring and summer at mid-latitudes. It is also shown that the turbulent heat flux feedback is weaker over large-scale areas, that no positive heat flux feedback sustains the SST anomaly "dipole" in the tropical Atlantic, and that the main SST anomaly mode in the North Pacific is damped by a negative heat flux feedback. The energy exchange with the atmosphere that results from the heat flux feedback can be substantial at mid-latitudes, but does not exceed 7 W m^-2 at basin scale.     

Covariability of SST and surface heat fluxes in reanalyses and CMIP3 climate models

The generation and dissipation of SST anomalies is mediated by the covariability of SST and surface heat fluxes. The connection between the variability of heat flux (including its radiative and turbulent components) and that of SST is investigated using the NCEP-NCAR and ERA-40 reanalyses and the CMIP3 multi-model collection of climate simulations. The covariance patterns of SST and heat flux are broadly similar in the two reanalyses. The upward heat fluxes are positively correlated with the SST anomalies in the tropics, the northern Pacific mid-latitudes, and over the Gulf Stream, and negatively correlated in the northern subtropics and the SPCZ region. Common covariance features are seen in all climate models in the tropics and the subtropics, while covariances differ considerably among models at northern mid-latitudes, where weak values of the ensemble mean are seen. Lagged covariances are broadly similar in the two reanalyses and among the models, implying that heat flux feedback is also similar. The heat flux feedback parameter is determined from the lagged cross-covariances together with the auto-covariance of SST. Feedback is generally negative and is dominated by the turbulent component. The strongest feedback is found at mid-latitudes in both hemispheres, with the largest values occurring in the western and central portions of the oceans with extensions to higher latitudes. The latter are also areas with large inter-model differences. The heat flux feedback strengthens in winter and fall and weakens in spring and summer. The magnitudes of the annual and seasonal feedback parameters are slightly weaker in most models compared to the reanalysis-based estimates. The mean model feedback parameter has the best pattern correlation and the smallest mean square difference compared to the reanalysis-based values, although spatial variances are weak. Model resolution shows no relationship with the heat flux feedback parameters obtained from model results. The SST-heat flux covariance is decomposed into components associated with surface heat flux feedback and atmospheric forcing processes. Heat flux feedback dominates over the atmospheric forcing and heat flux damps SST anomalies on average at northern Pacific mid-latitudes and southern Atlantic mid-latitudes; while the reverse occurs in the SPCZ and northern Atlantic mid-latitudes.     

Impact of the ocean diurnal cycle on the North Atlantic mean sea surface temperatures in a regionally coupled model

This study investigates the mechanisms by which the ocean diurnal cycle can affect the ocean mean state in the North Atlantic region. We perform two ocean-atmosphere regionally coupled simulations (20°N–80°N, 80°W–40°E) using the CNRMOM1D ocean model coupled to the ARPEGE4 atmospheric model: one with a 1 h coupling frequency (C1h) and another with a 24 h coupling frequency (C24h). The comparison between both experiments shows that accounting for the ocean diurnal cycle tends to warm up the surface ocean at high latitudes and cool it down in the subtropics during the boreal summer season (June–August). In the subtropics, the leading cause for the formation of the negative surface temperature anomalies is the fact that the nocturnal entrainment heat flux overcompensates the diurnal absorption of solar heat flux. Both in the subtropics and in the high latitudes, the surface temperature anomalies are involved in a positive feedback loop: the cold (warm) surface anomalies favour a decrease (increase) in evaporation, a decrease (increase) in tropospheric humidity, a decrease (increase) in downwelling longwave radiative flux which in turn favours the surface cooling (warming). Furthermore, the decrease in meridional sea surface temperature gradient affects the large-scale atmospheric circulation by a decrease in the zonal mean flow.     

Quantifying contributions to polar warming amplification in an idealized coupled general circulation model

An idealized coupled general circulation model is used to demonstrate that the surface warming due to the doubling of CO₂ can still be stronger in high latitudes than in low latitudes even without the negative evaporation feedback in low latitudes and positive ice-albedo feedback in high latitudes, as well as without the poleward latent heat transport. The new climate feedback analysis method formulated in Lu and Cai (Clim Dyn 32:873–885, 2009) is used to isolate contributions from both radiative and non-radiative feedback processes to the total temperature change obtained with the coupled GCM. These partial temperature changes are additive and their sum is convergent to the total temperature change. The radiative energy flux perturbations due to the doubling of CO₂ and water vapor feedback lead to a stronger warming in low latitudes than in high latitudes at the surface and throughout the entire troposphere. In the vertical, the temperature changes due to the doubling of CO₂ and water vapor feedback are maximum near the surface and decrease with height at all latitudes. The simultaneous warming reduction in low latitudes and amplification in high latitudes by the enhanced poleward dry static energy transport reverses the poleward decreasing warming pattern at the surface and in the lower troposphere, but it is not able to do so in the upper troposphere. The enhanced vertical moist convection in the tropics acts to amplify the warming in the upper troposphere at an expense of reducing the warming in the lower troposphere and surface warming in the tropics. As a result, the final warming pattern shows the co-existence of a reduction of the meridional temperature gradient at the surface and in the lower troposphere with an increase of the meridional temperature gradient in the upper troposphere. In the tropics, the total warming in the upper troposphere is stronger than the surface warming.     

On the interannual variability of surface salinity in the Atlantic

The mechanisms controlling the interannual variability of sea surface salinity (SSS) in the Atlantic are investigated using a simulation with the ECHAM4/OPA8 coupled model and, for comparison, the NCEP reanalysis and an observed SSS climatology. Anomalous Ekman advection is found to be as important as the freshwater flux in generating SSS anomalies, in contrast to sea surface temperature (SST) anomalies which are primarily caused by surface heat flux fluctuations. Since the surface heat flux feedback does not damp the SSS anomalies but generally damps existing SST anomalies, SSS anomalies have a larger characteristic time scale. As a result, they are more influenced by the mean currents and the geostrophic variability, which dominate the SSS changes at low frequency over much of the basin. The link between SSS anomalies and the dominant patterns of atmospheric variability in the North Atlantic sector is also discussed. It is shown that the North Atlantic Oscillation generates SSS anomalies much more by Ekman advection than by freshwater exchanges. At least in the coupled model, there is little one-to-one correspondence between the main atmospheric and SSS anomaly patterns, unlike what is found for SST anomalies.     

Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting

The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmospheric CO₂ concentration is analyzed using the IPSL-CM4 coupled ocean–atmosphere model. Two simulations are integrated for 70 years with 1%/year increase in CO₂ concentration until 2×CO₂, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization, which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years. This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows an identification as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface cooling due to the reduction in the air–sea temperature gradient as the atmosphere warms and the local freshening of convection sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the northward advection of positive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram Strait toward the convection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes contribute to a strong positive feedback, while feedback related to temperature processes is negative but remains small as there is a compensation between heat transport and surface heat flux in ocean–atmosphere coupled model. We conclude that in our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5.     

Coupled variability and air-sea interaction in the South Atlantic Ocean

A total of 52 years of data (1949–2000) from the NCEP/NCAR reanalysis are used to investigate mechanisms involved in forcing and damping of sea surface temperature (SST) variability in the South Atlantic Ocean. Organized patterns of coupled ocean–atmosphere variability are identified using EOF and SVD analyses. The leading mode of coupled variability consists of an SST pattern with a strong northeast–southwest gradient and an SLP monopole centered at 15°W, 45°S. The anomalous winds associated with this monopole generate the SST pattern through anomalous latent heat flux and mixed layer deepening. Other heat flux components and anomalous Ekman transport play only a secondary role. Once established, the SST pattern is attenuated through latent heat flux. The higher SST modes are also induced by anomalous winds and destroyed by latent heat flux. It thus appears that the coupled variability in the South Atlantic Ocean consists of atmospheric circulation anomalies that induce SST anomalies through anomalous latent heat fluxes and wind-induced mixed layer deepening. These SST anomalies are destroyed by latent heat flux with no detectable systematic feedback onto the atmospheric circulation. Atmospheric variability in the South Atlantic is found to be largely independent of that elsewhere, although there is a weak relation with ENSO (El Niño-Southern Oscillation).     

一个冰气相互作用数值模拟结果的可能统计解释

基于一个全球海-冰-气耦合模式的数值模拟结果,选取冬季格陵兰海海表面温度(SST)、海冰密集度、海表面感热通量等物理量以及3个相关区域海平面气压分别作经验正交函数展开,取第一模时间系数作相关分析。结果表明,上一年海冰密集度偏大(小)与来年的SST偏低(高)相联系,但二者同期相关性最大。当海气热通量交换变化超前一年时,其与SST相关性最大。模式最低层大气温度与海洋表面热通量之间的同时相关性最大,冬季模式最低层气温偏高(低)与海洋表面失去的感热、潜热通量偏少(多)相联系。气温、比湿都和冰岛低压区及格陵兰海的海平面气压相关性最强,冰岛低压气压偏低(高)与模式最低层气温和比湿偏高(低)相联系。所以,在海-冰-气年际尺度的相互作用中,主要关系是大气环流调整造成大气中云量和低层气温、湿度变化,进而影响海气界面上的通量交换,造成SST的变化。SST变化决定着海冰范围及海冰密集度的变化,但海冰变化时通过相变潜热的释放或吸收反过来对SST变化有较明显影响。     

The North Atlantic Oscillation—What Role for the Ocean?

The extent to which the North Atlantic Oscillation (NAO) is influenced by changes in the ocean state is an issue that has attracted much recent attention. Although there have been counter claims, the weight of evidence clearly suggests that forcing by the ocean of year-to-year changes in the NAO is a weak influence by comparison with atmospheric internal variability. The NAO is thus very different in character to the Southern Oscillation (SO), and its predictability—at least on seasonal-to-interannual timescales—is almost certainly much lower.Although weak, the influence of the ocean on the NAO is not negligible. In a previous study we found that wintertime North Atlantic climate, including the NAO, was significantly influenced by a tripole pattern of North Atlantic SST anomalies. Here we report the results of experiments to further elucidate the nature of this influence. We show that the tripole pattern induces a significant response both in the tropical Atlantic and at mid-to-high latitudes. The low latitude response is forced by the low latitude SST anomalies, but the high latitude response is influenced by the extratropical SST anomalies as well as those in the tropics. Furthermore, we find evidence of nonlinear interaction between the influence of the tropical and extratropical SST anomalies. Lastly, we investigate the feedback from the atmosphere onto the SST tripole. We find that the expected negative feedback is significantly modified at low latitudes by the dynamical response of the atmosphere.     

Weakened SST variability in the tropical Atlantic Ocean since 2000

A prominent weakening in equatorial Atlantic sea surface temperature (SST) variability, occurring around the year 2000, is investigated by means of observations, reanalysis products and the linear recharge oscillator (ReOsc) model. Compared to the time period 1982–1999, during 2000–2017 the May–June–July SST variability in the eastern equatorial Atlantic has decreased by more than 30%. Coupled air–sea feedbacks, namely the positive Bjerknes feedback and the negative net heat flux damping are important drivers for the equatorial Atlantic interannual SST variability. We find that the Bjerknes feedback weakened after 2000 while the net heat flux damping increased. The weakening of the Bjerknes feedback does not appear to be fully explainable by changes in the mean state of the tropical Atlantic. The increased net heat flux damping is related to an enhanced response of the latent heat flux to the SST anomalies (SSTa). Strengthened trade winds as well as warmer SSTs are suggested to increase the air–sea specific humidity difference and hence, enhancing the latent heat flux response to SSTa. A combined effect of those two processes is proposed to be responsible for the weakened SST variability in the eastern equatorial Atlantic. The ReOsc model supports the link between reduced SST variability, weaker Bjerknes feedback and stronger net heat flux damping.     

北大西洋高纬度海区湍流热通量对全球增暖的响应

大西洋经向翻转环流(the Atlantic Meridional Overturning Circulation,AMOC)由低纬输送大量热量至高纬度北大西洋海区,并通过热通量由海洋输送给大气,主导了附近区域的气候形态,并对北半球尺度的气候变化产生显著影响。本文根据CMIP5多模式多增暖情景的预估模拟结果,通过与增暖前控制试验的对比发现,全球增暖可导致该海区湍流热通量的减小,且减小的幅度随增暖强度增大,模拟结果与观测一致。进一步研究发现,热通量的减小存在季节差异,冬季的减小幅度远大于夏季。结合淡水扰动试验的分析表明,全球增暖下AMOC强度的减弱导致大西洋经向热输送减少,进而导致高纬度北大西洋海洋向大气的热输送减小。     

Summer interactions between weather regimes and surface ocean in the North-Atlantic region

This study aims at understanding the summer ocean-atmosphere interactions in the North Atlantic European region on intraseasonal timescales. The CNRMOM1d ocean model is forced with ERA40 (ECMWF Re-Analysis) surface fluxes with a 1-h frequency in solar heat flux (6 h for the other forcing fields) over the 1959–2001 period. The model has 124 vertical levels with a vertical resolution of 1 m near the surface and 500 m at the bottom. This ocean forced experiment is used to assess the impact of the North Atlantic weather regimes on the surface ocean. Composites of sea surface temperature (SST) anomalies associated with each weather regime are computed and the mechanisms explaining these anomalies are investigated. Then, the SST anomalies related to each weather regime in the ocean-forced experiment are prescribed to the ARPEGE Atmosphere General Circulation Model. We show that the interaction with the surface ocean induces a positive feedback on the persistence of the Blocking regime, a negative feedback on the persistence of the NAO-regime and favours the transition from the Atlantic Ridge regime to the NAO-regime and from the Atlantic Low regime toward the Blocking regime.     

包含详细水分循环和海冰物理过程的一维。气候模式与气候系统内反馈机制的研究

紧于水分循环和海冰物理过程是气候变化研究中两个比较薄弱的环节，而在以往的一些气候模式中往往简化甚至忽略了其中之一，给气候变化的研究带来了一定的不确定性。因此，我们设计了包含详细水分循环和海冰物理过程的一维气候模式，着重研究了存在，气候系统内部的反馈机制，得到以下几点结论：（１）无论在地表还是在大气中，水汽反馈和冰雪反照率反馈均为很强的正反馈，前者比后者要强一些，冰雪反照率反馈在极区比其它地区强一些。（２）降水过程无论在地表还是在大气中均表现为负反馈。（３）在大气中，蒸发过程表现为很强的正反馈；在地表，蒸发过程在中低纬度表现为很强的负反馈，而在高纬度却表现为正反馈。（４）大气中的潜热输送无论在大气中还是在地表均表现为正反馈，共正反馈效应通过放大水汽的温室效应体现出来。（５）大气中的感热输送无论在大气中还是在地表均表现为较弱的负反馈，其负反馈作用通过抑制冰雪反照率反馈而表现出来。（６）不同反馈之间的合成不是两者简单地线性相加，而是以一种北线性方式相互作用。     

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the “memory” of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.     

耦合模式中潮汐对北大西洋模拟的影响研究

将8个主要平衡分潮加入到耦合模式中,对比研究潮汐对北大西洋模拟影响。由于潮汐的引入,模式模拟SST在北大西洋中纬度区域偏差显著减小,高纬度区域SST降温明显。SST模拟的改变使潮汐试验的海表净热通量模拟误差下降了约30%,但高纬度海冰显著增加。模式中引入潮汐对北大西洋上层环流,尤其是西边界流的路径模拟改进显著,这是SST及海表净热通量模拟改变的主要原因。同时,北大西洋上层和深层西边界流在潮汐的作用下,都表现出环流减弱的特点,这也使得大西洋经向翻转环流在26.5°N处上层2 km的输送减弱,与观测数据更为接近。较弱的大西洋经向翻转环流导致海洋热量在中低纬度聚集而无法输送到高纬度区域,这是造成潮汐试验模拟的海温在中低纬度偏高、高纬度偏低的原因,较弱的热输送也同时导致了潮汐试验中北半球海冰面积增加。     

Impacts of the Autumn Arctic Sea Ice on the Intraseasonal Reversal of the Winter Siberian High

During 1979–2015, the intensity of the Siberian high(SH) in November and December–January(DJ) is frequently shown to have an out-of-phase relationship, which is accompanied by opposite surface air temperature and circulation anomalies.Further analyses indicate that the autumn Arctic sea ice is important for the phase reversal of the SH. There is a significantly positive(negative) correlation between the November(DJ) SH and the September sea ice area(SIA) anomalies. It is suggested that the reduction of autumn SIA induces anomalous upward surface turbulent heat flux(SHF), which can persist into November, especially over the Barents Sea. Consequently, the enhanced eddy energy and wave activity flux are transported to mid and high latitudes. This will then benefit the development of the storm track in northeastern Europe. Conversely, when downward SHF anomalies prevail in DJ, the decreased heat flux and suppressed eddy energy hinder the growth of the storm track during DJ over the Barents Sea and Europe. Through the eddy–mean flow interaction, the strengthened(weakened)storm track activities induce decreased(increased) Ural blockings and accelerated(decelerated) westerlies, which makes the cold air from the Arctic inhibited(transported) over the Siberian area. Therefore, a weaker(stronger) SH in November(DJ) occurs downstream. Moreover, anomalously large snowfall may intensify the SH in DJ rather than in November. The ensemble-mean results from the CMIP5 historical simulations further confirm these connections. The different responses to Arctic sea ice anomalies in early and middle winter set this study apart from earlier ones.     

Discrepancies in Simulated Ocean Net Surface Heat Fluxes over the North Atlantic

The change in ocean net surface heat flux plays an important role in the climate system. It is closely related to the ocean heat content change and ocean heat transport, particularly over the North Atlantic, where the ocean loses heat to the atmosphere, affecting the AMOC(Atlantic Meridional Overturning Circulation) variability and hence the global climate.However, the difference between simulated surface heat fluxes is still large due to poorly represented dynamical processes involving multisca...     

北半球高纬地区年际尺度循环过程中的气-海-冰相互作用关系

基于一个全球气-海-冰耦合模式数值模拟结果,对北半球高纬度地区年际尺度的气-海-冰相互作用进行了分析。在所使用的全球气-海-冰耦合模式中,大气环流模式和陆面过程模式来自国家气候中心,海洋环流模式和海冰模式来自中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室。采用一种逐日通量距平耦合方案实现次网格尺度海冰非均匀条件下大气环流模式和海洋环流模式在高纬地区的耦合。只对50 a模拟结果中的后30 a结果进行了分析。在分析中,首先对滤波后的北半球高纬度地区海平面气压、表面大气温度、海表面温度、海冰密集度及海表面感热通量的标准化距平做联合复经验正交函数分解,取第一模进行重建,然后讨论了在一个循环周期(约4 a)中北半球高纬度地区气-海-冰的作用关系。结果表明:(1)当北大西洋涛动处于正位相时,格陵兰海出现南风异常,使表面大气温度升高,海洋失去感热通量减少,海洋表面温度升高,海冰密集度减小;当北大西洋涛动处于负位相时,格陵兰海出现北风异常,使表面大气温度降低,海洋失去感热通量增多,海洋表面温度降低,海冰密集度增加。巴伦支海变化特点与格陵兰海相似,但在时间上并不完全一致。(2)多年平均而言,北冰洋内部靠近极点区域为冷中心。当北冰洋内部为低压异常时,因异常中心偏向太平洋一侧,使北冰洋内部靠近太平洋部分为暖平流异常,靠近大西洋一侧为冷平流异常。伴随着暖、冷平流异常,这两侧分别出现暖异常和冷异常,海表面给大气的感热通量分别偏少和偏多,上述海区海表面温度分别偏高和偏低,海冰密集度分别偏小和偏大。当北冰洋内部为高压异常时特点正好与上述相反。由上述分析结果可知,在海洋、大气年际循环中,大尺度大气环流变率起主导作用,海洋表面温度和海冰密集度变化主要是对大气环流变化的响应。     

冬季北半球大气对秋冬季巴伦支海海冰异常的敏感性研究

基于ERA-Interim再分析资料,借助大气模式CAM4,分析了北半球冬季不同月份的平均大气对巴伦支海不同振幅及不同季节海冰扰动的敏感性,并考察了中高纬度典型大气模态的分布变化情况.结果表明,冬季巴伦支海海冰的减少,会导致湍流热通量异常向上、局地异常变暖及水汽含量的异常升高,且相关异常的强度和范围随着海冰减少幅度的减...