北太平洋海温Victoria模态与ENSO年际关系的非对称特征

利用美国NOAA海表温度资料,重点分析了北太平洋海温异常EOF第二模态Victoria模态(VM)与ENSO年际关系的非对称特征.研究发现,VM和ENSO在年代际尺度上相关性较弱,而在年际尺度上有很好的相关关系,两者同期为负相关,VM超前1 a为正相关.然而,正负VM事件与ENSO冷暖位相在年际尺度上的联系存在着一定的...     

北太平洋副热带海区的两支东向逆流

分析SODA同化资料(1950～1999年)所描述的北太平洋副热带海区表层一次表层的东向逆流的空间分布和季节变化特征.从气候平均场看,北太平洋副热带的东向流主要包括东、西两部分,其中,太平洋中部夏威夷岛西侧的东支逆流位置偏南,强度夏季最大,春季最弱.海表风应力的旋度异常产生的Ekman抽吸是东支逆流形成的主要原因.位于西太平洋的西支逆流位置偏北,春季一夏季强度较大.西支逆流的形成和季节变化可以由副热带模态水的辐合解释.     

有关副热带太平洋对ENSO影响研究的综述

ENSO（El Niño-Southern Oscillation）的发生发展既受到来自热带西太平洋纬向海气过程的影响,也受到来自副热带太平洋经向海气过程的影响。本文概述了副热带太平洋海气异常影响ENSO研究方面的科学背景及研究进展,综述了前人提出的副热带太平洋大气海洋异常通过经向风应力以及北太平洋/南太平洋经向模态,影响ENSO发展演变的途径及相关物理机制,总结了近些年观测资料分析及数值模拟研究工作所提出的新观点,并讨论了相关研究中的学术分歧及有待进一步研究的问题。     

1979—2013年北太平洋海表面盐度变化及其与淡水通量的关系

利用海洋再分析资料,对北太平洋海表面盐度（Sea Surface Salinity,SSS）变化及其与淡水通量（Fresh Water Flux,FWF）的关系进行研究。结果表明：1914—2013年SSS存在增大趋势,且有25～30 a的周期变化;1979—2013年SSS存在先减小后增大趋势,且有7～12 a的周期变化。北太平洋SSS变化的活跃区域位于黑潮及其延伸区（A区）和北太平洋中部偏东地区（B区）。A区和B区SSS在2000年之前存在减小趋势,在2000—2009年出现明显增大趋势。A区和B区SSS变化与北太平洋FWF变化显著相关,其中A区SSS受局地FWF影响较大（最大相关系数出现在FWF超前16个月）,B区SSS受局地FWF影响较小（最大相关系数出现在FWF超前20个月）。北太平洋FWF与A区SSS的相关表明：它们存在较大范围的正相关区,正相关区主要位于黑潮延伸区（A区东部）,且正相关大值区随着FWF超前时间缩短而向东移动。对应于北太平洋温度年代际变化,SSS也存在显著的年代际变化,并且北太平洋关键区盐度变化能够表征北太平洋气候变率,它可以作为北太平洋气候变率的替代指数。     

冬季北太平洋优势气候模态的转移

采用EOF分解和小波分析,并引入相似度,分析冬季北太平洋的两个主要气候模态,即太平洋年代际振荡（PDO）模态与北太平洋涡旋振荡（NPGO）模态,及其结构特征随时间的演变。结果表明：1988/1989年的气候转移后,冬季海温距平（SSTA）优势模态为NPGO模态的年份越来越多,这种优势气候模态的转移现象表现出准18 a的年代际周期;SSTA与NPGO模态相似度的20年滑动平均在20世纪80年代中后期之后超过了SSTA与PDO模态的相应值,这表明此后SSTA的优势模态发生了转移,由PDO型转换为NPGO型;对典型时间段SSTA的合成分析显示,其优势模态由1988年前的PDO型转变为之后的NPGO型。     

Atmospheric anomalies related to interdecadal variability of SST in the North Pacific

Anomalous patterns of the atmospheric circulation and climate are studied corresponding to the two basic interdecadal variation modes of sea surface temperature (SST) in the North Pacific, namely, the 25-35-year mode and the 7-10-year mode. Results clearly indicate that corresponding to the positive and negative phases of the interdecadal modes of SST anomaly (SSTA) in the North Pacific, the anomalous patterns of the atmospheric circulation and climate are approximately out of phase, fully illustrating the important role of the interdecadal modes of SST. Since the two interdecadal modes of SSTA in the North Pacific have similar horizontal structures, their impacts on the atmospheric circulation and climate are also analogous. The impact of the interdecadal modes of the North Pacific SST on the atmospheric circulation is barotropic at middle latitudes and baroclinic in tropical regions.     

中国东部—西太平洋副热带季风和降水的气候特征及成因分析

利用1981—2000年候平均NCEP/NCAR再分析资料和CMAP全球降水资料,分析了从中国东部大陆到西太平洋副热带地区季风和降水季节变化的特征及其与热带季风降水的关系,探讨了季风建立和加强的原因。夏季东亚—西太平洋盛行的西南风开始于江南和西太平洋副热带的春初,并向北扩展到中纬度,热带西南风范围向北扩展的迹象不明显。从冬到夏,中国西部和西太平洋副热带的表面加热季节变化可以使副热带对流层向西的温度梯度反转比热带早,使西南季风在副热带最早开始;从大气环流看,青藏高原东侧低压槽的加强和向东延伸,以及西太平洋副热带高压的加强和向西移动,都影响着副热带西南季风的开始和发展;初夏江南的南风向北扩展与副热带高压向北移动有关,随着高原东侧低压槽向南延伸,槽前的偏南风范围向南扩展。随着副热带季风建立和向北扩展,其最大风速中心前方的低层空气质量辐合和水汽辐合以及上升运动也加强和向北移动,导致降水加强和雨带向北移动。热带季风雨季开始晚,主要维持在热带而没有明显进入副热带,江淮梅雨不是由热带季风雨带直接向北移动而致,而是由春季江南雨带北移而致。在热带季风爆发前,副热带季风区水汽输送主要来自中南半岛北部和中国华南沿海,而在热带季风爆发后,水汽输送来自孟加拉湾和热带西太平洋。     

冬季北太平洋副高面积和强度指数的一个计算方案

月（季）平均海平面气压场中的北太平洋副高（H,）是北半球的永久性大气活动中心,它与大气环流及区域气候异常关系密切。利用闭合气压系统面积指数S、强度指数P简要描述H,性状,并用它们分析H,气候及异常特征,以及H,与热带东太平洋海表温度异常等关系。因冬季H,明显减弱,在计算H,的S、P指数序列时,难以找出适于整个分析时段的、环流意义明晰的特征等压线。针对该问题,本文给出一个计算方案,先选择一个值较高的f0,用它计算多数年份环流指数5、P;再选择一个值较低的．东,计算少数H_P极端偏弱年份的环流指数S、P;最后用一元线性回归方程,将．矗计算结果S、P订正至f0计算结果S、P,得到S、P的完整序列。应用结果表明,由此求得的H,该完整序列是适当的。     

北太平洋冬季上层海温异常的NPGO模态

利用较高分辨率的全球海洋同化分析系统(SODA)资料, 对冬季北太平洋上层的海温异常做了整层经验正交函数(EOF)分析, 并主要讨论了第二模态的结果。该模态空间结构与经典的北太平洋涡旋振荡(NPGO)一致, 且时间系数与NPGO指数也吻合, 故北太平洋上层海温异常EOF第二模态可称为NPGO模态。这说明NPGO现象不单纯反映在海表面温度异常上, 在上层海温中该现象也存在。在该模态空间场上, 水深100 m以上25°N～30°N的副热带处, 沿纬圈从120°E向东延伸至中东太平洋均为海温正异常带, 其北面则为负异常带, 两者构成双带系统;其中在170°W附近分别有正、负异常大值区, 中心构成南北偶极子;在本州岛以东海域, 从海表直到海洋上层底则有小范围的海温强异常。该模态空间结构的形成与大气NPO模态关系密切, 并与中纬度西风大值带上的风应力异常有关, 是造成NPGO的直接原因。该模态表现出明显的准13年年代际变化, 且对其进行5年滑动平均后发现, 从20世纪70年代中期以来, 该序列的振幅越来越大, 1976/1977年和1988/1989年的两次气候年代际突变均处该序列峰值处。引入了冬季北太平洋上层海温异常的NPGO指数, 其能更好反映海洋上层的NPGO现象及其年代际变化。     

影响夏季西北太平洋副热带高压年际变率的关键海区及影响机制

西北太平洋副热带高压(西太副高)是影响东亚夏季气候的主要环流系统,其年际变率受热带多个海区的海-气相互作用过程的调控。为明确影响夏季西太副高的关键海区及其影响机制,在总结最近十余年来相关研究进展的基础上,归纳出影响夏季西太副高年际变率的5个关键海区,包括赤道中东太平洋、热带印度洋、副热带西北太平洋、海洋大陆附近海区以及热带大西洋。阐述了这5个关键海区的海温异常影响西太副高年际变率的机制,并探讨了5个关键海区海温异常的形成机制。围绕夏季西太副高的年际变率,回顾了当前气候模式的模拟和预测研究的现状。最后,提出了本领域亟待解决的关键科学问题,展望未来可能的研究热点。     

Deposition of atmospheric mineral particles in the North Pacific Ocean

Total deposition of atmospheric mineral particles (wet plus dry) has been measured during consecutive two-week sampling intervals from January, 1981 to March, 1982 at four island stations (Midway, Oahu, Enewetak, and Fanning) of the SEAREX Asian Dust Study Network in the North Pacific. The total deposition of mineral aerosol during the period from February to June is higher than that during the period from July to January at most of the stations. A systematic geographical trend is apparent in the dust flux, with greater fluxes at higher latitudes. The deposition values are correlated with the atmospheric mineral particle concentrations at these stations. The mineral particles are transported from arid regions in Asia to the North Pacific, and the annual dust deposition to the ocean appears to be dominated by sporadic dust events of short duration. Wet deposition dominates the removal of dust particles from the atmosphere over the North Pacific. The total deposition of atmospheric mineral material to the central North Pacific is estimated to be 20×10¹² g yr^-1.     

冬季北太平洋多尺度水汽输送和大气河的变化特征及其与PDO和ENSO的联系

利用1950-2015年NCEP/NCAR大气再分析资料和NOAA海表面温度资料,通过回归分析和合成分析的方法研究了冬季北太平洋不同尺度水汽输送和大气河(Atmospheric River,AR)的变化特征及其与PDO、ENSO的联系.结果表明,在PDO正位相时期,时间平均的水汽输送将大量水汽从太平洋北部和中部地区输送...     

A modeling analysis of rainfall and water cycle by the cloud-resolving WRF model over the western North Pacific

Simulated regional precipitation, especially extreme precipitation events, and the regional hydrologic budgets over the western North Pacific region during the period from May to June 2008 were investigated with the high-resolution （4-km grid spacing） Weather Research and Forecast （WRF v3.2.1） model with explicit cloud microphysics. The model initial and boundary conditions were derived from the National Centers for Environmental Prediction/Department of Energy （NCEP/DOE） Reanalysis 2 data. The model precipitation results were evaluated against the Tropical Rainfall Measuring Mission （TRMM） Multisatellite Precipitation Analysis 3B42 product. The results show that the WRF simulations can reason- ably reproduce the spatial distributions of daily mean precipitation and rainy days. However, the simulated frequency distributions of rainy days showed an overestimation of light precipitation, an underestimation of moderate to heavy precipitation, but a good representation of extreme precipitation. The downscaling approach was able to add value to the very heavy precipitation over the ocean since the convective processes are resolved by the high-resolution cloud-resolving model. Moreover, the water vapor budget analysis indi- cates that heavy precipitation is contributed mostly by the stronger moisture convergence; whereas, in less convective periods, the precipitation is more influenced by the surface evaporation. The simulated water vapor budgets imply the importance in the tropical monsoon region of cloud microphysics that affects the precipitation, atmospheric latent heating and, subsequently, the large-scale circulation.     

北太平洋风暴轴对黑潮延伸体系统变异的响应及其能量转换机制

西北太平洋纬向扰动海温经验正交函数（EOF）分解第一和第三模态、第二和第四模态分别代表同期黑潮延伸体和亲潮强弱的配置关系,将两者的典型位相合成,可以分别得到延伸体收缩和扩张状态时的典型模态海温,本文以此及气候态海温作为初始海温强迫场,利用CESM1.2.0模式,讨论了延伸体的系统变异对北太平洋风暴轴的影响及其在不同能量转换过程的主要影响机制,结果表明,延伸体收缩状态下,北太平洋风暴轴强度整体加强,而扩张模态下强度减弱。空间分布上,收缩模态下,风暴轴主要体现为经向方向的变化,中心及其以北强度加强,中心以南减弱;扩张状态下,则主要表现为纬向方向的差异,中心及以西强度减弱明显,中心以东有所增强。对能量转换的诊断分析表明,正压能量转换过程对涡动动能的变化贡献很小,且在风暴轴中心附近,其作用主要为消耗涡动动能,延伸体收缩状态下其消耗作用增强,而扩张状态下消耗作用减弱,这一差异主要是由于不同海温异常强迫下瞬变涡旋的形变不同造成;斜压有效位能释放比正压能量转换大一个量级以上,该过程几乎全部通过基流的经向温度梯度和经向涡动热量输送的相互作用完成,在这一过程中大气斜压性（经向温度梯度）起了关键性作用,大气斜压性异常、基流经向温度梯度异常、斜压有效位能释放异常与风暴轴异常的空间分布均具有较好的对应关系,该过程可能也是延伸体海温异常影响北太平洋风暴轴的主要物理过程;涡动有效位能需要进一步转换为涡动动能才能产生瞬变涡旋运动,涡动有效位能释放的量级与斜压有效位能的释放相当,但数值要小,这一过程通过冷暖空气的上升下沉运动完成,延伸体异常模态下,扰动垂直速度和扰动温度的负相关性的变化与涡动有效位能向涡动动能转换的变化也有较好的对应关系。     

北太平洋海温年代际变化与大气环流和气候的异常

对应北太平洋海表温度(SST)年代际变化的两个基本模态,即25～35年模和7～10年模,分析研究了北半球大气环流和气候异常的形势.其结果极为清楚地表明,对应北太平洋SST的年代际模的正、负位相,大气环流和气候异常的形势都近乎相反,充分说明SST年代际模的重要作用;由于北太平洋SST的两个年代际模有十分相近的水平结构特征,它们对大气环流和气候的影响也有十分相似的特征;北太平洋海温年代际模对大气环流的影响在中高纬度地区呈正压结构特征,而在热带地区的响应主要有斜压结构特征.     

Response of the Subtropical Gyre Circulation in the North Pacific Ocean to CO2 Quadrupling

ABSTRACT

This study investigates the response of the subtropical gyre circulation in the North Pacific Ocean to quadrupled CO₂ using the Community Earth System Model, version 1 (CESM1). In particular, an overriding technique is applied to isolate and quantify the effects of wind stress and thermal warming caused by CO₂ emissions. Results show that, in response to the increase in CO₂, the total mass transport in the subtropical gyre is reduced by approximately 11%. This reduction results mainly from negative anomalies of the wind stress curl over the subtropical region, with a smaller contribution from the thermal warming effect. Furthermore, a detailed analysis finds that the change in the subtropical gyre is baroclinic in nature [i.e., the gyre appears to be spin-up in the upper ocean (above 300?m) but spin-down in the lower thermocline (from 300 to 1500?m)]. This reversal between the upper ocean and lower thermocline is a result of the thermal warming effect, which intensifies ocean stratification, hindering the transfer of momentum from the upper layers to the lower layers and leading to an acceleration of the gyre in the upper ocean but a deceleration in the lower thermocline. Another feature of the response of the subtropical gyre to quadrupled CO₂ is the respective poleward and equatorward movements of its northern and southern boundaries, which is a result of the change in the zero wind stress curl lines.     

Impact of the Winter North Pacific Oscillation on the Surface Air Temperature over Eurasia and North America: Sensitivity to the Index Definition

This study analyzes the impact of the winter North Pacific Oscillation(NPO) on the surface air temperature(SAT)variations over Eurasia and North America based on six different NPO indices. Results show that the influences of the winter NPO on the SAT over Eurasia and North America are sensitive to the definition of the NPO index. The impact of the winter NPO on the SAT variations over Eurasia(North America) is significant(insignificant) when the anticyclonic anomaly associated with the NPO index over the North Pacific midlatitudes shifts westward and pronounced northerly wind anomalies appear around Lake Baikal. By contrast, the impact of the winter NPO on the SAT variations over Eurasia(North America)is insignificant(significant) when the anticyclonic anomaly over the North Pacific related to the NPO index shifts eastward and the associated northerly wind anomalies to its eastern flank extend to North America. The present study suggests that the NPO definition should be taken into account when analyzing the impact of the winter NPO on Eurasian and North American SAT variations.     

越南北部夏季降水特征及其与海温的联系

根据1958—1997年越南降水资料和NCEP／NCAR再分析资料，运用小波分析和相关分析等方法分析了越南北部降水特征及其与海温的联系。结果表明，越南北部降水主要集中在夏秋季；越南北部夏秋季降水具有明显的年际、年代际变化特征．并且与热带太平洋海温关系密切。在越南北部夏季多雨年，热带西太平洋海温异常偏高，中东太平洋海温异常偏低；而少雨年，则情况相反。     

次季节-季节尺度热带气旋活动研究和预测技术进展

从外部强迫和大气内部变率两个方面回顾次季节-季节尺度西北太平洋热带气旋活动的主要影响因子及相关机制研究进展,分析统计、动力及混合动力-统计混合3类预测技术的发展历史和现状,对该领域尚未解决的主要科学问题及预测技术发展趋势进行了探讨。     

Three Types of Tropical Waves Related to Tropical Cyclogenesis over the Western North Pacific

The present study applies a space-time filter to identify three dominant types of tropical waves： Madden-Julian oscillations （MJOs）, equatorial Rossby （ER） waves, and tropical depression （TD）-type disturbances. The impacts of these waves on tropical cyclones （TCs） were investigated based on 131 observations during the period 2000-07. The results suggest that 72% of TC geneses were related to the joint impacts of more than one type of wave. The composites for cases in different categories reveal that TCs related to the concurrence of the three types of waves have strong and large initial vortices at the time of TC genesis. In the absence of the MJO, ER- and TD-related TC genesis, embedded in easterly flow, exhibits a relatively fast initiation process and gives rise to a relatively small scale vortex. In contrast, without the ER wave contribution, TCs associated with ER and TD waves did not require strong convection at the time of genesis because an initial vortex can rapidly develop in the MJO active phase through persistent energy transfer. The MJO-related TC geneses were scattered in geographic distribution, as opposed to the clustered and eastward shift observed for genesis cases without contributions from MJOs.