全球海表温度在不同时间尺度的主模态对比分析

利用1880—2009年HadISST资料,去掉百年全球变暖的信号,研究发现东太平洋、北太平洋和北大西洋都有较强的年际和年代际振荡信号,特别是赤道东太平洋南侧的年代际振荡是不容忽视的。对全球范围的海表温度资料做EOF分析发现,存在3种主要的全球尺度信号,第一模态为太平洋型、第二模态为北大西洋型以及第三模态为赤道中太平洋型。特别指出,第三模态是CP ENSO在全球模态中的表现。这3种模态在年际和年代际尺度都有显著的信号,在无滤波的情况下,3种模态方差贡献之和为34%。在年代际以上时间尺度范围,3种模态方差贡献之和为61%。在各种时间尺度中,这3种信号与全球平均温度都有一定的联系,尤其第一、二模态的影响最为重要,在年代际尺度中,第一、二模态方差贡献之和达到50%。2005年以后全球并没有明显增温,可能与前2个模态同时下降有关。     

BCC_CSM1.1气候模式对全球海表温度年代际变化的回报能力评估

通过与观测资料和20世纪历史气候模拟试验结果(NoINT)的对比分析,评估了BCC_CSM1.1年代际预测试验(INT)中对全球海表温度(SST)年代际变化的回报能力。分析结果显示:(1)INT试验模拟的全球平均SST增暖趋势比NoINT的更加接近观测;(2)其在热带大西洋、热带西太平洋和热带印度洋有较高的预测技巧;(3)对于太平洋年代际振荡2个关键区——北太平洋和热带中东太平洋,模式的预测技巧较低,且海洋初始化的作用也很小;(4)在热带南印度洋,INT的预测技巧普遍高于NoINT,在提前3~6年和4~7年时技巧最高。这些结论与基于其他模式得到的已有研究结果类似,但是BCC模式对北大西洋,特别是其副极地区域的预测技巧明显低于其他模式。BCC模式无法合理模拟出北大西洋SST与热盐环流间的交替变化规律,可能是其预测技巧偏低的原因。     

CMIP研究计划的进展及其在中国地区的检验和应用前景

由世界气候研究计划(WCRP)推动制定的CMIP计划,是一整套耦合大气环流气候模式的比较计划.该计划旨在通过比较模式的模拟能力来评价模式的好坏,促进气候模式的发展;同时也为生态、水文、社会经济诸学科在全球变化背景下预估未来环境变化提供可靠的科学依据.CMIP计划从AMIP开始,经历了CMIP1、CMIP2、CMIP3几个阶段的发展,并已为模式研究提供了迄今为止时间最长、内容最为广泛的模式资料库.尽管模式的模拟结果仍不可避免的存在一些不足,但世界各国纷纷利用该资料库进行模式发展以及与气候变化相关的多学科研究,为预估未来的环境变化提供了不可替代的科学依据.对其作了简要回顾,并对其在中国地区存在的问题和潜在应用前景作了简要论述.     

北太平洋涡旋振荡研究进展

从观测事实和动力机制两方面,对近年发现的新的气候模态——北太平洋涡旋振荡（NPGO）的研究成果进行系统总结。NPGO的空间结构表现为北太平洋上海表高度异常（SSHA）的正负中心呈南北偶极子分布,当NPGO位于正位相时,南北涡流都加强,这种加强是由风应力旋度及风生涌流所驱动的。关于NPGO的机制研究发现,NPGO是中纬太...     

海洋模式初始化同化方案对IAP近期气候预测系统回报试验技巧的影响

基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所(IAP)近期气候预测系统(以下简称IAP Dec Pre S系统)发展了2种初始化方法:第一种采用Incremental Analysis Update(IAU)方案同化格点化的海洋温度和盐度客观分析资料EN3;第二种采用集合最优差值(EnOI)结合IAU(EnOI-IAU)的方案同化原始海洋温度和盐度观测廓线资料EN4。主要目的是比较基于2种初始化方案开展的年代际预测试验的技巧。时间相关系数、均方根技巧评分等指标均表明,基于EnOI-IAU方案的回报试验对与太平洋年代际振荡(PDO)有关的北太平洋海表面温度(SST)的回报技巧显著高于基于IAU方案的回报试验。而对于大西洋多年代际振荡(AMO),EnOI-IAU方案回报试验的技巧低于IAU方案回报试验。AMO存在副极地和热带北大西洋2个活动中心,EnOIIAU方案在热带中心的技巧仅略低于IAU方案,但是它在热带外区域模拟出了虚假的降温趋势,因此技巧远低于后者。     

FGOALS-s2海洋同化系统中东亚夏季风和前冬厄尔尼诺—南方涛动关系的年代际变化

海洋同化系统为年代际预测试验提供初值,其性能可能会影响年代际预测技巧,因此评估其对重要年代际变化现象的模拟能力非常必要。观测发现,东亚夏季风(EASM)和前冬厄尔尼诺—南方涛动(ENSO)的关系在1970s末加强,随后在1990s中期后减弱。基于FGOALS-s2耦合气候模式的海洋同化系统评估了其对这2次年代际变化的模拟能力。结果表明,决定模式能否再现EASM和前冬ENSO关系的年代际变化有2个重要因素:(1)与前冬ENSO有关的夏季印度洋—太平洋海温型的年代际变化;(2)模式西北太平洋反气旋对热带海温的响应偏差。模式中西北太平洋反气旋与东北印度洋的暖海温关系稳定,当1970s末前冬ENSO对夏季印度洋海温影响显著增强时,模式能够模拟出北印度洋降水以及赤道东印度洋至海洋大陆上空Kelvin波的增强,从而可再现EASM与前冬ENSO关系的增强;而1990s中期后模式中与前冬ENSO有关的东北印度洋海温异常进一步增强,与观测相反,使得模式未能再现观测中EASM与前冬ENSO关系的减弱。此外,1990s中期后模式对夏季中太平洋冷海温异常的Rossby波响应存在较大偏差,是其未能再现此次年代际变化的另一个原因。研究表明,与ENSO有关的热带印太海温的年代际变化预测水平和模式对海温的响应偏差将在一定程度上制约模式对EASM与ENSO关系的年代际预测能力。     

近20年来气候模式的发展与模式比较计划

20世纪80年代以来，全球气候观测系统的不断完善、国际大型外场观测试验的成功实施以及高性能计算机的飞速发展，为气候模式的迅猛发展提供了基础和条件。近20年来气候模式的复杂程度和模拟能力得到了显著的提高，目前已成为研究全球和区域气候的形成及变异、气候系统各圈层之间的相互作用以及全球变化等的有力工具。对气候模式（包括大气环流模式、陆面过程模式、海洋环流模式以及区域气候模式）的主要发展进行综合评述，并简要介绍了目前世界上一些主要的模式比较研究计划。     

北半球高纬海冰主要气候特征的全球海冰气耦合模式数值模拟

利用一个全球海冰气耦合模式对北半球高纬海冰的主要气候特征进行了数值模拟。结果表明 ,模拟结果中海冰的季节变化特征合理 ,冬季海冰的主要地理分布特征都模拟得很好 ,但夏季北冰洋内部靠近欧亚大陆部分边缘海区海冰密集度模拟得偏大。模拟结果中 ,北半球高纬地区冬季海冰密集度具有显著的年际变化 ,变化最显著区域位于格陵兰海 ,其次是巴伦支海 ,这些特征均与观测结果一致。对这个海冰气耦合模式在北半球海冰平均气候状况、季节变化和年际变化方面模拟能力的检验结果表明 ,当前的研究工作为下一步进行长期变化趋势的模拟打下了基础。     

东亚夏季降水与全球海温异常的年代际变化关系

利用1901—2010年GPCC逐月降水、Had ISST月平均海表温度、NOAA 20世纪再分析等资料,采用最大协方差分析(Maximum Covariance Analysis,MCA)、相关、回归等方法研究了东亚地区夏季降水与全球海表温度异常之间的年代际时空变化关系。MCA分析结果表明,东亚地区夏季降水与全球海温异常耦合关系在年代际尺度上主要表现为4个模态,分别受全球变暖、太平洋年代际涛动PDO、大西洋多年代际涛动AMO和北太平洋涡旋振荡NPGO影响,各自解释了27.7%,12.5%,8.9%和7.3%的方差。第一模态由于受全球变暖影响,东亚大部分地区水汽充足,因此东亚大部分地区降水均偏多。第二模态的降水异常表现为东亚中部地区降水偏多而南部和北部偏少的"南北旱中间涝"的三极型分布,其可能原因是太平洋年代际涛动使得东亚夏季风减弱,不利于水汽往北输送,引起水汽在东亚中部聚集,导致该地区降水偏多;同时西风带往南偏移,使得东亚中部地区对流增强,也引起该地区降水偏多。第三模态的降水异常则主要为"南涝北旱"的偶极分布型,可能原因是东亚大槽向东南方向偏移,东亚北部西风带减弱,使得东亚北部对流减弱、降水偏少,而东亚南部地区则对流增强、降水偏多。第四模态降水异常呈现出"南北涝中间旱"的三极型分布特征,其原因是东亚中部地区高层出现异常东风,对流活动减弱,导致东亚中部降水偏少,而南部和北部地区降水偏多。     

南极冰盖GLIMMER模式移动边界试验研究

利用欧洲冰盖比较计划(EISMINT)的移动边界条件EISMINT-1测试集,通过三维有限差分南极冰盖GLIMMER模式,采用浅冰近似计算了一个定义在方形冰盖积分区域的流场特征量,研究了冰盖在大尺度长时间序列条件下对气候变化的反馈,考察了稳定态下冰盖演化的周期性行为.试验表明:GLIMMER模式在EISMINT-1移动边界条件下可以模拟出气候强迫下的冰盖演化趋势,在长时间尺度上可以刻画出气候变化的反馈机制.同时,对南极冰盖数值模拟面临的问题、GLIMMER模式以及EISMINT冰盖比较计划的内容和框架做了说明,对EISMINT比较计划目前的发展状况和遇到的问题做了分析,并且对GLIMMER模式下一步的研究方向做了一些探讨.     

Progresses and Prospects for North Tropical Atlantic Mode Interannual Variability

North Tropical Atlantic Mode (NTAM) is the leading variability of the boreal spring sea surface temperature anomalies over the North Tropical Atlantic at interannual timescale. It is also known as the northern pole of the Atlantic Meridional Mode (AMM). NTAM shows significant impact on the shift of Intertropical Convergence Zone, the precipitation of the surrounding countries, the quasi-biennial oscillation of El Nino-Southern Oscillation (ENSO), and the recent global warming hiatus. Despite its distinct influence on global climate, NTAM has not received equivalent attention as other tropical variability (e.g. ENSO). By revisiting previous studies, this paper summarized the triggers and mechanisms responsible for the evolution and development of NTAM, including remote forcing from ENSO, south tropical Atlantic as well as North Atlantic Oscillation (NAO), local air-sea coupling, and the interactions among different triggers. Also, this paper detailedly introduced the ability of CMIP5 (The fifth phase of the Coupled Model Intercomparison Project) model simulation. The prominent model biases over the equatorial Atlantic significantly limit the study of NTAM. Finally, a future prospective of NTAM interannual variability was presented.     

Impacts of Initialization Schemes of Oceanic States on the Predictive Skills of the IAP Near-Term Climate Prediction System

Based on the near-term climate prediction system of the Institute of Atmospheric Physics (hereafter IAP-DecPreS), we developed two distinct initialization schemes for the Coupled Global Climate Models (CGCM), FGOALS-s2. The first scheme used the Incremental Analysis Update (IAU) to assimilate gridded oceanic temperature and salinity data derived from the EN3 dataset. The second scheme used the merge of the ensemble optimal interpolation (EnOI) and IAU scheme (hereafter EnOI-IAU) to assimilate raw observational oceanic temperature and salinity profiles. The predictive skills of the decadal prediction experiments based on the two schemes were compared. Several metrics including temporal correlation and root mean square skills score indicate that the experiment based on the EnOI-IAU shows significantly higher predictive skills in the Sea Surface Temperature (SST) anomalies in the North Pacific associated with the Pacific Decadal Oscillation (PDO), than the experiment based on the IAU. In contrast, for the Atlantic Multi-Decadal Oscillation (AMO), the predictive skills of the experiment based on the EnOI-IAU are lower than that based on the IAU. The AMO has two activity centers, located in the subpolar and tropical North Atlantic. The skills of the experiment based on the EnOI are close to that based on the IAU in the tropical North Atlantic, while much lower than the latter in the extratropical region due to a false simulation of the warming trend in the region.     

Assessment of the seasonal variation of simulated Wyrtki jet over the tropical Indian Ocean in CMIP5 models

Performances of the 24 Coupled Model Intercomparison Project Phase 5 (CMIP5) models in simulating the Wyrtki Jet over the tropical Indian Ocean are evaluated, and the results show large diversity in the simulated current intensity at seasonal timescale. These coupled models are able to capture the dominant spatial distribution of observed Wyrtki Jet, the central equatorial region. The simulated seasonal variations of Wyrtki Jet are also reproduced quantitatively, though the simulated amplitudes from CMIP5 models are quite spread among the CMIP5 models. Compared with the observation, some coupled models are not able to present the evolution of Wyrtki Jet in fall season and the decay phase has been postponed 1 month later. Further diagnostic illustrates that the simulated surface zonal wind has remarkable impact on the evolution of Wyrtki Jet in fall season over the tropical Indian Ocean. This study also points out that there is a common problem in these models that most of them present 1-month delayed Wyrtki Jets peak time than the normal climatological condition along the center equatorial Indian Ocean.     

基于CMIP6模式的黄河上游地区未来气温模拟预估

利用第六次国际耦合模式比较计划（CMIP6）提供的5个气候模式,并结合基于地面气象站的CN05.1气象资料,评估了CMIP6模式对黄河上游地区1961—2014年气温变化的模拟能力。基于7个共享社会经济路径及代表性浓度路径（SSP-RCP）组合情景,结合多模式集合平均预估了2015—2100年黄河上游地区年均气温和季平均气温的时空变化规律。结果表明：多模式集合平均能较好地模拟黄河上游地区历史平均气温的空间分布格局与年变化。7个未来情景一致表明,2015—2100年黄河上游地区年平均气温呈现波动上升趋势［0.03～0.82 ℃?（10a）^-1］。其中,低辐射强迫情景下（SSP1-1.9、SSP1-2.6及SSP4-3.4）气温先呈现增加趋势,21世纪中期到达增幅峰值,之后增温呈现放缓趋势;而中、高辐射强迫情景下（SSP2-4.5、SSP3-7.0、SSP4-6.0及SSP5-8.5）气温表现为持续上升态势。空间上,未来气温增幅显著的区域位于黄河上游西部地区;时间上,呈现夏季增温快,春季增温慢。四季增温的空间分布呈现出一致特征,表现为西部增温强于东部,北部增温强于南部。研究结果可为黄河流域水资源管理及气候变化的适应性研究提供科学依据。     

Interdecadal Relationship between the East Asian Summer Precipitation and Global Sea Surface Temperature Anomalies

This study investigated the decadal relationship between the East Asian (EA) summer precipitation (EASP) and global sea surface temperature anomaly (SSTA) patterns. Maximum covariance analysis (MCA) was used to identify the coupling relationship between EASP and global SSTA. Four leading coupling modes were identified by MCA and they explained 27.7%,12.5%,8.9%,and 7.3% of the total variance, respectively. The spatial pattern of EASP of the first leading mode exhibited more-than-normal precipitation in most regions of EA. The second mode of EASP depicted a north-south “-+-” tripole pattern. The third one showed a “wet south and dry north” pattern, and the fourth mode exhibited a north-south “+-+” tripole pattern. The four coupling modes were suggested to be modulated by the global warming, Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Pacific Gyre Oscillation (NPGO), respectively.The atmospheric processes and mechanisms underlying such modulations were also investigated. In the first coupling mode, global warming was favorable for increasing water vapor and precipitation over most parts of EA. In the second mode, PDO weakened the EA summer monsoon circulation, and it decreased precipitation in northern and southern EA regions and increased precipitation in the central EA region. The third mode was affected by AMO, which displaced the EA trough southward and weakened the convective activity over the northern EA region, thus leading to deficient precipitation in northern EA region. In the fourth mode, the EA summer monsoon was strengthened by NPGO, thus increasing precipitation in the northern and southern regions and decreasing precipitation in the central region.     

A review of observed and projected changes in climate for the islands in the Caribbean

Observed and projected changes in climate have serious socio-economic implications for the Caribbean islands. This article attempts to present basic climate change information—based on previous studies, available observations and climate model simulations—at spatial scales relevant for islands in the Caribbean. We use the General Circulation Model (GCM) data included in the Coupled Model Intercomparison Project phase 3 (CMIP3) and the UK Hadley Centre regional climate model (RCM) data to provide both present-day and scenario-based future information on precipitation and temperature for individual island states. Gridded station observations and satellite data are used to study 20th century climate and to assess the performance of climate models. With main focus on precipitation, we also discuss factors such as sea surface temperature, sea level pressure and winds that affect seasonal variations in precipitation. The CMIP3 ensemble mean and the RCM successfully capture the large-scale atmospheric circulation features in the region, but show difficulty in capturing the characteristic bimodal seasonal cycle of precipitation. Future drying during the wet season in this region under climate change scenarios has been noted in previous studies, but the magnitude of change is highly uncertain in both GCM and RCM simulations. The projected decrease is more prominent in the early wet season erasing the mid-summer drought feature in the western Caribbean. The RCM simulations show improvements over the GCM mainly due to better representation of landmass, but its performance is critically dependent on the driving GCM. This study highlights the need for high-resolution observations and ensemble of climate model simulations to fully understand climate change and its impacts on small islands in the Caribbean.     

Alternating Effects of Climate Drivers on Altamaha River Discharge to Coastal Georgia,USA

Freshwater delivery is an important factor determining estuarine character and health and may be influenced by large-scale climate oscillations. Variability in freshwater delivery (precipitation and discharge) to the Altamaha River estuary (GA, USA) was examined in relation to indices for several climate signals: the Bermuda High Index (BHI), the Southern Oscillation Index (SOI), the Improved El Niño Modoki Index (IEMI), the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the Pacific Decadal Oscillation (PDO), and the Pacific/North American Pattern (PNA). Discharge to this estuary has been linked to key ecosystem properties (e.g., salinity regime, water residence time, nutrient inputs, and marsh processes), so understanding how climate patterns affect precipitation and river discharge will help elucidate how the estuarine ecosystem may respond to climate changes. Precipitation patterns in the Altamaha River watershed were described using empirical orthogonal functions (EOFs) of the combined multidecadal time series of precipitation at 14 stations. The first EOF (67 % of the variance) was spatially uniform, the second EOF (11 %) showed a spatial gradient along the long axis of the watershed (NW–SE), and the third EOF (6 %) showed a NE–SW pattern. We compared the principal components (PCs) associated with these EOFs, monthly standardized anomalies of Altamaha River discharge at the gauge closest to the estuary, and the climate indices. Complex, seasonally alternating patterns emerged. The BHI was correlated with June–January discharge and precipitation PC 1. The SOI was correlated with January–April discharge and precipitation PC 2, and also weakly correlated with PC 1 in November–December. The AMO was correlated with river discharge and precipitation PC 3 mainly in December–February and June. The correlation patterns of precipitation PCs with PDO and PNA were similar to those with SOI, but weaker. There were no consistent relationships with two NAO indices or IEMI. Connections between climate signals and estimates of nutrient loading were consistent with the connections to discharge. The occurrence of tropical storms in the region was strongly related to the BHI but not to the other climate indices, possibly representing the influence of storm tracking more than the rate of storm formation. Comparison with the literature suggests that the patterns found may be typical of southeastern USA estuaries but are likely to be different from those outside the region.     

基于CMIP6气候模式的新疆积雪深度时空格局研究

积雪深度的变化对地表水热平衡起着至关重要的作用。选用了国际耦合模式比较计划第六阶段（CMIP6）中目前情景比较齐全的五个全球气候模式,通过对比新疆地区1979—2014年积雪深度长时间序列数据集,评估了气候模式在新疆地区模拟积雪深度的模拟能力,接着预估了未来不同SSPs-RCPs情景下新疆地区在2021—2040年（近期）、2041—2060年（中期）、2081—2100年（末期）相对于基准期（1995—2014年）的积雪深度变化。气温和降水对积雪深度变化有着重要的影响,因此还分析了新疆地区到21世纪末期气温和降水的变化趋势。结果表明：订正后的气候模式模拟的积雪深度数据与观测数据的相关系数均达到0.8以上,其中1月至3月与观测数据的结果更为吻合。气候模式基本上能够反映积雪深度年内变化的基本特征,气候模式模拟的积雪深度空间分布和观测数据具有相似的特征。气温和降水在未来不同情景下均会波动上升,其中气温的增幅相对比较明显,达0.43 ℃·（10a）^-1,而降水的增幅为0.63 mm·（10a）^-1,新疆未来的气候总体上呈现出变暖变湿的趋势。新疆地区的平均积雪深度在未来不同时期相对基准期均呈增加的趋势。SSP1-1.9情景下,21世纪近期、中期和末期北部大部分地区的积雪深度将会有所增加;SSP1-2.6情景下,北部阿尔泰山地区的积雪深度在21世纪近期有所减小,但中期和末期将会有所增加;SSP2-4.5情景下,21世纪不同时期东部地区的积雪深度将会有所增加,北部和中部大部分地区在不同时期积雪深度将会变小;SSP3-7.0情景下,21世纪不同时期北部和西南地区的积雪深度将会普遍变小,东部地区的积雪深度将普遍增加;SSP4-3.4和SSP4-6.0情景下,21世纪不同时期西南昆仑山地区的积雪深度将会普遍变小,东部地区的积雪深度将普遍增加;SSP5-8.5情景下,北部阿尔泰山地区和东部地区的积雪深度将普遍增加。     

新疆北部地区积雪深度变化特征及未来50a的预估

分析比较参加CMIP3计划的全球气候模式,在20C3M下各模式1961-1999年平均积雪深度和观测资料比较的基础上,检验了模式对积雪深度的模拟能力.在此基础上,选用INM-CM3.0和CGCM-T47_1模式对北疆地区未来50 a的积雪变化进行了预估.由于受GCM的空间分辨率和新疆北部地区地形、盆地沙漠下垫面、水汽来源和干旱气候环境的影响,CMIP3模式的GCM在新疆北部地区的模拟能力有限.通过相关系数和均方差误差的双重检验,选取了在新疆地区模拟能力较好的INM-CM3.0和CGCM-T47_1模式的模拟结果对新疆地区未来的积雪变化进行了预测.结果表明,在A1B、B1情景下,2002-2050年,总体上新疆北部地区的积雪深度均呈减少趋势;A2情景下,INM-CM3.0、CGCM-T47-1模式在准葛尔盆地地区积雪变化的模拟结果存在差异,但未来40 a新疆地区除天山附近外,积雪深度变化呈减少趋势.