NCAR CAM3全球气候模式对亚洲中部干旱区气候变化的模拟检验

以英国气象局哈德来环流中心提供的连续变化的海温和海冰资料为边界场,用NCAR CAM3全球气候模式对近百年来亚洲中部干旱区气候变化进行模拟,然后利用NCEP再分析资料、英国东安哥拉大学近100 a的CRUTEM2v气温格点序列资料及距平均方根误差、相关系数等方法对模拟的亚洲中部干旱区气候平均场进行检验,结果表明:CAM3.0对亚洲中部干旱区的高度场模拟较好,均方根误差均较小,相关系数较大,相关性较强;温度场除低层700 hPa均方根误差稍大外,其余对流层均较小,并且相关系数比较大;无论对经向风速还是纬向风速,模式模拟的均方差均较大、相关系数较小,模拟的效果较差,其原因尚待进一步研究;地面加热场模拟均方根误差分布具有明显的纬向性,局域和季节差异明显;数值实验模拟出了近百年来亚洲中部干旱区地面气温的变化趋势,但模拟的增温幅度更大,同时对季节变化的模拟存在差异。     

全球海洋资料同化系统ZFL_GODAS的研制和初步评估试验

本研究发展了一个全球海洋资料同化系统ZFL_GODAS。该系统是一个短期气候数值预测业务系统的子系统,为短期气候预测海气耦合模式提供全球海洋初始场。系统能够同化的观测资料包括卫星高度计资料、卫星海表温度(SST)资料,以及Argo、XBT、TAO等各种不同来源的现场温盐廓线资料。系统使用的海洋模式为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开发的气候系统海洋模式LICOM1.0,同化方案为集合最优插值(EnOI)方案。系统使用一个由海洋模式自由积分得到的静态样本来估计背景场误差协方差。这样的基于集合样本的背景场误差协方差具有多变量协变、各向异性的特征,且能反映海洋物理过程固有的空间尺度特征。针对EnOI同化程序的特点,开发了一套特色鲜明、负载均衡、高效的并行化同化程序。本文通过与不同类型观测资料的比较,对同化系统的性能进行了评估。通过比较海表温度和海面高度的年际变率,海表温度异常随时间的变化,SST、海面高度异常(SLA)以及次表层温盐预报产品的均方根误差,5年平均温度偏差廓线、平均盐度廓线、平均纬向流速廓线等发现:系统工作正常、同化效果较好;经过同化以后,各变量都更加接近观测,误差更小,与观测场的相关性更好,可以为短期气候预测系统提供较好的海洋初始场,也可以为物理海洋学的研究提供有效的再分析资料。     

CYGNSS海表风场观测数据验证及其可能的应用

海表面风场可以用于获取许多大气和海洋现象的信号,高质量、高时空分辨率的海表面风场数据产品将有利于海洋-大气动力过程的研究.本文使用全球热带系泊浮标阵列计划（Global Tropical Moored Array Programs）的锚定浮标风场数据和西沙通量塔气象观测资料验证了Cyclone Global Navigation Satellite System （CYGNSS）的35°N~35°S海面遥感风场观测数据.结果表明,CYGNSS海表面风场与实测资料存在着2.17 m/s左右的平均均方根误差（RMSD）,它可能源于观测数据和卫星遥感资料的观测误差,以及两者在空间和时间上未严格匹配而引起的代表性误差.另外,CYGNSS海表面风速的时间演变与实测资料非常一致,展现了CYGNSS在研究海洋-大气能量和动量交换过程方面的潜在应用价值.本文使用Madden-Julian Oscillation （MJO）和赤道东部印度洋上升流事件作为两个个例,说明了CYGNSS海表面风场资料的潜在应用价值.     

SODA月平均海洋数据集简介

SODA海洋数据集由全球简单海洋资料同化分析系统（Simple Ocean Data Assimilation）产生，该系统是美国马里兰大学（University of Maryland）于20世纪90年代初开始开发的分析系统，其目的是为气候研究提供一套与大气再分析资料相匹配的海洋再分析资料。     

全球多源海冰密集度融合资料研制试验

为了发展一套全球多源海冰密集度逐日融合资料,以欧洲气象卫星应用组织（EUMETSAT）海洋海冰应用中心（OSI SAF）海冰密集度数据、中国国家卫星气象中心（NSMC）的MWRI和VIRR全球海冰密集度数据、美国国家冰雪数据中心（NSIDC）的NISE海冰密集度数据、美国国家冰中心（NIC）的IMS北半球海冰数据为观测数据源,以ERA-Interim模式数据为背景场,采用以下方案开展融合试验。首先,对各数据源资料进行质量控制;其次,以OSI SAF海冰密集度数据为基准,采用概率密度函数（PDF）匹配方法订正其他卫星资料的系统误差;然后,根据订正后的误差生成超级观测场;最后,利用STMAS方法将超级观测场和作为背景场的ERA-Interim海冰密集度数据进行融合,生成全球逐日0.25°分辨率海冰密集度融合试验数据。通过与国际广泛使用的OISST、OSTIA海冰密集度数据对比,评估融合试验产品的质量。结果表明:融合方案中的PDF方法通过调整非基准资料的概率密度分布,实现非基准资料和基准资料概率密度分布一致,从而使3种海冰密集度卫星资料系统误差均显著减小;STMAS方法能够将超级观测场和背景场进行有效融合,生成融合试验产品;风云卫星数据的使用提高了融合数据生产的自主可控能力;同时,融合方案考虑了卫星数据源的时效性、获取的稳定性等因素。融合产品与OISST和OSTIA海冰密集度数据的空间分布在南、北极均高度吻合,相关系数均超过0.985,与OISST和OSTIA的偏差分别为?1.170%和0.276%,融合试验产品整体偏差介于两种资料之间,反映了试验产品系统误差较小的良好特性。可见,融合方案能够满足实时业务需要,融合试验产品具有较高的质量。      

GTS的温盐资料在BCC_GODAS中的同化结果分析

分析了从GTS(全球无线通讯系统)获得的2002-2007年海洋温盐观测资料在国家气候中心第2代全球海洋资料同化系统(BCC_GODAS 2.0)中的同化结果。与SODA(简易海洋同化数据)资料的比较表明:GTS中的海洋温盐资料同化对模式温盐场的改进之处主要表现在混合层暖区的范围和中心强度、温跃层中温度槽脊的深度、温跃层附近的温度梯度以及盐度高、低值区的范围和中心强度等方面,同化后全球温盐场的均方根误差得到一定程度的降低。挑选位于不同海区的单点温盐廓线与ARGO(地转海洋学实时观测阵)观测作了进一步比较,结果表明:大多数情况下,同化后温盐廓线的均方根误差得到明显降低,模拟的温盐垂向分布特征也更为准确。与TAO(热带大气海洋观测网)资料的比较也同样表明:同化后的温盐场特征会得到一定程度改善。     

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。     

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。     

IAP/LASG全球海-陆-气耦合系统模式的纬向平均大气气候态分析

分海洋和陆地两种情况来讨论IAP／LASG全球海－陆－气耦合系统模式（GOALS）四个版本的结果，并与观测资料进行对比分析，一些重要的大气变量包括表面空气温度，海平面气压和降水率用来评估GOALS模式模拟当代气候和气候变率的能力，总的来说，GOALS模式的四个版本都能够合理地再现观测到的平均气候态和季节变化的主要特征，同时评估也揭示了模式的一些缺陷，可以清楚地看到模拟的全球平均海平面气压的主要误差是在陆地上，陆地上表面空气温度模拟偏高主要是由于陆南过程的影响，值得注意的是降水率模拟偏低主要是在海洋上，而中高纬的陆地降水在北半球冬天却比观测偏高。通过模式不同版本之间的相互比较研究，可以发现模式中太阳辐射日变化物理过程的引入明显地改善了表面空气温度的模拟，尤其是在中低纬度的陆地上，太阳辐射日变化的引入对热带陆地的降水和中高纬度的冬季降水也有较大改进。而且，由于使用了逐日通量距平交换方案（DFA），GOALS模式新版本模拟的海洋上的温度变率在中低纬度有了改善。比较观测和模拟的年平均表面空气温度的标准度，可以发现GOALS模式四个版本都低估了海洋和陆地上的温度变率，中还对影响观测和模拟温度变率差异的可能原因进行了探讨。     

系统辨识(1):辨识导引

海气交界面的能量交换与海洋平流共同决定海表面温度（sea surface temperature,SST）异常的形成、维持与衰减。基于作者近期的研究,本文回顾了海表面热通量（surface heat flux,SHF）反馈以及SST方差与海表热通量及海洋热输送方差之间的关系。海表热通量异常可近似为一个与SST成正比的线性反馈项与一个大气强迫项之和。SHF的反馈参数取决于SST和SHF间的滞后交叉协方差以及SST自协方差。这种反馈总体上为负反馈,减弱SST异常,海表湍流部分起主导作用。最强的反馈可见于南北两半球的中纬度,最大值出现在大洋的西部和中部位置并延伸至高纬度地区。SHF反馈于北半球秋冬两季增强,春夏两季减弱。这些反馈特征在CMIP3耦合气候模式中得到合理的模拟。然而,多数模式中反馈的强度与再分析资料的估值相比略为偏弱。与再分析资料的估值相比,＂平均模式＂反馈参数比单一模式有更相似的空间形态以及较小的均方根差。基于海表面能量收支平衡,SST的方差可以表示为3个要素的积：1）海表面辐射和湍流通量以及海洋热输送的方差之和;2）一个衡量SST持续性的传输系数G;3）一个反映海表热通量以及海洋热输送之间协方差结构的有效因子e。SST方差的地理分布类似于海表热通量及海洋热输送的方差之和,但为G和e因子所修正。     

Evaluation of global high-resolution reanalysis products based on the Chinese global oceanography forecasting system: 基于中国全球海洋预报系统(CGOFS)的全球高分辨率再分析产品评估

The global high-resolution marine reanalysis products that were independently developed by the National Marine Environmental Forecasting Center based on the Chinese Global Oceanography Forecasting System (CGOFS), are evaluated by comparing their climatologies with internationally recognized data from WOA (Word Ocean Atlas), SODA (Simple Ocean Data Assimilation), AVISO (Archiving, Validation, and Interpretation of Satellite Oceanographic Data), and C-GLORS (Global Ocean Reanalysis System). The results show that the SST RMSEs of CGOFS and SODA against WOA are 0.51 °C and 0.43 °C respectively; and in the North Pacific, the SST of CGOGS is closer to that of WOA than SODA. The SSS RMSEs of CGOFS and SODA compared with WOA are 0.48 PSU and 0.40 PSU, respectively. CGOFS can reproduce the main large-scale ocean circulation globally, and obtain a similar vertical structure of the Equatorial Undercurrent as SODA. The RMSE of the CGOFS global sea-level anomaly against AVISO is 0.018 m. The monthly averaged sea-ice extents are between those of SODA and C-GLORS in each month; the growth and ablation characteristics of the ice volume are consistent with SODA and C-GLORS; but the ice volume of CGOFS is greater than that of SODA and C-GLORS. In general, the climatology of the CGOFS global high-resolution reanalysis products are basically consistent with similar international products, and can thus provide reliable data for the improvement of marine science and technology in China.摘要通过同化系统将观测资料与海洋数值模式融合得到的海洋再分析产品为海洋科学研究提供了重要的资料基础.本文采用WOA,SODA,AVISO和GLORS四种数据资料与我国自主研发的中国全球海洋预报系统(CGOFS)的气候态结果进行了对比, 结果表明:CGOFS和SODA的全球海表面温度与WOA的均方根误差分别为0.51 和 0.43°C.CGOFS和SODA的海表面盐度与WOA的均方根误差分别为0.48和0.40 PSU;海流方面, CGOFS能较好的刻画主要大洋环流分布及赤道潜流的垂向结构;CGOFS的全球海表面高度异常与AVISO的均方根误差为0.018m;多年月平均海冰外缘线覆盖面积介于SODA 和 GLORS之间, 海冰体积的生消规律与SODA 和 GLORS一致.总体来看, CGOFS全球高分辨率海洋再分析产品的气候态结果与国际同类产品基本一致, 可为提升我国海洋综合科技实力提供可靠的资料保障.     

A global ocean reanalysis product in the China Ocean Reanalysis (CORA) project

The first version of a global ocean reanalysis over multiple decades (1979–2008) has been completed by the National Marine Data and Information Service within the China Ocean Reanalysis (CORA) project. The global ocean model employed is based upon the ocean general circulation model of the Massachusetts Institute of Technology. A sequential data assimilation scheme within the framework of 3D variational (3DVar) analysis, called multi-grid 3DVar, is implemented in 3D space for retrieving multiple-scale observational information. Assimilated oceanic observations include sea level anomalies (SLAs) from multi-altimeters, sea surface temperatures (SSTs) from remote sensing satellites, and in-situ temperature/salinity profiles. Evaluation showed that compared to the model simulation, the annual mean heat content of the global reanalysis is significantly approaching that of World Ocean Atlas 2009 (WOA09) data. The quality of the global temperature climatology was found to be comparable with the product of Simple Ocean Data Assimilation (SODA), and the major ENSO events were reconstructed. The global and Atlantic meridional overturning circulations showed some similarity as SODA, although significant differences were found to exist. The analysis of temperature and salinity in the current version has relatively larger errors at high latitudes and improvements are ongoing in an updated version. CORA was found to provide a simulation of the subsurface current in the equatorial Pacific with a correlation coefficient beyond about 0.6 compared with the Tropical Atmosphere Ocean (TAO) mooring data. The mean difference of SLAs between altimetry data and CORA was less than 0.1 m in most years.     

Performances of seven datasets in presenting the upper ocean heat content in the South China Sea

In this study, the upper ocean heat content (OHC) variations in the South China Sea (SCS) during 1993- 2006 were investigated by examining ocean temperatures in seven datasets, including World Ocean Atlas 2009 (WOA09) (climatology), Ishii datasets, Ocean General Circulation Model for the Earth Simulator (OFES), Simple Ocean Data Assimilation system (SODA), Global Ocean Data Assimilation System (GODAS), China Oceanic ReAnalysis system (CORA), and an ocean reanalysis dataset for the joining area of Asia and Indian-Pacific Ocean (AIPO1.0). Among these datasets, two were independent of any numerical model, four relied on data assimilation, and one was generated without any data assimilation. The annual cycles revealed by the seven datasets were similar, but the interannual variations were different. Vertical structures of temperatures along the 18°N, 12.75°N, and 120°E sections were compared with data collected during open cruises in 1998 and 2005-08. The results indicated that Ishii, OFES, CORA, and AIPO1.0 were more consistent with the observations. Through systematic comparisons, we found that each dataset had its own shortcomings and advantages in presenting the upper OHC in the SCS.     

我国近海和邻近海的海洋环境对最近全球气候变化的响应

鉴于全球气候变暖对海洋环境和海洋生态及对经济和社会可持续发展影响的严重性,作者首先利用ERA-40再分析的风场资料以及HadISST 和SODA等海洋高分辨率再分析资料,分析了近50年来全球气候变化对中国近海(包括渤海、黄海、东海和南海)和邻近海(主要是热带和副热带西太平洋)海面附近的风力、海表纬向和经向风应力和海表温度的影响.分析结果表明: 由于受全球气候变暖的影响,1976年之后中国近海和邻近海上空的冬、夏季风变弱,从而引起中国近海冬、夏季海表风应力减弱(尤其是经向风应力),而海表水温明显上升; 并且,冬、夏季海表风应力的减弱和海水温度的上升在中国东海反映尤其明显,这些为中国近海赤潮的频繁发生提供了有利的海洋环境.此外,从中国近海上空环流散度分布的变化可见,中国近海上空从1976年之后大气环流辐散增强,这不利于中国近海上升流的形成,从而会对沿岸水域营养盐的输送产生影响.     

The rendition of the Atlantic Warm Pool in the reanalyses

The Atlantic Warm Pool (AWP) region, which is comprised of the Gulf of Mexico, Caribbean Sea and parts of the northwestern tropical Atlantic Ocean, is one of the most poorly observed parts of the global oceans. This study compares three ocean reanalyses, namely the Global Ocean Data Assimilation System of National Centers for Environmental Prediction (NCEP), the Climate Forecast System Reanalysis (CFSR) of NCEP, and the Simple Ocean Data Assimilation (SODA) for its AWP variation. The surface temperature in these ocean reanalyses is also compared with that from the Extended Range SST version 3 and Optimally Interpolated SST version 2 SST analyses. In addition we also compare three atmospheric reanalyses: NCEP-NCAR (R1), NCEP-DOE (R2), and CFSR for the associated atmospheric variability with the AWP. The comparison shows that there are important differences in the climatology of the AWP and its interannual variations. There are considerable differences in the subsurface ocean manifestation of the AWP with SODA (CFSR) showing the least (largest) modulation of the subsurface ocean temperatures. The remote teleconnections with the tropical Indian Ocean are also different across the reanalyses. However, all three oceanic reanalyses consistently show the absence of any teleconnection with the eastern equatorial Pacific Ocean. The influence of the AWP on the tropospheric temperature anomalies last for up to a one season lead and it is found to be relatively weak in R1 reanalyses. A simplified SST anomaly equation initially derived for diagnosing El Niño Southern Oscillation variability is adapted for the AWP variations in this study. The analysis of this equation reveals that the main contribution of the SST variation in the AWP region is from the variability of the net heat flux. All three reanalyses consistently show that the role of the ocean advective terms, including that associated with upwelling in the AWP region, is comparatively much smaller. The covariance of the SST tendency in the AWP with the net heat flux is large, with significant contributions from the variations of the surface shortwave and longwave fluxes.     

Assessing the Quality of Regional Ocean Reanalysis Data from ENSO Signals

The quality of regional ocean reanalysis data for “the joining area of Asia and the Indian-Pacific Ocean (AIPO)” has been assessed from the perspective of ENSO-related ocean signals. The results derived from the AIPO reanalysis, including SST, sea surface height (SSH), and subsurface ocean temperature and currents, are compared with those of Hadley Center Sea Ice and Sea Surface Temperature (HadISST) data set and Simple Ocean Data Assimilation (SODA) reanalysis data. Both the spatial pattern and the characteristics of evolution of the ENSO-related ocean temperature anomalies are well reproduced by the AIPO reanalysis data. The physical processes proposed to explain the life cycle of ENSO, including the delayed oscillator mechanism, recharge-discharge mechanism, and the zonal advection feedback, are reasonably represented in this dataset. However, the westward Rossby wave signal in 1992 is not obvious in the AIPO data, and the magnitude of the heat content anomalies is different from that of the SODA data. The reason for the discrepancies may lie in the different models and methods for data assimilation and differences in wind stress forcing. The results demonstrate the high reliability of the AIPO reanalysis data in describing ENSO signals, implying its potential application value in ENSO-related studies.     

The Tropical Pacific–Indian Ocean Associated Mode Simulated by LICOM2.0

Oceanic general circulation models have become an important tool for the study of marine status and change. This paper reports a numerical simulation carried out using LICOM2.0 and the forcing field from CORE. When compared with SODA reanalysis data and ERSST.v3 b data, the patterns and variability of the tropical Pacific–Indian Ocean associated mode(PIOAM) are reproduced very well in this experiment. This indicates that, when the tropical central–western Indian Ocean and central–eastern Pacific are abnormally warmer/colder, the tropical eastern Indian Ocean and western Pacific are correspondingly colder/warmer. This further confirms that the tropical PIOAM is an important mode that is not only significant in the SST anomaly field, but also more obviously in the subsurface ocean temperature anomaly field. The surface associated mode index(SAMI) and the thermocline(i.e., subsurface) associated mode index(TAMI) calculated using the model output data are both consistent with the values of these indices derived from observation and reanalysis data. However, the model SAMI and TAMI are more closely and synchronously related to each other.     

Impact of ECMWF,NCEP, and NCMRWF global model analysis on the WRF model forecast over Indian Region

The global model analysis has significant impact on the mesoscale model forecast as global model provides initial condition (IC) and lateral boundary conditions (LBC) for the mesoscale model. With this objective, four operational global model analyses prepared from the European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS), NCEP Global Forecasting System (GFS), and National Centre for Medium Range Weather Forecasting (NCMRWF) are used daily to generate IC and LBC of the mesoscale model during 13th December 2012 to 13th January 2013. The Weather Research and Forecasting (WRF) model version 3.4, broadly used for short-range weather forecast, is adopted in this study as mesoscale model. After initial comparison of global model analyses with Atmospheric Infrared Sounder (AIRS) retrieved temperature and moisture profiles, daily WRF model forecasts initialized from global model analyses are compared with in situ observations and AIRS profiles. Results demonstrated that forecasts initialized from the ECMWF analysis are closer to AIRS-retrieved profiles and in situ observations compared to other global model analyses. No major differences are occurred in the WRF model forecasts when initialized from the NCEP GDAS and GFS analyses, whereas these two analyses have different spatial resolutions and observations used for assimilation. Maximum RMSD is seen in the NCMRWF analysis-based experiments when compared with AIRS-retrieved profiles. The rainfall prediction is also improved when WRF model is initialized from the ECMWF analysis compared to the NCEP and NCMRWF analyses.     

BCC_CSM1.1对10年尺度全球及区域温度的预测研究

近期10～30年时间尺度的年代际预测是第五次耦合模式国际比较计划(CMIP5)重要内容之一。按照CMIP5试验要求, 国家气候中心利用气候系统模式BCC_CSM1.1完成并提交了年代际试验结果。本文评估了该模式年代际试验对10年尺度全球及区域地表温度的预测能力, 并通过与20世纪历史气候模拟试验的对比分析, 研究模式模拟对海洋初始观测状态的依赖程度。分析结果表明:(1)在有、无海洋初始化条件下, 模式均能模拟出1960～2005年间全球10年平均实测地表温度的变暖趋势, 但在有海洋初始化条件下, 可以明显减小BCC_CSM1.1模式模拟的全球升温趋势, 使得年代际试验比历史试验的结果更接近观测值。这一特点在观测资料相对丰富的南北纬50°以内地区更为显著。(2)在年代际试验预测前期, 通过Nudging方法, 利用SODA再分析海洋温度资料对模式进行初始化, 经过前期8～12月的协调后, 模式预测的第1年南北纬50°范围海洋、陆面的平均地表气温接近于观测值(CRUTEM3, HadSST2)。由于模式初值SODA再分析SST资料与HadSST2观测值存在明显的全球大洋系统暖偏差以及模式本身系统偏差的影响, 年代际试验模拟的地表气温在2～7年之内, 从观测SST状态逐渐恢复到模式系统本身状态。在同组Decadal试验中, 陆面和海洋恢复调整的时间长度几乎一致。(3) 从10年平均气候异常在区域尺度上的预报技巧来看, 有、无海洋初始同化对预测结果影响不大, 高预测技巧区主要分布在南半球印度洋中高纬度、热带西太平洋以及热带大西洋区域。(4)SST变化与下垫面热通量密切相关, 在热带和副热带海洋区域, 长波辐射和感热通量是影响10年时间尺度SST变化较大的物理量, 在中高纬度海洋, 洋面温度变化主要受潜热通量的影响相对较大。     

Evaluation of the tropical variability from the Beijing Climate Center’s real-time operational global Ocean Data Assimilation System

The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) has been run daily in a pre-operational mode.It spans the period 1990 to the present day.The goal of this paper is to introduce the main components and to evaluate BCC_GODAS2.0 for the user community.BCC_GODAS2.0 consists of an observational data preprocess,ocean data quality control system,a three-dimensional variational(3DVAR) data assimilation,and global ocean circulation model[Modular Ocean Model 4(MOM4)].MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction.Satellite altimetry data,SST,and in-situ temperature and salinity data are assimilated in real time.The monthly results from the BCC_GODAS2.0 reanalysis are compared and assessed with observations for 1990-2011.The climatology of the mixed layer depth of BCC-GODAS2.0 is generally in agreement with that of World Ocean Atlas 2001.The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales.Performances in predicting variations in the SST using BCC_GODAS2.0 are evaluated.The standard deviation of the SST in BCC-GODAS2.0 agrees well with observations in the tropical Pacific.BCC-GODAS2.0 is able to capture the main features of E1 Nino Modoki I and Modoki Ⅱ,which have different impacts on rainfall in southern China.In addition,the relationships between the Indian Ocean and the two types of E1 Nino Modoki are also reproduced.