CCM3大气环流模式月-季尺度预报初步试验

以1991和1994年NCEP再分析格点资料作初始场, 用NCAR气候模式CCM3进行了48次月、季预报, 针对500 hPa高度和中国降水资料对其预测能力进行了检验.结果表明, CCM3对月尺度的高度场的预报有一定的能力.对中国160站的降水距平进行月尺度和季节预报, 其准确程度可以和目前经验预报的水平相当.比较使用实际海温和用外推法预测的海温两种下边界条件所作的预报结果发现, 两者的效果差异不大.     

CCM3模式中LSM积雪方案的改进研究(Ⅰ):修改方案介绍及其单点试验

为了改进美国NCARCCM3全球模式中LSM陆面模型中的积雪方案的模拟效果,在Sun等[1]SAST积雪模型的基础上,作了部分修改后,加进CCM3模式LSM模型中.该方案根据格点区域平均积雪深度的不同,把地面雪盖划分为1到3层不等,能在积雪表层和中间层更好地描述温度的日变化和季节变化;较详细地考虑了雪的热传导、太阳辐射的穿透吸收、雪的融化、液态水的储存、渗透和再冻结等积雪内部的主要物理过程;根据Nimbus-7卫星实测雪深资料修改了积雪覆盖度和雪面反照率的计算方案.利用前苏联6个台站1978-1983年的实测积雪资料和大气强迫数据,进行了单点模拟试验,结果表明,新的积雪参数化方案能够较好地再现积雪深度和雪水当量的逐日和季节变化特征,部分提高了积雪参数化方案对积雪的模拟能力.     

CCM3/NCAR的辐射方案在IAP-AGCM模式中的应用

利用NCAR的CCM3 (The Community Climate Model version 3) 辐射模块, 对IAP9L－AGCM的辐射计算方案进行了替换, 并对改进的结果做了细致的评估。分析表明, 新版本的模式在大多数辐射场的空间平均和分布型的模拟上有了较为明显的改进, 特别是较好地克服了原模式中陆面净辐射场的偏差。在此基础上, 新版本计算的大气温度普遍升高。伴随这种变化, 模式中的海平面气压、 地表温度、 位势高度、 风场、 降水、 比湿等物理量都有了调整, 但是变化并不明显, 从而对模式的进一步发展和完善提出了新的要求。     

一个全球耦合模式的ENSO后报试验

A group of seasonal hindcast experiments are conducted using a coupled model known as the Flexible Global Ocean-Atmosphere-Land System Modelgamil1.11 (FGOALS-g1.11) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG).Two steps are included in our ElNi o-Southern Oscillation (ENSO) hindcast experiments.The first step is to integrate the coupled GCM with the Sea Surface Temperature (SST) strongly nudged towards the observation from 1971 to 2006.The second step is to remove the SST nudging term.The authors carried out a one-year hindcast by adopting the initial values from SST nudging experiments from the first step on January 1st,April 1st,July 1st,and October 1st from 1982 to 2005.In the SST nudging experiment,the model can reproduce the observed equatorial thermocline anomalies and zonal wind stress anomalies in the Pacific,which demonstrates that the SST nudging approach can provide realistic atmospheric and oceanic initial conditions for seasonal prediction experiments.The model also demonstrates a high Anomaly Correlation Coefficient (ACC) score for SST in most of the tropical Pacific,Atlantic Ocean,and some Indian Ocean regions with a 3-month lead.Compared with the persistence ACC score,this model shows much higher ACC scores for the Ni o-3.4 index for a 9-month lead.     

一个全球耦合模式的ENSO后报试验

A group of seasonal hindcast experiments are conducted using a coupled model known as the Flexible Global Ocean-Atmosphere-Land System Model-gamil1.11 (FGOALS-g1.11) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG). Two steps are included in our El Niño-Southern Oscillation (ENSO) hindcast experiments. The first step is to integrate the coupled GCM with the Sea Surface Temperature (SST) strongly nudged towards the observation from 1971 to 2006. The second step is to remove the SST nudging term. We carried out a one-year hindcast by adopting the initial values from SST nudging experiments from the first step on January 1st, April 1st, July 1st, and October 1st from 1982 to 2005. In the SST nudging experiment, the model can reproduce the observed equatorial thermocline anomalies and zonal wind stress anomalies in the Pacific, which demonstrates that the SST nudging approach can provide realistic atmospheric and oceanic initial conditions for seasonal prediction experiments. The model also demonstrates a high Anomaly Correlation Coefficient (ACC) score for SST in most of the tropical Pacific, Atlantic Ocean, and some Indian Ocean regions with a 3-month lead. Compared with the persistence ACC score, this model shows much higher ACC scores for the Nino3.4 index for a 9-month lead.     

包括大地形作用的大气环流模式的长时期性状

本文用一个两层斜压原始方程模式研究了包含大地形作用的大气环流模式的长时期性状.首先以刚体旋转为初值条件,用绝热无摩擦的两层斜压模式作了一个月的数值积分,研究了模式大气对纯粹地形强迫的响应.结果发现积分至第15天以后,中纬度西风渐弱,使得积分前期由地形强迫产生的槽脊难以辨认.本文通过不同模式之间的比较,对500hPa高度场上的球谐分析以及对动量方程的诊断,认为它是一种确定的动力学现象,而不是计算紊乱.在模式中引入纬向对称型加热和地面摩擦过程后,即使将模式积分长达5个月以上,由地形强迫激发的扰动所形成的槽脊仍可长久地维持,但它不是简单意义下的定常波,位相分析表明只有二波分量近似驻波,与转盘实验结果相似.     

CLM3.0模式中冻土过程参数化的改进及模拟试验

对NCAR CLM3.0(Community Land Model)的冻土过程参数化进行了改进.根据平衡态的热力学关系和考虑含冰量的土壤基质势的经验公式定义了冰点下的最大液态水含量,超过最大液态水含量的部分冻结为冰,并在水导率的计算中加入了冰的阻挡作用.利用青藏高原改则站2003年4月1日至2004年12月31日的观测...     

Climatic features related to Eastern China summer rainfalls in the NCAR CCM3

1. IntroductionThe broadly defined Asian monsoon actually consists of the indian monsoon and theEast Asian monsoon. The indian summer monsoon, as well as its connection with some otherclimatic variabilities. such as the ENSO event, has been studied extensively (Rasmusson andCarpenter, 1983; Shukla and Paolino, 1983; Shukla and Mooley, 1987; Ju and Slingo, 1995).To the East Asian monsoon, with its main part over the eastern China, its relationship withENSO and other large scale climati…     

大气环流模式CAM中土壤冻融过程改进对东亚气候模拟的影响

本文在改进了大气环流模式NCAR CAM3.1中的土壤冻融过程参数化的基础上,模拟研究了改进的冻土过程对东亚气候模拟的影响.模拟结果分析表明,改进冻融过程参数化后,冬季欧亚大陆上大部分地区大气对地表的加热偏强,而夏季地表对大气的加热偏强,尤其是青藏高原对大气的加热作用显著增强.东亚气候对冻土过程参数化方案非常敏感,冬、...     

Comparison of a very-fine-resolution GCM with RCM dynamical downscaling in simulating climate in China

Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution GCM. However, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine resolution, close to that of an RCM, and, if so, which is the better approach, are open questions. These questions are important for understanding and using these two kinds of simulation approaches, but have not yet been investigated. Accordingly, the present reported work compared simulation results over China from a very-fine-resolution GCM (VFRGCM) and from RCM dynamical downscaling. The results showed that: (1) The VFRGCM reproduces the climatologies and trends of both air temperature and precipitation, as well as inter-monthly variations of air temperature in terms of spatial pattern and amount, closer to observations than the coarse-resolution version of the GCM. This is not the case, however, for the inter-monthly variations of precipitation. (2) The VFRGCM captures the climatology, trend, and inter-monthly variation of air temperature, as well as the trend in precipitation, more reasonably than the RCM dynamical downscaling method. (3) The RCM dynamical downscaling method performs better than the VFRGCM in terms of the climatology and inter-monthly variation of precipitation. Overall, the results suggest that VFRGCMs possess great potential with regard to their application in climate simulation in the future, and the RCM dynamical downscaling method is still dominant in terms of regional precipitation simulation.     

中尺度模式中各种积云参数化方案的对比试验

利用非静力中尺度MM5数值模式，选择Anthes-Kuo、Grell、Kain-Fritsch和Betts-Miller4种积云对流参数化方案，对2003年7月25-26日台风登陆减弱为中尺度低压系统后影响云南产生的强降水过程进行模拟试验，重点分析了4种参数化方案模拟的降水分布、降水强度和中尺度低压的流场特征。结果表明：4种积云参数化方案对这次强降水过程均有一定的模拟能力，能够很好地模拟过程强降水中心的位置，但Grell、Kain-Fritsch和Betts-Miller3种方案模拟的大雨范围比实况大雨范围明显偏小，Betts-Miller方案模拟的降水强度比实况偏大，Anthes-Kuo方案的模拟结果与实况比较接近，它不仅能够很好地模拟强降水过程的降水区范围、降水强度和降水中心位置，还能很好地再现低压环流系统的一些中尺度特征。     

Empirical Estimates of Global Climate Sensitivity： An Assessment of Strategies Using a Coupled GCM

A control integration with the normal solar constant and one with it increased by 2.5% in the National Center for Atmospheric Research （NCAR） coupled atmosphere-ocean Climate System Model were conducted to see how well the actual realized global warming could be predicted just by analysis of the control results. This is a test, within a model context, of proposals that have been advanced to use knowledge of the present day climate to make ＂empirical＂ estimates of global climate sensitivity. The scaling of the top-of-the-atmosphere infrared flux and the planetary albedo as functions of surface temperature was inferred by examining four different temporal and geographical variations of the control simulations. Each of these inferences greatly overestimates the climate sensitivity of the model, largely because of the behavior of the cloud albedo. In each inference the control results suggest that cloudiness and albedo decrease with increasing surface temperature. However, the experiment with the increased solar constant actually has higher albedo and more cloudiness at most latitudes. The increased albedo is a strong negative feedback, and this helps account for the rather weak sensitivity of the climate in the NCAR model. To the extent that these model results apply to the real world, they suggest empirical evaluation of the scaling of global-mean radiative properties with surface temperature in the present day climate provides little useful guidance for estimates of the actual climate sensitivity to global changes.     

Analysis of Decadal Climate Variability in the Tropical Pacific by Coupled GCM

This study presents the spatial and temporal structures of the decadal variability of the Pacific from an extended control run of a coupled global climate model (GCM).The GCM used was version-g2.0 of the Flexible Global Ocean Atmosphere Land System (FGOALS-g2.0) developed at LASG/IAP.The GCM FGOALS-g2.0 re-produces similar spatial-temporal structures of sea surface temperature (SST) as observed in the Pacific decadal os-cillation (PDO) with a significant period of approximately 14 years.Correspondingly,the PDO signals were closely related to the decadal change both in the upper-ocean temperature anomalies and in the atmospheric circulation.The present results suggest that warm SST anomalies along the equator relax the trade winds,causing the SSTs to warm even more in the eastern equatorial Pacific,which is a positive feedback.Meanwhile,warm SST anomalies along the equator force characteristic off-equa-torial wind stress curl anomalies,inducing much more poleward transport of heat,which is a negative feedback.The upper-ocean meridional heat transport,which is asso-ciated with the PDO phase transition,links the equatorial to the off-equatorial Pacific Ocean,acting as a major mechanism responsible for the tropical Pacific decadal variations.Therefore,the positive and negative feedbacks working together eventually result in the decadal oscilla-tion in the Pacific.     

Improving Non-local Parameterization of the Convective Boundary Layer

We propose improvements in the “non-local” parameterization scheme of the convective boundary layer. The countergradient terms for components of the momentum fluxes are introduced in a form analogous to those for other scalars. The scheme also includes explicit expressions for entrainment fluxes of momentum, temperature, and humidity. A simplified procedure for calculating the boundary-layer height is proposed, consisting of two steps: the evaluation of the convection level, followed by the assessment of the depth of the interfacial layer.     

引入考虑凝结作用的连续性方程与积云对流参数化方案修正

文章研究了在热带海洋面上的水蒸发，发现水蒸发进入大气层将改变地面气压场，且蒸发潜热分为内潜热(水汽内能)和外潜热(水汽压力能)，蒸发内潜热立即成为大气热能的一部分，而蒸发外潜热直接对大气层作功，使得大气位能增加；研究了大气中的大尺度凝结降水和积云对流凝结降水对于环境气压场与位势高度场的直接影响。用郭晓岚积云对流参数化方案(已考虑凝结内潜热对大气的加热作用)，加入了考虑因大尺度凝结降水和积云对流参数化凝结降水造成地面气压场及高空位势高度场的变化，后者应是凝结外潜热过程作用的结果。在上述研究过程中，必须引入考虑凝结作用的连续性方程，且最终可以改变有积云对流凝结降水发生的数值预报模式动力框架。     

GCM Simulations of Stable Isotopes in the Water Cycle in Comparison with GNIP Observations over East Asia

In this paper, we examine the performance of four isotope incorporated GCMs, i.e., ECHAM4 (University of Hamburg), HadCM3 (Hadley Centre), GISS E (Goddard Institute of Space Sciences), and MUGCM (Melbourne University), by comparing the model results with GNIP (Global Network of Isotopes in Precipitation) observations. The spatial distributions of mean annual δD and mean annual deuterium excess d in precipitation, and the relationship between δ18 o and δD in precipitation, are compared between GCMs and GNIP data over East Asia. Overall, the four GCMs reproduce major characteristics of δD in precipitation as observed by GNIP. Among the four models, the results of ECHAM4 and GISS E are more consistent with GNIP observed precipitation δD distribution. The simulated d distributions are less consistent with the GNIP results. This may indicate that kinetic fractionation processes are not appropriately represented in the isotopic schemes of GCMs. The GCM modeled MWL (meteoric water line) slopes are close to the GNIP derived MWL, but the simulated MWL intercepts are significantly overestimated. This supports that the four isotope incorporated GCMs may not represent the kinetic fractionation processes well. In term of LMWLs (local meteoric water lines), the simulated LMWL slopes are similar to those from GNIP observations, but slightly overestimated for most locations. Overall, ECHAM4 has better capability in simulating MWL and LMWLs, followed by GISS E. Some isotopic functions (especially those related to kinetic fractionation) and their parameterizations in GCMs may have caused the discrepancy between the simulated and GNIP observed results. Future work is recommended to improve isotopic function parameterization on the basis of the high-resolution isotope observations.     

The Sensitivity of Numerical Simulation of the East Asian Monsoon to Different Cumulus Parameterization Schemes

In this paper, a 5-level spectral AGCM is used to examine the sensitivity of simulated East Asian summer mon-soon circulation and rainfall to cumulus parameterization schemes. From the simulated results of East Asian mon-soon circulations and rainfalls during the summers of 1987 and 1995, it is shown that the Kuo’s convective parameterization scheme is more suitable for the numerical simulation of East Asian summer monsoon rainfall and circulation. This may be due to that the cumulus in the rainfall system is not strong in the East Asian monsoon region.     

古尔班通古特沙漠大气边界层参数化方案的模拟评估[1]

为准确描述我国最大的固定/半固定沙漠-古尔班通古特沙漠区域的大气边界层结构,本文利用该沙漠腹地2017年的梯度铁塔和通量观测数据,基于中尺度气象模式WRF (Weather Research and Forecast v3.7.1),分析了5种边界层参数化方案在古尔班通古特沙漠的适用性。结果表明：1）采用WRF模拟沙漠腹地近地层内的边界层特征时,2m气温的模拟存在冷偏差,5种边界层参数化方案均能较好地模拟出四个季节2m气温的日变化特征,其中非局地方案ACM2(Asymmetric Convective Model version 2)对2m气温效果最好,局地方案BL方案的模拟偏差最大;2）5种边界层参数化方案均能够模拟出10m风速的日变化特征,其中局地方案BL(Bougeault-Lacarrere)对10m风速效果最佳;3）采用WRF模拟沙漠近地层内的地表通量特征时,感热通量存在高估现象,潜热通量存在低估现象,5种边界层参数化方案均能较好地模拟出四个季节模拟时间段内地表净辐射通量的日变化特征,其中局地方案MYJ(Mellor-Yamada-Janjie)的模拟精度最高。     

近海水汽初值和对流影响一次华南前汛期沿海强降水对流系统发展过程的机理研究

本研究在对华南季风降水试验（SCMREX）观测资料分析的基础上,采用数值模拟试验探讨南海北部区域湿度场初值误差和海上对流对2014年5月8日华南沿海地区的一次强降雨过程的中尺度对流系统（MCS）的发展和移动的影响。加密探空和风廓线观测分析表明在珠江口地区有西南风和偏东风急流形成的辐合区,为对流在该地区增强发展提供了条件。增加和减少近海湿度以及关闭积云和微物理过程潜热释放,所造成的温度场以及风场的变化对广东沿海地区的对流的强度和移动路径都有明显的影响。特别是增加海上关键区的湿度,由于海上对流的发展改变了整个区域的环流,抑制了陆地上对流的发展。关闭海上关键区对流过程潜热的释放,导致低空急流到达更加偏北的位置,对流系统在模拟的后期向东北移动。通过这些试验表明,海上的湿度等要素场和对流活动对沿海地区的降雨预报有着十分重要的影响,需要进一步加强海上观测及其资料同化方法。     

三维指数型迎风格式以及在环境数值模拟中的初步应用

为了适应大气、海洋的环境数值模拟需要,在前人工作基础上提出了三维随流格式和指数型迎风格式.随流格式能使方程对流项中的对流速度误差明显减小.三维指数型迎风格式能有效抑制对流占优问题的数值振荡,并用简单的七点差分格式获得O(h2)精度的三维模式数值结果.因此,所建的模式具有格式简单,计算稳定性良好和计算精度较高的优点.初步计算表明,这个模式能有效应用于强迫-耗散型大气、海洋运动和环境问题的数值模拟.