舍入误差对大气环流模式模拟结果的影响

此文旨在研究气候数值模式的长期计算时受舍入误差的影响。通过对大气环流谱模式SAMIL采用不同CPU数计算时获得的长时间积分结果进行分析,发现使用不同CPU数进行单精度计算时,其十年平均月平均500 hPa高度场随机误差在正负6～8 gpm范围内,而使用双精度计算时相应的误差为正负3～4 gpm。对于气候平均场而言,作者的试验表明SAMIL在并行计算时由于计算顺序改变而引起的误差在可接受范围之内。然而,虽然舍入误差的全球平均值不大,但其误差分布的差别范围并不小。数值试验得到的不同模拟结果之间误差大小与模拟结果的自身年际变化大小在同样的量级,因此对于“年际变化”这样的问题来说,其影响是不可忽略的,必须要使用集合预报的办法来减小误差的影响。文中列出了3种研究复杂数值模式舍入误差的实验方法,指出其一定条件下的等效性和不同适用范围,对于其他模式的舍入误差影响研究有一定的参考价值。在舍入误差分析的基础上,介绍了一种新型的专门针对舍入误差的集合预报方法（舍入误差平均集合,RME）,指出了其在气候模拟研究中的应用价值。     

赤道东太平洋海温异常对夏季东亚大气环流的影响

采用统计诊断和数值试验方法讨论了赤道东太平洋海温异常对东亚夏季大气环流异常的影响，研究表明赤道东太平洋海温的持续异常，引起南海－菲律宾附近地区对流异常的持续，从而导致东亚大气环流的持续异常；同时指出春季赤道东太平洋海温异常和夏季海温异常对夏季东亚大气环流的影响并非是线性叠加，海温持续性异常对东亚夏季气环流的影响在季节时间尺度上存在非线性相互作用。     

21个气候模式对东亚夏季环流模拟的评估II:年际变化

利用欧洲中期天气预报中心的ERA40再分析资料, 评估了参与政府间气候变化专门委员会第四次评估报告的21个全球海气耦合模式对东亚地区夏季大气环流年际变率的模拟能力,结果表明：（1）模式对东亚地区不同要素的年际变率模拟能力整体偏弱, 500 hPa高度场的模拟能力总体优于海平面气压场及850 hPa风场;（2）两大环流系统年际变率的模拟结果评估表明：就相关系数而言,副高强度、面积的模拟能力优于印度低压,多数模式能正确模拟出副高1970s后期增强的趋势;就标准差来看,模式对印度低压、印度低压东伸槽模拟效果相对较好;（3）评估三种季风指数的模拟能力结果显示,环流异常指数模拟效果略好,但多数模式都不能模拟出海陆气压差、经向风、环流异常季风指数的年际变化。     

大气环流模式SAMIL模拟的夏季全球加热场和东亚夏季风

各国科学家一直致力于从理论和数值模拟上对季风系统进行全面地研究。本文根据“热力适应”理论, 从分析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的最新版本大气环流谱模式(SAMIL2.4.7) 对全球非绝热加热场的模拟性能出发, 分析并解释了SAMIL对东亚夏季风 (EASM) 子系统的模拟情况。通过与再分析资料Reanalysis-2 ( NCEP/DOE AMIP-II Reanalysis ) 对比分析发现, SAMIL能很好地模拟出夏半球副热带地区加热场的四叶型分布 (LOSECOD), 但模拟的各加热场在强度上存在一定的偏差, 主要表现在感热加热在大陆上普遍偏高, 而潜热加热在印度半岛两侧、西太平洋地区(尤其在南北纬10°) 偏高, 赤道带、中南半岛、中国南海等地区偏弱。而对EASM子系统的分析发现, SAMIL能很好地模拟南亚高压; 较好地模拟西太平洋副热带高压的主体, 但西太平洋 (30°N附近) 潜热偏强使得模拟的副高强度偏强、 西伸脊点过于偏西; 模式也能较好地抓住夏季西风急流的两个中心, 但中纬度潜热、 感热的模拟偏弱造成急流两中心风速均小于Reanalysis-2资料 10 m/s左右。进一步的讨论可知, 造成感热和潜热偏差的主要原因是模式中云参数化方案和积云对流参数化方案的不足, 改进模式中相关的物理参数化方案将是SAMIL后续发展的首要工作。     

21个气候模式对东亚夏季环流模拟的评估Ｉ：气候态.

利用欧洲中期天气预报中心的40 a再分析资料(ERA40),评估了参与政府间气候变化专门委员会第四次评估报告(IPCC AR4)的21个全球海气耦合模式对东亚地区夏季大气环流气候态的模拟能力.结果表明:(1)尽管各模式模拟性能差异较大,但模式对东亚地区海平面气压场(SLP)、850 hPa风场及500 hPa位势高度场的气候态均有较好模拟;整体来说,500 hPa位势高度场模拟效果最好,SLP场模拟相对较差;(2)SLP在高原上模拟存在明显不足;多数模式能较好模拟850 hPa纬向、经向风场的基本特征;500 hPa位势高度场各模式模拟偏差一致性的区域性差异不明显;(3)模式对东亚地区夏季两大环流系统模拟整体偏弱,西太平洋副热带高压模拟明显偏弱.     

CMIP5气候模式对东亚夏季平均环流场模拟能力的评估

利用第五次耦合模式比较计划(Phase 5 of Coupled Model Intercomparison Project,CMIP5)提供的30个全球气候模式模拟的1961~2005年的夏季逐月环流场资料及同期NCEP再分析资料,引入泰勒图及各种评估指标,探讨全球气候模式对东亚夏季平均大气环流场的模拟能力,寻求具有较好东亚夏季环流场模拟能力的气候模式。结果表明:1)全球气候模式能够模拟出东亚夏季平均大气环流的基本特征,CMIP5模式的总体模拟能力较第三次耦合模式比较计划(CMIP3)有较大程度的提高,如CMIP5模式对东亚大部分地区夏季海平面气压(Sea Level Pressure,SLP)场的模拟偏差在6 h Pa以内。2)模式对不同层次环流场的模拟能力存在差异,500 h Pa高度场的模拟能力最强,其次为100 h Pa高度场、850 h Pa风场,SLP场最弱;对东亚夏季主要环流系统的模拟对比发现,模式对印度热低压及东伸槽强度指数的模拟能力最好。3)综合CMIP5模式对东亚夏季各层次平均环流场以及主要环流系统的模拟能力,发现模拟较好的5个模式为CESM1-CAM5、MPI-ESM-MR、MPI-ESM-LR、MPI-ESM-P和Can ESM2。4)相对于单一模式,多模式集合平均(MME)模拟能力较强,但较优选的前5个模式集合平均的模拟能力弱。     

春季赤道东太平洋海温异常对东亚大气环流春夏季节演变的影响

利用NCEP高度场、风场及OLR资料，分析了春季赤道东太平洋海温异常对东亚大气环流春夏季节演变的影响，结果表明春季赤道东太平洋海温偏暖年，南海－菲律附近出现异常反气旋，西太平洋副高偏强偏西（副高5月占据南海），南海季风爆发迟；而春季海温偏冷年，南海－菲律宾近出现异常气旋，西太平洋副高偏弱偏东（副高5月东移出南海），南海行风爆发早。数值试验腠季赤道东太平洋海温异常不仅对东亚大气环流春季季节变化有明显影响，而且此影响可持续到夏季。     

东亚-北太平洋区域冬季大气环流趋势分析

利用1948-2005年2．5°×2．5°的NCEP／NCAR再分析月平均高度场资料、温度场资料和高空风场资料,对冬季东亚-北太平洋区域环流进行了分析。结果表明,阿留申低压加深,西伯利亚高压减弱。500hPa高度场上,我国除了东北之外的其他地区位势高度存在明显的升高趋势;东亚温带西风急流和西太平洋西风急流增强,西太平洋西风急流存在向东延伸的趋势,东亚冬季风强度减弱;58年来冬季东亚-北太平洋区域内大陆上空大气变暖,海洋上空大气变冷,两者的温度差值增大。我国青藏高原和黄土高原变暖趋势明显。     

赤道东太平洋不同持续时间的海温正常异常对东亚夏季气候影响的数值 …

利用ＩＡＰ两层大气环流模式及９层大气环流谱模式,模拟研究了大气对不同持续时间的赤道太平洋正ＳＳＴＡ的响应,对积分结果进行分析发现,尽管ＳＳＴＡ的持续时间不同（分别为１月;１～２月及１～４月）,但其引起东亚夏季大气环流和气候异常的分布都十分相似,而且有十分相近的时间演变形式,因此,虽然赤道东太平洋ＳＳＴＡ作为一中外源强迫对东亚夏季大气环流和气候有羊明显的影响,但是这种影响对于ＳＳＴＡ的持续时间（１个     

山东夏季降水与北太平洋SST和大气环流的关系

计算发现赤道东太平洋和北太平洋流区海温与山东夏季降水相关性好，在此基础上，讨论了山东夏季旱涝年同期，前期ＳＳＴ异常的特征及其与大气环流的相互关系，发现同期ＳＳＴ异常显著，前期赤道东太平洋ＳＳＴ负异常与５００ｈＰａ，大气环流负ＷＰ相关型关系密切，北太平洋流区海温异常很可能受环流异常的调制，利用２－４月高相关区ＳＳＴＡ做当年夏季降水趋势预测的试验和利用赤道东太平洋区３月、北太平洋流区７月海温做长期夏季     

The Relationship between the East Asian Subtropical Westerly Jet and Summer Precipitation over East Asia as Simulated by the IAP AGCM4.0

Based on a 30-year Atmospheric Model Intercomparison Project（AMIP） simulation using IAP AGCM4.0, the relationship between the East Asian subtropical westerly jet（EASWJ） and summer precipitation over East Asia has been investigated, and compared with observation. It was found the meridional displacement of the EASWJ has a closer relationship with the precipitation over East Asia both from model simulation and observation, with an anomalous southward shift of EASWJ being conducive to rainfall over the Yangtze-Huaihe River Valley（YHRV）, and an anomalous northward shift resulting in less rainfall over the YHRV. However, the simulated precipitation anomalies were found to be weaker than observed from the composite analysis, and this would be related to the weakly reproduced mid-upper-level convergence in the mid-high latitudes and ascending motion in the lower latitudes.     

2019年夏季东亚大气环流异常及对我国气候的影响

为更好了解2019年夏季（6—8月）我国主要气候异常特征及成因,利用气象要素站点资料和NCEP/NCAR再分析大气环流资料分析了2019年夏季降水、气温的时空分布和东亚大气环流特征,并初步诊断了长江中下游降水偏少的可能原因。结果显示,2019年夏季全国气温偏暖明显,降水总量接近常年,但旱涝分布有明显的空间差异,东部主要多雨区位于江南至华南及东北地区,云南和黄淮等地气象干旱长时间持续。东部季风区降水还呈现出明显的季节内变化,尤其是江南等地在夏季前期降水过程密集,涝灾严重,但后期急速减少,高温事件迅速爆发。华南前汛期和江南梅雨开始早结束晚。2019年夏季,欧亚中高纬度地区两槽一脊的环流形势非常明显。其中黄海至日本海持续维持的低槽造成夏季西太平洋副热带高压强度偏强,位置略偏西偏南。这一低槽也是长江中下游少雨和江南多雨的直接原因。其在夏季前期位置明显偏南,和副热带高压脊线南北位置的演变非常一致。但在夏季后期,随着这一低槽的减弱北移,副热带高压迅速北跳,也造成雨带从江南快速移动到北方地区。     

Simulating the intraseasonal variation of the East Asian summer monsoon by IAP AGCM4.0

ABSTRACT This study focuses on the intraseasonal variation of the East Asian summer monsoon （EASM） simulated by IAP AGCM 4.0, the fourth-generation atmospheric general circulation model recently developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. In general, the model simulates the intraseasonal evolution of the EASM and the related rain belt. Besides, the model also simulates the two northward jumps of the westem Pacific subtropical high （WPSH）, which are closely related to the convective activities in the warm pool region and Rossby wave activities in high latitudes. Nevertheless, some evident biases in the model were found to exist. Due to a stronger WPSH, the model fails to simulate the rain belt in southern China during May and June. Besides, the model simulates a later retreat of the EASM, which is attributed to the overestimated land-sea thermal contrast in August. In particular, the timing of the two northward jumps of the WPSH in the model is not coincident with the observation, with a later jump by two pentads for the first jump and an earlier jump by one pentad for the second, i.e., the interval between the two jumps is shorter than the observation. This bias is mainly ascribed to a shorter oscillating periodicity of convection in the tropical northwestern Pacific.     

Simulation of East Asian Summer Monsoon by Using an Improved AGCM

The IAP 2-L AGCM is modified by introducing a set of climatological surface albedo data into the model for substituting the model’s original surface albedo parameterization. The comparison between the observations and the simulation results by the modified model shows that the general features of the East Asian summer monsoon can be well reproduced by the modified IAP 2-L AGCM. Especially for the simulation of monsoon precipitation, the modi-fied model can well reproduce not only the monthly mean features of the summer monsoon rainfall over East Asia, but also the stepwise advance and retreat of the East Asian summer monsoon rainbelt. Analysis results demonstrate that the good simulation of the monsoon rainfall is closely related to the reasonable simulation of the large scale gen-eral circulation over East Asian region, such as the western Pacific subtropical high, Asian monsoon low and the low level flows. The good performance of the modified model in the rainfall simulation shows its great potential to serve as a useful tool for the prediction of summer drought / flood events over East Asia.     

The Influence of Regional SSTs on the Interdecadal Shift of the East Asian Summer Monsoon

East Asia has experienced a significant interdecadal climate shift since the late 1970s. This shift was accompanied by a decadal change of global SST. Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift. However, the individual roles of different regional SSTs remain unclear. In this study, we investigated these roles using ensemble experiments of an atmospheric general circulation model, GFDL (Geophysical Fluid Dynamics Laboratory) AM2. Two kinds of ensembles were performed. The first was a control ensemble in which the model was driven with the observed climatological SSTs. The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions. The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics, although the latter contribute to the shift modestly. The variations of summer monsoonal circulation systems, including the South Asian High, the West Pacific Subtropical High, and the lower-level air flow, were analyzed. The results show that, in comparison with those induced by extratropical SSTs, the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed. In particular, the observed SST shift in the tropical Pacific Ocean, rather than the Indian Ocean, contributed significantly to the shift of East Asian summer monsoon since the 1970s.     

Potential Correlation between the Decadal East Asian Summer Monsoon Variability and the Pacific Decadal Oscillation

This study discusses the potential contribution of the Pacific decadal oscillation(PDO)to the weakening of the East Asian summer monsoon(EASM)and the evident correlation between the positive PDO and"Southern flood and Northern drought(SFND)"summer rainfall pattern over East China.The mechanism behind this contribution is also discussed.     

数值积分过程中截断误差和舍入误差的分离方法及其效果检验

本文讨论数值积分过程中截断误差和舍入误差的分离方法和理论,解析地给出某些数值计算方法的理论截断误差,并以此来分离计算结果中的误差.然后引入参考解的办法,用来分离更为一般的微分方程求解过程中的截断误差和舍入误差.以参考解算法为基础,对一个偏微分方程的数值解进行计算,所得结果与采用理论截断误差得到的结果进行了对比,发现:(...     

冬季北太平洋涛动异常与东亚冬季风和我国天气气候的关系

用1948-2000年的北半球海平面气压场月平均资料，计算了北太平洋涛动指数和东亚冬季风指数，并研究了北太平洋涛动与东亚冬季风及我国冬季天气气候的关系。研究表明，北太平洋涛动异常变化与我国冬季天气、气候关系密切。强涛动年，东亚冬季风偏弱，我国气温普遍偏高，长江中下游地区降水偏少，而华南降水偏多；而弱涛动指数年，东亚冬季风偏强，我国气温普遍偏低，降水偏少。此外，还指出，强(弱)INPO年大气环流具有弱(强)WP型和强(弱)EU遥相关型。     

Phase transition of the Pacific decadal oscillation and decadal variation of the East Asian summer monsoon in the 20th century

This paper focuses on the relationship between the phase transition of the Pacific decadal oscillation (PDO) and decadal variation of the East Asian summer monsoon (EASM) in the twentieth century. The first transition occurred in the 1940s, with an enhanced SST in the North Pacific and reduced SST in the tropical eastern Pacific and South Indian Ocean. In agreement with these SST changes, a higher SLP was found in most parts of the Pacific, while a lower SLP was found in the North Pacific and most parts of the Indian Ocean. In this case, the EASM was largely enhanced with a southerly anomaly in the lower troposphere along the east coast of China. Correspondingly, there was less rainfall in the Yangtze River valley and more rainfall in northern and southern China. An opposite change was found when the PDO reversed its phase in the late 1970s. In the tropical Indian Ocean and western Pacific, however, the SST was enhanced in both the 1940s and 1970s. As a result, the western Pacific subtropical high (WPSH) tended to extend westward with a larger magnitude in the 1970s. The major features were reasonably reproduced by an atmospheric general circulation model (IAP AGCM4.0) prescribed with observed SST and sea ice. On the other hand, the westward extension of the WPSH was exaggerated in the 1970s, while it was underestimated in the 1940s. Besides, the spatial pattern of the simulated summer rainfall in eastern China tended to shift southward compared with the observation.     

东亚-太平洋遥相关型波列对夏季东北亚阻塞高压年际变化的影响

利用1980～1988年9年的观测资料,分析了夏季东北亚阻塞高压的年际变化及其与江淮地区夏季降水之间的关系,指出夏季东北亚阻塞高压具有十分明显的年际变化,同时它与江淮地区夏季降水之间存在着较密切的关系:当夏季东北亚阻塞高压频发时,江淮地区降水偏多;而当夏季东北亚阻塞高压维持日数少时,江淮地区降水偏少。为考察产生上述结果的原因,我们分析了全球海温异常,并利用合成的热带西太平洋海温异常模拟研究了热带西太平洋海温异常对东北亚阻塞高压形成和维持的影响。最后指出热带西太平洋海温异常引起的东亚-太平洋型遥相关波列是产生夏季东北亚阻塞高压的年际变化及其与江淮地区夏季降水之间关系的一个重要原因。