1998年东亚夏季风过程的数值模拟

The 1998 East Asian Summer Monsoon is simulated by use of an improved nine-level p-σ model, the boundary forcing is the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from May 1 to August 31, 1998. It is found that basic features of the atmospheric circulation (such as the South Asia high and the West Pacific subtropical high) can be simulated fairly. However the South Asia high is a little stronger than the observed, while the West Pacific subtropical high a little weaker. Seen from variations of the time correlation coefficient, this model is good for the short-time climate simulation (less than two months), while for the long-time simulation, its climate drift is a little obvious. It can be also seen from the spatial distribution of correlation coefficient that the worse simulation areas of the model are located in the Tibetan Plateau and the adjacent northwest Indo-China Peninsula. For the simulation of precipitation, the movement of rain belt from May to June can be simulated, but the simulation of July and August precipitation shifts obviously to north of the observed. It is also found from the analysis of sensitive experiment that the improvement of the nested boundary condition has a great impact on the simulation results, especially on the precipitation, so the model and the nesting technique need further improvements.     

耦合模式FGOALS_s模拟的东亚夏季风

本文评估了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海气耦合模式FGOALS_s对东亚夏季风的模拟能力, 并通过与观测海温强迫下单独大气模式SAMIL试验结果的比较, 分析了海气耦合过程对模式性能的影响。结果表明, FGOALS_s基本能够模拟出东亚夏季风系统的气候态分布及其演变过程, 但也存在明显偏差, 主要表现为模拟的温度场在对流层中上层一致性偏冷, 导致模式中环流系统强度偏弱; 而温度经向梯度模拟的不足, 直接影响到东亚副热带西风急流的模拟。通过与观测海温强迫下SAMIL模拟结果的对比发现, SAMIL模拟的温度场、 环流场以及风场较之耦合模式结果更接近观测, 但也存在与FGOALS_s类似的模式偏差。因此, 大气模式固有的偏差对耦合模式的模拟偏差有重要影响。分析发现, 对于西太平洋降水的模拟而言, 耦合模式结果更加合理, 表明海气相互作用过程对模式性能有重要影响。本文的结果表明, 大气模式自身的误差是导致耦合模式误差的主要原因。通过更新云－辐射模块改进大气模式模拟的温度场, 应是FGOALS_s后续发展的首要工作。     

p—σ混合坐标全球模式模拟夏季气候的性能及系统性误差分析

将球带范围的ｐ－σ混合坐标系五层原始方程模式发展成为包含极区的全球大气环流模式，并用ＧＦＤＬ多年平均气候分析资料检验了模式对夏季气候平均状态的模拟性能，分析了ｐ－σ混合坐标系全球大气环流模式模拟夏季气候的系统性误差。结果表明：ｐ－σ混合坐标系全球大气环流模式能较好地模拟夏季气候平均态，各高度上的主要环流系统都可以模拟出来，与球带模式的结果相比有一定的改进，而且陆地上的模拟结果优于海洋上的。     

区域气候模式侧边界的处理对东亚夏季风降水模拟的影响

在区域气候模式模拟中,侧边界的作用是引入大尺度强迫场。如何处理好侧边界,即大尺度强迫场和区域气候模式本身之间的关系问题,对于区域气候模式模拟和预报东亚夏季风降水具有重要意义。本文利用美国纽约州立大学Albany分校的区域气候模式（SUNYA-ReCM）,设计了两种不同的侧边界处理方法,来探讨侧边界对东亚夏季风降水模拟的影响。驱动区域模式的大尺度强迫场来自欧洲中期天气预报中心（ECMWF）及热带海洋大气研究计划（TOGA）的分析资料场。试验结果表明:（1）当模式的区域较大时,采用较小的侧边界缓冲区会在缓冲区与模式内部的交界处产生不连续;扩大缓冲区并且考虑不同尺度强迫在垂直方向上的不同作用,可以避免这一缺陷。（2）更重要的是采用后一种方案,即减少了区域气候模式在模拟大尺度环流场方面所起的作用,使得模式更多地依赖侧边界来得到更真实的、对东亚夏季风降水起重大影响的一些气流,如副高、西南季风和南海季风,对东亚夏季风降水无论是在大小上还是在雨带位置的演变上都能进行更好的模拟。     

东亚夏季风降水和环流数值模拟对不同对流参数化方案的敏感性

A 5-level spectral AGCM (ImPKU-5LAGCM) is used to examine the sensitivity of the simulated results of the summer monsoon rainfall and circulation in East Asia to different cumulus parameterization schemes in the climatological-mean case and in the cases of weak and strong Asian summer monsoons,respectively. The results simulated with the Arakawa-Schubert＇s(hereafter A-S＇s), Kuo＇s and Manabe＇s cumulus parameterization schemes show that these simulated distributions of the summer monsoon rainfall and circulation in East Asia depend strongly on the cumulus parameterization schemes either in the climatological-mean case or in the cases of weak and strong Asian summer monsoons. From the simulated results, it might be shown that the Kuo scheme appears to be more suitable for the simulation of the summer monsoon rainfall and circulation in East Asia than the A-S scheme or the Manabe scheme, although the A-S scheme is somewhat better in the simulations of the tropical rainfall. This might be due to that the Kuo＇s cumulus parameterization scheme is able to reflect well the characteristics of rainfall cloud system in the East Asian summer monsoon region, where the rainfall system used to be a mixing of cumulus and stratus.     

1998年东亚夏季风过程的数值模拟(英文)

利用改进的九层 Ｐ－σ模式和 １９９８年南海季风试验从 ５月 １日到 ８月３１日共 １２３天的再分析资料对该年的东亚夏季风进行模拟,发现基本的大气环流形势（南亚高压和西太平洋副高）均能模拟出来,但南亚高压模拟偏强,西太平洋副高模拟偏弱。由时间相关系数分析可以发现,该模式对于短期气候模拟（约２个月）效果较好,对于长期积分,则气候飘移较明显;由空间相关系数分析发现,模拟的较差区域位于青藏高原及其相邻的中南半岛西北部等地区。降水的模拟是较差的,五、六月份能模拟出雨带的大致移动,七、八月份模拟的降水明显较观测场偏北。由敏感性试验的分析结果发现,嵌套边界条件的改善对于降水的模拟影响较大。     

东亚季风区夏季风强度和降水的配置关系

1979～2000年东亚地区夏季风强度和夏季总降水之间的关系被分为四种类型:A:强季风、强降水;B:强季风、弱降水;C:弱季风、强降水;D:弱季风、弱降水.通过研究不同关系对应的大气环流特征和SST异常,并分析不同要素在季风和降水关系变化中的作用,发现在季尺度上东亚季风区夏季风强度和地区同期降雨总量的关系具有多面性特征,此关系取决于环流场的整体配置,其中西太平洋副高﹑南亚高压和中高纬阻塞形式为三个起主导作用的因素.另外,海温变化对东亚季风和总降水的关系有明显的影响,尤其是北太平洋﹑印度洋和南海区域海温.合成分析结果表明500 hPa东亚异常波列和东亚夏季风强度密切相关,但波形与东亚季风区夏季总降水强弱没有明显联系.     

东亚夏季风指数的年际变化与东亚大气环流

文中从夏季东亚热带、副热带环流系统特点出发 ,定义了能较好表征东亚夏季风环流年际变化的特征指数 ,并分析了东亚夏季风指数的年际变化与东亚大气环流及夏季中国东部降水的关系。文中定义的东亚夏季风指数既反映了夏季东亚大气环流风场的变化特征 ,也较好地反映了夏季中国东部降水的年际变化特征。此外 ,还探讨了东亚夏季风指数变化的先兆信号     

MRI-CGCM模式对东亚夏季风的模拟评估及订正

本文利用CMAP月降水资料、NCEP再分析资料、NOAA的ERSST资料和日本气象厅海气耦合模式（MRI-CGCM）的输出结果,从东亚夏季风气候态、主模态和年际变率等方面分析了MRI-CGCM模式对东亚夏季风的预测性能,并且利用观测的东亚夏季风指数（EASMI）与模拟PC（principal component）的关系建立多元线性回归方程来订正EASMI（简称PC订正法）。结果表明:MRI-CGCM模式能够较好再现东亚夏季风降水和低层风场的气候态,但模拟的西北太平洋反气旋偏弱、偏东,使得模拟的副热带地区降水量偏小。模式较好地模拟出东亚夏季风降水第一模态（EOF1）及相应的低层风场,能够较好再现出EOF1对应El Ni?o衰减位相;模拟降水的EOF1与观测之间的空间相关系数（ACC）为0.72,且能较好地再现其对应的年际变率,其时间系数PC1与观测之间的相关系数为0.41,能模拟出观测EOF1的2 a和5 a主导周期;但模拟的我国以东梅雨锋区雨带位置偏南,这与模拟的西北太平洋反气旋位置偏南有关。模式对降水第二模态EOF2的模拟能力比EOF1明显下降,模拟EOF2与观测之间的ACC降到0.36;虽然模式能较好地再现出EOF2对应El Ni?o发展位相,但模拟的西太平洋反气旋位置偏南,使得雨带位置偏南,模拟的我国梅雨锋区雨带位于江南,与观测场上江南少雨相反。模式较好地模拟出我国东部夏季降水和气温空间异常分布和年际变化,模拟与观测夏季降水和气温的多年平均ACC分别为0.74和0.68。模式模拟我国东部、江淮流域和华南地区夏季降水多年平均PS评分分别为69、70和68分,略高于我国夏季降水业务预测多年平均评分（65分）。模拟的我国东部夏季气温与观测多年平均PS评分为74分。PC订正后EASMI与实况的相关系数由0.51提高到0.65、符号一致率由84%升到91%、标准差由0.75增大到1.4、大于1个标准差年数由6年变为12年,订正后在模拟变幅偏小和梅雨锋区雨带偏南等方面均有一定的改善,对应西太平洋反气旋位置和梅雨锋区雨带位置与实况较为吻合。     

IPCC AR4气候模式对东亚夏季风年代际变化的模拟性能评估

文中使用多种观测资料和分类的方法评估了IPCC AR4(政府间气候变化委员会第4次评估报告)气候模式(亦称Coupled Model Intercomparison Program 3, CMIP3)对东亚夏季风降水与环流年代际变化的模拟性能.结果表明,在评估的19个模式中,有9个模式可以较好地再现中国东部地区多年平均降水场,但仅有3个模式(第1类模式)可以较好地对东亚夏季风降水的年代际变化作出模拟,这3个模式是:GFDL-CM2.0、MIROC3.2(hires)和MIROC3.2(medres),其中模式GFDL-CM2.0具有最好的模拟性能.进一步的分析表明,大部分模式对东亚夏季风变化模拟能力的缺乏是因为这些模式没有抓住东亚夏季风降水变化的主要动力和热力学机制,即东亚地区在过去所出现的大范围对流层变冷和变干.而第1类模式由于较好地再现了东亚地区垂直速度场(动力学因子)和水汽场(热力学因子)的变化特征,因此较好地模拟出中国东部南涝北旱的气候变化特征.本文的评估清楚地表明,当选择不同模式进行集合时,模式对某一研究变量的模拟性能好坏极大地影响了集合的结果.当模拟性能较好的模式在一起进行集合时,所得到的结果更加接近于真实的观测结果.就特定的研究变量而言,这种集合更加优于将可得到的所有模式进行集合.这说明,虽然多模式集合一般优于单个模式的结果,但应考虑使参与集合的模式对所研究变量具有一定的模拟能力.     

Simulation of East Asian Summer Monsoon with IAP CGCM

ＳｉｍｕｌａｔｉｏｎｏｆＥａｓｔＡｓｉａｎＳｕｍｍｅｒＭｏｎｓｏｏｎｗｉｔｈＩＡＰＣＧＣＭＣｈｅｎＱｉｙｉｎｇ（陈起英），①ＹｕＹｏｎｇｑｉａｎｇ（俞永强）ａｎｄＧｕｏＹｕｆｕ（郭裕福）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，Ｃｈ...     

东亚和南亚季风协同作用对西南地区夏季降水的影响

为探究东亚夏季风(EASM,East?Asian?summer?monsoon)和南亚夏季风(SASM,South?Asian?summer?monsoon)相互作用及其强弱变化对西南地区夏季降水的影响,利用1979—2019年西南地区161站逐日降水观测资料和ERA-5提供的1979—2019年全球再分析资料,通过对...     

Baseline predictability of daily east Asian summer monsoon circulation indices

The nonlinear local Lyapunov exponent (NLLE) method is adopted to quantitatively determine the predictability limit of East Asian summer monsoon (EASM) intensity indices on a synoptic timescale. The predictability limit of EASM indices varies widely according to the definitions of indices. EASM indices defined by zonal shear have a limit of around 7 days, which is higher than the predictability limit of EASM indices defined by sea level pressure (SLP) difference and meridional wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and meridional wind shear shows a faster growth than indices defined by zonal wind shear. Furthermore, the indices defined by zonal wind shear appear to fluctuate at lower frequencies, whereas the indices defined by SLP difference and meridional wind shear generally fluctuate at higher frequencies. This result may explain why the daily variability of the EASM indices defined by zonal wind shear tends be more predictable than those defined by SLP difference and meridional wind shear. Analysis of the temporal correlation coefficient (TCC) skill for EASM indices obtained from observations and from NCEP’s Global Ensemble Forecasting System (GEFS) historical weather forecast dataset shows that GEFS has a higher forecast skill for the EASM indices defined by zonal wind shear than for indices defined by SLP difference and meridional wind shear. The predictability limit estimated by the NLLE method is shorter than that in GEFS. In addition, the June-September average TCC skill for different daily EASM indices shows significant interannual variations from 1985 to 2015 in GEFS. However, the TCC for different types of EASM indices does not show coherent interannual fluctuations.     

ENSO循环在夏季的不同位相对东亚夏季风的影响

采用ＳＳＴＡ、风场、ＯＬＲ以及中国１６０站降水、气温等资料,根据赤道中东太平洋ＳＳＴＡ的逐季变化,将ＥＮＳＯ循环过程在夏季的位相分为５种型。对其相应的Ｗａｌｋｅｒ环流的显著性检验发现,Ａ型与Ｃ型夏季的差别最为显著。夏季要素场合成分析发现。Ａ型与Ｃ型的情形差别最明显。Ａ型夏季的要素场与弱夏季风年的相似;Ｃ型夏季的要素场与强夏季风年的相似。     

Projected change in East Asian summer monsoon precipitation under RCP scenario

Future changes in East Asian summer monsoon precipitation climatology, frequency, and intensity are analyzed using historical climate simulations and future climate simulations under the RCP4.5 scenario using the World Climate Research Programme’s (WCRP) Coupled Model Intercomparison Project 5 (CMIP5) multi-model dataset. The model reproducibility is evaluated, and well performance in the present-day climate simulation can be obtained by most of the studied models. However, underestimation is obvious over the East Asian region for precipitation climatology and precipitation intensity, and overestimation is observed for precipitation frequency. The overestimation of precipitation frequency is mainly due to the large positive bias of the light precipitation (precipitation <10 mm/day) days, and the underestimation of precipitation intensity is mainly caused by the negative bias of the intense precipitation (precipitation >10 mm/day) intensity. For the future climate simulations, simple multi-model ensemble (MME) averages using all of the models show increases in precipitation and its intensity over almost all of East Asia, while the precipitation frequency is projected to decrease over eastern China and around Japan and increase in other regions. When the weighted MME is considered, no large difference can be observed compared with the simple MME. For the MME using the six best models that have good performance in simulating the present-day climate, the future climate changes over East Asia are very similar to those predicted using all of the models. Further analysis shows that the frequency and intensity of intense precipitation events are also projected to significantly increase over East Asia. Increases in precipitation frequency and intensity are the main contributors to increases in precipitation, and the contribution of frequency increases (contributed by 40.8 % in the near future and by 58.9 % by the end of the twenty-first century) is much larger than that of intensity increases (contributed by 29.9 % in the near future and by 30.1 % by the end of the twenty-first century). This finding also implies an increased risk of intense precipitation events over the East Asian region under global warming scenario. These results regarding future climate simulations show much greater reliability than those using CMIP3 simulations.     

夏季亚洲季风区的水汽输送及其对中国降水的影响

利用1948-2005年NCEP/NCAR逐日及月平均资料,研究了亚洲季风区水汽输送的气候特征及其与中国夏季降水的关系.结果表明:(1)亚洲夏季风区不论在纬向和经向输送上,都表现了其独特性.夏季亚洲季风区为强大的水汽汇,东亚大陆和印度季风区均有较强的水汽辐合中心.(2)大部分水汽集中在对流层中下层,主要来自印度季风区,而对于对流层中上层,则以西太平洋和中纬西风带的输送为主.(3)印度季风在5-7月纬向向东的输送加强,东亚季风在6-7月以经向向北的输送加强为主,7月达最强,8到9月季风减弱直至结束.亚洲季风区青藏高原南侧的南支西风对东亚的水汽输送有重要作用,表现为春季最强,中高纬和热带西风输送变化同步,在盛夏达到最大,7月热带西风输送的水汽占三支水汽总输送的80%左右,来自中高纬地区的水汽约占18%.(4)季风爆发后,大量水汽从南半球输送到亚洲季风区.水汽辐合增加最大在孟加拉湾、中南半岛和南海地区,中国大陆的水汽主要经南海北边界输入.(5)水汽输送的北进与雨带的北推相一致.水汽输送场的时空分析表明,EOF1和EOF2分别代表强弱季风年的水汽输送特征.EOF1反映了东亚季风区一致的异常向北输送,并且在1970年代末发生了明显减弱.它与华北降水相关密切,表明自1980年代以来东亚季风向北水汽输送的减弱是华北干旱的主要原因.EOF2的主要特征是从1980年代之后,来自东北和西南的异常水汽在长江流域辐合,导致长江流域降水增多.相关分析表明,东亚夏季风在年代际尺度上的变化对此起了重要作用.     

东亚季风区的季风类型

从地面流场正、斜压分量的冬夏季节转换的特征 ,对东亚至西太平洋季风区季风的性质进行了分析研究。结果表明 :这一地区的季风可分为 3种类型 :南海、华南沿海和低纬西太平洋主要为斜压流型季风区 ;华北北部、东北地区沿海主要为正压流型季风区 ;我国东部沿海和长江流域以及 2 7°N附近的西太平洋地区为正斜压流型共同形成的混合型季风区。     

Space-time variability of low frequency oscillations and Asian summer monsoon precipitation

Summary In this study, we provide an observational synthesis of several aspects of MJO (Madden Julian Oscillation) and ISO (Intra Seasonal Oscillation) waves and the manner in which they seem to affect the Asian summer monsoon variability. We examine a number of features such as the passage of MJO waves around the globe from west to east, excitation of ISO waves over the equatorial Indian Ocean, meridional propagation of ISO waves and the role of the local Hadley cell over the monsoon domain in its propagation. The geographical distribution of the amplitude and phase speed of ISO waves over the Asian summer monsoon domain shows that the ISO has prominent centers of action, with small scales of the order of a few 1000 km and that these features vary interannually in amplitude and in their geographical locations. It was also seen that some of the interesting features of the WET and DRY season rainfall distribution can be obtained by compositing the extremes of the amplitude oscillations of these ISO centers. We also noted that the amplitudes of ISO waves generally decay as they propagate north but have an occasional built up in their amplitudes when they seem to encounter and interact with heavy rain producing monsoon disturbances. The issue of these low frequency modes and the modulation of monsoonal dry and wet spells are examined in the context of this broad scenario.     

通用地球系统模式对亚洲夏季风降水的模拟能力评估

通过与观测/再分析资料和参加第五次耦合模式比较计划(CMIP5)的模式模拟结果进行对比,评估了通用地球系统模式(CESM,1.0.3版本)对亚洲夏季风降水的模拟能力。结果表明:CESM能够合理地模拟出亚洲夏季风降水的气候平均态,但与其他CMIP5模式模拟结果类似,对中国东南地区降水模拟偏少,而对中国西部高原地区降水模拟偏多;CESM可以再现亚洲季风区降水冬弱夏强、雨带北进南退的季节变化特征,其模拟偏差具有区域性和季节性差异;从EOF分析结果来看,CESM能够模拟出亚洲夏季风降水的时空变化特征,且能较好地抓住亚洲夏季风降水与厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,简称ENSO)的相关关系。总的说来,CESM对亚洲夏季风降水的模拟是合理的,模拟水平与4个最好的CMIP5模式相当。     

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.