国家气候中心MJO监测预测业务产品研发及应用

热带大气低频振荡 (MJO) 和北半球夏季季节内振荡 (BSISO) 对全球范围天气气候事件有重要影响,是次季节-季节 (S2S) 预报最主要的可预报性来源之一。国家气候中心 (BCC) 基于我国完全自主的T639全球分析场数据、风云三号气象卫星射出长波辐射 (OLR) 资料以及BCC第2代大气环流模式系统的实时预报,发展了MJO实时监测预测一体化业务技术,建立了ISV/MJO监测预测业务系统 (IMPRESS1.0),已投入实时业务运行,在全国气象业务系统得到应用。该文着重介绍该系统提供的MJO和BSISO指数监测预测数据和图形产品,并描述了这些业务产品在2015年对MJO典型个例的实时监测预测应用情况。监测分析和预报检验表明,基于我国自主资料的监测结果能够较为准确地表征MJO和BSISO指数的振荡和演变过程,该系统对MJO和BSISO事件分别至少具备16 d和10 d左右的预报技巧。因此,基于IMPRESS1.0的MJO/BSISO监测预测一体化业务产品可为制作延伸期预报提供重要的参考依据。     

Simulations of the Tropical Intraseasonal Oscillation by the Atmospheric General Circulation Model of the Beijing Climate Center

The performance of BCC (Beijing Climate Center) AGCM 2.0.1 (Atmospheric General Circulation Model version 2.0.1) in simulating the tropical intraseasonal oscillation (TIO) is examined in this paper.The simulations are validated against observation and compared with the NCAR CAM3 (Community Atmosphere Model version 3) results.The BCC AGCM2.0.1 is developed based on the original BCC AGCM (version 1) and NCAR CAM3.New reference atmosphere and reference pressure are introduced into the model.Therefore,the origi...     

Impacts of the MJO on Winter Rainfall and Circulation in China

Impacts of the MJO on winter rainfall and circulation in China are investigated using a real-time multivariate MJO index.Composite results using the daily rainfall anomalies and "rainy day" anomalies according to eight different MJO phases show that the MJO has considerable influence on winter rainfall in China. Rainfall anomalies show systematic and substantial changes(enhanced/suppressed) in the Yangtze River Basin and South China with the eastward propagation of the MJO convective center from the Indian Ocean to the western Pacific.When the MJO is in phase 2 and 3(MJO convective center is located over the Indian Ocean),rainfall probability is significantly enhanced.While in phase 6 and 7(MJO convective center is over the western Pacific),rainfall probability is significantly reduced. MJO in winter influences the rainfall in China mainly through modulating the circulation in the subtropics and mid-high latitudes.For the subtropics,MJO influences the northward moisture transport coming from the Bay of Bengal and the South China Sea by modulating the southern trough of the Bay of Bengal and the western Pacific subtropical high.For the mid-high latitudes,the propagation of the low frequency perturbations associated with the eastward-propagating MJO convection modulate the circulation in the mid-high latitudes,e.g.the East Asian winter monsoon and the low trough over central Asia.     

An Assessment of MJO and Tropical Waves Simulated by Different Versions of the GAMIL Model

Simulated outgoing longwave radiation (OLR) outputs by two versions of the grid-point atmospheric general circulation model (GAMIL) were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation (MJO) and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the MJO, Kelvin, equatorial Rossby (ER), mixed Rossby-gravity (MRG), and inertio-gravity (IG) waves. The performances of different versions of the GAMIL model (version 1.0 (GAMIL1.0) and version 2.0 (GAMIL2.0)) were evaluated by comparing the power spectrum distributions of these waves among GAMIL1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1–3, suggesting that GAMIL1.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model’s performance.     

The Dynamical and Climate Tests of an Atmospheric General Circulation Model Using the Second-Order Adams-Bashforth Method

The Asselin-Robert time filter used in the leapfrog scheme can degrade the accuracy of calculations. The second-order Adams-Bashforth method with the same accuracy as the leapfrog scheme is not subject to time splitting instability. A new semi-implicit atmospheric general circulation spectral model is developed on the basis of NCAR (National Center for Atmospheric Research) CAM3.0 (Community Atmosphere Model3.0). In this new model, the second-order Adams-Bashforth method is used as an alternative to the leapfrog scheme, and a Crank-Nicholson scheme is incorporated for the treatment of fast gravity modes. In this paper, the new model is tested by the Held-Suarez test and an idealized baroclinic wave test. Results of the Held-Suarez test show that the second-order Adams-Bashforth model has similar climate states to those of many other global models and it converges with resolutions. Based on the idealized baroclinic wave test, the capability of di?erent time di?erencing methods for keeping the initial steady-state are compared.This convinces a better ability of the second-order Adams-Bashforth method in maintaining the stability of the initial state. Furthermore, after the baroclinic wave is triggered through overlaying the steady-state initial conditions with the zonal perturbation, the second-order Adams-Bashforth method has an excellent property of convergence, and can represent the process of the baroclinic wave development much better than the original scheme in CAM3.0. A long-term integration of the new model during the period of 1980-1999 is also carried out and compared with that of CAM3.0. It is found that due to the reduction of simulation errors of prognostic variables, the second-order Adams-Bashforth method also has a better simulation ability for the diagnostic variables, such as precipitation.     

准两年振荡及其对东亚大气环流和气候的影响

通过多年资料分析,本文研究了平流层准两年振荡(QBO)的演变特征及其对东亚及西太平洋地区大气环流和气候变化的影响.结果表明,平流层QBO的演变特征是:东风向西风转换最早出现在印度洋赤道地区;西风向东风转换最早出现在美洲和西太平洋赤道地区.中国东部降水量、气温以及西太平洋副高和东亚急流都有准两年周期变化,并同平流层QBO有密切关系;平流层QBO对西太平洋台风活动也有一定影响,QBO的西风位相期西太平洋台风偏少.另外,ENSO对于平流层QBO有明显影响,一般在ENSO发生之后,QBO的西风位相期持续时间缩短.     

全球变化背景下北半球冬季MJO传播的年代际变化

利用1979~2013年实时多要素MJO（Madden-Julian Oscillation）监测（RMM）指数,美国NOAA逐日长波辐射资料和NCEP/NCAR再分析资料等,分析了全球变化背景下北半球冬季MJO传播的年代际变化特征。从全球平均气温快速增暖期（1985~1997）到变暖趋缓期（2000~2012）,MJO 2~4位相频次减少,5~7位相频次增多,即MJO对流活跃区在热带印度洋地区停留时间缩短、传播速度加快,而在热带西太平洋停留时间加长、传播明显减缓。进一步分析发现,以上MJO的年代际变化特征与全球变化年代际波动有关。当太平洋年代际涛动（PDO）处于负位相时,全球变暖趋缓,热带东印度洋—西太平洋海温异常偏暖,使其上空对流加强,垂直上升运动加强,对流层低层辐合,大气中的水汽含量增多,该区域的湿静力能（MSE）为正异常。当MJO对流活跃区位于热带印度洋地区时,MJO异常环流对季节平均MSE的输送在强对流中心东侧为正、西侧为负,有利于东侧MSE扰动增加,使得MJO对流扰动东移加快;而当MJO对流活跃区在热带西太平洋地区,MJO异常环流对平均MSE的输送形成东负西正的形势,东侧MSE扰动减小,不利于MJO快速东传。因此,全球变化背景下PDO引起的大气中水汽含量及MSE的变化可能是MJO传播年代际变化的重要原因。     

Coupling the Common Land Model to ECHAM5 Atmospheric General Circulation Model

The ECHAM5 model is coupled with the widely used Common Land Model(CoLM). ECHAM5 is a state-of-theart atmospheric general circulation model incorporated into the integrated weather and climate model of the Chinese Academy of Meteorological Sciences(CAMS-CSM). Land surface schemes in ECHAM5 are simple and do not provide an adequate representation of the vegetation canopy and snow/frozen soil processes. Two AMIP(Atmospheric Model Intercomparison Project)-type experiments using ECHAM5 and ECHAM5-CoLM are run over 30 yr and the results are compared with reanalysis and observational data. It is found that the pattern of land surface temperature simulated by ECHAM5-CoLM is significantly improved relative to ECHAM5. Specifically, the cold bias over Eurasia is removed and the root-mean-square error is reduced in most regions. The seasonal variation in the zonal mean land surface temperature and the in situ soil temperature at 20-and 80-cm depths are both better simulated by ECHAM5-CoLM. ECHAM5-CoLM produces a more reasonable spatial pattern in the soil moisture content, whereas ECHAM5 predicts much drier soils. The seasonal cycle of soil moisture content from ECHAM5-CoLM is a better match to the observational data in six specific regions. ECHAM5-CoLM reproduces the observed spatial patterns of both sensible and latent heat fluxes. The strong positive bias in precipitation over land is reduced in ECHAM5-CoLM, especially over the southern Tibetan Plateau and middle–lower reaches of the Yangtze River during the summer monsoon rainy season.     

1998年大气环流异常及其对中国气候异常的影响

１９９８年受ＥＮＳＯ事件和青藏高原冬春季积雪多等因素的影响,北半球大气环流的主要特征是：５００ｈＰａ西太平洋副高强大,夏季副高脊线位置偏南;冬、夏季风均较弱;赤道辐合带偏弱,在西太平洋生成和登陆影响我 斩台风和热带风暴异常偏少;夏季亚洲中高纬度经向环流发展,其它季节则以纬向环流为主;环流异常是影响１９９８年中国气候极其异常的主要原因。     

Interdecadal change in the Northern Hemisphere seasonal climate prediction skill: part II. predictability and prediction skill

The interdecadal change in seasonal predictability and numerical models’ seasonal forecast skill in the Northern Hemisphere are examined using both observations and the seasonal hindcast from six coupled atmosphere-ocean climate models from the 21 period of 1960–1980 (P1) to that of 1981–2001 (P2). It is shown that the one-month lead seasonal forecast skill of the six models’ multi-model ensemble is significantly increased from P1 to P2 for all four seasons. We identify four possible reasons accounting for the interdecadal change of the seasonal forecast skill. Firstly, the numerical model’s ability to simulate the mean state, the time variability and the spatial structures of the sea surface temperature and precipitation over the tropical Pacific is improved in P2 compared to P1. Secondly, an examination of the potential predictability of the atmosphere, estimated by the ratio of the total variance to the variance due to the internal dynamics of the model atmosphere, reveals that the atmospheric potential predictability is significantly increased after 1980s which is mainly due to an increased influence of El Niño-Southern Oscillation signal over the North Pacific and North American regions. Thirdly, the long-term climate trends in the atmosphere are found to contribute, to some extent, to the increased seasonal forecast skill especially over the Eurasian regions. Finally, the improved ocean observations in P2 may provide better initial conditions for the coupled models’ seasonal forecast.     

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。     

The African Climate as Predicted by the IAP Grid-Point Nine-Layer Atmospheric General Circulation Model (IAP-9L-AGCM)

ＴｈｅＡｆｒｉｃａｎＣｌｉｍａｔｅａｓＰｒｅｄｉｃｔｅｄｂｙｔｈｅＩＡＰＧｒｉｄ－ＰｏｉｎｔＮｉｎｅ－ＬａｙｅｒＡｔｍｏｓｐｈｅｒｉｃＧｅｎｅｒａｌＣｉｒｃｕｌａｔｉｏｎＭｏｄｅｌ（ＩＡＰ－９Ｌ－ＡＧＣＭ）ＣｈｉｎｅｋｅＴｈｅｏＣｈｉｄｉｅｚｉｅ①，...     

The Impact of Cloud Representation on the Sub-Seasonal Forecasts of Atmospheric Teleconnections and Preferred Circulation Regimes in the Northern Hemisphere

Abstract

The impact of cloud representation on the simulation of mid-latitude recurrent large-scale flows and forecast skill of mid-latitude atmospheric teleconnections is evaluated using the Community Climate System Model, version 4 (CCSM4), and the super-parameterized CCSM4 (SP-CCSM4). Patterns of low-level atmospheric circulation anomalies and convection associated with the Madden–Julian oscillation (MJO) are affected by the method used for the representation of cloud processes. The configuration of the model using super-parameterization for the representation of cloud processes produces MJO-related patterns that agree better with observations than the configuration of the model using a conventional cloud parameterization scheme. The recurrent circulation regimes of the mid-latitudes are also sensitive to the representation of cloud processes. In the North Atlantic sector, the inability of CCSM4 to simulate the Scandinavian blocking regime is corrected in the super-parameterized version of the model. In the North Pacific sector, the strength of the clustering (measured by a variance ratio) is too large in CCSM4 compared with observations and SP-CCSM4. The SP-CCSM4 model has better forecast skill for the MJO amplitude and phase than the model with conventional representation of moist convective processes. In turn, the improved forecast skill of the super-parameterized model results in better forecast skill for mid-latitude teleconnections in 500 hPa geopotential height anomalies forced by the MJO convection.     

分块地形坐标大气环流模式的动力框架及其整体性质

介绍了分块地形坐标大气环流模式的动力框架及该框架微、差分方程组的整体性质.目前该框架水平分辨率为4°× 5°,垂直分辨率有9层和21层两个版本.给出了该框架的控制方程组及其差分形式、边界条件、时间积分方案等.该框架的微、差分控制方程组均满足总质量守恒、平流项二次守恒、科里奥利力不作功和总有效能量守恒;且未引入虚假的源和汇,保持了该框架计算过程中的物理真实性.该模式框架在主流微机上能长时间稳定积分,并可作有关地形的数值试验.     

2008年海洋和大气环流异常及对中国气候的影响

2008年,尽管总体来看,全国天气气候的持续异常较弱,未发生大范围持续干旱和严重洪涝灾害,但依然出现了非常显著的天气气候异常特征,如全国平均年降水量比常年偏多,为近10年来降水最多的年份;夏季华南降水异常偏多,黄淮降水偏多;年平均气温偏高,但冬季气温偏低,年初南方遭遇罕见低温雨雪冰冻灾害;在南海和西太平洋生成的台风个数明显偏少,但是登陆台风偏多,初台异常偏早.分析发现,2008年赤道中东太平洋总体处在冷水位相,受海洋异常强迫和海气相互作用的影响,北半球大气环流表现出的主要特征是:500hPa西太平洋副高强度和位置变化较大;冬夏季风均偏强;冬春季西太平洋暖池区热带对流活动偏强,夏秋季则偏弱;1月份,亚洲中高纬度经向环流异常发展,2至4月份则以纬向环流为主,春季后期至秋季,经纬向环流的转换较快,环流的持续性较弱.这些环流异常是影响2008年中国气候异常的主要原因.     

Decadal predictability and prediction skill of sea surface temperatures in the South Pacific region

The South Pacific Ocean is a key driver of climate variability within the Southern Hemisphere at different time scales. Previous studies have characterized the main mode of interannual sea surface temperature (SST) variability in that region as a dipolar pattern of SST anomalies that cover subtropical and extratropical latitudes (the South Pacific Ocean Dipole, or SPOD), which is related to precipitation and temperature anomalies over several regions throughout the Southern Hemisphere. Using that relationship and the reported low predictive skill of precipitation anomalies over the Southern Hemisphere, this work explores the predictability and prediction skill of the SPOD in near-term climate hindcasts using a set of state-of-the-art forecast systems. Results show that predictability greatly benefits from initializing the hindcasts beyond the prescribed radiative forcing, and is modulated by known modes of climate variability, namely El Niño-Southern Oscillation and the Interdecadal Pacific Oscillation. Furthermore, the models are capable of simulating the spatial pattern of the observed SPOD even without initialization, which suggests that the key dynamical processes are properly represented. However, the hindcast of the actual phase of the mode is only achieved when the forecast systems are initialized, pointing at SPOD variability to not be radiatively forced but probably internally generated. The comparison with the performance of an empirical prediction based on persistence suggests that initialization may provide skillful information for SST anomalies, outperforming damping processes, up to 2–3 years into the future.     

大气环流模式中云系的超级参数化方案及其特征线方法之研究

就大气环流模式中如何有效处理云系,我们的目标:建立能考虑各种尺度和各种过程之间相互作用的多重尺度云系动力学(下称:云系超级参数化),并应同时考虑如下云的几何学与辐射传输两个问题:1)云的几何学,考虑如何描写云内结构的三维不均匀性和表面特征的几何不光滑性;2)云的辐射,考虑复杂云结构的辐射计算问题,并最终在大气环流模式中具体实现.本研究是理论部分,主要论述云系超级参数化框架和计算方法问题,主要结论如下:1)阐明了从多重尺度角度研究大气模式中云系的超级参数化方案是完全必要的.2)本云系超级参数化方案是3维完全Euler流体方程组,保留了全Coriolis力,Ertel全PV守恒,考虑声波等对云和降水微物理过程的影响.该云系超级参数化方案需要与大气大尺度动力学方程组进行耦合.3)关键问题为确定云系局部解的存在时间长度,不必考虑整体解.因为在实际大气中各物理量的不光滑,甚至不连续和间断,是有充分的物理意义的.大气中的间断除粘性和热传导等不可逆过程外,同时伴随着成云致雨的相变过程.4)在可积性和连续性条件下,证明了特征线的存在性;在Lipshitz条件下,证明了特征线的存在性和唯一性.5)给出了特征线积分的Picard方法的具体计算步骤,并同时给出了特征线积分稳定步长的具体条件.6)沿着特征线,初始场随着时间的推移,将发生平移、旋转与纯变形三种位移的几何和,这就是球面上平流方程的保形问题.     

2010年10月大气环流和天气分析

2010年10月大气环流特征是:北半球高纬度地区存在两个极涡中心,强度偏弱;中高纬呈现4波型,其中乌拉尔山高压脊偏强,对应大片40 gpm的正距平区;副高强度偏弱.全国平均气温为10.1℃,比常年同期(9.6℃)偏高0.5℃.全国平均降水量为42.6 mm,比常年同期(37.0 mm)偏多15.1%.月内我国主要天气事...