夏季对流性降水量的完全预报法

本文应用部分实时资料和数值预报产品,以对流参数化方案为基础,依据湿绝热过程中饱和湿静力总能量守恒原理,实现积云形成所需凝结水汽量及积云面积比等大气参数的计算,进而实现对流性降水量的计算。对所计算出的降水量再做经验订正,建立对流性降水量经验预报公式。计算效果很好。     

WRF模式对浙江2011年夏季降水和温度预报评估及其湿过程敏感性分析

检验评估是数值天气预报的一个重要组成部分,评估结果是模式改进及其产品解释应用的重要依据。利用全省1500多个包括区域自动站在内的站点观测资料,采用要素的空间分布、时间演变和统计检验3种方法评价了WRF模式对浙江省2011年夏季（6—8月）降水和温度的整体预报性能;在此基础上,进一步对比分析了不同湿过程参数化方案对梅雨典型过程的预报效果,探讨了不同微物理参数化方案和积云参数化方案对模式预报降水的影响。结果表明,WRF模式能基本预报出降水和气温的细致空间分布形态及整体演变趋势,对于主要降水落区、高温区具有较好的指示性;就浙江省区域平均而言,在实况出现较大降水期间模式预报误差较小,而在实况出现小到中雨期间误差较大,主要表现为降水量的高估和气温的低估;模式湿过程中积云参数化方案对降水影响明显,它可以导致整体雨带偏移,采用Betts-Miller-Janjic积云对流参数化方案的预报降水更接近实况。这些信息对改进模式的精细化预报能力和高分辨率数值产品的解释应用具有一定的参考作用。     

对流凝结加热对华北夏季锋面影响的数值模拟研究

本文利用改进的ＭＭ２模式，用干、湿过程模拟了一次夏季华北锋面结构。干模式仅能模拟出大尺度特征和明显偏弱的锋面环流，而湿模式可模拟出某些重要的中尺度流场特征。表明只要具有合理的模式物理过程，使用大尺度资料，也可以在一定程度上模拟出中尺度系统。对流参数化的试验表明，系统演变和降水预报对湿润因子ｂ和增温廓线很敏感。在此工作基础上，设计了考虑下沉气流的积云参数化方案。初步结果表明，这种方案使降水量预报有改进。     

多积云参数化方案热带气旋路径集合预报试验

利用MM5模式采用5种积云参数化方案选项研究了2004～2006年共8个热带气旋路径的集合预报。结果表明，热带气旋路径预报对积云参数化方案的选取是敏感的，积云参数化方案之间优劣互补，而选择无积云参数化方案选项对热带气旋路径的预报有积极的贡献。采用3种路径集合预报方案研究的结果表明，集合方法对热带气旋路径预报有明显的改善，其中无积云参数化Grell、Betts—Miller和Kain—Fritsch4种积云参数化方案选项组合的集合预报效果最好，平均路径误差最小。     

用积云对流方法计算MCC的降水

根据郭晓岚的对流加热方法，计算积云对流对ＭＣＣ和加热，增湿的贡献，估计其降水效率，从而推算ＭＣＣ的降水量，计算结果与实际降水量及降水分布比较接近，可用于ＭＣＣ６－１２ｈ的降水估计和预报。     

短期集合预报技术在梅雨降水预报中的试验研究

数值预报的误差来源于初始场和模式的误差,集合预报技术是减小这些误差的有效方法。该文以MM5模式作为试验模式框架,模式的积云参数化方案分别取Anthes-Kuo、Grell、Kain-Fritsch和Betts-Miller方案,边界层参数化方案分别取MRF和Eta方案,通过组合4种积云参数化方案和两种边界层参数化方案产生8个集合成员,对1999年华东地区梅雨期间3个降水个例进行48 h集合预报试验。结果显示不同集合成员的预报结果各不相同,积云参数化方案对降水的影响比边界层参数化方案对降水的影响大;不同集合成员预报降水的偏差也各不相同,大多存在湿偏差,量级小的降水的湿偏差程度比量级大的降水的湿偏差程度小;对于不同个例,各成员中预报效果相对较好的成员是不同的,集合平均后可以得到一个比较稳定的预报结果;从集合预报结果中还能得到客观化和定量化的降水概率预报,它能对可能发生的天气现象发出信号。     

一种改进的质量通量积云参数化方案及预报试验

用国家气象中心有限区域业务预报模式,以１９９８年８月一次热带风暴降水过程为试验个例,对引入了下曳气流的质量通量积云对流参数方案和模式中的原质量通量积云参数化方案进行了对比试验。结果显示;引入了下曳气流后,通过提高对流降水量使降雨强度预报得以提高,更接近于实况;改进后的方案对大雨以上预报水平有一定的改善,各项评分结果均有所提高。     

两种不同积云参数化方案对1998年中国夏季洪涝灾害数值模拟的比较研究

利用国家气候中心的全球T63谱模式，以1998年夏季(6-8月)我国长江中下游和东北嫩江—松花江流域发生的特大洪水为试验个例，分别采取原来模式中的Kuo积云参数比方案和UKMO/unifled的Gregory积云参数比方案进行了整个夏季的逐月降水预报的对比试验。结果表明：Gregory质量通量方案能给出较Kuo方案更加合理的降水落区，并且对降水量的预报也有显著的改进。此外，Gregory质量通量方案对大尺度环流背景场的预报也较Kuo方案好。从整个夏季的预报来看，Gregory参数化方案能较Kuo方案更好地模拟出1998年的降水的总体趋势，尽管Gregory方案模拟的降水与实况相比，仍然存在着系统性的误差，还需要进一步改进。     

补偿性下沉气流对积云发展影响的数值模拟

本文用带有积云外补偿性下没气流参数化方法的积云－维时变模式讨论了补偿性下沉气流对积云发展的影响，并与虚质量系数模式作了比较。计算结果表明，选择合适的参数β就能比较合理地模拟降水性积云和非降水性积云的发展情况。     

夏、秋积云的雷达回波和降水特征及其估算

利用湖南1979—1988年夏秋外场观测的资料，分析了积云雷达回波和降水的特征，建立了用雷达回波参数估算单站积云降水量、水层厚、总降水量和雨强的回归关系式，并用湖南积云降水资料和广东积云降水资料进行了检验。结果表明:这种估算积云降水的方法对我国南方的广大地区有一定实用性。     

WRF模式物理参数化方案对一次局地大暴雨预报的影响研究

基于WRF(Weather Research and Forecasting)模式及其3Dvar(3-Dimentional Variational)资料同化系统,采用36、12、4 km嵌套网格进行快速更新循环同化和不同的微物理及积云对流参数化方案对比试验,对2011年5月8日鲁中一次局地大暴雨过程进行了研究。结果表明,快速更新循环同化地面观测资料是影响模式降水落区预报准确性的关键因素,不同的微物理和积云对流参数化方案主要影响降水强度预报。采用不同的微物理参数化方案和积云对流参数化方案进行降水预报对比试验表明,LIN方案和WSM6(WRF Single-Moment 6-class)微物理参数化方案对降水预报均较好,LIN方案降水预报较WSM6方案略强。4 km网格预报使用K-F (Kain-Fritsch)积云对流参数化方案或不使用积云对流参数化方案,预报的降水均较好。4 km网格使用旧的K-F积云对流参数化方案,预报的近地层大气风场偏弱,导致大气动力抬升作用偏弱,从而造成模式降水预报偏弱。     

THE LIMITATION OF CLOUD-BASE MASS FLUX IN CUMULUS PARAMETERIZATION AND ITS APPLICATION IN A HIGH-RESOLUTION MODEL

A large area of unrealized precipitation is produced with the standard convective parameterization scheme in a high-resolution model, while subgrid-scale convection that cannot be explicitly resolved is omitted without convective parameterization. A modified version of the convection scheme with limited mass flux at cloud base is introduced into a south-China regional high-resolution model to alleviate these problems. A strong convection case and a weak convection case are selected to analyze the influence of limited cloud-base mass flux on precipitation forecast. The sensitivity of different limitation on mass flux at cloud base is also discussed. It is found that using instability energy closure for Simplified Arakawa- Schubert Scheme will produce better precipitation forecast than the primary closure based on quasi-equilibrium assumption. The influence of the convection scheme is dependent on the upper limit of mass flux at cloud base. The total rain amount is not so sensitive to the limitation of mass flux in the strong convection case as in the weak one. From the comparison of two different methods for limiting the cloud-base mass flux, it is found that shutting down the cumulus parameterization scheme completely when the cloud-base mass flux exceeds a given limitation is more suitable for the forecast of precipitation.     

一维积云模式初始参数优化的研究

福建省人工增雨指挥系统在预报积云降水和评估增雨效果中曾采用一维时变积云模式。关于该模式初始场的确定 ,考虑到不同天气类型对模式初始参数的影响 ,并采用了以确定敏感参数为主 ,综合考虑其他影响参数为辅的方法。经分类调试 ,证明了一维模式初始场确实与天气类型有关 ,并得到旱期降水预报率大于 75%和可预报积云云顶高度的结果。通过对模拟云和实测云高度的线性回归分析 ,以及经拟合敏感参数初始扰动温度与平均地面最高气温 ,均存在较好的相关。     

Experimental Dynamical Forecast of an MJO Event Observed during TOGA-COARE Period

With a hybrid atmosphere-ocean coupled model we carried out an experimental forecast of a well documented Madden-Julian Oscillation (MJO) event that was observed during the period of Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). The observed event, originated in the western Indian Ocean around 6 January 1993, moved eastward with a phase speed of about 6.2 m s-1 and reached the dateline around February 1. The hybrid coupled model reasonably forecasts the MJO initiation in the western Indian Ocean, but the predicted MJO event propagates too slow (~ 4.4 m s-1). Results from previous observational studies using unprecedented humidity profiles obtained by NASA Aqua/AIRS satellite suggested that two potential physical processes may be responsible for this model caveat. After improving the cumulus parameterization scheme based on the observations, the model is able to forecast the same event one month ahead. Further sensitivity experiment confirms that the speed-up of model MJO propagation is primarily due to the improved convective scheme. Further, air-sea coupling plays an important role in maintaining the intensity of the predicted MJO. The results here suggest that MJO prediction skill is sensitive to model cumulus parameterization and air-sea coupling. Citation: Fu, X., B. Wang, Q. Bao, et al., 2008: Experimental dynamical forecast of an MJO event observed during TOGA-COARE period, Atmos. Oceanic Sci. Lett., 1, 24-28     

下曳气流在积云对流中的作用

利用国家气象中心高分辨率有限区域业务预报模式（ＨＬＡＦＳ）对有无下曳气流的积云参数化方案进行了对比试验,通过对积云内容各物理量及大尺度物理量场的诊断分析研究下曳气流对积云对流发生发展的作用以及对大尺度热力,动力场的影响。结果表明：（１）下曳气流具有湿冷的特征,主要出现在强对流时段时流层中下层;（２）下曳气流的引入,促进了模式中强积云对流的发生发展,并在更高更多的空间层次上更强地加热及干化环境大气,     

Impacts of Cumulus Convective Parameterization Schemes on Summer Monsoon Precipitation Simulation over China

By using the Betts-Miller-Janjic, Grell-Devenyi, and Kain-Fritsch cumulus convective parameterization schemes in theWeather Research and Forecasting (WRF) model, long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summer monsoon precipitation simulation over China. The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation. The observed north-south shift of monsoon rain belt is also well simulated by the three schemes. Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others. Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.     

Sensitivity of the Simulated Tropical Intraseasonal Oscillation to Cumulus Parameterizations

The sensitivity of the simulated tropical intraseasonal oscillation or MJO (Madden and Julian oscilla tion)to different cumulus parameterizations is studied by using an atmospheric general circulation model (GCM)-SAMIL(Spectral Atmospheric Model of IAP LASG).Results show that performance of the model in simulating the MJO alters widely when using two different cumulus parameterization schemes-the moist convective adjustment scheme(MCA)and the Zhang-McFarlane(ZM)scheme.MJO simulated by the MCA scheme was found to be more realistic than that simulated by the ZM scheme.MJO produced by the ZM scheme is too weak and shows little propagation characteristics.Weak moisture convergence at low levels simulated by the ZM scheme is not enough to maintain the structure and the eastward propagation of the oscillation.These two cumulus schemes produced different vertical structures of the heating profile.The heating profile produced by the ZM scheme is nearly uniform with height and the heating is too weak compared to that produced by the MCA,which maybe contributes greatly to the failure of simulating a reasonable MJO.Comparing the simulated MJO by these two schemes indicate that the MJO simulated by the GCM is highly sensitive to cumulus parameterizations implanted in.The diabatic heating profile plays an important role in the performance of the GCM.Three sensitivity experiments with different heating profiles are designed in which modified heating profiles peak respectively in the upper troposphere(UH), middle troposphere(MH),and lower troposphere(LH).Both the LH run and the MH run produce eastward propagating signals on the intraseasonal timescale,while it is interesting that the intraseasonal timescale signals produced by the UH run propagate westward.It indicates that a realistic intraseasonal oscillation is more prone to be excited when the maximum heating concentrates in the middle-low levels,especially in the middle levels,while westward propagating disturbances axe more prone to be produced when the maximum heating appears very high.     

舟曲泥石流天气过程中云团合并的卫星观测

利用极轨和静止气象卫星红外云图资料,对2010年8月7日甘肃舟曲发生的特大泥石流天气过程中出现的对流云合并现象进行分析。从卫星监测结果来看,多个对流单体合并而成的中尺度对流系统,在发展过程中产生了局地强降水,从而引发了特大泥石流灾害。整个过程中有5个阶段出现了合并现象:首先,多个对流单体合并形成中尺度对流系统; 在中尺度对流系统的发展和维持过程中,3个阶段出现了新旧对流系统的合并; 在系统即将消散的阶段又出现了两个强中心的合并。合并过程不仅促成中尺度对流系统的生成,使得云体增强发展,而且为对流系统维持补充了能量,使系统生命史延长。另外,在5个阶段的合并过程中,合并机制可以归结为内部动力结构变化和外致碰撞合并两大类。其中,在系统形成阶段,外致碰撞合并是主要机制; 而在发展维持阶段,包括气压梯度力、辐合抬升、下沉-上升环流加强等在内的内部动力结构变化影响是发生合并的主要原因。     

An improvement of the mass flux convection parameterization scheme and its sensitivity tests for seasonal prediction over China

A modified cumulus parameterization scheme, suitable for use in a seasonal forecast model, is presented. This parameterization scheme is an improvement of the mass flux convection scheme developed by Gregory and Rowntree (1989; 1990). This convection scheme uses a “bulk” cloud model to present an ensemble of convective clouds, and aims to represent shallow, deep, and mid-level convection. At present,this convection scheme is employed in the NCC T63L20 model (National Climate Center, China Meteorological Administration). Simulation results with this scheme have revealed some deficiencies in the scheme,although to some extent, it improves the accuracy of the simulation. In order to alleviate the deficiencies and reflect the effect of cumulus convection in the actual atmosphere, the scheme is modified and improved.The improvements include (i) the full estimation of the effects of the large-scale convergence in the lower layer upon cumulus convection, (ii) the revision of the initial convective mass flux, and (iii) the regulation of convective-scale downdrafts. A comparison of the results obtained by using the original model and the modified one shows that the improvement and modification of the original convection scheme is successful in simulating the precipitation and general circulation field, because the modified scheme provides a good simulation of the main features of seasonal precipitation in China, and an analysis of the anomaly correlation eoetfieient between the simulation and the observations confirms the improved results.     

用一维积云模式预报积云的试验

本文将改进的一维积云模式用于积云人工增雨作业报告。在1993一1995年春季飞机增雨作业期间,对广西南宁地区的21个个例的计算中,进行人工增雨作业可能性预报,预报成功率可达67％以上。