NWP产品在强对流天气诊断分析中的应用

利用ECMWF、T213、T106数值预报产品及各物理量场,对已知中尺度系统发生发展的大尺度条件,预报中尺度环流出现的统计概率进行探讨:首先将武汉中心气象台过去总结的强对流天气模型与数值预报产品中的环流形势进行对比分析,当所预报的环流形势满足强对流天气模型时,认为大尺度条件将会促进中尺度天气的发生发展。再对数值预报产品中的有关物理要素场和值进行诊断分析,当所诊断的结果反映出有中尺度次级环流出现或有利中尺度对流天气发生时,最后对强对流天气落区、落点及降水性质进行诊断分析。同时,还利用AREM中尺度数值模式对2002年7月21~24日过程进行诊断分析,预报效果较好。,通过诊断分析,得出了强对流天气落区、落点及降水性质与各要素之间预报场和值的关系,同时也为今后精细化预报提供了启示和参考。     

北京地区风廓线仪布网方案的数值研究

文中利用北京地区中尺度数值天气预报业务系统 ,通过进行多个例数值对比试验 ,对在北京地区如何进行风廓线仪布网进行了数值研究。结果表明大气风场随高度的垂直分布和变化对天气过程有明显的作用 ,在较短时期就可对大气的空间特征形成深厚的影响 ,天气系统对大气风场的垂直结构特征是较为敏感的。其可在短期天气过程中影响天气系统的温度场结构及相关降水过程 ,且在以上影响随着预报时效的增加而增强的同时 ,影响范围也随预报时效的增加而扩大。对中尺度数值预报和北京地区的风廓线仪布点方案来说 ,以核心区域 (北京市城区 )为中心的呈近等边三角形的布网方案具有与近正四边形布网方案相当的探测效果 ,选择近等边三角形布网方案 ,较选择较近正四边形布网方案更为合理。可节省大量的资源及经费。文中所研究方法和结果对在有限区域如何选择风廓线仪布网方案具有广泛的借鉴意义和实际应用价值。     

Testing a radiative upper boundar condition in a nonlinear model with hybrid vertical coordinate

Summary The application of a radiative upper boundary condition (RUBC) in a mesoscale numerical weather prediction (NWP) model with hybrid vertical coordinate is presented. Results of two- and three-dimensional numerical simulations are discussed. Starting from earlier work by Klemp and Durran (1983) and Bougeault (1983) the radiative upper boundary condition is formally derived for a hybrid vertical coordinate. The basic assumptions include hydrostaticity, linearity, neglect of Coriolis effects and restriction to internal gravity waves. The resulting RUBC is global in space and local in time. In a second step. the RUBC is tested in a twodimensional vertical-plane version of the NWP model, in which essential properties of the full three-dimensional model have been preserved. Gravity wave experiments clearly show the superiority of the RUBC over the commonly used lid-type upper boundary condition. For the setting with an isolated bell-shaped mountain with resolution-independent steepness, the RUBC tends to work more effectively with increasing horizontal resolution. At the same time, the application of a radiative instead of a lid-type, and thus reflecting, upper boundary condition appears to become more important with decreasing mesh width. Finally, the RUBC is introduced into the full three-dimensional NWP model. This requires further approximations. In particular for a limited-area model, the geopotential field at the uppermost model level needs to be bi-periodic. Here, a linear detrending technique is applied. First results for a weather situation with strong northwesterly flow towards the Alps show that application of the RUBC drastically reduces the development of unrealistic standing, hydrostatic mountain waves, which become apprent as distinct mesoscale ridge-trough structures in the simulation with the lid-type upper boundary. Implications of the RUBC on the time-stepping procedure of the NWP model are also discussed. In the experiments whown, the additional RUBC-terms are treated explicitly.     

一种基于进化策略的气象学反问题求解算法研究

数值天气预报准确性直接取决于好的预报模式和初始场。在预报业务中,依赖观测数据调整初始场和模式参数属气象上的反问题。通过对模式参数识别和初始场调整问题进行等价转化,提出了一种基于进化策略的气象学反问题求解算法。在一维扩散方程和Lorenz-96简单预报模式进行了两类理想数值试验,试验结果表明经过优化后的预报误差均控制在非常小的范围内且预报稳定,从而验证了方法的有效性。     

MOMS 中尺度模式的多元最优插值客观分析方法

数值预报模式的预报结果与初始值关系较为密切。因此改善初始场的客观分析效果，是提高预报准确率的一个重要方面。该文针对MOMS中尺度模式的特点，研究设计了多元最优插值客观分析方法。采用T42模式预报结果作为初估值，在测站的选择、记录的订正、测站资料补缺等诸方面都考虑了中尺度模式的特点。该客观分析方案为中尺度数值天气预报及诊断分析提供了较好的初值，对提高中尺度模式的预报效果起到了较好的作用。     

中尺度大气数值模式发展现状和应用前景

对国内外当前一些先进的中尺度大气数值模式的发展现状,应用前景及发展趋势作了概要综述。其内容包括：模式动力学的改进,叫就度模拟系统特征,区域谱模 发展积云参数化和显式云物理方案,行星边界层参数化,大气辐射参数、四维资料同化,区域实时数值天气预报,中尺度数值天气预报应用前景及新一代中尺度模式发展趋势。     

北京地区中尺度非静力数值预报系统的开发与实时预报应用

国家气象中心与北京市气象局联合开发并将于1999年底建成“北京地区中尺度数值天气预报业务系统”。作为开发的第一阶段,以PSU/NCAR的MM5非静力中尺度模式为基础,在国家气象中心IBM/SP2机并行运算环境下与国家气象中心资料源连接并应用北京地区加密地面观测资料,初步建成了“北京地区中尺度数值天气预报试验系统”（以下简称BJ-MM5V.1）。模式设计为垂直23层,水平分辨率分别为45和15km的两重双向嵌套网格。在IBM/SP2计算机上用24个节点作36 h预报所需机时为2 h 20 min,满足实时业务预报需要。该系统于1997年夏季进行了实时运行试验,可提供北京地区每小时降水量预报每3 h多种气象要素预报,预报产品在北京市气象局试用。结果表明,系统有较强的稳定性和实用性,对降水时空分布的预报效果较好。     

The active tropical cyclone season of 2005–2006 over Northwest Australia: Operational model performance and high resolution case studies

Summary There are three main aims of this study. First, the main features of the active 2005–2006 Australian region tropical cyclone (TC) season are summarized, with particular emphasis on the northwest Australian region. Second, an assessment is made of the skill of the available operational global and regional numerical weather prediction (NWP) models for three of the most significant TCs (TCs Clare, Glenda and Hubert), each of which made landfall on the northwest coast of Australia. Third, high-resolution numerical modelling simulations of these same three TCs are described in detail. The numerical weather prediction (NWP) model used here was developed at the University of Oklahoma, and in this study it utilises initial and boundary conditions obtained from archived analyses and forecasts provided by the Australian Bureau of Meteorology, as well as a 4D-Var data assimilation scheme to ingest all available satellite data. The high-resolution numerical model is multiply two-way nested, with the innermost domain having a resolution of 5 km. It was found that unlike the operational models, which were restricted by relatively low resolution and less data, the high resolution model was able to capture most of the major features of all three TC lifecycles including development from initial tropical depressions, intensification, and their tracks, landfall, and associated rainfall and wind fields.     

Climatology of cyclones over the southwest Pacific: 1992–2001

Summary The Australian east coast is subject to a range of synoptic/mesoscale weather systems ranging from low-pressure troughs, small explosive low-pressure systems near the Australian east coast, to synoptic scale maritime low-pressure systems, and both tropical and extra-tropical cyclones. These systems vary dynamically in intensity and structure across a spectrum that includes both weak and intense cold-cored systems, to warm-cored tropical cyclones and “hybrid” systems. A preliminary 10 year climatology, from 1992 to 2001, is presented that concentrates on those cyclones in open waters that threaten life and property as a result of heavy coastal rain or the combined effects of wind, sea state and swell, including both long fetch and storm surges. There are 28 systems in the 10-year climatology. In terms of their development, the most numerous were the 50% of storms that occurred as systems within an easterly trough, followed by 21% that occurred as circulations on decaying Tasman Sea cold fronts. In addition, a numerical weather prediction (NWP) modelling case study of the ‘hybrid’ sub-tropical cyclone system of March 2001 was carried out using archived real-time data. Operational numerical weather prediction (NWP) model forecasts of this system, which was not named in accordance with Australian classification policy, were all poor except for the US MRF model, which provided marginally useful guidance. None of the operational global and regional models available to forecasters predicted an intense cyclone, and only the US MRF model predicted landfall. A high-resolution forecast using all available data produced significantly improved predictions over the operational models up to four days before landfall.     

Numerical Weather Prediction in China in the New Century ——Progress, Problems and Prospects

This paper summarizes the recent progress of numerical weather prediction(NWP)research since the last review was published.The new generation NWP system named GRAPES(the Global and Regional Assimila- tion and Prediction System),which consists of variational or sequential data assimilation and nonhydrostatic prediction model with options of configuration for either global or regional domains,is briefly introduced, with stress on their scientific design and preliminary results during pre-operational implementation.In ad- dition to the development of GRAPES,the achievements in new methodologies of data assimilation,new improvements of model physics such as parameterization of clouds and planetary boundary layer,mesoscale ensemble prediction system and numerical prediction of air quality are presented.The scientific issues which should be emphasized for the future are discussed finally.     

长江中下游地区暴雨值预报试验

本文利用NCAR／PSU联合研制的中尺度天气数值模式MM5，对长江中下游地区在1996年6月下旬至7月中旬发生的暴雨过程，以国家气象中心业务运行的合球谱模式T63的分析场作为初值和侧边界条件，进行了一系列的数值预报试验，结果表明，该模式较好地预报了实况相近的降雨区的位置，但对暴雨的中心落点和强度，其预报结果与实测有一定程度的偏差，如何模式提前12小时开始积分，则可在一定程度上克服模式中凝结降水的施转加强问题，使预报的降水强度等有明显的改善。     

和预报员谈数值预报

用尽可能非专业的词语,向预报员介绍数值预报的成就、问题与应用。在简单回顾数值预报发展历史的基础上,重点分析了近十几年来数值预报的主要技术进步与有待解决的问题,对比了数值预报与主观经验预报的各自优势与不足,提出了优势互补对于提高业务预报的重要性。还分析了数值预报的技术进步对于数值预报产品释用的影响,以及预报员参与数值预报发展的可能性与必要性。     

中尺度数值预报模式初边值作用的试验研究

通过一次影响华南地区的锋面降水过程实例，进行了静力与非静力中尺度模式、不同驱动模式、不同初边值组合、不同边值更新周期、不同起报时次等27组对比试验。较全面细致地从不同侧面分析讨论了初、边值对中尺度模式的影响规律及特点，得出了一些有学术和应用价值的结论。如中尺度模式预报的总体趋势决定于其驱动模式，初值仅显著影响中尺度模式大约前10小时的预报，以后的预报趋势则主要决定于边值的信息；边值对模式内区的影响主要通过各种时间尺度天气信息(天气波动)的传播和移动来实现；土壤含水量等模式外参量初值可影响较长时效的预报；模式通过边界只能引入大于等于边值更新周期4倍的时间尺度的信息，更快的信息则被过滤掉；等等。其中一些结论对今后发展中尺度数值预报及其资料同化具有参考价值。     

伴随模式同化系统在修正模式误差中的应用研究

资料误差和模式误差都是制约数值预报结果准确性提高的关键因素,传统四维资料同化都是假设模式完全正确仅对初始资料进行修正,忽略了模式误差本身造成的预报误差。伴随模式同化系统不仅具有修正资料误差的能力,也可应用于修正模式误差方面的研究。本文将卫星中心导风系统提供的GMS5卫星风场与非常规温度资料用于MM5伴随同化系统修正模式地形误差进行试验性研究表明,该方法能够反演出一个既与初始气象要素场相匹配,又与模式更协调的地形场,得到比一般包络地形更好的效果,改善模式对强降水中心及降水区域的预报;数值试验结果还揭示模式误差对模式预报造成一定的影响,用伴随方法对观测资料进行修正的同时也对模式误差进行修正的方法是可行的。     

两年来北京气象中心业务数值预报的进展

本文回顾了两年来北京气象中心业务数值预报的进展。对效果有明显改进的几个方面作了详细叙述。统计检验结果表明短期数值预报业务有一定改进,但与世界先进国家预报水平相比仍存在相当的差距。     

国家级强对流天气综合业务支撑体系建设

国家级强对流天气预报业务正在从以短期预报为主调整到短期和短时预报并重的业务格局。文章从强对流天气预报技术发展与服务需求的角度,重点介绍了国家级强对流天气综合业务支撑平台及其核心技术。该平台以气象数据组织和图形化表达两个核心要求为牵引,发展了数据分析处理系统、自动气象绘图系统和WEB检索与显示系统。数据分析处理系统基于多源观测资料、中尺度数值预报和全球数值预报,发展了集约、高效的强对流天气监测和临近预报、短时预报和短期预报等数据分析处理技术,是整个平台的核心;主要核心技术包括:从不稳定与能量、水汽、抬升与垂直风切变等条件出发,以归纳总结的分类强对流天气概念模型为基础的分类强对流短期预报分析技术;应用"配料法"发展的分类分等级的强对流天气客观概率预报技术;强对流短时预报技术包括高分辨率数值预报释用、多模式预报集成、对流尺度分析、实况和模式探空分析等多项技术,重点实现了从过去3 h实况到未来12 h预报的无缝隙衔接;强对流的监测和临近预报技术在基于多源资料的强对流天气实况与强对流系统监测技术基础上,发展了基于雷达特征量、强对流实况、各类强对流指数和预警信号等多源信息的报警技术。自动气象绘图系统实现了高效、便捷地接入多种数据、自动进行数据分析和制图等多项功能。在预报服务方面,基于WebGIS发展了县级分类强对流预警信号和国家级分类强对流预警预报产品共享技术,实现强对流短时预报业务的高交互性与上下互通的功能。     

MM5-HPAC simulation experiments

Summary We evaluate mesoscale model predicted boundary-layer flow and the subsequent HPAC (Hazard Prediction and Assessment Capability) dispersion computation. The HPAC software allows for prediction of the effects of surface release of hazardous material into the atmosphere and collateral damage on civilian populations using either observed or numerical weather model data. The advanced mesoscale weather model MM5 was employed in the study. The real-data MM5 model simulations were verified with high-resolution observations from the West Texas Mesonet. MM5 worked well in simulating meteorologically relatively quiescent conditions. We examined the sensitivity of HPAC computations to the MM5 model’s grid resolution, lateral boundary conditions, and input weather data. Results suggest that the MM5-HPAC conjugation can provide useful prediction of airborne transport of hazardous materials near the surface. However, the accuracy of diffusion computations strongly depends on the performance of MM5, which in turn is likely to be a function of weather scenarios. A given state-of-the-art mesoscale model may perform well in some cases but not in others. There is a potential benefit of using several different model winds separately to run HPAC. A composite result of the HPAC runs could give a more comprehensive depiction of the transport of surface hazardous agents.     

Ｅ网格变量分布下差分格式的性质

本文用线性化的浅水波方程系统地分析、讨论了Ｅ网格变量分布下差分计算的性质；指出了目前有关讨论Ｅ网格差分性质在方法上存在的问题；给出了一种解决Ｅ网格中两个Ｃ网格分离的方法；提出了一种Ｅ网格用于海洋计算时，海洋侧边界条件的处理方法。初步的数值试验证明了这些方法对抑制Ｅ网格中的计算躁声是有效的。     

2008年广西罕见低温雨雪冰冻天气成因及数值预报产品性能分析

通过对2008年初影响广西的罕见低温雨雪冰冻天气的环流演变情况、环流异常特征、数值预报产品预报能力的分析,得出此次低温雨雪冰冻天气的主要成因是:500hPa欧亚地区环流形势异常稳定、地面冷空气堆积明显,冷高压中心异常偏强、850hPa锋区强盛、华南中低层逆温明显。数值预报产品对此次低温雨雪冰冻天气过程大部时次的预报较为准确,但部分时段、个别要素预报仍存在较大误差,使用应注意。