COSMIC资料在GRAPES全球三维变分同化系统的初步研究

利用COSMIC获得的GPS无线电掩星数据所反演得到的大气温湿度廓线资料,在GRAPES全球三维变分同化系统中做连续循环同化试验,研究了加入COSMIC资料后得到的GRAPES分析场及其5天中期预报是否有所改善。研究结果表明：通过加入COSMIC资料连续循环同化得到的分析场,相对原来没有加COSMIC资料连续同化出来的GRAPES分析场有明显改善,由此GRAPES全球模式全球5天中期预报水平有明显提高,其中加入没有稀疏化后COSMIC资料对南半球GRAPES分析场的改善以及GRAPES全球模式5天中期预报水平的提高都比较显著;加入稀疏化后的COSMIC资料对北半球GRAPES分析场的改善以及GRAPES全球模式5天中期预报水平的提高都有比较显著的效果。     

雷达TREC风的三维变分同化应用与试验

介绍了雷达TREC风场在中国气象科学研究院开发的三维变分同化系统GRAPeS-3DVar中的应用,研究了GRAPES-3DVar系统同化雷达TREC风场资料的一些基本特性,发现雷达TREC风场在GRAPES-3DVar中有较好的应用价值,能有效地提高分析产品的质量,并通过一个热带气旋登陆变性过程的数值试验,说明了在GRAPES-3DVar中加入雷达TREC风场也能改善预报效果。     

GRAPES地面风场同化方案研究

随着预报准确度要求以及同化分析循环周期的缩短,具有高时空分辨率的地面观测资料在同化系统中也越来越受到重视,而且一个好的资料同化系统应该能够给出模式近地面动力、热力和湿度状况的合理分析。利用GRAPES区域同化预报系统(GRAPES——Global and Regional Assimilation and Prediction Enhanced System),在近地层Monin_Obukhov相似理论的基础上,考虑了边界层的动力和湿热力约束,建立新的地面风场观测算子。将此新方案与目前GRAPES系统使用的三次样条插值的地面同化方案进行高度场预报试验、统计试验以及降水预报的TS评分比较,结果表明,加入新方案地面风场资料同化后,预报效果和对降水的预报能力都比旧方案有所提高。     

云迹风资料的三维变分同化及对台风预报的影响试验

主要研究云迹风资料对三维变分同化分析场及台风预报的影响。首先分析了不同通道和层次的静止气象卫星云迹风产品的误差特征；然后，把云迹风资料放到GRAPES三维变分同化系统中进行同化，通过将不同观测类型资料的同化结果进行对比，探讨了红外通道和水汽通道云迹风资料对数值预报分析场的影响；最后，把同化后的分析场作为初始场，用WRF模式对2002年“森拉克”台风做24小时预报实验。结果表明，不同通道和层次的云迹风资料具有不同的误差特征；云迹风资料可以提高分析场和预报场中风压场的质量；而且在台风预报试验中可以更准确地预报台风的路径和降水。     

ASSIMILATION METHOD FOR RETRIEVING HORIZONTAL WIND FIELD FROM SINGLE-DOPPLER DATA

Doppler weather radar can provide the wind information such as the radial velocity,and hasbecome one of the most powerful means for studies of severe mesoscale and microscale weathersystems.Usually the radar observation provides only plane position indicator(PPI)scanning dataand range height indicator(RHI)scanning data.and this makes some retrieval methods usingthree-dimensional volume scanning data impractical in operation.In order to use these data moreefficiently,a plane assimilation retrieval(PAR)method is developed using data assimilationtechnique on the PPI scanning plane.The PAR method is tested with the observation data ofChinese Academy of Meteorological Sciences(CAMS)Doppler weather radar and the result isencouraging.     

IMPACTS OF ATOVS DATA ASSIMILATION ON PREDICTION OF A RAINSTORM OVER SOUTHEAST CHINA

Using the Advanced Research WRF (ARW WRF) model and the Gridpoint StatisticalInterpolation (GSI) three-dimensional variational analysis (3DVAR) system, the impact of assimilatingATOVS (Advanced TIROS Operational Vertical Sounder) radiance through the prototype CommunityRadiative Transfer Model (pCRTM) is evaluated on the forecasting of a heavy rainstorm occurring over thecentral Guangdong province in the southeast of China on 20-21 June 2005. A pair of comparisonexperiments (NODA and DA) for this case is conducted with multiple configurations, including nestingdomains with 4-km and 12-km grid distances. The results showed that by changing the initial conditionthrough data assimilation, a modified divergence and moisture field with the structure of dipoles has beenadded to the axis of the rainband with a southwest-northeast orientation. When more moisture carried by asouthwesterly low level jet (LLJ) was converged into the northeast portion of the rainband around theobservatory station of Longmen, the amplitude of moisture static energy (MSE) increased substantially atlow levels much more than at middle levels, resulting in the enlarging of differences in MSE between 500hPa and 850 hPa; the atmosphere became more unstable. Consequently, the convective rainfall increased inthe northeast part of the province around the Longmen station, which was consistent with the observeddistribution of rainfall.     

新一代数值预报系统GRAPES研究进展

中国气象科学研究院 (灾害天气国家重点实验室) 自2000年起, 先后在科技部“973”重大基础项目“我国重大天气灾害形成机理和预测理论研究”和“十五”重点攻关项目“中国气象数值预报系统技术创新研究”支持下, 主持承担了中国气象局新一代全球/区域多尺度通用同化与数值预报系统GRAPES (Global/Regional Assimilation and PrEdiction System) 的研究开发, 围绕着资料同化、模式动力框架、物理过程、大型软件工程等核心技术开展了自主创新研究, 取得了非静力中尺度模式、三维变分资料同化、标准化、模块化、并行化模式程序软件等方面的突出成果, 部分成果已在业务上得到了应用, 显示了良好的技术性能和业务发展潜力。GRAPES系统是完全依靠中国科学家的力量自主研究发展的、先进的新一代数值预报系统。该文简要介绍GRAPES的研究内容、主要研究进展和初步应用, 以及未来发展的初步计划。     

NUMERICAL SIMULATION ON THE RESPONSE OF LAND SURFACE TO SEVERE WEATHER

A coupled model of RAMS3b(Regional Atmospheric Modeling System,Version 3b)andLSPM(a land surface process model),in which some basic hydrological processes such asprecipitation,evapotranspiration.surface runoff,infiltration and bottom drainage are included,has been established.With the coupled model,we have simulated the response of soil to the severeweather process which caused the disastrous flood in north italy during 4-7.November,1994,simultaneously compared with the observation and the original RAMS3b,which has a soil andvegetation parameterization scheme(hereafter,SVP)emphasizing on the surface energy fluxes,while some hydrological processes in the soil are not described clearly.The results show that the differences between coupling LSPM and SVP exist mainly in theresponse of soil to the precipitation.The soil in the SVP never saturates under the strong input ofprecipitation,while the newly coupled model seems better,the soil has been saturated for one dayor more and causes strong surface runoff,which constitutes the flood.Further sensitivityexperiments show that the surface hydrological processes are very sensitive to the initial soilmoisture and soil type when we compared the results with a relatively dry case and sandy soil.The coupled model has potentiality for simulation on the interaction between regional climateand land surface hydrological processes,and the regional water resources research concerningdesertification,drought and flood.     

NUMERICAL SIMULATION OF SOUTH CHINA SEA MONSOON ONSET BASED ON GRAPES MODEL AND EXPERIMENTS ON INITIAL MODELFIELDS

The Global and Regional Assimilation and Prediction System (GRAPES), a limited-arearegional model, was used to simulate the onset of South China Sea summer monsoon. In view of therelatively insufficient information about the initial field in simulation predictions, the AdvancedMicrowave Sounding Unit-B (AMSU-B) data from a NOAA satellite were introduced to improve the initialvalues. By directly using the 3-dimensional variational data assimilation system of GRAPES, two schemesfor assimilation tests were designed. In the design, Test 1 (T1) assimilates both sounding and AMSU-Bdata, and Test 2 (T2) assimilates only the conventional sounding data, before applying the model insimulation forecasts. Comparative experiments showed that the model was very sensitive to initial fieldsand successful in reproducing the monsoon onset, allocation of high- and low-level wind fields during thepentad of onset, and the northward advancement of the monsoon and monsoon rain bands. The scheme,however, simulated rainfall and the location of the subtropical high with deviations from observations. Thesimulated location of the subtropical high was more westward and northward and the simulated rainfall forthe South China Sea was larger and covered a broader area.     

数值天气预报中卫星资料同化应用现状和发展

卫星资料已大量应用于数值天气预报,占据了所用观测资料的主体并对数值天气预报效果的改善具有明显的作用。目前卫星资料的同化应用一方面在努力解决受地表辐射、云和降水影响的卫星观测资料的同化问题,以充分利用现有卫星资料并发挥其效能,同时发展适应伴随全球观测系统建立而带来大数量和多种类新类型卫星资料的同化应用。文章介绍了为满足卫星资料在数值天气预报中同化应用现状与发展而建立的两个卫星资料同化研究中心(JCSDA:Joint Center of Satellite Data Assimilation和NWP SAF:Satellite Applications Facility for Numerical Weather Prediction)的基本情况,并简要讨论我国数值天气预报中卫星资料同化应用。     

AREM模式对0604、0605号台风的预报分析

卫星资料已大量应用于数值天气预报,占据了所用观测资料的主体并对数值天气预报效果的改善具有明显的作用.目前卫星资料的同化应用一方面在努力解决受地表辐射、云和降水影响的卫星观测资料的同化问题,以充分利用现有卫星资料并发挥其效能,同时发展适应伴随全球观测系统建立而带来大数量和多种类新类型卫星资料的同化应用.文章介绍了为满足卫星资料在数值天气预报中同化应用现状与发展而建立的两个卫星资料同化研究中心(JCSDA:Joint Center of Satellite Data Assimilation和NWP SAF:Satellite Applications Facility for Numerical Weather Prediction)的基本情况,并简要讨论我国数值天气预报中卫星资料同化应用.     

GRAPES全球三维变分同化业务系统性能

近年来,GRAPES全球三维变分同化系统分析性能和稳定性有了长足进步。该文简要介绍了近两年GRAPES全球:三维变分同化技术的发展与改进情况,包括同化框架技术、资料同化应用技术与系统稳定性等方面。分析诊断了两年的同化循环试验结果,以探空资料作为参考,对ERA-Interim再分析场、NCEP FNL分析场和GRAPES全球三维变分分析场的统计特征进行了比较;以ERA-Interim再分析场作为参考,对NCEP FNL分析场、T639分析场和GRAPES全球三维变分分析场进行比较。结果表明:GRAPES分析场的质量明显优于T639分析场,性能上达到了业务化的要求,但相比NCEP FNL分析场还有一定差距,特别是对流层内湿度分析场的误差还比较大。     

基于雷达资料同化的2003年7月一次暴雨过程的数值模拟及分析

利用我国CINRAD/SA多普勒雷达资料与中尺度模式ARPS的资料分析系统ADAS,对初始场进行调整,然后利用高分辨率的中尺度模式WRF对2003年7月4-5日的暴雨过程进行了数值模拟,在模拟结果可信的前提下,对暴雨过程中的中尺度对流系统(MCS)的结构及演变过程进行了分析.表明:多普勒雷达资料有助于提高暴雨模拟的精确度,利用其对中尺度系统进行高分辨率数值模拟,可以进一步认识中尺度系统的细致结构及演变情况;在中-β对流系统发展的过程中,大尺度环境场的有利条件可以对其发展起到促进作用,但具有中尺度特征的水汽条件、上升运动等因素也会起到关键的作用;中-β对流系统中可以同时有一支或多支的上升气流支出现,与降水有密切关系;2003年7月4-5日的两个中-β对流系统在发展过程中有从低空向高空移动的现象,即在发展初期,系统的中心位于低空,而在其旺盛时期则移至高空.     

BDA方案在台风路径预报中的应用

利用PSU／NCAR中尺度非静力有限区域MM5及其伴随模式,以T106分析资料为背景场,设计两种台风Bogus方案对台风的初始场进行优化,并进行了数值模拟试验。对9608号台风个例的数值模拟试验研究表明,经过优化的台风初始场较好地改进了由于海洋上资料缺乏所造成的台风中心位置不准、台风环流偏弱和台风内部结构不完整等问题,提高了台风路径预报的准确率。通过试验对比发现,BDA方案优化的初始场更合理,其台风路径预报效果优于GFDL方案。     

极轨卫星高层通道在GRAPES同化系统中的应用

针对GRAPES(Global/Regional Assimilation and Prediction System)模式三维变分系统高层背景场温湿廓线外推方案的局限性,提出以气候垂直廓线重新构造高层温湿垂直结构,以减小外推方案的偏差。首先采用一维变分同化系统,展开模拟实验:分析目前模式中使用的外推方案误差及其对反演结果的影响,利用高层大气气候廓线构造垂直结构并分析同化偏差。最后,运用GRAPES全球分析预报系统进行同化实验并分析改进程度。结果显示:模拟研究表明采用高层背景场温湿廓线外推方案与实际观测相比最大偏差在1 h Pa附近可达数十度以上,不仅影响平流层,而且对对流层也有影响;用气候温度数据修正GRAPES高层温度数据,可以减少50%以上的偏差,证明了用气候值高层数据优化现行GRAPES模式中同化系统高层插值方案的可行性。全球GRAPES三维变分同化试验结果显示,改进方案不仅显著的改善平流层分析质量,对对流层中高层也有改进。     

BASIC CHARACTERISTICS OF SURFACE WIND. PRESSURE AND TEMPERATURE IN PLATEAU OF MONGOLIA

After analyzing the mean pressure, dominant wind and temperature data of 40 observation sta-tions in Mongolia from 1961 to 1990, we reach some conclusions as below: (a) The warm advec-tion in the free atmosphere hardly reaches the ground in the west in winter. Because of thermody-namic differences of various meso- and micro-topography, there are "multi-centers" in the pressurefield, and the dominant wind field is "disordered": the temperatures on the convexi-concave orog-raphy and sun-shady slope are different significantly. There is cold advection in the east side,which can reaches the ground and the air pressure field is a "unity". The wind field is dominated bythe west wind. The temperature differences of various slope directions are small, and becomesmaller with height. (b) In summer, the upper control flow (planetary west wind) becomes weak-er, and the orographic air pressure centers in the east develop. Over the windward side of themountain high pressure prevails, and over the lee side low pressure does. These areas becomedeserts for dryness and lack of rainfall. Air temperature in summer can be expressed by latitude,longitude and elevation.     

偏北大风的数值预报释用方法研究

本文利用欧洲中心中期数值预报结果,从不同侧面选取因子,建立了日最大平均风速的四种统计预报方程,在此基础上设计了几种集成方法对预报结果进行集成,结果表明,我们设计的最大值－阀值综合集成法取得了很好的效果,特别是2－3天的大风预报准确度较高。     

THE INITIAL WIND SCHEME OF THE HEMISPHERIC SPECTRAL MODEL AND ITS EFFECT ON THE DATA ASSIMILATION

A series of data assimilation and forecast test have been carried out with a hemispheric spectralmodel(T42L9H).It is found that the numerical scheme for determining hemispheric initial wind isimportant to data assimilation and forecast.An inappropriate scheme may cause computationalsources of divergence near the equator,which are responsible for the spurious strong precipitationand corresponding latent heat release.Obviously,this problem differs from either thehemispheric/global domain effect or the tropical data effect pointed by Dalley et al.(1981).Basedon the previous studies,the new scheme of divergence and vorticity correction is presented,andthe difference with other schemes and its effects on the data assimilation are discussed against thecontrol test.Preliminary tests have shown that the new divergence correction scheme proposed in thispaper may be a preferable choice to overcome the initial computational errors in the hemisphericdata assimilation.     

曲率修正线性平衡方程及其在变分同化风压约束中的应用

针对强涡旋系统（热带气旋、一些中尺度系统）变分同化分析中风压平衡约束关系的特点,提出了一个新的风压平衡约束关系——曲率修正线性平衡方程,它具有形式与线性平衡方程相同,并清晰地包含了曲率的作用,同时,当曲率较小时可退化成线性平衡方程。曲率修正线性平衡方程能方便地应用于中国数值预报研究中心开发的三维变分同化分析系统Grapes3DV中,试验结果证明其具有较好的效果和较理想的特性,提高了分析质量,并改善预报水平。