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1.
Impact of 4DVAR assimilation of rainfall data on the simulation of mesoscale precipitation systems in a mei-yu heavy rainfall event 总被引：1，自引：0，他引：1
The multi-scale weather systems associated with a mei-yu front and the corresponding heavy precipitation during a particular heavy rainfall event that occurred on 4 5 July 2003 in east China were successfully simulated through rainfall assimilation using the PSU/NCAR non-hydrostatic, mesoscale, numerical model （MM5） and its four-dimensional, variational, data assimilation （4DVAR） system. For this case, the improvement of the process via the 4DVAR rainfall assimilation into the simulation of mesoscale precipitation systems is investigated. With the rainfall assimilation, the convection is triggered at the right location and time, and the evolution and spatial distribution of the mesoscale convective systems （MCSs） are also more correctly simulated. Through the interactions between MCSs and the weather systems at different scales, including the low-level jet and mei-yu front, the simulation of the entire mei-yu weather system is significantly improved, both during the data assimilation window and the subsequent 12-h period. The results suggest that the rainfall assimilation first provides positive impact at the convective scale and the influences are then propagated upscale to the meso- and sub-synoptic scales.
Through a set of sensitive experiments designed to evaluate the impact of different initial variables on the simulation of mei-yu heavy rainfall, it was found that the moisture field and meridional wind had the strongest effect during the convection initialization stage, however, after the convection was fully triggered, all of the variables at the initial condition seemed to have comparable importance. 相似文献
Through a set of sensitive experiments designed to evaluate the impact of different initial variables on the simulation of mei-yu heavy rainfall, it was found that the moisture field and meridional wind had the strongest effect during the convection initialization stage, however, after the convection was fully triggered, all of the variables at the initial condition seemed to have comparable importance. 相似文献
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3.
The AREMv2.3 mesoscale numerical model is used to explore storm processes in South China during the pre-rainy season in 2006 by imposing perturbations on the initial fields of physical variables (temperature, humidity, and wind fields). Sensitivity experiments are performed to examine the impacts of initial uncertainties on precipitation, on the error growth, and on the predictability of mesoscale precipitation in South China. The primary conclusion is that inherent initial condition uncertainties can signi... 相似文献
4.
使用不同的天气尺度初值作强对流暴雨预报的差别及其原因 总被引：6，自引：0，他引：6
分别用暴雨开始前和暴雨刚开始两个探空时次的天气尺度初值场作1982年6月19～20日鄂东特大暴雨过程的中尺度模拟预报.前者相当成功,后者完全失败.探究其原因说明中尺度数值预报可以用天气尺度初始场的一个重要条件是模式初始时刻在关注的区域及其附近不存在即将造成或已经造成强降水的强中尺度扰动.如若不然,则可能由于模式起转(Spinup)的延误,实际存在的中尺度扰动对天气尺度变化的强大反馈作用不能体现,会使天气尺度的预报从一开始就显著歧离实际,其带来的结果不是中尺度时、空细节的预报误差,而是全区域性的预报失败.这个试验还进一步证实伴随暴雨的强非绝热反馈作用是暖切变型梅雨锋发展和准静止持续乃至周边区域形势维持的最重要的直接因子. 相似文献
5.
利用常规观测资料、自动区域站雨量、卫星TBB资料、雷达资料,对恩施州2016年6月24—25日发生的一次大范围暴雨过程进行分析。结果表明:本次强降水,具有典型的两槽一脊"单阻型"梅雨环流特征,在有利的大尺度环流背景下,在高空槽、低层低涡切变、西南急流、地面中尺度辐合线等中尺度天气系统的共同影响、相互作用下,形成了此次大范围强降水。此次暴雨空间上分布不均,局地性强,表现为明显的中尺度对流性特征,雷达回波图上降水性质表现为混合型降水,暴雨的直接影响系统是中β尺度对流系统,且中β尺度对流系统在多个中尺度对流云团合并后加强,时间尺度约为5 h。此次暴雨过程是在上干冷下暖湿强的大气层结不稳定条件下,梅雨锋、边界层辐合线和地形槽的触发作用将前期积累的能量释放产生的强对流天气,同时,副高外围西南气流将南海和西太平洋的水汽向恩施输送,为暴雨的发生提供了有利的条件。 相似文献
6.
初始扰动对一次华南暴雨预报的影响的研究 总被引：2，自引：1，他引：1
本文选取了2006年华南前汛期的一次暴雨过程, 采用AREMv2.3中尺度数值模式进行数值模拟, 分别在模式初始场的物理量场 (温度场、 风场、 湿度场) 上加扰动, 分析不同物理量场上的扰动对降水预报的影响, 以及物理量预报误差和扰动能量的增长情况。同时, 通过本个例讨论误差增长与湿对流的关系, 扰动振幅对误差增长的影响和华南区域的中尺度降水的可预报性问题。数值试验结果表明: 初始时刻不同物理量场加实际振幅的正态分布的随机扰动时, 对降水的影响是不同的。对于24小时降水预报, 温度场对降水的影响最大。误差的增长与湿对流不稳定有着密切的关系。小尺度小振幅误差增长很快, 而且是非线性增长。这意味着短期的较小尺度降水的可预报性很小。与大振幅扰动相比, 小振幅扰动造成的误差较小。但是小振幅扰动的迅速发展, 很快就会对降水预报造成较大的影响。因此, 只能有限地提高预报质量, 而且由于扰动非线性增长很快, 在预报时间的提前上, 不会有太大的改善。 相似文献
7.
~~EXPERIMENTAL STUDY OF THE ROLE OF INITIAL AND BOUNDARY CONDITIONS IN MESOSCALE NUMERICAL WEATHER PREDICTION@闫敬华$Guangzhou Institute of Tropical & Marine Meteorology, CMA, Guangzhou 510080 China
@Detlev Majewski$Duetscher Wetterdinst, Offenbach, Germany~~National Project "973" (Research on Heavy Rain in China) and BMBF of Germany (WTZ- Project CHN01/106)… 相似文献
8.
贵州大暴雨个例形成机制数值模拟 总被引：1，自引：0，他引：1
利用3层嵌套的中尺度数值模式MM5 V3.5,模拟了2007年6月24～25日发生在贵州中南部的一次大暴雨过程.利用模式输出的高分辨率资料,对这次暴雨天气及中尺度低涡的形成机制进行了诊断分析.模式较成功地模拟出了中尺度系统的演变和降水的分布特征.中尺度低涡的发展、稳定维持是造成贵州这次大暴雨天气的直接原因.暴雨、大暴雨出现在低涡的西南侧.在低层正涡度、辐合、强烈的上升运动和高层负涡度、辐散的有利配置下,形成深厚的上升运动柱,这种中尺度动力配置结构,不仅与暴雨区和暴雨发生时段相对应,而且是引起此次暴雨的中尺度低涡发展和持续的动力机制之一.暴雨区与强烈上升运动区,正涡度区相对应. 相似文献
9.
C. Cacciamani D. Cesari F. Grazzini T. Paccagnella M. Pantone 《Meteorology and Atmospheric Physics》2000,72(2-4):147-159
Summary In this paper we describe the results of several numerical experiments performed with the limited area model LAMBO, based
on a 1989 version of the NCEP (National Center for Environmental Prediction) ETA model, operational at ARPA-SMR since 1993.
The experiments have been designed to assess the impact of different horizontal resolutions and initial conditions on the
quality and detail of the forecast, especially as regards the precipitation field in the case of severe flood events. For
initial conditions we developed a mesoscale data assimilation scheme, based on the nudging technique. The scheme makes use
of upper air and surface meteorological observations to modify ECMWF (European Centre for Medium Range Weather Forecast) operational
analyses, used as first-guess fields, in order to better describe smaller scales features, mainly in the lower troposphere.
Three flood cases in the Alpine and Mediterranean regions have been simulated with LAMBO, using a horizontal grid spacing
of 15 and 5 km and starting either from ECMWF initialised analysis or from the result of our mesoscale analysis procedure.
The results show that increasing the resolution generally improves the forecast, bringing the precipitation peaks in the flooded
areas close to the observed values without producing many spurious precipitation patterns. The use of mesoscale analysis produces
a more realistic representation of precipitation patterns giving a further improvement to the forecast of precipitation. Furthermore,
when simulations are started from mesoscale analysis, some model-simulated thermodynamic indices show greater vertical instability
just in the regions where strongest precipitation occurred.
Received March 2, 1999/Revised May 30, 1999 相似文献
10.
初边界条件不确定性对AREM模拟一次华南致洪暴雨的影响 总被引：1，自引：0，他引：1
利用AREM（advanced regional E-gridη-coordinates model）模式,针对2005年6月21日发生在华南的一次特大致洪暴雨过程,研究了模式初始场和边界场的不确定性对AREM模拟大暴雨过程的影响。研究表明：模式初始场和边界场对模式模拟降水的不同时段影响存在明显差异,初始扰动误差越大模式误差也越大;误差增长先在中小尺度内伴随着湿对流不稳定,且增长极其迅速,接着向大尺度传播,由于对流有效位能的逐渐释放,大气不稳定度降低,误差在大尺度上增长缓慢;在初始场和边界场相同精度的情况下,增加边界场的中尺度信息,尤其是400 km以下尺度的信息,比增加初始场的中尺度信息更能有效抑制误差的增长。 相似文献
11.
利用中尺度非静力WRF(Weather Research and Forecasting)模式及其三维变分同化系统,对2007年7月淮河流域的一次强降雨过程进行多普勒雷达径向速度资料的三维变分同化试验,重点考察雷达资料的不同稀疏化方式对同化结果以及对暴雨数值模拟的影响。结果表明:同化多普勒雷达径向速度资料使得模式初始风场包含了更丰富的中尺度特征信息,有效调整了初始场的环流结构,能够改善模式对暴雨过程的模拟效果;以不同的稀疏化处理方式同化多普勒雷达径向速度资料对分析场会产生不同的影响,进而影响模式的降水预报效果,本次试验中当极坐标网格径向分辨率取10 km的时候降水过程的预报效果最好。 相似文献
12.
对2013—2016年汛期ECMWF、JMA及中尺度WRF模式的预报结果进行检验,基于合理的时间尺度,制作了动态权重集成面雨量预报(DWI)、分步集成面雨量预报(SI)和等权重集成面雨量预报(EWI)产品,并对2017—2020年汛期降水期间多种集成面雨量预报产品和ECMWF、JMA、WRF的单个模式面雨量预报产品进行对比评估.结果表明:3种集成面雨量预报效果整体上优于单一数值预报模式,尤其是预报致灾严重的暴雨等级降水优势明显;DWI和WRF对强降水的面雨量预报正确率最高,其他2种集成面雨量预报结果次之,ECMWF及JMA较差;模式集成预报弱降水过程的优势不明显. 相似文献
13.
Accurate forecast of rainstorms associated with the mei-yu front has been an important issue for the Chinese economy and society. In July 1998 a heavy rainstorm hit the Yangzi River valley and received widespread attention from the public because it caused catastrophic damage in China. Several numerical studies have shown that many forecast models, including Pennsylvania State University National Center for Atmospheric Research’s fifth-generation mesoscale model (MM5), failed to simulate the heavy precipitation over the Yangzi River valley. This study demonstrates that with the optimal initial conditions from the dimension-reduced projection four-dimensional variational data assimilation (DRP-4DVar) system, MM5 can successfully reproduce these observed rainfall amounts and can capture many important mesoscale features, including the southwestward shear line and the low-level jet stream. The study also indicates that the failure of previous forecasts can be mainly attributed to the lack of mesoscale details in the initial conditions of the models. 相似文献
14.
利用中尺度非静力MM5模式研究不同初始扰动（误差）对2003年7月4—5日发生在江淮流域的一次梅雨锋暴雨数值预报不确定性的影响,并着重分析了提前36h定量降水的可预报性。结果表明,利用常规观测资料和NCEP/NCAR分析资料形成初始场的控制试验能够提前36h做出较好的模拟。扰动温度场的敏感性试验表明,扰动温度的均方差愈大,降水预报不确定性也愈大。误差演变特征和增长机制分析表明,误差增长具有升尺度特征,误差首先在对流层低层和高层增长,然后大值区向对流层中层扩展;湿降水过程是对流层中低层误差增长的主要机制;对流层高层的误差增长是大气干动力与湿过程共同作用的结果,前期以干过程为主,后期以湿过程为主。 相似文献
15.
The mesoscale moist adjoint sensitivities related to the initiation of
mesoscale convective systems (MCSs) are evaluated for a mei-yu heavy
rainfall event. The sensitivities were calculated on a realistic background
gained from a four-dimensional variational data assimilation of
precipitation experiment to make the sensitivity computation possible and
reasonable within a strong moist convective event at the mesoscale. The
results show that the computed sensitivities at the mesoscale were capable
of capturing the factors affecting MCS initiation. The sensitivities to the
initial temperature and moisture are enhanced greatly by diabatic processes,
especially at lower levels, and these sensitivities are much larger than
those stemming from the horizontal winds, which implies that initiation of
MCSs is more sensitive to low-level temperature and moisture perturbations
rather than the horizontal winds. Moreover, concentration of sensitivities
at low levels reflects the characteristics of the mei-yu front. The results
provide some hints about how to improve quantitative precipitation forecasts
of mei-yu heavy rainfall, such as by conducting mesoscale targetted
observations via the adjoint-based method to reduce the low-level errors in
the initial temperature and moisture. 相似文献
16.
本文利用高分辨率中尺度数值预报模式WRF和两组再分析资料,在研究不同模式初值对华南暖区暴雨预报质量差异明显的基础上,利用合成初值方法进行了模式初值对暖区暴雨预报的敏感性数值试验研究,讨论了模式初始场关键物理量对暖区暴雨预报质量的影响,重点开展了模式初值湿度场质量对华南暖区暴雨降水预报的敏感性分析。结果表明：模式初始场质量的较小差异,可显著影响本次华南暖区暴雨预报的降水强度、降水落区以及降水发生时间等的质量。初始水汽场对暖区暴雨预报影响最大,也最为敏感,是准确预报对流单体的发生发展以及地面强降水的基础。风场和温度场对暖区暴雨预报的影响相对较小。对流层低层较强的风速辐合是本次暖区暴雨强对流单体触发、生成和加强发展以至产生暖区强降水的物理基础。 相似文献
17.
雷达和卫星资料对江淮暴雨数值模拟的影响 总被引：2，自引：0，他引：2
将“713”测雨雷达和GMS卫星云图资料引入PSU／NCAR中尺度模型，以改变初始湿度场，对两个不同类型的江淮暴雨过程进行了数值模拟敏感试验，并与控制试验作了比较分析。结果表明：加入雷达和卫星资料，能通过水汽和辐合上升运动的调整有效降水过程，引入雷达和（或）卫星资料所产生的影响有所不同。 相似文献
18.
The influences of boundary layer parameterization schemes on mesoscale heavy rain system 总被引：2，自引：0，他引：2
1.Introducti0nThemesoscaleoperationalmodel-whichisoftenused,isMM4orMM5'butMM4isusedfrequentlyonlO3kmscale.Thephysicalprocessesinthismodeldevelopconstantly.FororiginalMM4,thecomputationofsurfacefluxesisnotaccurate,andKmodelfortheturbu-lencefluxesbetweenany2levelsneedstobeimprovedbynewtreatment.Inordertostudytheinfluencesofboundarylayerparameterizationschemesonmesoscaleheavyrainsystem,sur-facefluxesandKmodelinoriginalMM4areimprovedbytherecentresearchinthispaPer.Theflux-profilerelationsforv… 相似文献
19.
本文对江淮流域持续性暴雨事件（PHREs）的多尺度物理模型和能量转换特征以及青藏高原东部对流系统东移影响下游地区降水的研究成果进行了总结。从欧亚大陆Rossby波列能量频散的角度揭示了江淮流域PHREs中纬度系统槽脊稳定的机制,定量分析了冷暖空气的源地和输送路径,提出了江南型和江北型PHREs的多尺度物理模型。从天气尺度和次天气尺度之间的能量转换角度呈现了不同尺度系统相互作用的物理图像,指出背景场的能量供给是直接触发暴雨的次天气尺度系统维持的最重要因子,尤其是在对流层的低层,动能的降尺度级串（即能量由背景场传递给次天气尺度系统）最强。研究表明青藏高原东部对流系统东移影响江淮流域的降水是一系列天气系统配合和活跃的结果,主要由青藏高原和四川盆地、二级地形和东部平原之间的热力环流、西南涡、二级地形以东中尺度涡旋和对流系统的共同影响。除了本文总结的内容,还有一些影响PHREs的因子值得深入研究,多尺度相互作用中的Rossby波源及其波列如何影响天气系统,中尺度系统对其背景场的能量反馈等。 相似文献
20.
We investigated the impact of tuning the length scale of the background error covariance in the Weather Research and Forecasting(WRF) three-dimensional variational assimilation(3DVAR) system.In particular,we studied the effect of this parameter on the assimilation of high-resolution surface data for heavy rainfall forecasts associated with mesoscale convective systems over the Korean Peninsula.In the assimilation of high-resolution surface data,the National Meteorological Center method tended to exaggerate the length scale that determined the shape and extent to which observed information spreads out.In this study,we used the difference between observation and background data to tune the length scale in the assimilation of high-resolution surface data.The resulting assimilation clearly showed that the analysis with the tuned length scale was able to reproduce the small-scale features of the ideal field effectively.We also investigated the effect of a double-iteration method with two different length scales,representing large and small-length scales in the WRF-3DVAR.This method reflected the large and small-scale features of observed information in the model fields.The quantitative accuracy of the precipitation forecast using this double iteration with two different length scales for heavy rainfall was high;results were in good agreement with observations in terms of the maximum rainfall amount and equitable threat scores.The improved forecast in the experiment resulted from the development of well-identified mesoscale convective systems by intensified low-level winds and their consequent convergence near the rainfall area. 相似文献