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基于雷达资料快速更新四维变分同化 (RR4DVar) 技术和三维数值云模式,初步研发了一个针对对流尺度数值模拟的快速更新雷达四维变分分析系统。系统通过对京津冀6部多普勒天气雷达资料进行RR4DVar同化,并融合5 min自动气象站观测和中尺度数值模式结果,可快速分析得到12~18 min更新的低层大气三维动力、热力场的对流尺度结构特征。针对2009年7月22日发生在京津冀的一次强风暴个例,通过一系列敏感性试验,并利用局地加密资料进行检验对比,表明有效的雷达资料RR4DVar同化及自动气象站和中尺度模式资料融合方案、恰当的中尺度背景场设置和动力约束方法是获得合理结果的关键。研究也表明:恰当的系统配置能够模拟出与对流生消发展密切相关的近风暴环境特征,包括低层入流、垂直风切变、低层辐合上升和暖舌等,以及风暴自身形成的冷池、出流等与风暴演变密切相关的对流尺度结构。 相似文献
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目前,北京地区的天气预报系统对局地对流性定量降水预报能力较弱,远不能满足人们生产、生活和防灾、减灾工作的需要。针对北京地区对提高0-12 h短时临近天气,尤其是夏季局地对流性降水预报能力的需求,基于中国气象局北京城市气象研究所变分多普勒雷达分析系统（VDRAS）的雷达热动力反演资料,建立了WRF模式初始化模块,采用四维资料同化（FDDA）方法,将VDRAS系统高时空分辨率三维热动力结构分析场资料同化到WRF模式中,实现了北京地区VDRAS分析场资料在WRF中尺度模式系统中的应用。通过降水个例的高分辨率同化模拟试验分析了雷达热动力反演资料同化对模式预报结果的影响。研究结果表明:雷达热动力反演资料的同化能够提高模式系统对近地面温、湿、风大气要素和降水过程的模拟能力,改善2 m比湿、降水落区、降水量级、降水时间的预报效果,减少降水漏报的现象。温度和比湿的同化比风的同化对模拟降水结果的改善更重要。虽然研究表明雷达热动力反演资料在WRF模式中的同化能够明显改善模式对选取降水个例的模拟效果,但其对模式尤其是数值业务模式系统预报效果的影响需要进一步更全面、更系统的检验,为业务化应用奠定更坚实的基础。 相似文献
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自20世纪90年代,我国开展大规模新一代天气雷达建设以来,已初步形成一个对大、中、小尺度灾害性天气监测的天气雷达业务网,并在防灾减灾中发挥了重要作用。本文利用我国新一代天气雷达网获得的大量实例资料分析了新一代天气雷达在实际应用中对大尺度天气系统如:冷锋、温带气旋、江淮切变线、低空急流、台风,中尺度天气系统诸如强对流天气系统的飑线、阵风锋、冰雹和雷暴高压,以及对我国产生重要影响的梅雨锋暴雨的监测能力。同时分析了现有天气雷达业务观测模式中的扫描策略、雷达适配参数设置以及雷达技术体制的特点与存在的问题。在不对现有雷达技术体制和结构做重大改变前提下,有针对性提出了:(1)改进现有业务观测模式:一是增加晴空模式和RHI垂直扫描模式增强对晴空回波以及垂直结构精细化探测能力;二是增设高山观测模式增强对边界层的探测覆盖能力。(2)改进雷达适配参数,采用相位编码技术和双PRF技术,把距离不模糊作为第一优先原则,来解决多普勒脉冲雷达体制下的距离与速度模糊问题。(3)增强雷达对弱回波探测能力,提高雷达的时空分辨率。(4)充分利用雷达网的组网技术,开展协同观测实现对大、中、小灾害性天气系统的时间与空间同步观测。(5)利用双偏振技术,进一步提高雷达定量估测降水的精度以及对相态的识别。并在上述5方面改进的基础上,提出了目前雷达技术升级改造的初步方案。展望了未来天气雷达技术的发展。 相似文献
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从新一代天气雷达径向速度资料中反演出可靠的三维风场对提高新一代天气雷达的应用水平有重要的作用，将雷达直接观测的径向速度转换成台站预报员更为熟悉的风场结构，对识别中小尺度信息有很大帮助。为此该文对4DVAR同化技术在风场业务反演中应用的可能性进行了探讨，利用广州、济南新一代多普勒天气雷达观测资料，从是否加入云模式湿过程以及迭代次数、计算时间、背景场、初始场、分辨率和反演区域等方面对干模式的4DVAR系统进行了讨论，并从风场结构、均方根差别等方面对反演结果进行分析。多种试验表明，干模式的4DVAR系统与湿的云模式反演结果差异不大。模式的初始场和背景场对反演结果具有较高的敏感性，利用前一时次的反演结果作为背景场迭代15～20次的干模式结果可以很好地在业务上试运行，对台站预报员提高中小尺度天气预报的准确率有着很重要的作用。 相似文献
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With the data from the Tropical Cyclone Yearbooks between 1970 and 2001, statistical analyses
were performed to study the climatic features of landfall TCs (noted as TCs hereafter) in China with particular
attention focused on landfall frequency, locations, sustaining, decaying, transition, intensification and
dissipation etc. The results indicate that the sustaining periods of TC over land are quite different for different
landfall spots, and increased from Guangxi to Zhejiang. The most obvious decreasing of TC intensity occurs mainly
within 12 hours after landfall. The stronger a TC is，the more it decays. The areas over which TCs are dissipated
can be in Heilongjiang, the northernmost, and Yunnan, the westernmost. Besides, Guangxi is an area with high
dissipating rate and subject to TC dissipation as compared with the other coastal regions. 相似文献
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This study investigated the effects of landfall on the structure of a
tropical cyclone (TC). Numerical simulations were performed using the
Weather Research and Forecasting Model on a β-plane. Two landfall
experiments, one with an east--west and another with a north--south oriented
coastline, were performed.
Similar to previous studies on an f-plane, large-scale flows in the
low-to-middle troposphere were modified due to friction. A pair of counter
rotating gyres was found, which was shown to be consistent with the slight
deflection of the TC relative to the control experiment without land.
Compared to previous f-plane simulations, because of the inherent asymmetries
due to the β-gyres, the large-scale pattern of flows and
convergences/divergences related to friction were found to depend on
coastline orientations. On the other hand, regardless of the coastline
orientation, convergences were found to be stronger to the left for both
cases near landfall, as in previous f-plane simulations. Such a convergence
pattern subsequently induced a change in convection and rainfall at the
eyewall. 相似文献
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利用1979—2017年欧洲中期天气预报中心提供的ERA-Interim再分析数据与中国气象局-上海台风研究所(China Meteorological Administration-Shanghai Typhoon Research Institute,CM A-STI)、美国联合台风警报中心(Joint Typhoon Warning Center,JTWC)整编的西北太平洋热带气旋(Tropical Cyclone,TC)资料集,分析东亚高层(200hPa)纬向风季节内振荡(Intraseasonal Oscillation,ISO)与7—8月登陆中国大陆TC频数年际变化的联系。结果表明:7—8月中国大陆登陆TC频数与西风急流出口区南侧(北侧)纬向风为显著负(正)相关,南侧显著相关区与北侧的差定义的东亚西风急流指数(East Asian Westerly Jet Index,EAWJI)可定量描述急流经向移动,EAWJI负异常时急流北移、登陆TC偏多,反之急流南移、登陆TC偏少。急流北移,TC活动区域对流层高层呈偏东风异常,产生异常东风切变,有利于TC登陆过程的维持,使登陆中国大陆TC频数增多。东亚高层纬向风ISO与年际变化的标准差场、EOF模态的高度相似性说明两者由同一空间主导模态所控制,表明若其ISO偏北偏南振荡发生频率为非正态分布,剩余偏差将改变其季节平均。TC登陆多年,东亚西风急流指数ISO呈更高频率偏北移动,引起急流出口区南侧ISO尺度扰动涡度通量辐合,使季节平均西风减小,急流位置北移,说明高层纬向风ISO可通过间接调制影响TC登陆的大尺度环流进而与登陆TC频数的年际变化相联系。 相似文献
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广东省登陆热带气旋活动异常成因分析 总被引：43，自引：26，他引：43
利用1970～2001年热带气旋年鉴资料，对32年来西太平洋热带气旋登陆我国的频率、位置、维持、衰减、变性、加强及消亡等进行统计分析，揭示热带气旋登陆活动的一些事实和特征。研究表明：在我国沿海不同地区(不包括岛屿)登陆的热带气旋，其陆上维持时间明显不同，从广西至浙江，维持时间向北增加；热带气旋登陆后的明显衰减主要发生在登陆后12小时内，登陆时越强的热带气旋，衰减得越厉害；热带气旋在我国陆上消失的位置最北是黑龙江、最西可至云南，广西是登陆我国热带气旋消失数最多的地区。 相似文献
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华南登陆热带气旋“珍珠”和“派比安”的对流非对称分布观测分析 总被引：1，自引：1，他引：0
采用广东省中尺度地面气象站和天气雷达的观测资料,对2006年登陆华南的热带气旋(TC)"珍珠"和"派比安"的对流非对称分布进行了分析.结果表明:在登陆TC"珍珠"和"派比安"从登陆前12小时到登陆后6小时期间,强对流主要位于TC中心的"东"、"北"象限,即TC移动路径的右侧和前方;同时TC对流在垂直方向也存在明显的差异.分析还发现,虽然登陆TC"珍珠"和"派比安"都有相同的对流非对称分布,但是引起这种对流非对称分布的原因并不完全相同,登陆TC"珍珠"的对流非对称分布主要与强的环境垂直风切变、低层水平风场切变、低层辐合和辐散的影响有关,而登陆TC"派比安"的对流非对称分布主要与低层辐合和辐散的影响有关. 相似文献
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This study explored the impact of coastal radar observability on the forecast of the track and rainfall of Typhoon Morakot(2009)using a WRF-based ensemble Kalman filter(EnKF)data assimilation(DA)system.The results showed that the performance of radar EnKF DA was quite sensitive to the number of radars being assimilated and the DA timing relative to the landfall of the tropical cyclone(TC).It was found that assimilating radial velocity(Vr)data from all the four operational radars during the 6 h immediately before TC landfall was quite important for the track and rainfall forecasts after the TC made landfall.The TC track forecast error could be decreased by about 43% and the 24-h rainfall forecast skill could be almost tripled.Assimilating Vr data from a single radar outperformed the experiment without DA, though with less improvement compared to the multiple-radar DA experiment.Different forecast performances were obtained by assimilating different radars, which was closely related to the first-time wind analysis increment, the location of moisture transport, the quasi-stationary rainband, and the local convergence line.However, only assimilating Vr data when the TC was farther away from making landfall might worsen TC track and rainfall forecasts.Besides, this work also demonstrated that Vr data from multiple radars, instead of a single radar, should be used for verification to obtain a more reliable assessment of the EnKF performance. 相似文献
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登陆中国大陆不同区间的热带气旋特征初步分析 总被引：3，自引：1，他引：2
利用地理信息系统及程序计算得到了1949—2008年登陆中国大陆的热带气旋(TC)登陆点经纬度信息,在此基础上对登陆中国大陆的TC进行分析,最终选择110～122°E海岸线为研究区域,7—9月为研究时段,且将110～122°E海岸线以1°E为间隔划分为12段,分析这12段海岸线登陆TC的基本特征发现:118°E以东的区间TC登陆前后平均维持时间及登陆前平均强度基本上为大于118°E以西的区间,登陆后平均强度东西两段相差不大;定义了TC登陆前(后)破坏潜力指数TDP1(TDP2),TDP1(TDP2)最大值出现在区间[119,120°E)([110,111°E));ENSO事件对7—9月登陆110～122°E段的TC频数、平均登陆点位置影响并不明显,对各区间登陆TC的影响也不尽相同;各区间平均TDP1冷暖事件年对比差别较大,平均TDP2在暖事件年基本上比冷事件年大;1961—2008年,各区间对应的暴雨总站次,118°E以东的区间要远大于以西的区间,就空间分布而言,较大值的分布出现在区间[119,120°E),[110,111°E)。 相似文献
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The correlation and composite analysis are carried out in this paper to study major factors affecting the track of tropical cyclones (TCs) after their landfall in the east of China. The mid-tropospheric environmental steering flow is found to dominate the movement of a TC even after landfall, with the inertia and Coriolis force two other subordinates. A key region is discovered covering the east of China and Yellow Sea, in which the environmental flow significantly affects the movement of TCs making landfall in this part of China. When the subtropical high in this region strengthens and extends westward, accompanied by northward shrink of the westerly trough, the TC tends to move westward after landfall and disappear inland. However, when the subtropical high in this region weakens and shrinks eastward, accompanied by southward push of the westerly trough, the TC tends to recurve after landfall and re-enter the sea at a location to the north of the site of landfall. The environment before the landfall of a TC has little impact on its post-landfall track, which is sensitive to the environmental change 12 – 24 hours after landfall. A 6-hour lag is found between the environmental change and the movement of a TC after landfall. 相似文献
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The physical processes associated with changes in the convective structure
of an idealized tropical cyclone (TC) during landfall on a beta-plane were
studied using the fifth-generation Pennsylvania State University--National
Center for Atmospheric Research Mesoscale Model, version 3 (MM5). The
simulation results suggested that the suppression of moisture supply and
increased friction acted to enhance the convection from the left and front
quadrants of the TC to the front and right of the TC during different
periods of landfall. When surface moisture flux was turned off, convection
in other parts of the quadrant was clearly suppressed and the total rainfall
was reduced. When surface friction was increased, precipitation showed a
marked increase after the TC made landfall.
Wetter air at low and intermediate levels, and drier air at high levels
around the onshore side of the coastline led to a high value of convective
available potential energy (CAPE). Consequently, convection was enhanced
immediately downstream of this area when the surface moisture flux was cut
off. When surface friction was increased, the physical process was similar
prior to landfall. After landfall, increased convergence at the onshore side
of the land resulted in enhanced convection in front of the TC.
Consistent with previous findings, our results suggest that during landfall
the TC structure changes from one of thermodynamic symmetry to asymmetry due
to differential moisture flux between the land and sea surface. The
asymmetry of the thermodynamic structure, which can be explained by the
distribution of CAPE, causes an asymmetric rainfall structure. 相似文献
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利用1949～2001年热带气旋年鉴资料,对53年登陆我国并经过内陆湖泊的热带气旋特征进行统计分析.结果表明:登陆过湖泊热带气旋在陆上维持时间长,登陆时强度较强;湖泊地带能延缓登陆TC强度的衰减;热带气旋经过内陆湖泊时大多表现为中心气压维持不变或降低,风速增大;长江中游地区是登陆过湖泊热带气旋消失数最多的区域. 相似文献