Polly(9216)台风登陆后的地面中尺度系统分析

1992～1994年夏季,85-906国家科技攻关项目07课题组织进行了台风现场科学和业务试验。Polly（9216）台风是一个影响面很广的试验目标台风。本文使用了1992年8月30日0000～9月2日0000 UTC该台风试验期间,受其影响的11个省市、共有673个气象台站、27996站次的地面加密观测资料,进行了该台风中心临近登陆及登陆后的每小时地面加密观测分析,提示了该台风登陆后主要地面中尺度系统的分布、发展和演变。     

一次特大暴雨(雪)天气过程的微物理模拟

利用非静力中尺度模式MM5(V3.7)模拟了2007年3月3-5日发生在辽宁地区的一次特大暴雨(雪)天气过程.分析在相同的天气形势背景下,不同降水类型中心各种水成物的相态分布特点,重点对各种水成物的源项进行详细分析.结果表明:雨水碰并雪成雨是雨水产生的主要云微物理过程,雪、霰和云水的碰并对雨水的形成起着非常重要的作用,...     

中国暴雨中尺度系统发生与发展的诊断分析和数值模拟(Ⅰ)诊断分析

通过对我国三次(“81.7”、“81.8”和“91.7”)典型大暴雨过程的动力学和热力学诊断来探讨暴雨中尺度系统发生与发展的问题。大、中尺度天气分析指出,无论是发生在我国东部的“91.7”暴雨过程,还是出现在西部地区的“81.7”和“81.8”暴雨过程,都与在特定大尺度环流形势下持续发展的中尺度系统直接关联。涡度诊断表明,高、低空正涡度中心的叠加和耦合、并形成一个正涡度柱是这类暴雨中尺度系统持续发展的一种共同特征。根据场分解涡度方程获得的涡源诊断表明,涡源对这类中尺度系统的发生和发展具有重要的动力学贡献。中尺度热量和水汽收支诊断揭示,视热源 Q_1和视水汽汇 Q_2的垂直积分高值区,与低涡或低涡切变线及其暴雨区基本一致;Q_1(Q_2)的面积平均最大加热(增湿)区间出现在对流层中、上(下)部;由于感热和潜热对流涡动通量辐合的加热,在其上部近乎等于凝结释放潜热量的一半。     

引发暴雨的西南低涡特征分析

利用NCEP1°×1°再分析资料、逐时卫星云图资料和自动站资料,分析了与4次暴雨过程密切相关的中尺度系统西南低涡。结果表明,引发暴雨的西南低涡相对于环境场是湿涡,南边界是主要水汽输送方向。在西南低涡形成阶段,整层均为正涡度,一般维持深厚的上升气流,具有较为深厚的暖心结构。在其发展旺盛阶段,正涡度呈上升趋势,对流层中低层...     

基于指标叠套法的安徽省强对流天气潜势预警研究

对2005－2007年4-9月安徽省冰雹、雷雨大风等强对流天气日数进行统计,分析了基于探空资料计算的不稳定指标与强对流天气发生的关系。结果表明：K指数、A指数、沙氏指数和对流有效位能、归一化对流有效位能和对流抑制能量这几个指标对于强对流天气指示意义较好。基于此结果,挑选K指数、沙氏指数和对流有效位能针对不同季节划分阈值,建立强对流天气潜势预警指标,并利用中尺度模式MM5的数值预报产品计算该指标,对2005-2010年13个强对流天气过程预报结果进行对比检验表明,MM5模式给出的强对流天气潜势预警产品对大多数过程均能起到预警作用。对其中两次强对流天气过程的进一步分析表明,模式具备预报强对流发生潜势的能力,预报结果对强对流天气发生的时间、落区有预警意义。     

Circulatory Patterns of Air Pollutants within the Barcelona Air Basin in a Summertime situation: Lidar and Numerical Approaches

This work examines circulatory patterns of airpollutants in the area of Barcelona (Spain), a regionwith strong coastal and orographic influences. Thiswas achieved through exploitation ofelastic-backscatter lidar data and by numericalsimulation of the atmosphere with a meteorologicalmesoscale model (MEMO). Lidar data were acquired inJuly 1992 during a collaborative campaign between LosAlamos National Laboratory (LANL) and the PolytechnicUniversity of Catalonia (UPC). The lidar providedinformation about the distribution of aerosols and theprevailing winds, determined by application of amaximum cross-correlation algorithm toelastic-backscatter lidar data. Lidar winds are usedto evaluate high altitude winds simulated by themodel. This study showed that circulatory patterns inBarcelona are correlated with daytime convectivevertical mixing, sea-breeze circulations, and verticalforcing caused by mountain thermal and mechanicaleffects.     

Numerical Study On Cloud Lines Over An Urban Street In Tokyo

`Kanpachi Street Cloud (KSC)' is an unusual small-scalecumulus cloud line visible during calm summer conditions over a major street in the Tokyo metropolitanarea. In order to understand the mechanism leading to the formation of this cloud line,numerical simulations have been performed using the Regional Atmospheric Modelling System.The general characteristics of the simulated KSC agree well with observations. On alarge-scale view, the KSC can be characterized as a cumulus cloud line generated at the convergenceline of two sea breezes on the western side of Tokyo Bay, while on the microscale view, it resemblesBenard-type thermal convection modified longitudinally by wind shear.The location of the convergence line leading to the KSCformation coincides withthe Kanpachi street location, although the street itself does notmake any direct effect on the KSC formation. Additional numerical experiments were performed toidentify causes of the KSC formation in accordance with urbanization, by changing anthropogenicheat impact, land-cover and grid resolution.They confirmed that the formation of the KSC requirestwo meteorological processes at the same time:(1) the convergence of two sea breezes – the localsouth-eastern sea breeze from Tokyo Bay andan extended southern sea breeze from thePacific Ocean, respectively; (2) Forcing due to an urban heat island. It is shown that urbanization couldchange the intensity and position of the KSC through enhancement of local upward motions and changesin the near-surface horizontal pressure gradient between urban and sub-urban areas. Further,fine horizontal grid resolution is needed to be able to resolve these local thermal convection issues.     

A Modelling Approach For Optimizing Flight Patterns In Airborne Meteorological Measurements

A method is presented for selecting the optimal flight patterns for airbornemeteorological measurements in various flow situations. The method is basedon systematic utilisation of mesoscale model fields. Flow overan Arctic sea-ice boundary zone is modelled, and it is assumed that the mesoscale model fields represent the true state of the atmosphere, and that each possible flight pattern yields a different sample of the true fields. A plan for the basic structure of the flight pattern is assumed, and then the unexplained variance, i.e., the difference between the true variance and the sample variance, of a quantity of interest is calculated for a variety of possible flight patterns. Different target quantities are considered, such as wind speed, air temperature, and the turbulent fluxesof momentum and sensible heat. The optimal flight pattern is defined byminimisation of the unexplained variance, and often depends on the quantitywe are interested in. For sawtooth patterns, the optimal flight pattern was sensitive to the maximum ascent angle of the aircraft. In flight patterns designed for turbulence measurements, the optimal pattern was different for the unexplained variance of the turbulent fluxes and for the unexplained total heat content of the convective layer.     

一次降雪过程持续原因分析

利用多种观测资料和中尺度数值模拟资料,对2011年2月14日发生在江淮地区的一次预报失误的持续性降雪过程进行较为全面的分析.结果表明:前期的降水导致近地面维持较大湿度,补充南下的冷平流促使低层大气接近饱和,降雪持续期间,水汽集中在对流层低层浅薄的层次中;对流层中层发展和维持的强冷平流导致降水区上空迅速降温减湿,从而在对流层中低层,逐渐建立起弱对流不稳定层结.而叠置其上的稳定层则将对流活动和水汽的向上输送限制在对流层低层内,使得水汽和能量得以在一定范围内集中;不断补充南下的冷空气强迫近地层风场发生扰动,形成的中尺度切变线,为这种浅薄层次下的弱对流活动提供了触发条件.尽管辐合抬升较弱,但与其它季节相比,气温较低的冬季,在抬升凝结高度较低的大气中,水汽易凝结成云致降水.造成这次预报失误的原因,是忽略了近地层系统的变化.另外,对补充冷空气的影响作用考虑不充分.     

2013年6月26—29日江西暴雨过程的中尺度数值模拟分析

利用NCEP再分析资料和WRF模式,对2013年6月26—29日江西大范围暴雨过程进行了数值模拟分析。结果表明,西太平洋副热带高压脊线稳定维持在21°N附近,副高北侧强盛西南气流将水汽向江南北部地区输送是暴雨产生和稳定维持的主要原因。超低空偏南急流的建立、发展和维持是这次连续暴雨过程产生的一个重要因素,同时低空低涡南侧出现一串近似东西向排列的30～60km更小尺度的强对流系统,它们与大暴雨区相吻合;整层水汽通量密集区的南北界位置和暴雨区南北界位置基本吻合,整层水汽的大值中心的范围和大暴雨中心的范围具有明显的正相关关系;水汽通量散度最大辐合中心为暴雨的产生输送了大量的水汽,水汽辐合中心与暴雨的落区有很好的一致性;强降水落区与假相当位温最大值区相对应。