Impact of Cloud Microphysical Processes on the Simulation of Typhoon Rananim near Shore. Part I: Cloud Structure and Precipitation Features

By using the Advanced Regional Eta-coordinate Model (AREM), the basic structure and cloud features of Typhoon Rananim are simulated and verified against observations. Five sets of experiments are designed to investigate the effects of the cloud microphysical processes on the model cloud structure and precipitation features. The importance of the ice-phase microphysics, the cooling effect related to microphysical characteristics change, and the influence of terminal velocity of graupel are examined. The resu...     

云微物理过程对台风数值模拟的影响

将中国气象科学研究院（CAMS）混合双参数云微物理方案用于中尺度天气模式WRF,开展了对2013年超强台风天兔（1319）的模拟,通过与台风最佳路径、强度及热带降雨测量卫星（TRMM）资料对比,分析CAMS云微物理方案在模拟台风中的适用性及云微物理过程对模拟台风天兔的影响机制。设计了3组敏感性试验:修改雪粒子质量和落速系数（EXP1）,采用海洋性云滴参数（EXP2）,同时修改雪粒子质量和落速系数并采用海洋性云滴参数（EXP3）。结果表明:EXP1和EXP3由于霰碰并雪速率的增加及减小的雪下落通量,导致雪含量显著降低,同时也减少了整体冰相物的含量;EXP2和EXP3模拟的台风眼区对流有效位能快速减小,再现了前期台风的快速增强过程,路径偏差也最小;各试验模拟的小时降水率总体偏强,EXP3的降水空间分布与实况更接近,明显降低雪粒子含量,并一定程度上改善模拟的台风路径、强度及降水分布等。该结果不但可为改进适用于台风的云微物理参数化方案提供思路,也可加深云微物理过程对台风影响的认识。     

Impact of Cloud Microphysical Processes on the Simulation of Typhoon Rananim near Shore.Part Ⅱ:Typhoon Intensity and Track

The impact of cloud microphysical processes on the simulated intensity and track of Typhoon Rananim is discussed and analyzed in the second part of this study.The results indicate that when the cooling effect due to evaporation of rain water is excluded,the simulated 36-h maximum surface wind speed of Typhoon Rananim is about 7 m s-1 greater than that from all other experiments; however,the typhoon landfall location has the biggest bias of about 150 km against the control experiment.The simulated strong outer rainbands and the vertical shear of the environmental flow are unfavorable for the deepening and maintenance of the typhoon and result in its intensity loss near the landfall.It is the cloud microphysical processes that strengthen and create the outer spiral rainbands,which then increase the local convergence away from the typhoon center and prevent more moisture and energy transport to the inner core of the typhoon.The developed outer rainbands are supposed to bring dry and cold air mass from the middle troposphere to the planetary boundary layer (PBL).The other branch of the cold airflow comes from the evaporation of rain water itself in the PBL while the droplets are falling.Thus,the cut-off of the warm and moist air to the inner core and the invasion of cold and dry air to the eyewall region are expected to bring about the intensity reduction of the modeled typhoon.Therefore,the deepening and maintenance of Typhoon Rananim during its landing are better simulated through the reduction of these two kinds of model errors.     

台风利奇马登陆期间的对流结构特征及对强降雨影响

2019年9号台风利奇马在浙江造成极端降水,其中8月9日白天浙江东部受台风外围螺旋雨带长时间影响,9日夜间在台风内核对流影响下降水有显著增强;降水中心与浙江临海地区的天台山、括苍山和雁荡山等地形特征密切相关。GPM(Global Precipitation Measure)卫星遥感反演表明近岸台风螺旋雨带以层积混合型降水为主,台风眼墙区域以热带暖云对流型降水为主;眼墙区雨滴有效直径更大、雨滴数密度更高,有利于形成高降水强度。台风登陆前移动速度较慢,浙江沿海地区维持低层锋生和辐合,有利于外围螺旋雨带降水维持和增强;登陆前后受环境垂直切变等因素影响,台风中心左前侧眼墙区域对流活跃,在登陆点附近强降水区偏向于台风中心左侧。分钟级降水观测表明台风登陆期间浙江近海山区降水强度2～3倍于平原地区,其中地形性降水增幅效应与台风对流非对称结构差异对降水影响程度基本相当,有利于在台风中心左前侧的括苍山—雁荡山山区形成强降水中心。     

Impact of Different Cloud Microphysics Parameterization Schemes on Typhoon Intensity and Structure

The impact of different cloud microphysics parameterization schemes on the intensity and structure of the Super-strong Typhoon Rammasun (1409) in 2014 is investigated using the Weather Research and Forecasting model version 3.4 with eight cloud microphysics parameterization schemes. Results indicate that the uncertainty of cloud microphysics schemes results in typhoon forecast uncertainties, which increase with forecast time. Typhoon forecast uncertainty primarily affects intensity predictions, with significant differences in predicted typhoon intensity using the various cloud microphysics schemes. Typhoon forecast uncertainty also affects the predicted typhoon structure. Greater typhoon intensity is accompanied by smaller vortex width, tighter vortex structure, stronger wind in the middle and lower troposphere, greater height of the strong wind region, smaller thickness of the eyewall and the outward extension of the eyewall, and a warmer warm core at upper levels of the eye. The differences among the various cloud microphysics schemes lead to the different amounts and distributions of water vapor and hydrometeors in clouds. Different hydrometeors have different vertical distributions. In the radial direction, the maxima for the various hydrometeors forecast by a single cloud microphysics scheme are collocated with each other and with the center of maximum precipitation. When the hydrometeor concentration is high and hydrometeors exist at lower altitudes, more precipitation often occurs. Both the vertical and horizontal winds are the strongest at the location of maximum precipitation. Results also indicate that typhoon intensities forecast by cloud microphysics schemes containing graupel processes are noticeably greater than those forecast by schemes without graupel processes. Among the eight cloud microphysics schemes investigated, typhoon intensity forecasts using the WRF Single-Moment 6-class and Thompson schemes are the most accurate.     

台风“天鹅”对“莫拉克”强度维持影响的模拟分析

为探究重灾台风0908号莫拉克(Morkot)成灾的内在原因,利用NCEP/NCAR1°×1°资料和WRF数值模式,以及观测分析和数值模拟方法,对"莫拉克"过台湾岛强度始终维持在960hPa不减的现象进行研究。观测分析发现"莫拉克"强度不减与其西南方向的0907号台风天鹅(Goni)相互作用有关,物理量诸如水汽、散度、涡度等持续从"天鹅"输入"莫拉克",如水汽输入层次主要集中在950～850hPa,600hPa以上很少;涡度(垂直速度)也存在低层正涡度(负散度)输送,高层负涡度(正散度)输送。利用WRF数值模式作控制试验和抹掉台风天鹅的敏感试验,试验结果表明有涡度、水汽通量、散度等物理量从天鹅向莫拉克输送卷入,从而对莫拉克过台湾岛强度的维持不减存在一定的支持作用。     

祁连山夏季地形云结构和云微物理过程的模拟研究(II):云微物理过程和地形影响

本文是祁连山夏季地形云结构和微物理过程模拟的第II部分。文中利用第I部分中祁连山夏季两个地形云降水个例的模拟结果,详细分析了地形云及其降水发展期间云微物理过程的特征及变化,并通过与平坦地面条件下模拟结果的对比,研究了云发展过程中的地形影响。研究表明,地形云中微物理过程的发展受地形影响很大,冰相微物理过程明显增强;地形影响下云的主要降水机制也受到影响甚至被改变。     

云微物理方案在高原低涡个例模拟中的应用效果分析

以一次高原低涡东移造成甘肃河东地区强降水天气过程为例,利用NCEP再分析资料为背景场驱动WRF模式进行了数值模拟,并区分是否使用微物理方案和使用何种方案进行了26组试验,结果表明:本案例中开启微物理方案对高原低涡移动路径和强度的模拟能力均有显著提升;通过对各方案对比分析,在降水量级和落区方面Morrison 2-mom...     

一次层状云飞机播云试验的云微物理特征及响应分析

根据2005年3月21日在河南进行的层状云飞机播云试验的探测资料,对人工增雨催化前后层状云的宏微观物理量进行对比分析.结果表明,播云前在4200m高度平飞中观测到的小云粒子数浓度最大值为1.36×108个/m3,相应平均直径在5μm左右;小云粒子数浓度和云液态水含量在催化后均减小,播撒层下方变化较之播撒层变化更加显著;5000m高度小云粒子平均直径由催化前的17.32μm增加到催化后的18.07μm,平均直径明显增大,这些作业前后微观物理量的变化表明了人工催化层状云的物理响应.不同高度飞行具有相似的粒子谱分布.     

祁连山夏季地形云结构和云微物理过程的模拟研究(I):模式云物理方案和地形云结构

对三维非静力中尺度模式ARPS的云降水微物理方案进行了改进,利用改进后的ARPS模式模拟了祁连山地区夏季的两个地形云个例,通过对各自模拟结果的对比分析并结合实况资料研究了夏季祁连山地区地形云的发展状况、动力场特征、降水特征以及云微物理结构特征。研究结果表明,地形云的发展受地形影响很大,地形的抬升促进了云和降水的发展,地形的作用也改变了地面降水特征,使云的宏、微观物理结构发生较大变化。     

台风眼壁的云结构与降水形成机制分析

使用带有详细微物理过程的ARPS模式,对台风韦帕（Wipha）进行三重嵌套细网格模拟,利用模式结果,对台风眼壁强降水中心的云结构和降水形成机制进行分析,结果表明：冰相微物理过程是启动和形成台风眼壁暴雨的主要降水形成机制。在9000～14000 m高空,云水在很低的温度下经均质核化产生冰晶,或经非均质核化形成云冰;冰晶通过凝华增长（psfi,贝吉龙过程）、雨水收集云冰产生雪（praci）和冰晶粘附雨水成雪（piacr）过程生长为雪;霰产生主要包括4个过程：冰晶接触雨水使其成霰（piacr）、雪撞冻云水使其成霰（psacr）、雨水收集云冰转化成霰（praci）或雨水冻结为霰（pgfr）;霰粒子通过收集云冰干增长（dgaci）,霰撞冻云滴增长（dgacw）等过程生长;霰融化（pgmlt）和雪融化（psmlt）成雨水后再通过碰并云水等暖云生长过程,最后形成雨水。霰过程的强弱在雨水形成机制中很重要。（29.5°N、121.8°E）和（28.3°N、120.4°E）强降水中心冰晶转化率没有太大差别,但是（29.5°N、121.8°E）强降水中心上空冰晶通过贝吉龙过程快速成长为雪和霰,霰粒子增长过程远远强于（28.3°N、120.4°E）强降水中心,低空又有较高的云水转化率,使降水粒子在暖云中继续快速生长,冷暖云过程的有利配置使（29.5°N、121.8°E）出现较强雨水转化率。     

切向风速水平廓线对台风路径和强度的影响

用一个β平面的准地转模式和一个高分辨率的f平面准地转模式，实施了6组试验，研究了初始台风切向风速水平廓线对台风路径和强度的影响。结果表明：切向风速峰值区狭窄，最大风速半径较小的廓线，与偏西北方向的路径以及强度维持或增强相对应；峰值区宽平，最大风速半径较大的廓线，与北折转向的路径以及强度衰减相对应。     

Impacts of Two Ice Parameterization Schemes on the Cloud Microphysical Processes and Precipitation of a Severe Storm in Northern China

A severe storm that occurred over Beijing in northern China on 23 June 2011 was simulated with two different ice crystal parameterization schemes(the DeMott scheme and Meyers scheme) by using the Regional Atmospheric Modeling System. Compared with the DeMott scheme, the simulation results with the Meyers scheme have the following characteristics:(1) Updrafts are stronger and more numerous;(2) The cloud is better organized and contains a greater peak of ice-phase hydrometeor mixing ratios;(3) Cloud water and hail mixing ratios increase while graupel mixing ratios decrease;(4) The surface precipitation is initially greater. However, at the end of the simulation, less precipitation is produced. In short, the differences between the two schemes are not obvious, but the De Mott scheme has a relatively more reasonable result.     

云微物理参数化对华北降雪影响的数值模拟

对发生在华北地区的一次降雪过程进行了中尺度数值模拟。结果表明,高纬强冷空气南下和低纬倒槽的水汽输送是造成这次长时间降雪过程的主要原因。采用混合方案的中尺度数值模拟表明,这次降雪天气不是对流云造成的,而是稳定性的非对流云降雪。敏感性试验也表明,采用其他积云参数化方案对模拟的降雪量基本没有影响。控制试验模拟的24h降雪量与实际观测比较吻合。模拟结果表明,当采用Dudhia简单冰相方案时,会有过多的云冰、过冷却水及雪;当采用Reisner 1混合相方案时,会有过多的云冰和雪;修改的各个Reisner 2方案对此次降雪的预报改进不大,但各个Reisner 2方案的敏感性试验中云冰混合比、过冷却水混合比和雪混合比稍微有差异。     

初始场与云微物理参数方案在飑线数值模拟中的对比研究

采用CM1模式以200 m的高精度水平网格距对一次东北冷涡下的飑线过程进行模拟,采用1 km的水平网格距进行对比试验探究网格距的影响,并通过探空资料的替换与修改研究不稳定能量和垂直风切变对飑线发展的影响。研究表明,水平网格距增大主要使系统演变减缓,强度也有一定的减弱;初始场的不稳定能量减小会使飑线减弱明显,直至无法生成;垂直风切变对飑线的形成影响较小,主要改变了飑线的结构,没有垂直风切变时形成的飑线更为松散。最后的敏感性试验研究了7种云微物理参数方案对飑线内水粒子分布的影响,发现不同的云微物理参数方案会使水粒子的含量和分布出现变化,进一步影响固、液态的降水,飑线模拟采用的NA方案高层冰和雪含量最高,但由于雨和降落到地表的雹、霰含量低,使得累计降水量最小。     

Simulation of the Microphysical Processes and Effect of Latent Heat on a Heavy Rainfall Event in Beijing

An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that：（1） The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.（2） 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.（3） The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.（4） Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.（5） The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.     

台风Rananim登陆期间地形对其降水和结构影响的数值模拟试验

应用非静力平衡中尺度模式MM5(V3.6),对0414号台风Rananim在登陆期间移动路径和所产生的降水进行了数值模拟研究,模式较好地再现了台风Rananim的移动路径和所产生的降水,但模拟的过程降雨量与实况值还有所偏差。多普勒雷达探测资料表明,台风Rananim登陆期间,强回波带出现在台风移动的右前方,螺旋云带中镶嵌着大量的对流云团;垂直液态水含量的高值区出现在台风中心的西北侧。作者通过在浙江、福建东部沿海一带进行有无地形的数值对比试验,着重讨论了台风登陆期间地形对台风降水、台风结构特征变化的影响。结果表明:（1）台风登陆期间, 地形的影响对台风降雨量有明显的增幅作用。由地形强迫产生的降雨量和地形走向相一致,迎风坡降雨量增加,背风坡降雨量减少,地形影响使浙江东部一带增加的平均降雨量约占该地区模拟平均总降雨量的40%左右。（2）台风登陆期间,地形的强迫作用有利于在低层台风眼的西北侧形成明显的辐合带,高层为明显的辐散区;在中尺度环流场上,地形的影响有利于台风中心西北侧低层中尺度气旋性涡旋系统的发生发展,从而激发中尺度对流云团,形成中尺度雨团,造成了台风中心南北雨区和雨量的不对称分布。（3）地形的强迫作用,可以使台风流场局部发生改变。当地形强迫产生与台风环流同向的中尺度扰动时,将使台风环流局部明显增强;当地形强迫产生与台风环流反向的中尺度扰动时,将使台风环流局部明显减弱。（4）台风登陆期间,地形的影响可以使台风靠近陆地一侧眼壁内的垂直上升速度增大,位涡明显增强,从而造成台风涡旋的增强。     

FY-2C云迹风资料同化应用对台风预报的影响试验研究

针对0505号台风“海棠”, 采用WRF区域中尺度模式进行控制试验和两个同化试验, 利用WRF-3DVAR同化系统同化FY-2C红外和水汽两个通道云迹风反演产品, 同化分云迹风经质量控制和未经质量控制两组同化试验。通过三组试验分析云迹风资料对降水和风场等的预报结果的影响, 并进行24小时降水量分级Ts评分检验以及风场点对点检验。结果表明: 同化经质量控制云迹风资料可以提高降水落区和强度预报的准确度, 不同等级的Ts评分较其它试验都有较明显改进; 风场预报模拟也有所改善。增加两例台风, 使用与“海棠” 相似的处理方法进行模拟试验, 并对模拟结果24小时降水分析与检验, 得到与“海棠”类似结论。因此, 经过合理性选择的云迹风资料的加入, 有利于补充初始场中可能未包含的中尺度信息, 从而提高试验中对于降水、风场等的模拟效果, 提高WRF模式的模拟预报能力。     

Rainfall Microphysical Properties of Landfalling Typhoon Yagi (201814) Based on the Observations of Micro Rain Radar and Cloud Radar in Shandong,China

The development and evolution of precipitation microphysical parameters and the vertical structure characteristics associated with Typhoon Yagi(201814) are analyzed in the city of Jinan, Shandong Province based primarily on the observations of a micro rain radar(MRR), a cloud radar, and a disdrometer. The precipitation process is further subdivided into four types: convective, stratiform, mixed, and light precipitation according to the ground disdrometer data, which is in agreement with the vertical profile of the radar reflectivity detected by the MRR. Vertical winds may be the main source of MRR retrieval error during convective precipitation. Convective precipitation has the shortest duration but makes the largest contribution to the cumulative precipitation. Collision-coalescence is the main microphysical process of stratiform precipitation and light precipitation below the bright band observed by the MRR. It is worth noting that as Typhoon Yagi(201814) transformed into an extratropical cyclone, its raindrop size distributions no longer had the characteristics of maritime precipitation, but become more typical of the characteristic of continental precipitation, which represents a very different raindrop size distribution from that which is normally observed in a landfalling typhoon.     

台风苏迪罗登陆次日分散性暴雨成因及预报着眼点

利用常规气象观测,卫星、雷达资料,数值模式和中央气象台定量降水预报数据以及FNL分析数据等对台风苏迪罗的定量降水预报进行检验,探讨台风登陆次日分散性暴雨成因和预报着眼点。苏迪罗登陆次日,暴雨分布相对较分散,各家数值模式对其把握均较差。NMC的24 h定量降水预报虽在模式基础上有较好订正,但仍存在明显的暴雨空、漏报现象:暴雨落区预报较实况偏南,导致南侧空报、北侧漏报。受环境场和台风非对称结构影响,强降水产生的有利动力、水汽条件均位于台风北侧和东部沿海地区。台风东北象限对流层低层存在两条强辐合带,其间为降水较弱的弱辐散和下沉运动区。预报员对台风结构的非对称性及风场的非均匀性把握不足,对台风中心附近和两条辐合带间的弱降水区预报偏强,造成暴雨空报。在地形作用下,浙江沿海不断有强降水产生,随后沿切线方向发展为螺旋雨带并逐渐北扩。预报员对地形不断强迫作用下降水沿螺旋雨带的发展及向外围的扩散没有预期,导致浙江北部暴雨漏报。台风登陆次日分散性暴雨的预报着眼点包括:台风非对称性、风场非均匀性、螺旋雨带发展及地形作用等。非对称性影响较大尺度的降水落区;低层风场非均匀的辐合带及急流分布则引起螺旋雨带的发展、演变,决定了台风的精细强降水落区。除地形对局地降水具有增幅作用外,强降水沿螺旋雨带的发展还会对下游地区产生影响。