韶关"7.19"暴雨成因分析

通过对常规气象资料、卫星云图和多普勒雷达资料的分析，发现在西南季风爆发的背景下，当高空槽超前于低层切变和地面锋面，在高空槽附近有不稳定能量积累，华南中部生成的中尺度对流云团往北发展造成了韶关南部的连续暴雨；而韶关北部的强降水则属于典型的锋面低槽降水。     

1991～2004年不同环流背景下南宁市降水化学成分变化特征的研究

利用1991～2004年广西南宁市降水化学成分资料，结合NCEP／NCAR再分析资料，分析了不同大气环流背景下南宁市降水化学成分的变化特征。结果表明，南宁市的酸雨属硫酸型，酸雨的形成与大气环流密切相关，影响南宁市酸雨的大气环流主要是高空槽锋面，其次是高压后部和热带气旋，受高空槽锋面特别是东路冷空气影响时，出现酸雨的频率最高，pH值最小，雨水中SO4^2-明显增多，热带气旋降水时，雨水酸度最轻，离子浓度甚至比高空槽锋面影响低2～3倍。     

台风“卡努”登陆前强度突增天气成因分析

利用MICAPS资料6、h 1次的CIMSS资料和卫星云图资料,对台风“卡努”登陆前强度突增天气成因进行了分析。结果表明:当台风向高空槽靠近时,高空槽前的正涡度平流能增强台风上空的辐散,而且高空槽使台风上空产生明显的热通量辐散,把台风产生的热量迅速带走;当台风处于海上太平洋副高西南侧时,太平洋副高适当增强,可使副高与台风间的东南气流增强以及环境风场垂直切变减弱。由于上述原因,台风“卡努”登陆前强度突然增加。     

中纬度高空槽—台风相互作用对台风“利奇马”远距离暴雨的影响

利用NCEP提供的0.25°×0.25° FNL资料和国家气象信息中心提供的高分辨率三源融合降水资料,以台风"利奇马"为研究个例,从动力和热力因素两个方面研究了中纬度高空槽与台风之间的相互作用对台风远距离暴雨的影响。研究认为中纬度高空槽—台风的相互作用是此次台风远距离暴雨的主要原因之一。在高空槽—台风的相互作用中,随着弱正PV异常从中纬度高空槽向台风区域的水平平流,台风西北部地区逐步处于高空槽前西南急流的次级环流的上升区域,而对流层深厚的暖平流恰好位于台风西北部3~5个纬距的地区,此热成风暖平流的作用增强了台风西北地区的上升运动。另外,中纬度高空槽后的干冷空气的逼近,促进了在台风西北部地区的中纬度斜压锋生,斜压锋面进一步增强了台风远距离暴雨处的动力抬升作用。同时还发现当台风与中纬度槽的距离大约是10个纬距时其相互作用最为显著。     

绥化市一次暴雨天气过程分析

2017年8月3-4日受高空槽和南部低压系统共同影响,自南至北绥化市出现一次暴雨、大暴雨天气过程。本文利用MICAP3.2资料、常规观测资料、自动站资料,卫星、雷达资料对暴雨产生进行分析,这次暴雨产生的主要原因是高空槽与南部的低压系统共同影响,低空西南急流为暴雨带来了充足的水汽和不稳定能量,充分的动力条件和大量的水汽是导致本次暴雨产生的主要原因。     

副高外围影响下遵义市区域性暴雨的高空形势场特征研究

利用常规观测资料和NCEP1°×1°再分析资料,发现2007-2016年6～8月有8次区域性暴雨天气过程是由副高东退、引导高空槽东移的大尺度背景条件下,配合低层系统造成的,将其分类后得到三种类型：低涡槽型、高空槽气旋旋转型和高空槽低涡切变型;对每种类型的高空形势进行合成分析,找出了暴雨落区与高空系统、物理量配置之间的关系。     

环江县“2005-04—25”大暴雨天气过程分析

通过分析常规观测资料和物理量资料，对环江县2005年4月25日大暴雨天气过程进行特征分析，指出此次大暴雨天气是高空槽与850hPa，切变线相互作用下产生的；低层暖湿舌的建立及不稳定能量区是产生强降水的条件；4月由于暖湿气流不活跃，对强降水过程除了常规资料分析外，相关物理量的分析也很重要。     

副高影响下遵义市区域性暴雨的天气系统特征研究

利用常规观测资料和NCEP1°×1°再分析资料,对2007—2016年6—8月8次副高影响下的区域性暴雨天气过程,采用统计学、天气学方法和合成技术进行分析,结果表明:在副高东退、引导高空槽东移的大尺度背景条件下,配合低层辐合系统是造成遵义市区域性暴雨过程的天气系统;暴雨过程有3种类型:低涡槽型、高空槽气旋旋转型和高空槽低涡切变型; 3种类型的天气系统进行合成分析后,找出了暴雨落区与高空系统、物理量配置之间的关系。     

共和蔬菜交易市场倒塌的天气分析

通过对事发地的详尽调查，结合天气形势和本地资料分析，共和蔬菜交易市场的倒塌，主要是大尺度的高空槽前原已存在的上升运动区受南下冷空气激发而产生更加强烈的对流运动，以雷雨大风形势释放大量不稳定能量所致。     

1996年7月洞庭湖流域持续性暴雨过程分析

1996年7月洞庭湖流域发生了严重的洪涝灾害。利用观测资料进行诊断分析表明:(1)这次大洪水是由梅雨锋西端高空槽前的持续性大面积暴雨引起；(2)引起持续性暴雨的直接原因是MCS形成后停滞少动，并在同一地区连续多次生消；(3)由于高空槽长时间维持在长江中游地区，对流层低层的暖平流等大尺度强迫使暴雨区能较长时间维持上升运动，同时低层持续强的水汽辐合和位势不稳定能量的输送为暴雨持续地发生提供了充足的水汽和能量。     

宁夏夏季降水概念模型及预测模型

在相关普查及分析各因子物理意义的基础上，建立了宁夏夏季降水的概念模型和预测模型，结果表明：夏季500hPa高度场上欧亚中高纬地区为乌山脊、巴尔喀什湖至贝加尔湖地区为槽，赤道东太平洋海温低，印度低压弱，以及西太平洋副热带高压脊线位置偏北时，宁夏夏季易多雨，反之易少雨。     

内蒙古西部一次沙尘暴环流背景和动力机制分析

利用相关资料对2009年4月23日内蒙古西部地区发生的沙尘暴天气的环流形势及动力机制进行分析。分析表明:强冷空气活动是本次沙尘暴天气发生的主要原因;造成本次沙尘暴的高空系统是斜压性很强的蒙古横槽及槽后的偏北急流,地面系统是强烈发展的蒙古气旋;从动力机制来看,沙尘暴发生时,由于高层辐合、低层辐散而形成的强烈下沉运动,使得高空偏北急流带的动量下传到地面,中低层波动发展形成的次级环流使动量下传效率更高。高空蒙古横槽南压、转竖是冷空气爆发南下的关键,高空偏北急流带以及与急流出口区相对应的地面蒙古气旋的强烈发展是形成沙尘暴的必要条件,地面冷锋后气压梯度的持续加强会加剧冷空气爆发的速度,强烈的高层辐合、低层辐散使得沙尘暴形成的可能性更大。     

江西一次暴雨过程的诊断分析

利用NCEP 1°×1°再分析资料、地面与探空资料、卫星资料等,对2012年5月12日发生在江西省中部的一次暴雨过程进行诊断分析。结果表明：本次暴雨过程发生在冷锋南侧地面倒槽区,由高层西风槽、低层低空急流及切变线、低涡共同影响所致。中低层西南气流的加强,一方面使暴雨区有充足的水汽输送,同时也使该区对流不稳定度加大,加强了暴雨区上空的对流上升运动。中尺度辐合线是强对流暴雨的触发机制,而冷锋影响使地面东风气流加强,冷空气入侵致中尺度辐合线演变为中尺度低压,中尺度低压是江西短时强降水长时间持续的机制;500hPa高空槽东移,槽前正涡度平流向江西上空输送,利于低层低涡生成和维持、上升运动加强,从而导致降水增强。冷空气影响初始阶段,〉10mm·h-1 的中尺度雨团产生在中尺度辐合线及其所演变成低压的1、2象限即中尺度辐合线或中尺度低压偏北一侧,随着冷空气的进一步入侵,中尺度雨团产生于中尺度低压的偏南一侧。     

一次高空槽在青藏高原上诱发切变线的Q矢量分析

通过对1982年6月1—6日一次高空槽在青藏高原上诱发切变线的过程进行了Q矢量分析，发现高原切变线产生、维持在明显的呈东西向的500 hPa Q矢量辐合带内，而且低层500 hPa ▽·Q0。这说明宽广的上升运动的存在和加强，是产生、维持切变线的重要机制。高原切变线的产生、维持还与锋生情况有一定的关系。     

Role of synoptic-scale forcing in cyclogenesis over the Bay of Bengal

The cyclone frequency distribution over the Bay of Bengal during 1990–2009 was distinctly bimodal, with a primary post-monsoon peak and a secondary pre-monsoon peak, despite the very high convective available potential energy (CAPE) during the pre-monsoon. The location of the monsoon trough over the bay is a primary factor in tropical cyclogenesis. Because the trough was in the northernmost bay during the pre-monsoon season, cyclogenesis was inactive in the southern bay, where a strong southwesterly wind shear was found. In this season, moreover, a hot, dry air mass extending vertically from 950 to 600 hPa was advected from northwestern India toward the bay. Moist, warm southwesterly winds penetrating below the deep, dry air mass caused a prominent dryline to form aloft on the northwestern side of the bay. The synoptic-scale hot, dry air forcing to the bay suppressed the active convection necessary for cyclogenesis. The strength of the stable environmental layer, represented by convective inhibition (CIN), was extremely large, and acted as a cap over the northern and northwestern bay. Conversely, during the post-monsoon, there were no horizontal temperature or moisture gradients, and CAPE and CIN were fairly modest. The entire bay was covered by a very deep, moist layer from the surface to 700 hPa transported from the east. The monsoon trough position and the environmental CIN in combination can explain the lower frequency of cyclogenesis during the pre-monsoon compared with the post-monsoon season.     

登陆热带气旋降水增幅的合成诊断分析

利用NCEP/NCAR再分析资料,采用动态合成分析方法,对登陆后降水增幅类和非增幅类热带气旋的大尺度环流特征做了合成分析和动力诊断.结果表明:增幅类热带气旋处于强经向型环流之中,中高纬度为阻塞形势,高层有急流入口区南侧的强辐散,并与西风槽相互叠加;低层有急流和水汽通道的长时间联结;热带气旋东侧还有次级环流相伴.非增幅类热带气旋环流背景相对平直,高空辐散弱,无西风槽叠加;低空急流减弱迅速,且水汽通道较早出现断裂;无次级环流出现.增幅类热带气旋高层存在显著非地转运动,高层南风急流入口区的强次地转运动和降水增幅紧密相关.     

A diagnostic study of heavy rainfall in karachi due to merging of a mesoscale low and a diffused tropical depression during South Asian summer monsoon

This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression. The former low was located over Pakistan‘s desert region and the latter depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in the diagnosis. The relationship between the heavy precipitation process and large-scale circulations such as monsoon trough, subtropical high, westerly jet, low level jet and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It was found that: (1) the mesoscale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence on 24 July 2003 over the lndian Rajistan area. (2) On the same day, a low that formed over the Bay of Bengal was transformed into a monsoon depression and moved westward to the mesoscale low which existed over southwest India and the adjoining southeastern parts of Pakistan. (3) Initially, the mesoscale low received moisture supply from both the Bay of Bengal as well as the Arabian Sea, whereas the Bay of Bengal maintained the continuous supply of moisture to the monsoon depression. (4) After the depression crossed central India, the Bay‘s moisture supply was cut off and the Arabian Sea became the only source of moisture to both the closely located systems. On 27 July, both of the systems merged together and the merger resulted in a heavy downpour in the Karachi metropolitan and in its surroundings. (5) With the intensification as well as the southeastward extensionof the subtropical high and the shift of the monsoon trough axis from southwest-west to northeast-east,the monsoon depression moved southwestward. In this situation, there existed a very favourable condition for a merger of the two systems in the presence of cross-latitude influence. (6) A number of convective cloud clusters were developed and organized in the mesoscale low. Probably, interactions existed among the multi-scale systems.     

Study on a Mesoscale Convective Vortex Causing Heavy Rainfall during the Mei-yu Season in 2003

The strong heavy rainfall on 3-5 July 2003 causing the severe flooding in Huaihe River basin (HRB), China is studied. It is noted that there are sometimes mesoscale convective vortex (MCV) in East Asia during the mei-yu season. Simulation results from the ARPS (Advanced Regional Prediction) data analysis system (ADAS) and WRF model were used to study the development of the mesoscale convective system (MCS) and mesoscale convective vortex (MCV). It is confirmed that the MCV formed during the development of a...     

Occurrence of Kelvin-Helmholtz Billows in Sea-breeze Circulations

Centred at the interface between the sea-breeze and the return flow aloft, Kelvin-Helmholtz billows (KHB) are an important feature of the turbulent structure of some sea-breeze circulations (SBCs). In other SBCs, there are no prominent KHBs observed. Factors governing the appearance of billows are determined from a database of 139 sea breezes, constructed from two years of summertime surface observations at a site on the south coast of England. Post-frontal oscillations occur in the surface data for some SBCs and are interpreted as indicating possible KHBs aloft. The SBCs are formed under a wide range of synoptic conditions, enabling various measures of possible billow occurrence to be related to properties of the large-scale, ambient flow. Consistent with laboratory experiments of density currents, KHBs are suppressed for propagation into a head wind and enhanced with a tail wind. They are also found to be enhanced for stronger ambient wind speeds, while large-scale coast-parallel flow is effective in suppressing the billows.     

内蒙古河套地区两次暴雪过程对比分析

利用常规气象资料和自动站数据,对2007年2月6日一8日和2011年2月25日一27日发生在内蒙古河套地区的两次暴雪过程进行对比分析,结果表明,500hPa中亚和东亚分别有冷槽活动,中亚槽前有分裂冷槽东移推动两槽间暖脊发展东移至河套以东,河套西部处在西南气流控制下。当500hPa分裂东移的冷槽与700hPa高原低槽、西北涡或切变线和地面河套倒槽或河套气旋垂直叠置,高空槽后有冷空气下沉锲入到暖湿气层底层形成动力抬升时,触发暴雪产生。低层负散度、正涡度,深厚的负垂直速度,高、低空急流垂直耦合形成的抽吸作用,高、低层冷暖平流造成的热力不稳定,较长时间水汽和热量输送、积聚,使高能、高湿舌伸人河套形成的位势不稳定,河套外围三面环山形成的地形抬升作用叠置在抬升区上空,为触发暴雪产生提供了强劲动力。