一次缓慢东移的黄河气旋暴雨的诊断分析

利用NCEP/NCAR再分析资料和常规气象资料,对2001年6月28-29日发生在河南的一次黄河气旋暴雨过程进行了诊断分析。结果表明：黄河气旋的稳定少动是造成这次暴雨的直接原因,高层辐散与中层正涡度平流对黄河气旋形成和发展起了重要作用。这次过程的水汽主要来自副高东南侧的海上,孟加拉湾的水汽也有一定的贡献。暴雨区的中低层对称不稳定的存在,导致上升运动和水汽输送的加强,造成降水的增幅。     

湿位涡诊断分析在河南台风远距离降水中的应用

应用湿位涡理论,分析了两个发生在河南的台风远距离降水个例,讨论了湿位涡与台风远距离降水形成的关系。结果表明：两个个例中,河南具有有利于强降水发生的湿位涡特征;异常暴雨的发展与湿位涡的变化有很好的对应关系：湿位涡的异常区域对应着最强的降水,对流层高层ζMPV1（湿位涡的垂直分量）正值区与低层ζMPV2负值区相互作用,即高层下滑的干冷空气与中低层由东南急流输送的高温高湿空气交汇,容易储存和释放湿对流不稳定能量,有利于强降水产生。湿位涡理论在河南台风远距离降水诊断中有很好的应用前景。     

高空形势与山东半岛冷流暴雪的关系

采用常规观测资料和NCEP1°×1°资料,对山东半岛2005年、2008年、2010年的几次典型冷流暴雪过程进行了分析。分析结果表明：冷流暴雪的高空形势主要分为高空冷涡型和高空横槽型。高空冷涡型较高空横槽型降雪量偏大,暴雪站点多。高空冷涡型500hPa层以上的位涡值较高空横槽型偏大,高层位涡有利于低层正涡度的加强,促使低层产生低压环流及辐合上升运动,上升运动加强了海面水汽的垂直输送,故高空冷涡型上升速度较高空横槽型强,湿层较厚,高空冷涡型较高空横槽型更容易产生暴雪过程。     

Study on the Dynamic Characteristics of an Eastward-offshore Mesoscale Vortex along the Meiyu-Baiu Front

The eastward-moving Meiyu-Baiu frontal mesoscale vortices (MBFMVs) appear frequently and often cause heavy rainfall events along their tracks. A move-off-shore MBFMV was selected to enhance our understanding of this type of vortex. Synoptic analyses indicate that the MBFMV is a type of meso-α vortex and mainly occurs in the lower troposphere. A short wave trough near the coastline is highly favorable for the formation, sustainment, and displacement of the MBFMV. Vorticity budgets indicate that at lower levels of the MBFMV, convergence is the dominant factor for the increase of positive vorticity, and at high levels of the MBFMV, the vertical transportation associated with convective activities is the most important factor. The hori-zontal transportation was the main factor decreasing the positive vorticity. The land and sea environments are crucial to the evolution of the MBFMV. The characteristics of the Meiyu-Baiu Front (MBF) are also vital to the variation of the vortex.     

INSTABILITY OF SYMMETRIC TYPHOON CIRCULATION AND ADAPTIVE OBSERVATION

This study presents a new way to identify the sensitive areas for typhoon adaptive observations, that is, sensitive areas are determined by invoking the negative anomalies of moist potential vorticity (MPV). It is found that the areas of negative MPV are the symmetric instability areas and can be taken as sensitive areas for typhoon adaptive observations. Three typhoons in 2008, Nuri, Fung-wong, and Fengshen, were simulated with the help of MM5 model. It is shown that these typhoons are well simulated in the first 12 hours. Based on these investigations, the calculations of MPV are carried out sequentially. The result shows that the negative maxima of MPV are always around the typhoon eyes for all the cases, which means that the sensitive areas are also near them all the time.     

Mesoscale Vortex Generation and Merging Process： A Case Study Associated with a Post-Landfall Tropical Depression

An observational analysis of satellite blackbody temperature (TBB) data and radar images suggests that the mesoscale vortex generation and merging process appeared to be essential for a tropical-depression-related heavy rain event in Shanghai, China. A numerical simulation reproduced the observed mesoscale vortex generation and merging process and the corresponding rain pattern, and then the model outputs were used to study the related dynamics through diagnosing the potential vorticity (PV) equation. The t...     

2007年淮河流域暴雨期间大气环流特征分析

利用NCAR/NCEP再分析资料及国家气象信息中心30年气候平均降水资料,通过动力诊断与分析手段研究了2007年6—7月发生在我国淮河流域的暴雨。结果表明,淮河流域的环流垂直结构和降水有着非常好的对应关系。暴雨期间,鄂霍茨克海阻高与乌拉尔山阻高这种双阻高形势对于淮河流域的持续降水提供了很好的条件;南亚高压高层(200 hPa)基本为正散度区,低层(850 hPa)为负散度区,上下层强烈的抽吸结构对暴雨的发生也是非常有利的条件,同时,在淮河暴雨期问,南亚高压(200 hPa)与500 hPa西太平洋副热带高压有着相向而行的移动路径;位涡对于分析冷空气的活动,有着比较清晰的意义,暴雨发生前,有明显的正位涡异常从高纬度向低纬度伸展。大气非绝热加热分析结果显示,视热源和视水汽汇两者的高值中心与相应时段暴雨中心位置一致。     

“珍珠”（0601）异常急翘路径和内核结构变化的诊断分析及数值研究

使用FY2卫星TBB资料、NCEP最终分析资料(1°×1°)和中尺度模式WRF,对0601号强台风"珍珠"的"急翘"异常转向路径和内核结构变化进行诊断分析和数值模拟。结果表明:"珍珠"移向变化与环境引导气流和位涡倾向1波分量正异常有关,"急翘"前12小时,环境引导气流向北偏转,位涡倾向1波分量正异常对应着"珍珠"移动方向变化;内核非对称结构发展与环境风垂直切变演变有关,垂直切变使得涡旋倾斜,涡旋倾斜方向出现较强的上升运动,导致"珍珠"内核偏南象限对流活动较强。     

A Case Study on a Quasi-Stationary Meiyu Front Bringing About Continuous Rainstorms with Piecewise Potential Vorticity Inversion

A 4-day persistent rainstorm resulting in serious flooding disasters occurred in the north of Fujian Province under the influences of a quasi-stationary Meiyu front during 5-8 June 2006. With 1°× 1° latitude and longitude NCEP reanalysis data and the ground surface rainfall, using the potential vorticity （PV） analysis and PV inversion method, the evolution of main synoptic systems, and the corresponding PV and PV perturbation （or PV anomalies） and their relationship with heavy rainfall along the Meiyu front are analyzed in order to investigate the physical mechanism of the formation, development, and maintenance of the Meiyu front. Furthermore, the PV perturbations related to different physics are separated to investigate their different roles in the formation and development of the Meiyu front. The results show： the formation and persistence of the Meiyu front in a quasi-WE orientation are mainly due to the maintenance of the high-pressure systems in its south/north sides （the West Pacific subtropical high/ the high pressure band extending from the Korean Peninsula to east of North China）. The Meiyu front is closely associated with the PV in the lower troposphere. The location of the positive PV perturbation on the Meiyu front matches well with the main heavy rainfall area along the Meiyu front. The PV inversion reveals that the balanced winds satisfying the nonlinear balanced assumption represent to a large extent the real atmospheric flow and its evolution basically reflects the variation of stream flow associated with the Meiyu front. The unbalanced flow forms the convergence band of the Meiyu front and it mainly comes from the high-pressure system in the north side of the Meiyu front. The positive PV perturbation related to latent heat release in the middle-lower troposphere is one of the main factors influencing the formation and development of the Meiyu front. The positive vorticity band from the total balanced winds is in accordance with the Meiyu front band and the magnitude of the posit     

A Diagnostic and Numerical Study on a Rainstorm in South China Induced by a Northward-Propagating Tropical System

A strong cyclonic wind perturbation generated in the northern South China Sea （SCS） moved northward quickly and developed into a mesoscale vortex in southwest Guangdong Province, and then merged with a southward-moving shear line from mid latitudes in the period of 21-22 May 2006, during which three strong mesoscale convective systems （MCSs） formed and brought about torrential rain or even cloudburst in South China. With the 1° ×1° NCEP （National Centers for Environment Prediction） reanalysis data and the Weather and Research Forecast （WRF） mesoscale model, a numerical simulation, a potential vorticity inversion analysis, and some sensitivity experiments are carried out to reveal the formation mechanism of this rainfall event. In the meantime, conventional observations, satellite images, and the WRF model outputs are also utilized to perform a preliminary dynamic and thermodynamic diagnostic analysis of the rainstorm systems. It is found that the torrential rain occurred in favorable synoptic conditions such as warm and moist environment, low lifting condensation level, and high convective instability. The moisture transport by strong southerly winds associated with the rapid northward advance of the cyclonic wind perturbation over the northern SCS provided the warm and moist condition for the formation of the excessive rain. Under the dynamic steering of a southwesterly flow ahead of a north trough and that on the southwest side of the West Pacific subtropical high, the mesoscale vortex （or the cyclonic wind perturbation）, after its genesis, moved northward and brought about enormous rain in most parts of Guangdong Province through providing certain lifting forcing for the triggering of mesoscale convection. During the development of the mesoscale vortex, heavy rainfall was to a certain extent enhanced by the mesoscale topography of the Yunwu Mountain in Guangdong. The effect of the Yunwu Mountain is found to vary under different prevailing wind directions and intensities. The location o