Analysis of a Wenzhou-Hitting Exceptionally Strong Rainstorm Associated with a Typhoon Inverted Trough in September,1999

Using T106 numerical products, MM5 simulations in conjunction of Q-vector scheme-computed NCEP results, observations and satellite cloud images, study is undertaken for an exceptionally intense rainstorm event afflicting the Wenzhou region of Zhejiang province far away from the tropical storm center happening early on the morning of September 4, 1999 （TS9909 hereinafter）. Evidence suggests that, like previously-studied typhoons landing in autumn south of Xiamen to the eastern part of Guangdong, TS9909 has an inverted trough in the central south of the coastal belt of Zhejiang province that produces the rainstorm from the meso convective complex （MCC） on the warm, moist shear inside; the time and order of the magnitude of the rainfall are bound up with the development of the pattern of strong Q-vector divergence gradients during the event for the study area; the NE - SW coastline and the unique topography of the Yandang mountains inside the region are favorable for air lifting are the major contributors to the torrential rains.

Analysis of the Rainstorm Falling Zone in Guangxi during Influence Period of the 0906 Typhoon "Molave"

[ Objective] The research aimed to analyze rainstorm falling zone in Guangxi during influence period of the 0906 typhoon ＂ Molave＂. [ Method] For the heavy precipitation falling zone in southern and central parts of Guangxi after 0906 typhoon ＂ Molave＂ landed, 500 hPa circula- tion, physical quantity field, satellite cloud chart and terrain effect were analyzed. [ Result] 500 hPa subtropical high caused asymmetry of the ＂Me- lave＂ circulation, playing a key role for the strong precipitation falling zone in Guangxi. Physical quantity field analysis pointed out that after ＂ Me- lave＂ landed, water vapor convergence center was in southeast Guangxi, providing adequate moisture condition for the heavy precipitation in south- ern and central parts of Guangxi. The maximum positive vorticity center appeared at the middle and low layers in southern and central parts of Guangxi for a long time. At 200 hPa, there was a maximum divergence center. At 700 hPa, there was a maximum convergence center. High-level divergence and low-level convergence created conditions for heavy precipitation in the region. From satellite cloud chart, the heavy precipitation fall- ing zone related to asymmetric structure of the ~ Molave＂. In addition, uplifting effect of the terrain was conducive to occurrence of the large precipi- tation. [ Conclusion] The research provided reference for reduction and prevention of this kind of heavy precipitation.

Analysis of Special Strong Wind and Severe Rainstorm Caused by Typhoon Rammasun in Guangxi, China

Based on conventional meteorological observation data, NCEP 1° × 1° reanalysis data, reanalysis data with resolution 0.75° × 0.75° from ECMWF and Doppler weather radar, we analyzed the weather conditions and physical characteristics of Super Typhoon Rammasun (1409), which caused special strong wind and severe rainstorm in Guangxi. The results show that: 1) Typhoon Rammasun offshore sudden strengthening in one of the main reasons was that loop pressure ridge superimposed into the westward extension of subtropical high, to making enable rapid strengthening of the subtropical high, so the subtropical high advanced faster than the Rammasun move, Rammasun center of the subtropical high distance reduced and the gradient increased;2) Rammasun northward to south china coast with plenty of vapor following ITCZ, before landing, southwest monsoon and cross-equatorial flow were involved, Rammasun got latent heat of monsoon jet, enabling it to strengthen in offshore;3) Rammasun from the Qiongzhou Strait into the northern Gulf, therefore the Strait of short passages and both sides belong to the low zone, friction consumption smaller, that was the main reason what was able to maintain the strength of the super typhoon, when Rammasun into the Beibu Gulf;4) Diagnostic analysis shows that Rammasun before entering the northern Gulf and into the Beibu Gulf later, vorticity weakened, divergence and vapor flux divergence changed were smaller, meanwhile, vertical ascent speed and latent heat transport both increased, which was important reason of severe rainstorm caused by Rammasun.

Analysis of a Rainstorm Process Far from the Typhoon "Haitang"

Based on multiple kinds of observation data and NCEP/NCAR reanalysis data,the circulation background,cloud clusters and radar characteristics of a rainstorm far from the typhoon " Haitang" in Lianyungang,Jiangsu on the morning of July 31,2017 were analyzed,and causes of convection were discussed from the aspects of dynamic,thermal and water vapor conditions. The results showed that the rainstorm process was caused by convection cells with low center of mass,and strong convection mainly occurred in a position where temperature gradient at cloud top was the largest. In North China at 850 hP a,eastern cold air on the south side of anticyclonic circulation moved southwards and joined southeast air flow on the periphery of typhoon,which was the main reason for the occurrence of convection. The circulation of upper-level divergence and lowerlevel convergence was beneficial to the maintaining of convection. The convergence of southeast wind speed on the periphery of typhoon made water vapor accumulate,thereby providing enough water vapor for the appearance of heavy rainfall. K index had good denotative meaning to convection activity,and the process of convection with weak Cape value needs to be paid special attention to in business. The prediction effect of rainfall distribution and areas by the models EC and ECRC was superior to other models.

ON RELATION OF MESO-α INERTIA WAVE DEVELOPMENT TORAINSTORM ENHANCEMENT IN TYPHOON POLLY

Numerical simulation and diagnosis show that the amplified rainstorm from Typhoon Poily is related to the development/migration of meso-α gravity waves, inhomoseneous stratification distribution andcumulus convection latent heating feedback in the storm; such waves at a large scale are excited bylarge-scale nonlinear advection; substantially amplified ageostrophic wind perturbation resulting fromthe latent heating gives rise to intensified wave amplitude, leading to enhanced rising and thus torrentialrainfall; as the waves migrate towards reduced stability, wave energy is most likely to increase.

Numerical Study of the Mesoscale Systems in the Spiral Rainband of 0509 Typhoon Matsa

The Advanced Weather Research and Forecasting Model （ARW） is used to simulate the local heavy rainstorm process caused by Typhoon Matsa over the northeastern coast of Zhejiang Province in 2005. The results show that the rainstorm was caused mainly by the secondary spiral rainband of the Stationary Band Complex （SBC） structure. Within the secondary spiral rainband there was a strong meso-β-scale convergence line generated in the boundary layer, corresponding very well to the Doppler radar echo band. The convergence line comprised several smaller convergence centers, and all of these convergence columns inclined outward. Along the convergence line there was precipitation greater than 20 mm occurring during the following one hour. During the heavy rainstorm process, the Doppler radar echo band, convergence line, and the precipitation amount during the following one hour, moved and evolved synchronously. Further study reveals that the vertical shear of radial wind and the low-level jet of tangential wind contributed to the genesis and development of the convergence columns. The combined effect of the ascending leg of the clockwise secondary circulation of radial wind and the favorable environment of the entrance region of the low-level jet of tangential wind further strengthened the convergence. The warm, moist inflow in the lower levels was brought in by the inflows of the clockwise secondary circulation and uplifted intensely at the effect of convergence. In the convectively instable environment, strong convection was triggered to produce the heavy rainstorm.

ANALYSIS OF RAINSTORMS ASSOCIATED WITH SIMILAR TRACK TROPICAL CYCLONES HAITANG (0505) AND BILIS (0604)

It is generally thought that the influence of comparable track typhoons is approximately similar, but in fact their wind and especially their rainstorm distribution are often very different. Therefore, a contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604), which are of a similar track, is designed to help understand the mechanism of the TC rainstorm and to improve forecasting skills. The daily rainfall of TC Haitang (0505) and Bilis (0604) is diagnosed and compared. The result indicates that these two TCs have similar precipitation distribution before landfall but different precipitation characteristics after landfall. Using NCEP/GFS analysis data, the synoptic situation is analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence. The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang (0505) and Bilis (0604) before landfall results from a peripheral easterly wind, a combination of the tropical cyclone and the terrain. After landfall and moving far inland of the storm, the precipitation of Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in the coastal area. One of the important contributing factors to heavy rainstorms in southeast Zhejiang is a southeast jet stream, which is maintained over the southeast coast. In contrast, the South China Sea monsoon circulation transports large amounts of water vapor into Bilis – when a water-vapor transport belt south of the tropical cyclone significantly strengthens – which strengthens the transport. Then, it causes water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much stronger on the south side than that on the north side. After Bilis travels far inland, the cold air guided by a north trough travels into the TC and remarkably enhances precipitation. In summary, combining vertical wind shear with water vapor transportation is a good way to predict rainstorms associated with landing tropical cyclones.

A Case Study of a Regional Torrential Rain in North China Caused by Typhoon Damrey (2012)

By using the NCEP/GFS analysis data, CIMISS data, JMA and China’s Typhoon Networks, heavy rainstorm occurred in east of North China associated with Typhoon Damrey from August 3rd to 4th, 2012 was analyzed. Results show during Damrey was going nearby Tianjin City and Hebei province of China, heavy rainstorm was observed in the cities of Qinhuangdao and Tangshan. The southerly jet stream from the southern side of the subtropical high and the periphery of Typhoon Saola is the conveyor belt for water vapor and energy, which enables Damrey to maintain for a long time and provide water vapor and heat conditions for rainfall in east of North China. The structure of Damrey caused a strong updraft in east of North China with a K-index greater than 35°C, which provided a favorable condition for the heavy rainstorm. The typhoon rainstorms in North China are the result of the interaction of the westerly, subtropical and tropical systems. In this heavy rain period, there was an obvious interaction between subtropical and tropical systems. This study has investigated the interaction between the northwestern Pacific typhoon and the North China heavy rainstorm, including the circulation characteristics of the typhoon and North China before and after the regional heavy rainstorm. Additionally, the climate background provides a reliable basis for the heavy rain forecast.

诱发台风暴雨型滑坡的降雨阈值研究——以泰顺县为例

在我国东南沿海地区,台风暴雨诱发了大量山体滑坡。建立诱发台风暴雨型滑坡的降雨阈值模型,可为该地区的滑坡预警提供参考依据。基于浙江省泰顺县2007—2022年以来发生的滑坡信息和日降雨量数据,进行了诱发滑坡的台风暴雨事件编目,初步揭示了台风暴雨型滑坡的发育规律和触发降雨特征,通过降雨强度(I)、降雨历时(D)的幂律关系构建了滑坡临界降雨阈值模型,并开展了不同台风降雨雨型的阈值模型对比。结果表明:台风暴雨型滑坡大量发生在与台风登陆方向接近的迎风坡,坡表植被多为乔木和竹林;诱发滑坡的台风降雨一般持续2~3 d,且降雨过程集中,降雨雨型以单峰型为主,总降雨量一般在200 mm以上;台风暴雨诱发滑坡的降雨阈值显著高于一般性的降雨,这种差异与台风降雨模式及大尺度气候环境有关;雨型也会显著影响降雨阈值,随着降雨峰值的后移,阈值逐渐降低,表明台风暴雨型滑坡对长时间降雨后出现的强降雨事件更加敏感。通过降雨阈值模型对9次台风降雨事件是否诱发滑坡进行了预测,预测结果与实际情况比较吻合,证明该模型及研究思路对台汛期东南沿海的滑坡监测预警有较强的参考价值。

The Influence of Typhoon Usagi on Shaoyang City

[Objective] The research aimed to study the influence of typhoon Usagi on Shaoyang in 2013. [Method] By using synoptic analysis, physical quantity diagnosis and Doppler radar, a rainstorm process caused by typhoon Usagi was analyzed. [ Result] Sufficient water vaper and strong ascending motion caused by high-altitude divergence were favorable conditions for rainstorm generation in Shaoyang. Uplifting effect of the terrain in Shaoyang was also one of favorable conditions for rainstorm generation in Shaoyang. [Conclusion] The research could provide reference for flood prevention and disaster reduction in Shaoyang area.

Analysis on "96. 8" Heavy Rainstorm Process in Handan

[ ObjEtive] The research aimed to analyze ＂96.8＂ heavy rainstorm process causing flood disaster in Handan. [ Method] Based on ac- tual situation data, satellite cloud data and NCEP reanalysis data in the first dekad of August in 1996, ＂96.8＂ heavy rainstorm process causing flood disaster in Handan was analyzed to understand occurrence reason of the flood disaster. [ Result] Two meso-scale convective cloud clusters which developed and went north in turn caused ＂96.8＂ heavy rainstorm in Handan. Typhoon and inverted trough were main weather systems induced flood disaster in Handan. In going north process of the low-level jet, due to blocking of the subtropical high, water vapor and energy accumulated in Handan, providing material basis for formation of the heavy rainstorm. Development and eastward movement of the short-wave trough at middle lati- tude and continuous invasion of the reflux weak cold air at the low layer were direct reason for triggering generation and development of the convec- tive cloud cluster, and further causing continuous rainstorm. Wet layer over the rainstorm zone was deep and thick. Meridional distribution of the wet zone was wider than latitudinal distribution. South China Sea and Bay of Bengal were water vapor sources for the rainstorm zone. In the whole rain- storm period, it was convergence at low layer and divergence at high layer in the rainstorm zone. It was positive vorticity at low layer and negative vorticity at high layer. Precipitation intensity changed as convergence and divergence. Rainstorm zone had strong ascending motion. As strengthe- ning and uplifting of the ascending motion strong center, strong precipitation also strengthened. Rainstorm center was near the biggest vertical ve- locity center. Strong precipitation changed as vertical ascending motion. [ Conclmion] The research provided scientific basis for disaster prevention and reduction and decision-making service.

基于注意力机制的CNN-LSTM-XGBoost台风暴雨电力气象混合预测模型

极端台风暴雨灾害具有非线性、极差大以及多峰值等特点。为使电网及时获取预警信息,提出一种基于注意力机制的CNN-LSTM-XGBoost台风暴雨电力气象混合预测模型。首先,利用基于注意力机制的卷积神经网络(CNN)辨识关键台风暴雨灾害特征;然后,利用长短期记忆网络(LSTM)训练时间序列预测模型以挖掘台风暴雨时序特征,使用极限梯度提升算法替换模型输出层以缓解过拟合问题;最后,以2023年台风泰利为例验证所提方法的有效性。算例分析表明,所提模型具有较高的准确性,对预测精度的提升可达40.84%以上。

台风“美莎克”对黑龙江的影响及其非对称结构特征

使用常规观测资料及ERA5(0.25°×0.25°)再分析资料,对2009号台风“美莎克”进行分析。结果表明:此次过程,副热带高压异常强大,位置偏北,并与北侧阻高合并形成高压坝阻挡;“美莎克”沿副高外围北上与中纬度低涡及冷空气相互作用,变性后斜压性明显加大,低涡增强;“美莎克”携带大量水汽,同时中低空急流将海上水汽持续向黑龙江输送,并在黑龙江强烈辐合,形成强的水汽辐合区和水汽辐合带;高低空急流耦合构成强的垂直环流,对应非常强的垂直上升速度;副热带高压向西北伸展,高空引导气流和热成风方向转为西北-东南向,促使“美莎克”登陆后向西北移动,穿过黑龙江,是黑龙江出现大暴雨的主要原因。分析台风中心涡度、散度、垂直速度、位温、湿位涡等物理量的三维结构变化,认识台风在北上登陆中的变性过程以及降水出现非对称结构的原因。

台风暴雨型泥石流启动机理物理模型试验研究

台风暴雨型泥石流具有很高的突发性、群发性和破坏性,对这种特殊类型泥石流启动机理的研究尤为重要。以“利奇马”台风引发的安徽宁国抽水蓄能电站库区泥石流灾害为典型案例,在现场勘探、调查、测试的基础上,查明了泥石流沟谷特征、形成条件及物源分布;采用人工降雨物理模型试验方法,监测降雨过程中土体孔隙水压力、体积含水率、土压力和侵蚀特征等指标变化,研究了台风暴雨型泥石流的启动机理。结果表明:①台风暴雨型泥石流过程分为降雨入渗、超渗径流、物源侵蚀堆积、短历时强降雨启动4个阶段。②台风暴雨型泥石流发生在浅层土体达到高含水率和高孔隙水压力之后,需要前期一定的累积降雨。③较小雨强条件下沟谷产生稀性泥石流,降雨强度的陡增引起径流强度及侵蚀作用急剧加强,大量固体物质启动,暴发的泥石流由稀性转为黏性,沟口可见较大规模堆积扇。④整个沟谷均可见侵蚀沟道不同程度贯通分布,沟道侵蚀深度随高程的降低呈现增大趋势。研究结果可为台风暴雨型泥石流灾害风险防控提供参考。

1632年华北地区暴雨洪涝事件研究

以历史文献为主要代用资料,重建了1632年华北地区暴雨洪涝事件的雨情、水情、灾情等,从而识别出1632年8月河南地区暴雨事件的时空范围,并与有器测记录的2021年河南极端降水事件进行对比。1632年华北地区大规模降水始于7月17日,从6月18日—11月11日,整个华北不同区域皆存有长时间降雨记录,且有多次强降水记录,造成黄淮地区雨涝,并使得黄淮交溃,对社会经济造成较大影响。梳理降水和洪涝的过程,区分了本地降水与客水的分布。将1632年8月河南暴雨洪涝与2021年7月河南极端降水事件对比发现,强降水位置相似,降水前后都有两个台风输送水汽,且1632和2021年华北地区夏季降水皆受到拉尼娜的影响,整体偏涝。

两次北上台风引发冀北极端降水的对比分析

利用NCEP/NCAR再分析资料、自动气象观测站数据,分析发生在河北省承德市的“安比”(1810)台风暴雨和“海棠”(1710)台风暴雨过程,比对冷空气活动、作用形式及其对降水的影响。结果表明:(1)两次过程在中纬度西风槽冷空气影响下的降水差异明显,“海棠”暴雨雨强明显强于台风“安比”,但后者降水生命史更长;(2)“海棠”残余环流北上影响承德市时,西风槽冷空气主体沿西北气流入侵环流,而台风“安比”暴雨过程仅受西风槽分裂出的弱冷空气影响。由于冷空气影响形式不同,前者的正涡度带沿切变区分布,大值区位于残余环流东侧,而后者的正涡度沿西风槽和台风环流分布,大值区位于环流西北侧。两次过程低层冷空气入侵均先于高层,较强冷空气影响台风环流时,有利于降水强度增强;弱冷空气影响环流时,则有利于降水强度维持。

副热带高压内部台风远距离暴雨特征和机制个例分析

为了提高对副高内部台风远距离暴雨特征和机制的认识,综合利用多源观测和ERA5再分析资料,对2018年台风“山竹”在副高内部引发的一次远距离暴雨过程进行分析。结果表明:①这次暴雨发生在500 hPa副高内部高温、高湿、高能的强对流不稳定环境中,暴雨区位于低层台风倒槽北端、偏南气流风速辐合区和高空急流入口区右侧。②低层暖湿平流提供了充足的水汽和能量,促使对流不稳定层结发展和维持;高层强辐散耦合低层辐合形成强烈上升运动,为暴雨提供有利动力条件。③中尺度对流系统有3个演变阶段:带状对流组织和建立、对流带北移南侧超级单体发展和移动、北部对流减弱南部对流带新建发展,造成了两个阶段的极端短时强降水(100 mm/h以上)。④低层华北高压先后与台风倒槽、海上高压结合,增强了低层辐合并维持了切变线(地面辐合线),利于对流的发展和维持。台风倒槽是初始对流带的触发和组织者,雷暴冷池出流是超级单体发展移动的关键因素。⑤高空急流的辐散抽吸强迫中层辐合,正涡度和低槽发展,暴雨区垂直风切变增强,利于南部对流带发展。当低纬度有台风活动时,500 hPa副高内部低层有台风倒槽,台风倒槽北端的辐合区是远距离暴雨预报的着眼点。

极端异常台风“美莎克”北上过程诊断分析

为更好地分析极端异常北上台风“美莎克”的影响机制,利用ERA50.5°×0.5°逐6 h再分析资料,FY-2G卫星资料,NCEP再分析资料及东北地区常规气象观测资料,就台风北上过程的大尺度环流背景、动力、热力、水汽条件等方面进行诊断分析。结果表明,西太平洋副热带高压与鄂霍茨克海上的高压脊合并加强、稳定维持是造成“美莎克”北上的主要原因,与西风带低涡相互作用使得台风持续时间较长,台风结构在与西风带系统逐渐融合且北上的过程中强度逐渐减弱,雨强也随之迅速减弱。高空急流的抽吸作用及低层辐合、高层辐散的配置,使降水稳定维持,3条水汽通道的建立使多地区出现台风暴雨,物理量条件的非对称性分布造成了降水的非对称性。台风登陆前后不稳定性有所变化,登陆后短时间内不稳定性增强对应着降水的增幅,登陆后主要以稳定性降水为主。干冷空气入侵初期增强了降水不稳定性,冷空气的深入使台风暖心结构遭到破坏,随后减弱变性。

台风“安比”变性机制及其对内蒙古大暴雨影响的数值模拟研究

台风“安比”是首个进入内蒙古的热带气旋,引发了该地区中东部的罕见致灾性大暴雨。本文利用中尺度数值预报模式(Weather Research Forecast,WRF)输出的模拟结果、美国国家环境预报中心/国家大气研究中心(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)再分析资料、台风路径数据及常规观测资料等,对“安比”北上过程中的变性机制及其对内蒙古大暴雨天气的影响进行了分析。结果显示:大暴雨过程的大尺度环流背景是台风与中高纬西风带高空槽的相互作用,西风槽提供的冷空气与台风的暖湿气流交汇引发了此次大暴雨;在西风槽并入台风的过程中,冷空气自西向东楔入并向下扩散东移,产生强烈的冷平流,推动暖湿空气抬升,破坏了台风的正压暖心结构,并形成“东暖西冷”的不对称温度结构,导致台风变性为温带气旋;主要的降水区域位于MPV1正值区与MPV2负值区的重叠区,区域的对流不稳定和斜压不稳定能量积聚,促进强降水的发展;冷暖空气的交汇区出现强锋生作用,形成明显锋区,为大暴雨提供动力条件,锋生带附近有明显次级环流圈形成,锋前为上升气流,锋后为下沉气流,强降水区域对应上升气流最强区域。

台风暴雨下某建筑边坡稳定性分析研究

福建省由于独特的地理和气候条件,经常遭遇台风暴雨,导致滑坡灾害频发。基于强度折减理论,采用FLAC^(3D)软件,对福建龙岩市受2023年9月台风“海葵”中影响的某建筑边坡进行稳定性分析。考虑自重和台风暴雨2种工况,分析边坡的变形破坏机理。结果表明,在自重条件下边坡安全系数为1.676,处于稳定状态;台风暴雨后,安全系数下降至1.230,低于规范值,显示出失稳破坏的风险。台风季节的滑坡风险显著增加,边坡截面中塑性贯通破坏区域约5.0 m^(2),与实际滑坡面积相比误差为11.1%,为极端天气条件下的边坡稳定性评估提供了重要参考。