AN OBSERVATIONAL ANALYSIS OF A TORRENTIAL RAINSTORM IN THE WARM SECTOR OF SOUTH CHINA COASTAL AREAS

On May 20 th 2007, a brief but severe downpour rainstorm occurred in the coastal areas of Maoming and Yangjiang with rainfall of 115 mm per hour. Data from NCEP/NCAR reanalysis with 1°×1° resolution, Doppler weather radar, conventional surface observations, high-altitude radiosonde and wind profiler radar were used to analyze characteristics and contributions of synoptic scale and mesoscale systems during this torrential rainstorm. The results showed that:(1) the storm was caused by a quasi-linear mesoscale convective system(MCS) and the slow-movement of this system was the primary trigger of the torrential downpour;(2) water vapor was abundant, nearly saturated and in steady state throughout the atmosphere before the storm; intrusion of the weak dry and cold air in the middle level and a striking "dry above and wet below " structure had increased the atmospheric instability;(3) low-level southwesterly airflow from a low pressure(trough) at the Beibu Gulf provided abundant water vapor at the onset of the rainstorm; a deep dry layer was formed by dry and cold air behind the high-level trough, which facilitated latent heat release;upper-level divergence and low-level convergence circulations also provided vertical uplift for warm and moist air at the lower level;(4) Topography only played a minor role as the MCS developed and strengthened over relatively flat coastal terrain. Low level density flow induced by convection triggered new convective cell generation at the leading edge of the convective system, thereby playing a key role in the change of temperature gradient at lower layers, and resulting in strengthening atmospheric instability.

Study on Temporal-spatial Distribution of Heavy Rain and Rainstorm in Different Functional Areas of Chongqing

To discuss response ability of five functional areas to rainstorm flood in Chongqing,by taking 8 districts（ counties） as research object,monthly occurrence times of heavy rain and rainstorm in different functional areas over the years and appearance month of the maximum rainfall were conducted statistics. Results showed that frequency distribution of heavy rain in whole year in different functional areas was different,but it was similar in the same functional zone. Temporal-spatial distribution of rainstorm was more independent,and there were different performances in various districts of each functional area. In urban functional core area and urban functional expansion area,rainstorm times was more,and the maximum precipitation was larger. In urban development new district,rainstorm times and the maximum precipitation were relatively smaller in whole Chongqing. In ecological conservation development area of northeast Chongqing,rainstorm duration was longer,and we needed prevention and control during June- September. In ecological protection area of southeast Chongqing,although rainstorm occurrence times was the most in Chongqing,the heavy rainstorm was less.

基于FloodArea模型的山西山谷地区暴雨洪涝灾害风险特征分析

基于1992—2021年降水观测数据和气象灾情数据,采用FloodArea模型对沁水经济技术开发区所在山谷地区不同重现期下的暴雨洪涝淹没范围进行模拟评估.结果表明:研究区所在地区不同重现期小时雨型呈多峰分布,山谷效应导致雨水汇流,淹没水深和面积增加,具有一定的暴雨洪涝风险;区内大部分淹没面积在10cm^(2)以下;内涝等级为一般性内涝风险(10~25cm)的淹没面积为0.48km^(2),主要呈散点状分布于研究区各片区;中度内涝风险(25~50cm)的淹没面积为0.41km^(2),主要呈散点状分布在端氏综合服务中心周围;严重内涝风险(50~80cm)的淹没面积较少,为0.32km^(2);特别严重内涝风险(>80cm)的淹没面积为4.74km^(2),主要集中分布于北部产业片区和南部产业片区的偏西地区.各重现期淹没风险较大的区域主要分布在各个片区内低洼地区,与实际灾情相符.

Study of One Rainstorm Being Affected by Two Weather Systems in Jinzhou Area

[Objective] The aim was to study one rainstorm process being affected by two weather system. [Method] Influenced by high trough and Mongolia cold front, high latitude trough and subtropical high shear, rainstorm occurred in Jinzhou from October 19 to 22 in 2010. In order to make the analysis clear, there were two precipitation stages. Considering precipitation, weather situation, satellite image and numerical forecast, the rainstorm process was discussed. [Result] There were two raining stages during this precipitation. The first stage was affected by high altitude trough and ground Mongolia cold front, and the last stage was influenced by high altitude trough and subtropical high shear;the high latitude air, low latitude shear,low air torrent,subtropical high and their mutual coupling effect were the main influencing system and cause for this rainstorm. Satellite image suggested that there was convective cloud developing,weakening, disappearing and regenerating around the convective cloud of water vapor passage, showing distinct train operation state. The strengthening and weakening cloud image fitted the real precipitation. Numerical forecast precisely predicted the upper air and ground situation of the generation of rainstorm, especially the report of the east-retreating and south-falling trend of subtropical high;European center forecast fitted reality. There was certain error in predicting T639. Precipitation forecast was fine. [Conclusion] The study provided basis for the meteorological service work in future.

Study on the damage of the “91．7” rainstorm in Sihu drainage area with remote sensing application technique

In this paper, the water equilibrium and ground truth are analyzed for '91.7' rainstormin Sihu drainage area, Hubei Province, China. The flood and waterlogging situation of ' 91.7'rainstorm in this area are investigated using remote sensing, especially the estimation of inundatedarea, the analysis of temporal and spatial characters of this flood and waterlogging damage. Andthe way of flood-trace using remote sensing is explored. At last, the disastroiis conditions are evalu-ated.

Output Characteristics of Non-point Nitrogen and Phosphorus from a Typical Small Watershed in Yimeng Mountainous Area during a Rainstorm

[ Objective] The study aimed to reveal the output characteristics of non-point nitrogen and phosphorus from a typical small watershed in Yimeng mountainous area during a rainstorm. [Method] The dynamic changes of pollutant concentration, precipitation and flow during the rainstorm on August 12, 2010 were monitored at the outlet of Menglianggu watershed. [ Result] During the rainstorm, the generation of runoff was sudden and ephemeral, and the peak of the runoff lagged behind that of rainfall intensity; the concentration of AN and TN increased firstly and then tended to be stable, while NN concentration had no significance change at the beginning of the rainfall, then improved gradually and tended to be stable fi- nally; DOP concentration had no obvious change during the rainstorm, but the concentration of DIP, DP, PP and TP rose firstly and then tended to be stable, and the peak values appeared before the peak of the flow. In addition, the output concentration of TN and TP was far higher than the standard concentration of water eutrophication. [ Conclusion] The study can provide scientific references for the reasonable control of non-point source pollution pollution in Yimeng mountainous area.

某工程泄水建筑物泄洪雾化范围计算分析

为了减少泄洪雾化带来的工程影响和损失,笔者结合工程实例,根据理论公式对表孔溢洪洞、泄洪冲沙洞在不同水位下的雾化范围进行估算,并依据估算结果提出针对性工程设计建议。结果表明:表孔溢洪洞在校核洪水位下雾化影响范围最大;该工程的厂区虽位于强暴雨区横向影响范围以外,但处于雾流降雨区范围之内,设计时需考虑雾化对厂区电气设备带来的不利影响;出口边坡局部位于强暴雨区和雾流降雨区范围内,需对边坡进行加固处理并采取表面防护措施,确保边坡运行安全稳定。计算成果可为工程布置、设计提供理论支撑。

基于综合强度指数和受灾面积的区域性暴雨过程的客观识别及特征分析

本文提出一种基于综合强度指数和受灾面积的区域性暴雨过程客观识别标准确定方法。以河北省为例,利用1971~2020年河北省142个国家气象观测站逐日降水数据,选取最大过程降水量、最大日降水量、影响范围、持续时间、平均强度和平均范围为评估指标,构建了6种区域性暴雨过程综合强度指数模型;基于综合强度指数与受灾面积相关性分析,判定最优的综合强度评估方法,进而确定了河北省区域性暴雨过程的最优客观识别标准。利用本标准对河北省区域性暴雨过程进行识别,并分析时空变化特征。结果表明:本方法可有效确定区域性暴雨过程识别标准,识别结果与灾情资料具有较好的一致性和相关性,适用于区域性暴雨过程客观化识别,易于应用推广。1971~2020年,河北省共发生区域性暴雨过程252次,年均5.0次,发生次数呈下降趋势,综合强度指数呈不明显下降;区域性暴雨过程4~11月均有发生,主要集中在7、8月,出现次数占全年总次数的77%;区域性暴雨过程发生站次分布呈西北少东南多的趋势,主要集中在中部、南部和环渤海地区,西北地区最少。

湿润地区暴雨特征对城市化响应研究

人类活动使得暴雨发生频率和强度增加,暴雨特征发生显著改变。厘清城市化对暴雨特征的影响对城市防洪减灾具有重要意义。以中国广东省广州市为例,利用处于不同行政区的11个雨量站点在2006—2019年期间收集到的逐15min降水数据,识别场次暴雨;从暴雨雨量、日数、雨强、次数、雨型、雨峰占比和雨峰系数7个方面,分析湿润地区暴雨特征对城市化的响应表现。结果表明:(1)城市化率较高区的暴雨雨量、日数、强度和次数均高于城市化率较低区,暴雨次数在时序变异性上则相反;(2)城市化对暴雨雨型无显著性影响,广州市各区雨型占比差异不大,且暴雨大多为单峰型,占比约63%;(3)暴雨雨峰占比对城市化响应不明显,其与降雨历时呈负相关关系,短历时暴雨特征由峰值雨量主导,而长历时和超长历时的暴雨事件中的持续时间是影响雨量的主要因素;(4)广州短历时和超长历时暴雨雨峰系数受城市化影响显著,城市化率较高区明显高于城市化率较低区;此外,广州暴雨雨型大多为前期集中型单峰暴雨,但城市化率较高区的超长历时暴雨大多偏后期集中型,需要特别注意。

2021年6月东北冷涡暴雨水汽来源和源区贡献分析

本文针对2021年6月2~3日发生在东北地区的冷涡暴雨过程,首先利用传统欧拉方法,初步分析了此次初夏东北冷涡暴雨过程的水汽输送与辐合特征,进而利用拉格朗日轨迹追踪模式FLEXPART和水汽来源与源区定量贡献分析方法,揭示出此次暴雨过程的水汽源地和源区定量贡献。结果表明:此次初夏冷涡暴雨过程期间,副热带高压偏南,东北地区主要受东北冷涡和其下游日本海弱高压脊影响,但对流层低层,副高主体与日本海弱高压脊之间存在气旋性切变流场,促成一支低空急流沿我国沿海地区北上,有利于东北地区南侧水汽向北输送,与东北冷涡后部干冷空气在辽宁和吉林省交汇,触发强降水。拉格朗日轨迹追踪显示,60%以上的目标气块来自降水区西侧和西北侧的亚欧大陆地区,这些气块初始位置高度较高,途径我国东海、黄海一带时,高度显著降低,并汇入偏南暖湿气流,进而流入目标降水区;还有部分气块来自贝加尔湖及其以东地区以及我国南海和中南部大陆地区,气块初始位置及行进过程中高度均较低。水汽源区对目标降水区的水汽定量贡献显示,东海—黄海至西北太平洋地区贡献最大(贡献率37.04%),中国大陆中东部紧随其后(贡献率30.05%),显著的水汽摄取和较低的沿途损失,使得上述两区域水汽贡献显著,而降水区局地摄取水汽的贡献排在第三位;此外,贝加尔湖及其以东地区和亚欧大陆中西部亦有一定贡献(尽管亚欧大陆中西部的水汽摄取总量亦较大,但绝大部分水汽在远距离输送过程中损耗),而印度半岛至中国南海地区水汽贡献最小。相对于传统的欧拉方法,拉格朗日方法可以更清晰地给出暴雨过程主要的水汽源地及其贡献。

河西走廊西部一次暴雨过程降水特征及极端性分析

2022年8月12日20:00至13日20:00(北京时)酒泉市金塔县发生一次极端暴雨过程,金塔站24 h降水量和小时降水量均突破历史极值。利用逐分钟、逐小时、日降水观测数据及地面-雷达-卫星三源融合降水分析产品(CMA Multi-source Merged Precipitation Analysis System, CMPAS)1 h降水量数据,分析了此次暴雨天气过程的降水特征及极端性。结果表明:此次暴雨过程具有过程雨量大,局地性强,小时雨强强,对流性明显等特征,主要降水时段为夜间,暴雨中心位于酒泉市金塔县。11个气象观测站累计雨量达建站以来最大值,金塔站88 mm,是酒泉市所有国家气象观测站降水观测的次大值,超过62年来(1961-2022年)汛期平均值的58%;13个气象观测站小时降水量达建站以来最大值,金塔站56.2 mm,位居酒泉市所有气象站小时降水量的首位,接近62年来金塔站8月平均雨量的3倍,历史极端性明显。金塔站有3个降水时段,强降水主要发生在第二时段,逐分钟降水强度强,持续时间长。强降水中心首先出现在金塔站东南部,随后向西北移至金塔站附近,且强降水范围扩大,持续3 h后降水强度减弱并向东南方向移出,暴雨区降水过程结束。

2020年我国梅雨期暴雨特征及ECMWF暴雨落区订正分析

利用常规地面和高空资料对2020年我国梅雨期暴雨特征进行初步分析,按照925hPa锋区性质对暴雨过程进行分型,最后通过两个典型暴雨个例讨论ECMWF数值预报的订正思路.结果表明:①在27次梅雨期区域性暴雨中,有26次暴雨与925hPa切变线位置吻合,只有18次与850hPa切变线位置吻合.②按照925hPa锋区位置和强弱,可将梅雨期暴雨分为无锋区暴雨、强锋区暴雨、弱锋区暴雨和混合型暴雨;按照锋区移动方向可将强锋区暴雨分为南压型、静止型和北抬型暴雨;按照暴雨落区与锋区位置关系可将弱锋区暴雨分为弱强迫暴雨和冷区暴雨.③EC对无锋区型暴雨预报较差,对强锋区暴雨预报有偏北趋势(20次中有14次偏北,2次正确,4次偏南),对弱锋区暴雨预报有偏南趋势(11次中有8次偏南,1次正确,2次偏北).④从典型暴雨个例上也能看到,925hPa切变线和温度锋区位置与暴雨落区相吻合;中尺度数值模式有时候能较好地弥补EC全球数值模式对锋区降水的不足.

Dry Intrusion Analysis of A Heavy Rainstorm in Southern Shaanxi

[Objective] One regional rainstorm weather in the south area of Shaanxi was expounded.[Method] By employing the NCEP/NCAR 1°×1°reanalysis data,routine observation and automatic precipitation station data,the large scale circulation background field of regional precipitation in the south area of Shaanxi province from July 16-18 in 2010 was expounded.By dint of physical quantity such as the meridional wind,relative humidity and false relative temperature,the characteristics of dry intrusion and its role in rainstorm were expounded.[Result] The mild and high latitude at 500 hPa was stable.The continental high pressure and subtropical high pressure were stable.The 700 and 850 hPa shear lines or low vortexes were the main influence system that resulted into large scale of rainstorm in south Shaanxi.The landing typhoon had distinct influences on the importance of storm.The influence of typhoon and subtropical high was mutual.It not only formed and strengthened the torrent in the low air,also transmitted water vapor and energy incessantly to the south area of Shaanxi,playing an important role in augment of rainstorm.There were two distinct dry intrusions in the rainstorm process,showing a dense dry layer in the high layer of convective layer.The existence of dry layer was conductive to the accumulation of convective unstable energy in the low layer.The release of convective unstable energy could transmit warm and wet airstream in the low level to the higher level,being conductive to the occurrence of precipitation.The analysis of θse in the warp direction vertical profile suggested that there was frontal zone in this rainstorm process and the dry air activity in this rainstorm process was very strong.[Conclusion] The study provided theoretical reference to the forecast in future.

江西省宜春市城区暴雨统计特征及致涝分析

文章基于宜春国家基准站1961-2020年日雨量资料、气象灾害风险普查资料、暴雨日天气形势场资料、江西WebGis雷达拼图产品和历史内涝信息等资料,对宜春城区暴雨日特征进行统计并开展致涝分析。结果表明:宜春市城区年平均暴雨日4.0天,年平均大暴雨日0.6天,2天以上连续暴雨占7.4%,有显著单波峰月、季分布特征,年代变化表现为20世纪70年代陡然减少之后缓慢增加;利用小波分析表明,暴雨日高频周期由2~4年增加到4~6年,2000年后出现14~16年低频周期变化特征,Mann-Kenddall检验表明2018年发生突变;宜春城区暴雨天气形势主要有槽前切变急流暴雨、梅雨锋暴雨、副高边缘暴雨、台风外围暴雨和冬季冷空气暴雨等;多普勒雷达回波表现为絮状、块状或短带状,中心强度经常达到50~55 dBZ;从历史洪水事件和近10年短时强降水致涝来看,36 h降雨量超过150 mm是出现大面积洪水内涝的基本条件,而对于短时强降水,连续2 h降水量超过45 mm时,则容易出现严重内涝,连续2 h降水量达到60 mm以上,内涝范围将显著增加。研究结果为宜春城区暴雨预报提供参考依据。

多灾情景下城市区域Natech风险应对分析

为更好地应对自然灾害诱发的技术灾难(Natech事件)产生的复杂多灾情景风险,提出城市区域Natech风险应对需求满足性评估方法,基于对城市区域单元的划分,评估单元的风险应对需求等级和单元内的风险应对资源满足性,并完成对我国某市某区域风险应对需求满足性的分析,提出对策建议。然后,基于国内外城市暴雨—洪涝案例,运用情景理论构建城市区域暴雨—洪涝的情景模型,定量分析风险应对要素在Natech事件多灾情景中的应急响应作用。研究结果表明:只有当各种类型的风险应对需求均满足时,才能更好地提升应急响应水平。研究结果可为多灾情景下的城市区域Natech风险应对提供科学参考和建议。

皖南初春平行线状对流系统引发的大暴雨分析

利用多源气象观测资料和欧洲中心ERA5再分析资料研究2022年3月中旬安徽南部的一次大暴雨过程。结果表明:受稳定的贝湖东部低槽、西北太平洋副热带高压与东移加强的华西疏散槽共同影响,地面冷锋快速南下,引发大暴雨的中尺度平行线状对流系统形成于地面冷锋附近大别山区南部迎风坡上并向东移动,呈现出列车效应。对流层中低层西南急流、低涡切变、大的垂直风切变为其发展、维持提供了有利的环境条件;复杂地形对平行线状对流系统的发展演变具有重要作用,山地增强了南北水平温度梯度,并通过迎风坡或喇叭口的近地面风场辐合不断产生新的上升气流,低层对流触发后不断随着偏南气流北移,形成线状对流系统,呈现出后向传播特征;整个平行线状对流随着中层引导风向偏东方向移动,强降水中心太湖不仅有东南风与北侧绕大别山区南下的东北风辐合,且处于迎风坡的喇叭口,地形抬升加强辐合作用,对流发展最为旺盛;双偏振雷达参量和雨滴谱仪显示,太湖上空为粒子数密度大的大雨滴,降水效率高。

2023年里下河地区暴雨洪水分析

里下河地区地势平缓,河网错综复杂,水势传播较慢,易发生超警戒洪水过程。为研究里下河地区梅雨期降雨特点,采用皮尔逊Ⅲ型频率曲线法、距平分析法和降雨水位逐时过程图法,针对里下河地区2023年梅雨期暴雨洪水过程,通过与历史梅雨期降雨进行对比,全面分析了里下河地区梅雨期暴雨洪水特征。结果表明,里下河局部地区无降雨与极端降雨情况并存,在最大1天降雨中存在特大暴雨,最大3天降雨中出现特大暴雨的地方占8.4%。短时间强降雨加上里下河地区河网地势特征是发生超警戒洪水过程的主要原因。洪水过程下沿江抽排及五大港抢排对里下河地区水位变化有较明显影响。

基于多普勒雷达探测技术的沿海地区暴雨预警方法

依靠单一的波束反射率特征信息,其预警结果的虚假警报比例较高,对此,提出基于多普勒雷达探测技术的沿海地区暴雨预警方法。运用多普勒雷达探测技术捕捉雷达波束反射因子后,提取隐藏的径向辐合参量,得到全面的天气雷达数据,并通过退速度模糊方法进行数据修正。以梯度下降算法为核心,对目标气象数据进行反演分析。通过TITAN算法识别暴雨云团,建立雷达回波特征匹配方法明确暴雨云团状态。最后,通过WSR-88D探测算法计算暴雨指数,实现沿海地区暴雨预警。结果表明,所提方法的虚假警报比降低了17%与24%,准确完成了沿海地区的暴雨预警。

浙江沿海两个台风暴雨环流过程的对比分析

“烟花”和“梅花”是两个均在浙江舟山登陆,并在浙江沿海产生强降水的热带气旋。本文利用常规气象站观测资料和ERA5再分析资料,对两个台风影响浙江沿海并造成台风暴雨的成因进行对比分析。结果表明:①“烟花”受多系统、缺少明确引导气流环境的影响,移动缓慢,降水时间长;“梅花”受冷空气南下渗透影响,台风变性,多集中性暴雨发生。②“烟花”有两条水汽输送带和两个明显的水汽辐合区,为长时间暴雨提供充足水汽;“梅花”只有一条水汽输送通道,但有一个相较“烟花”更加强烈的水汽辐合区,使暴雨落区更加集中,雨强更大。③“烟花”受长时间低层暖湿气流和垂直风切变维持的影响,降水时间长,但强度较弱;“梅花”影响期间,上升运动强烈,降水效率高,降水多由短时暴雨形成。

四川盆周山地暖季单站暴雨事件的精细特征

利用四川省2010—2019年2165个气象站逐小时降水资料,分区统计了四川盆周山地暖季(5—9月)单站暴雨事件的精细特征。结果表明:(1)四川省单站暴雨事件频数在川西山地与川西南山地呈密集的带状分布。川西与川西南山地通常在降水开始不久就达到雨量最大值,而川东北山地的峰值时间集中在暴雨事件中段。(2)盆周山地的暴雨系统整体呈自南向北由前半夜向后半夜传播的特征。川西南山地和川东北山地的暴雨系统分别呈现较弱的自南向北和自西向东传播,而川西山地的暴雨系统则存在明显的自西向东的传播特征。(3)长历时暴雨事件的峰值出现时间略落后于短历时暴雨事件。暴雨持续时间在空间上存在显著的经向差异,大值区主要位于川西山地和川东北山地一带,暴雨雨量、频次和峰值基本不随持续时间变化,但川西南山地的暴雨峰值则随持续时间的加长而推迟。(4)在四川省大部区域,单站暴雨事件的降水量、频次和强度均表现出随海拔高度升高而减小的特征。在成都平原西南部、东部以及川东北山地,夜间暴雨事件持续时间越长,降水量和频次在较高海拔越易出现最大值。