台风变性过程中下游环流发展的个例对比研究

台风在温带变性过程(Extratropical Transition,ET)中与中纬度系统的相互作用会引起下游环流的发展,选取3个台风个例,通过分析涡动动能收支和理想化模拟实验对其下游发展机制进行研究。3个台风的变性过程所引起的下游发展都具有共同的机制,即首先在上层下游有脊和槽先后发展,随后激发低层涡旋生成,并与之耦合,形成一个贯穿整个对流层的深厚气旋系统。促使下游脊生成和发展的非地转位势通量源于台风,高层系统向下输送的垂直非地转位势通量在低层辐合,使得涡旋在低层发展。模拟实验表明,台风出流向中纬度急流区域输送低位涡(Potential Vorticity,PV)空气,使得其PV梯度增大和斜压性增强,从而激发了Rossby波在急流中生成并沿之向下游传播,而下游槽脊对引起更下游波型的发展也是通过Rossby波的频散而达成。     

超强台风Saomai(0608)加强成因分析及 海温影响的数值试验研究*

以严重影响我国的2006年8号超强台风Saomai为研究对象,首先从大尺度环流特征和物理量场对其登陆前强度不断加强成因作诊断分析,指出台风加强与副高的加强和南落、低空持续加强的水汽输送、高空流出气流的强辐散、台风移向垂直切变小值区和暖洋面密切相关。然后,利用中尺度数值模式MM5分析了海温高低对台风强度变化的影响,试验结果表明台风强度对海温十分敏感,海温改变可以引起台风强度的迅速变化,海温降低2℃将使台风最终减弱19hPa。边界层通量的分析表明,海温变化对台风强度的影响中潜热通量的作用是主要的,而感热输送的作用较小。就海温变化是否引起诸多台风强度影响因子分析发现,高海温使台风区域低空气旋式环流和高层辐散流出加强,导致低空更多的水汽向该区辐合,暖海面上空潮湿空气的辐合上升释放大量的凝结潜热为台风的发展加强提供了更多的水汽和能量。对比试验还表明,正位涡向下输送预示着台风将快速加强。另外,本次试验中海温变化对台风移动路径影响不明显, 因而对环境风的垂直切变影响较小。     

长江三角洲区域性暴雨的统计诊断分析

利用1954年～1983年5月～8月气象资料,统计了影响长江三角洲地区的区域性暴雨类型。分析了1962年14号强台风的路径、暴雨落区以及产生暴雨的气象条件。诊断结果表明,有利大气环流形势、台风倒槽辐合线、低空东南急流、上升运动和强大的水汽通量与通量辐合是产生"6214"台风大暴雨的重要条件。     

“4·23”南疆翻山型强沙尘暴动力结构特征分析

利用2014年4月22日-23日高空、地面、区域自动气象站加密观测和1°×1°NCEP/NCAR再分析资料,分析4月23日南疆翻山型强沙尘暴天气的高低空环流及动力结构特征。结果表明:巴尔喀什湖低槽引导极地干冷空气爆发性南下进入南疆,造成4×10-2h Pa·km-1剧烈的气压梯度和地面冷锋,引发了大风、强沙尘暴,盆地中尺度低压辐合使尉犁加强为"黑风";300 h Pa极锋急流快速南下至南疆盆地,动量下传形成低空急流,高低空急流是此次强沙尘暴形成的动力条件;急流附近高空辐散、低层辐合及层结不稳定,有利于沙尘暴发生。本次强沙尘暴动力结构特征:干冷与干暖空气剧烈交绥,激发热力不稳定,产生热力对流;高空辐散、低层辐合与高低空急流、地面冷锋配合,加强上升运动,使地面沙尘卷入空中并输送;高低空急流抽吸加强冷暖空气垂直运动,位能向动能转化,引起了地面大风,驱动沙尘暴发生。     

新一代天气雷达常用产品在我国人工影响天气工作中的应用

随着新一代天气雷达的组网建设,常用雷达产品逐渐在人工影响天气（以下简称＂人影＂）工作中发挥了重要作用。如利用反射率因子产品分析降水系统的移向、移速、强度以及降水性质等特征为人影作业指挥提供参考;利用径向速度产品选择人影作业的最佳时机和部位;利用垂直积分液态水含量产品识别冰雹云并指导防雹作业;综合应用多种雷达产品建立人影...     

登陆台风精细结构的观测、预报与影响评估

2015年立项的国家重点基础研究发展计划项目(973计划)"登陆台风精细结构的观测、预报与影响评估"将通过进行登陆台风精细结构的野外科学试验,开展登陆台风精细结构的多源资料分析理论和方法研究,探索登陆台风精细化结构演变规律及其对风雨分布的影响机理,发展高分辨率台风数值预报模式关键技术,开展台风灾害影响(预)评估方法研究等,揭示环境因子及其自身内部的多尺度系统相互作用如何影响登陆台风精细化结构的演变,以及精细结构的演变如何影响台风风雨强度和分布,力争提高登陆台风精细结构的模拟、预报和影响评估能力。     

多通道地基微波辐射计在0713号"韦帕"台风登陆前后探测性能及特征分析

利用上海市气象局2007年9月进行的"韦帕"台风探测试验资料和地面常规观测资料,对多通道地基微波辐射计在0713号"韦帕"台风登陆前后探测性能及特征进行了分析。结果表明:多通道地基微波辐射计探测的温度和相对湿度趋势与GPS探空得到的基本一致,尽管二者之间存在一些小的差异,但也表明了微波辐射计对台风具有一定的探测能力。0713号"韦帕"台风登陆前后温度和水汽密度场上,甚短生命史的冷暖气柱和高水汽密度柱十分活跃,体现了"韦帕"台风登陆前后的阵性特征。     

基于探地雷达检测的岩溶岸坡内部宏观裂隙响应规律研究

岩体内部宏观裂隙的发育程度对水库区岩溶岸坡稳定性有着重要影响。为了有效地探测和识别岩体内部宏观裂隙的几何形态和分布特征,对三峡库区巫峡典型岩溶岸坡中岩体内部的垂直裂隙进行模型简化。基于无损伤的探地雷达物探技术,通过理论分析、数值模拟,研究了岩体内部垂直裂隙的宽度、长度、倾角等发生变化时,雷达回波剖面中裂隙对应的时距曲线形态和振幅特征的变化规律。研究表明:裂隙顶端和底端对应的雷达回波响应为双曲线形态,可作为裂隙识别的标志;裂隙的宽度与雷达回波最大振幅和能量团的关系密切;裂隙倾角大小会影响到雷达回波能量团的形态。现场测试结果表明,900MHz天线频率的探地雷达可以较好地用来探测岩溶岸坡内部约1.5m深度范围内厘米级宽度垂直宏观裂隙的分布,并可作为调查库水区岸坡岩体内部宏观裂隙扩展的一种监测手段。     

2017年6月湖南致洪暴雨的天气分析

利用实况观测资料和欧洲中长期天气预报中心再分析资料,对2017年6月底湖南一次致洪暴雨过程进行诊断分析。结果表明:高空冷涡和副高的稳定维持为暴雨发生提供了有利的大尺度环流条件,中低层低涡切变线和地面锢囚锋是此次暴雨的主要影响系统。2支高空急流增强和靠近诱发了低空急流爆发,高低空急流耦合形势的增强促进了暴雨的持续和加强。低空急流为暴雨发生提供了充沛的水汽和不稳定能量,暴雨区表现为显著的对流不稳定,并且在假相当位温垂直梯度增加的阶段对应暴雨强度亦增大。水汽通量以及辐合大值区对暴雨落区预报具有一定的指示意义。     

黑龙江省两次温带气旋暴雪过程对比分析

利用多种资料对黑龙江省两次由江淮气旋和蒙古气旋合并引发的暴雪过程的水汽、热动力条件和中尺度特征进行了对比分析。结果表明：（1）两次暴雪过程都发生在北支槽和短波槽合并、北支槽北部有冷涡的背景下,850 hPa上低涡合并促使江淮气旋和蒙古气旋合并;气旋合并后,低空急流为降雪提供了充足水汽,强暖平流使气旋爆发性发展,导致降雪加强。（2）两次降雪过程都表现出逗点云系的合并发展,"1211 "暴雪过程中高层形成涡旋偏西,700 hPa低涡东部偏南风引导气旋北上西折,低空急流和地形共同作用使暖湿空气强烈辐合上升,产生对流云,暴雪发生在A类逗点云系的头部,降雪强度大,范围广;"1412"暴雪过程高空槽低涡位置偏东,700 hPa低涡东部西南风始终引导气旋向东北方向移动,近地面层具有冷垫,暴雪主要发生在B类气旋逗点云系头部西侧中低云团中,降雪范围和强度较"1211"过程小。（3）低层（0.3 km）冷空气侵入和中高层（5.5 km）转为偏北风对判断降雪开始和结束有很好的表征意义。（4）冷涡前部强高压脊使冷涡移动缓慢,从而延长了降水的持续时间,气旋移动路径与高压脊伸展方向密切相关。     

Analysis of a major storm over the Dongjiang reservoir basin associated with Typhoon Bilis (2006)

An unexpected major storm on July 14, 2006, resulted in great loss to the Dongjiang reservoir basin in Zixing City, Hunan Province, China, during the dominance of Typhoon Bilis (2006). The rainfall characteristics and temporal evolution of this major storm were studied with rain gauge data and high-resolution radar reflectivity data to investigate the connections between typhoon, reservoir and convective storm. Our investigations found that the intense convective storm, which was characterized by a banded structure, brought heavy rainfall concentrated in the Dongjiang reservoir basin while the center of Typhoon Bilis was nearly 450 km away from the basin. By applying geographical information system techniques, analyses of radar reflectivity demonstrated that the topography of the Dongjiang reservoir has big influence on the development of convective storm. Furthermore, intense convective cells with strong radar reflectivity (>50 dBZ) arose more frequently over the edges of the reservoir, especially over the southern mountain valley in the basin. More importantly, our investigations indicate that the occurrence of this convective storm is closely related to a strong atmospheric inversion by examining the Atmospheric Infrared Sounder data.     

晚更新世末期黄、渤海陆架沙漠化环境的形成

未次盛冰期气候寒冷，温度降低，冰川发育，海面下降，黄、渤海陆架全部出露，东海陆架的大部分也裸露成陆，并成为亚洲大陆的一部分。降低了的气温使蒙古高压得到进一步增强，经常给亚洲大陆带来冷而干的气流，吹蚀亚洲内陆，也吹蚀出露了的陆架。根据多年来在陆架地区获得的浅地层剖面仪测量记录，陆架发生沙漠化的证据有：统一海相地层的解体、大面积的混杂堆积、漫长的风蚀基面、休止角型沉积结构以及埋藏沙丘群的发现等。     

"云娜"台风的监视和预报

2004年“云娜”台风的监视和预报工作中，在应用常规天气资料的基础上加强了对历史热带气旋资料、天气雷达资料和过去对台风与台风暴雨分析预报研究成果的运用。在台风登陆前、登陆过程中和登陆后三个不同阶段中，应用多种资料进行有针对性的分析判断，并向防台风指挥部门及时提供信息服务，在防台工作中发挥了有效作用。，     

An analysis of coastal and inland fatalities in landfalling US hurricanes

Improvements in hurricane forecasts allowing for more timely evacuations from storm-surge zones are credited with reducing lethality of US landfalling hurricanes. The deadly reach of a hurricane, however, is not limited to storm-surge zones. About 80% of direct US hurricane fatalities since 1970 occurred outside of landfall counties, with most of these fatalities caused by inland flooding. We construct a geographic information system database combining the location and cause of fatalities, estimated wind speeds, and rainfall amounts for the entire track of the storm for landfalling US hurricanes between 1970 and 2007. We analyze the determinants of total fatalities and deaths due to freshwater drowning and wind. Inclusion of inland fatalities results in no downward trend in lethality over the period, in contrast to prior research. Local storm conditions significantly affect lethality, as one-inch and one-knot increases in rainfall and wind increase total fatalities by 28 and 4%. Rainfall significantly increases freshwater-drowning deaths and is insignificant for wind deaths, while the opposite relation holds for wind speed. While coastal counties do not exhibit a significantly higher amount of lethality risk versus inland counties for total or wind-driven fatalities, freshwater-drowning fatalities occur most frequently in inland counties along the center of the storm path and its outer county tiers as we have defined them.     

Sensitivity of tropical cyclone characteristics to the radial distribution of sea surface temperature

Sea Surface Temperature (SST) is crucial for the development and maintenance of a tropical cyclone (TC) particularly below the storm core region. However, storm data below the core region is the most difficult to obtain, hence it is not clear yet that how sensitive the radial distribution of the SST impact the storm characteristic features such as its inner-core structures, translational speed, track, rainfall and intensity particularly over the Bay of Bengal. To explore the effects of radial SST distribution on the TC characteristics, a series of numerical experiments were carried out by modifying the SST at different radial extents using two-way interactive, triply-nested, nonhydrostatic Advanced Weather Research and Forecast (WRF-ARW) model. It is found that not only the SST under the eyewall (core region) contribute significantly to modulate storm track, translational speed and intensity, but also those outside the eyewall region (i.e., 2–2.5 times the radius of maximum wind (RMW)) play a vital role in defining the storm’s characteristics and structure. Out of all the simulated experiments, storm where the positive radial change of SST inducted within the 75 km of the storm core (i.e., P75) produced the strongest storm. In addition, N300 (negative radial changes at 300 km) produced the weakest storm. Further, it is found that SST, stronger within 2–2.5 times of the RMW for P75 experiment, plays a dominant role in maintaining 10 m wind speed (WS ₁₀), surface entropy flux (SEF) and upward vertical velocity (w) within the eyewall with warmer air temperature (T) and equivalent potential temperature (??_e) within the storm’s eye compared to other experiments.     

浙江省滑坡灾害预警预报的降雨阀值研究

根据浙江省降雨的特点,将降雨分为台风降雨和非台风降雨,采用统计方法研究了区域性滑坡灾害与台风区和非台风区降雨量及降雨强度的相关性,通过相关性分析确定了有效降雨量模型;得到了浙江省区域性滑坡发生的临界降雨量和降雨强度阀值,为实时时间预警提供了定量依据;将滑坡灾害的空间易发性与降雨量和降雨强度相结合确定了滑坡灾害的空间预警区划指标和等级;最后初步研究了滑坡发生的滞后时间。     

An evaluation of the impacts of land surface modification, storm sewer development, and rainfall variation on waterlogging risk in Shanghai

Despite continuing efforts to upgrade the urban storm sewer system since the late 1950s, the City of Shanghai is still vulnerable to persistent rainstorm waterlogging due to excess surface runoff and sewer surcharge, which frequently cause significant damage to buildings and disruption to traffic. Rapid urbanization and associated land cover changes are the major factors contributing to waterlogging. However, it is unclear to what extent changes in rainfall variability over the past few decades are also involved. This paper investigates the combined impacts of land use and land cover change, storm sewer development, and long-term variations in precipitation. Evidence of persistent waterlogging is presented first. We then give an account of land surface modifications during the process of urbanization and the development of the city??s urban storm sewer system. Statistical analysis suggests that the increase in runoff coefficient due to conversion of lands from agricultural to industrial, commercial, and residential uses is a major factor driving greater waterlogging risk. In particular, historical analysis of aerial photographs reveals the rate and extent of modification to river networks in the past few decades. The natural drainage network has shrunk by 270?km, significantly reducing the city??s capacity to transport excess surface flow. In line with other studies, we find no significant overall trends in annual rainfall totals (at Baoshan and Xujiahui). However, seasonal and monthly rainfall intensities have increased. At the daily scale, we find that compared to pre-1980s: (i) there has been an increase in the number of wet days with precipitation exceeding 25?mm (Heavy Rainfall) and decrease in those below 25?mm and (ii) the number of consecutive wet days with precipitation maximum and average exceeding the threshold known to cause waterlogging shows an increasing trend. Since rainfall intensity is expected to increase under climate change, this could further compound the impacts of land use changes and place even greater pressure on the existing storm sewer system.     

无人机探测“海鸥”台风中心附近的资料初步分析

2008年7月18日和19日,在中国大陆首次利用无人机探测手段对台风"海鸥"(0807号)进行了探测,根据19日台风减弱为热带风暴过程中的飞行探测资料,初步分析结果如下:飞行高度500 m,飞行时间近3小时,距离台风中心最近距离约为100 km,获取了探测期间的全部气象要素数据(温度、相对湿度、气压和风速),数据获取率达到90%以上.探测期间内的气压平均值为949.1±9.7 hPa,温度平均值为24.2±1.3℃,探测期间内,无人机基本处于降水云系中.故相对湿度较高,平均值为(88.4±6.1)%.通过对探测数据的初步分析,说明这种小型无人机具有探测台风边界层气象要素的能力.