A STUDY OF RAPID DECAY TYPHOONS IN OFFSHORE WATERS OF CHINA     

郑峰  曾智华  雷小途  陈联寿  杨涛  朱景 《热带气象学报(英文版)》2017,23(4):471-480

On the basis of NCEP/NCAR reanalysis data and yearbooks of CMA tropical cyclones, statistical analysis is performed for 1949—2013 offshore typhoons subjected to rapid decay(RD). This analysis indicates that RD typhoons are small-probability events, making up about 2.2% of the total offshore typhoons during this period. The RD events experience a decadal variation, mostly in the 1960 s and 1970 s(maximal in the 1970 s), rapidly decrease in the 1980 s and 1990 s and quickly increase from 2000. Also, RD typhoons show remarkable seasonal differences: they arise mainly in April and July-December, with the prime stage being in October-November. The offshore RD typhoons occur mostly in the South China Sea(SCS) and to a lesser extent in the East China Sea(ECS); however, none are observed over the Huang Sea and Bo Sea.Composite analysis and dynamic diagnosis of the RD typhoon-related large-scale circulations are performed.Physical quantities of the composite analysis consist of 500-h Pa height and temperature fields, vapor transfer, vertical wind shear(VWS), density of core convection(DCC), and high-level jet and upper-air outflow of the typhoon. The results suggest that(1) at the 500-h Pa height field, the typhoon is ahead of a westerly trough and under the effects of its passing trough;(2) at the temperature field, the typhoon is ahead of a temperature trough, with an invading cold tongue present;(3) at the vapor transfer field, water transfer into the RD typhoon is cut off; and(4) at higher levels, the related jet weakens and the outbreak of convection becomes attenuated in the typhoon core. In addition, VWS bears a relation to the RD typhoon; in particular, strong VWS favors RD occurrence.The differences in RD events between the SCS and ECS show that for the RD, the VWS of the ECS environmental winds is markedly stronger in comparison with its SCS counterpart. The cold advection invading into the typhoons is more intense in the SCS than in the ECS, and the low-level vapor transfer and high-level outflow are weaker in the SCS RD typhoons.Data analysis shows that sea surface temperature(SST), VWS, and DCC can be employed as efficient factors to predict RD occurrence. With appropriate SST, VWS, and DCC, a warning of RD occurrence can be given 36, 30-36,and 30 h, respectively, in advance. These values suggest that atmospheric SST responses lag. Owing to this time lag,the prediction of RD typhoons is possible.  相似文献   

长江中上游平原地区冬季雾观测分析   总被引：4，自引：3，他引：1  

费冬冬  牛生杰 《气象科学》2017,37(3):376-384

长江中上游年平均雾日数达到20~106 d,是我国主要雾区之一。利用2010年12月在江汉平原观测获得的边界层廓线和雾滴谱资料,重点分析了该地区冬季雾过程的边界层结构及其生消过程。结果表明:荆州冬季雾多出现在寒潮过境1~2 d后,多为平流辐射雾;雾顶发展是水汽在上层逆温下积累,并伴随200~300 m高度冷平流降温引起;近地层冷平流降温导致饱和水汽压减小,同时上层系统性下沉增温引起逆温增强,水汽积累促使强浓雾过程产生;低空急流促使外界偏干气流与雾体混合后雾滴蒸发,是该地区雾顶迅速下降的主要原因;平均数浓度为150~406个·cm-3,极大值达到1 983个·cm-3,平均液水含量为0.014~0.118 g·m-3,极值达到0.786 g·m-3,与南京和重庆强浓雾观测值相似,超过其他地区观测值。城市地区高气溶胶浓度,配合充足的水汽条件,使得荆州雾过程微物理参量数值较大,易出现能见度小于50 m,持续时间4~9 h的强浓雾过程。  相似文献   

WINTERTIME MIDDLE EAST SUBTROPICAL WESTERLY JET STREAM INTERANNUAL VARIATION CHARACTERISTICS AND ITS POSSIBLE PHYSICAL FACTORS   总被引：1，自引：0，他引：1  

吴玲玲  张建伟  邓伟涛  倪东鸿 《热带气象学报(英文版)》2017,23(4):380-395

Using National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) monthly reanalysis data and an extended reconstruction of the sea surface temperature data provided by National Oceanic and Atmospheric Administration, the basic characteristics of the interannual variation in the wintertime Middle East subtropical westerly jet stream (MEJ) and its possible physical factors are studied. The results show that the climatological mean MEJ axis extends southwestward-northeastward and that its center lies in the northwest part of the Arabian Peninsula. The south-north shift of the MEJ axis and its intensity show obvious interannual variations that are closely related to the El Ni?o-Southern Oscillation (ENSO) and the mid-high latitude atmospheric circulation. The zonal symmetric response of the Asian jet to the ENSO-related tropical convective forcing causes the MEJ axis shift, and the Arctic Oscillation (AO) causes the middle-western MEJ axis shift. Due to the influences of both the zonal symmetric response of the Asian jet to the ENSO-related tropical convective forcing and the dynamical role of the AO, an east-west out-of-phase MEJ axis shift is observed. Furthermore, the zonal asymmetric response to the ENSO-related tropical convective forcing can lead to an anomalous Mediterranean convergence (MC) in the high troposphere. The MC anomaly excites a zonal wave train along the Afro-Asian jet, which causes the middle-western MEJ axis shift. Under the effects of both the zonal symmetric response to the ENSO-related tropical convective forcing and the wave train along the Afro-Asian jet excited by the MC anomaly, an east-west in-phase MEJ axis shift pattern is expressed. Finally, the AO affects the MEJ intensity, whereas the East Atlantic (EA) teleconnection influences the middle-western MEJ intensity. Under the dynamical roles of the AO and EA, the change in the MEJ intensity is demonstrated.  相似文献   

东亚高空急流协同变化对冬季欧亚遥相关型气候效应的影响   总被引：3，自引：0，他引：3  

汪宁  许遐祯  王莹  张耀存  吴伟 《大气科学》2017,41(3):461-474

利用NCEP/NCAR再分析资料和我国地面735站气温和降水资料,首先分析了欧亚遥相关型的时间演变和结构特征,在此基础上探讨了欧亚遥相关型不同位相时东亚大气环流的差异,并进一步研究了欧亚遥相关型影响我国冬季气温和降水过程中东亚高空急流的重要作用。从结构上看,欧亚遥相关型位势高度异常中心位于250 hPa高度,表现出准正压的结构。欧亚遥相关型位于正位相时,东亚温带急流强度偏弱且位置向北移动;副热带急流强度偏强,两支急流在45°N附近有明显分界;西伯利亚高压和阿留申低压强度增强;东亚大槽加深,槽线倾斜不明显。负位相时则相反。欧亚遥相关型与东亚高空急流的联系是其影响我国气温降水的重要原因。正欧亚遥相关型时,偏弱的温带急流区较强的北风分量有利于北方冷空气南下,从而造成我国气温偏低;偏强的副热带急流区增强的南风将副热带地区暖湿空气向北输送,两支急流协同变化,影响我国冬季降水异常的分布。去掉温带急流或副热带急流偏强的年份,欧亚遥相关型与我国温度、降水的相关性显著减弱,说明欧亚遥相关型是通过东亚高空急流协同变化的桥梁,对我国温度和降水异常产生影响。进一步研究发现,欧亚遥相关型与副热带急流的关系不如其与温带急流稳定,导致在欧亚遥相关型同一位相时东亚高空急流存在两种不同的配置,这种高空急流配置的不唯一性使得东亚高空急流能对欧亚遥相关型的气候效应起到调控作用。  相似文献   

海上风机吸力式桶形基础承载特性研究综述     

毋晓妮  廖倩  李晔 《海洋技术学报》2020,39(1):91-106

风机基础作为海上风机整体结构的重要组成部分,承受着上部风机所受到的风浪流荷载,并且对风机的安全性及可靠性至关重要。吸力式桶形基础由于其安装简单和可重复利用等优点,在海洋平台基础中得到了广泛应用,并逐步应用于海上风机基础中。但由于海上风机与海洋平台在海洋环境中的荷载工况有一定的差别,仍需要通过对其承载特性研究现状进行全面认识,以实现吸力式桶形基础在海上风机基础中的可靠应用。文中通过总结和评价现有研究对桶形基础在不同土体条件以及荷载条件下进行试验及数值模拟分析得到的研究结果,综述了静荷载和循环荷载作用下砂土和黏土中的吸力式桶形基础的承载特性研究现状,以及海上风机吸力式桶形基础的相关研究。文章展望了目前应用于海上风机基础的桶形基础仍缺乏的研究,为海上风机吸力式桶形基础的可靠应用及后续研究提供重要参考。  相似文献   

高压旋喷桩单桩承载力分析     

王勃  行小盈 《岩土工程技术》2020,(1):48-52

高压喷射注浆于1968年首创于日本。我国于20世纪70年代初相继引进并开始研究高压喷射注浆技术。目前,高压旋喷工艺应用最为广泛,工艺技术最为成熟。对旋喷桩成桩质量及单桩承载力进行研究分析,为旋喷桩在地基与基础工程、水利水电工程、止水、加固工程中的应用提供设计参考依据。该试验在陕西省延安市某建成小区内选三个试验点,按不同旋喷桩施工工艺成桩,通过对桩身完整性检测、单桩承载力试验,分析旋喷桩成桩质量及单桩承载力。  相似文献   

基于并行计算的海洋平台谱分析疲劳筛选技术研究     

李洛东  刘成名  梁园华 《海洋工程》2018,36(5):56-64

为了得到海洋平台疲劳失效风险最大的焊接区域,提出了以有限元网格单元应力为基础的谱分析筛选方法,并开发了程序。程序采用并行计算架构,单次完成数万个单元的累积损伤度/疲劳寿命计算,并通过有限元软件以云图方式显示疲劳寿命。采用该程序计算双浮筒半潜式平台的疲劳寿命。结果表明,该型平台疲劳失效风险较高的区域为立柱与上壳体下浮体连接对角线转角区域、浮筒中纵舱壁与立柱连接区域。并行计算方法的引入,大大缩减疲劳损伤度计算的分析时间,采用22核心的CPU,时间缩短为原来的1/18.5,17小时完成全平台外壳单元谱分析计算。  相似文献   

提高地浸钻孔出水量的有效技术措施          下载免费PDF全文

胥虹 《探矿工程》2020,47(1):48-52

地浸钻孔是一种以采矿为目的的钻孔，提高钻孔出水量就是提高钻孔的采矿量。通过对多年地浸钻孔施工经验和理论进行分析，发现影响钻孔出水量的主要因素为钻井泥浆的成分和性能以及人工过滤层的渗透性差异，提出在地浸钻孔施工方案中采用植物胶净化泥浆钻进和扩孔、投砾罐射吸式填砾、物理化学组合洗井3种技术措施，对比前后施工钻孔的出水量大小，证明了该技术措施对提高地浸钻孔出水量具有良好的效果。  相似文献