Lightning and Doppler radar observations of a squall line system

A typical squall line with damaging wind and hailstones occurred on 28 April 2006 in Shandong Province, middle eastern China, and caused great economic loss. The characteristics of cloud-to-ground lightning (CG) in the squall line were studied in detail by combining the data from the ground-based CG location network, two Doppler radars and the Lightning Imaging Sensor on the TRMM satellite. Results show that positive CG flashes accounted for 54.7% of the total CG flashes. During the initial developing stage, the CG flash rate was lower than 0.5fl min^{− 1} and most of the CG flashes were positive. It increased significantly, up to 4.5fl min^{− 1}, along with the rapid development of the squall line, and the percentage of positive CG was more than 75% during this period. The CG flash rate began to decrease but the percentage of negative CG flash increased gradually and exceeded that of positive CG during the mature and dissipating stages. Positive CG flashes tended to occur on the right flank and negative ones on the left flank. Strong wind at the surface occurred in or near the regions with dense positive CG flashes. Almost all positive CG flashes occurred near the strong radar echo regions, in the front parts of the squall line. However, the negative CG flashes almost exclusively occurred in the regions with weak and uniform radar echoes. The total flash rate in the storm was very high, up to 136fl min^{− 1}, and its ratio of intracloud flashes (IC) to CG flashes was 35:1. Dense positive CG flashes corresponded to updraft regions, they did not occur in the core of the updraft, but just behind and close to the main updraft instead. The rear inflow jet, between 3 and 6 km, played an important role in the formation of the bow echo and very strong wind at surface. The CG distribution features in the squall line were obviously different from that of an ordinary MCS. The charge structure could be roughly described as an inverted charge structure.     

Variations in the summer monsoon rainbands across eastern China over the past 300 years

Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty (1736–1911),the drought/flood index data mainly derived from Chinese local gazettes from 1736–2000, and the observational data gathered since 1951,the spatial patterns of monsoon rainbands are analyzed at different time scales.Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual(e.g.,5–7-yr and 2–4-yr)as well as inter-de...     

西北太平洋热带气旋频数和强度变化趋势初探

利用1951—2006年西北太平洋 (含南海) 热带气旋资料, 研究了不同强度热带气旋的气候变化特征。结果表明:超强台风 (近中心最大风速≥58m/s, 简称超强台风Ⅱ) 频数、强度和初、终旋日期的变化特征都不同于其他级别热带气旋; 西北太平洋热带气旋的总频数有长期减少趋势, 主要由热带低压和超强台风Ⅱ的长期减少趋势引起; 随着热带气旋强度增强, 出现月最大频数的月份逐渐推迟; 超强台风月频数最大值发生在秋季; 超强台风Ⅱ频数的年变化与除了超强台风Ⅰ(近中心最大风速为51~58m/s) 外的其他级别热带气旋反相关; 受超强台风Ⅱ减少影响, 热带气旋年平均最大风速有减小的长期趋势; 热带气旋的初、终旋日期没有显著的长期变化趋势, 但超强台风Ⅱ的初旋日期有推迟趋势, 终旋日期有提前趋势, 发生时间缩短。     

山地云观测中常见的几个问题

本文总结分析了雷波山地地面气象观测中,对云的目测时经常出现的一些问题,并以老观测员多年的经验对其加以分析,指出原因。强调云的观测应坚持实事求是的原则,切实提高云的观测水平和测报质量。     

钻孔应变观测现状与展望

钻孔形变观测是研究地壳运动的主要观测手段,同时在地震前兆观测中占有重要地位。本文介绍钻孔应变观测的特点,日本、美国等发达国家在钻孔应变观测开展的情况,目前中国在钻孔应变观测中采用的主要的观测设备、仪器特点,中国应变监测台网的分布,以及中国目前开展的深井地震综合观测系统。     

中国大陆科学钻探(CCSD)主孔岩芯榴辉岩中的重晶石副矿物研究

中国大陆科学钻探主孔岩芯190～320m榴辉岩中的富锶重晶石作为副矿物存在于超高压变质和退变质阶段,其中大部分的重晶石发现于绿辉石的退变质后成合晶中。具有不同Sr含量的重晶石在榴辉岩中至少具有3种产出状态,形成于3个变质阶段:Ⅰ超高压榴辉岩相阶段,存于石榴石包裹体中,SrSO4含量约在45mol%;Ⅱ早期退变质阶段,存于后成合晶(单斜辉石+钠长石)中,SrSO4含量变化范围很大,在0mol%～21mol%之间;Ⅲ晚期角闪岩相阶段,作为黄铁矿的氧化边存在,SrSO4占2mol%～5mol%。重晶石的形成与流体作用相关,富锶重晶石能反映原赋存流体的Sr/Ba值比较高。重晶石与其伴生矿物尤其硫化物的结构关系对岩体的相对氧化还原环境具有重要指示意义。本文通过榴辉岩中重晶石副矿物学研究,确定了榴辉岩曾经历超高压变质阶段的氧化环境、早期退变质阶段的还原环境和角闪岩相阶段的氧化环境。     

多层位超深试验观测井施工技术

鄂尔多斯盆地西南缘,白垩系志丹群的6个岩组分布俱全,地质与水文地质信息丰富。介绍了位于该区的具有勘探与长观双重意义,集全孔段取心、四层分层抽水试验、三层长期观测于一井的B5号井的井身结构设计和施工工艺。通过B5号多层位超深试验观测井的施工,证明了一井多用途的经济性和可能性,积累了多层位超深观测井施工经验,为整个鄂尔多斯盆地水文地质调查起到了示范作用。     

中长期预报在邢台海河流域的应用

在分析子牙河水系海河流域降雨径流的基础上,应用回归统计法,通过优选因子进行预报。西台峪站位于邢台临城县境内,属半干旱、半湿润山丘区,年降水主要集中在6—9月,其河流特性为暴涨暴落。通过优选因子建立预报方程。因子的选取我们从物理成因和数理统计等各方面来考察各个影响因素,挑选出具有明确物理意义的预报因子,并把其应用到实际工作中去。探讨了中长期预报在半干旱、半湿润地区的适用性,对计算成果分析遇到的问题提出了一些解决方法。     

广西岩溶塌陷区某中学教学楼地基灌浆加固处理工程实例

建于中细砂层上的多层教学楼,下伏灰岩岩溶发育,地下水活动剧烈,使用7 a后,室内外地面出现陷坑,楼两端也过量沉降.文中介绍了为抢险而进行的工程物探、钻探补充勘察,进而开展地基加固治理设计、施工及沉降变形观测,及时恢复了教学楼的使用,为既有建筑物在岩溶地质灾害发育区的勘察、治理设计及施工积累了工程经验。     

基于ArcView GIS的沉降观测数据三维分析研究

本文在了解国内外沉降观测研究现状的基础上,从变形观测的理论出发,探求提高沉降观测操作的质量,并结合亚奥国家广场建筑物沉降观测实例,对测量所得到的沉降监测数据进行科学整理。文章从理论分析入手,结合沉降观测收集数据,然后在相关理论支持下进行监测数据的分析。在数据分析过程中,着重运用GIS软件实现沉降的三维模拟,并绘制沉降等值线,直接、美观的再现了沉降的过程。经过分析,得出亚奥国际广场建筑物沉降状况的合理性,并提出了提高沉降观测质量、科学整理数据和成果分析的相关建议。