一次全省性强雷暴天气的地闪特征

2009年6月26日浙江出现全省范围的雷暴天气,此次过程中出现的地闪频数是自2006年闪电定位系统建立以来出现最多的一次。利用闪电定位实测资料、加密雨量站雨量实况以及多普勒天气雷达产品,对这一过程的地闪特征进行了分析。结果表明:此次地闪以负地闪为主,负地闪广泛分布于25～55dBz雷电回波区域内,而正闪多出现在25～35dBz回波中;地闪多出现在回波发展和前进的一侧,且密集分布在回波的梯度最大处,强回波中心处地闪较少出现;在回波开始减弱到中心强度为35dBz左右的区域没有地闪发生。地闪频数与全省过程累积降水量有很好的相关性,地闪的出现及其频数的增加意味着影响某地的强对流风暴正在发展或正向本地移来,对于单站来说雨强峰值滞后于地闪频数峰值半个小时以上,对于全省累积降水量则提前1～2h。因此地闪资料可以作为强对流天气的短时强降水预报的预警依据。     

链状裸甲藻赤潮消亡过程及其与休眠包囊关系的初步研究

本文对2018年6月10−14日在泉州湾海域发生的一次链状裸甲藻（Gymnodinium catenatum）赤潮的消亡过程进行研究。在现场跟踪监测,共设置4个站位,进行6个航次海洋环境及浮游植物的调查。结合本文对泉州湾海域甲藻包囊的调查研究,探索休眠包囊与赤潮生消过程的关系。研究结果显示,赤潮发生时海况良好,水温和盐度分别介于27.1～28.2℃和29.7～31.4之间,活性磷酸盐和无机氮浓度分别介于未检出至0.045 4 mg/L和0.050～0.281 mg/L之间,赤潮生物密度与营养盐浓度没有呈现显著的相关关系,大风大浪是导致赤潮消亡的重要原因;赤潮消亡过程中共鉴定出浮游植物3门48属100种,硅藻门种类最多;赤潮消亡期间浮游植物群落结构发生变化,前期链状裸甲藻占绝对优势,最高密度达（7.02±0.11）×10⁶ cells/L,后期中肋骨条藻（Skeletonema costatum）和旋链角毛藻（Chaetoceros curvisetus）代替链状裸甲藻成为优势种,且浮游植物种类数明显增加;同时在泉州湾海域共鉴定甲藻包囊5大类37种和1种未定种,平均丰度为574 cysts/g,以异养型甲藻包囊为主;休眠包囊在赤潮生消过程中起着重要作用,赤潮消亡时形成休眠包囊,包囊数量会随着时间呈下降趋势,但仍有萌发的可能,具有重新暴发赤潮的潜在性,需要引起重视。     

以风浪成长阶段因子为参量的波高分布

在风的直接作用下产生的风浪,由于复杂的生成和发展条件,使其具有外观上的不规则性和随机性,内在的非线性性.早在五十年代初期,人们就针对风浪的随机性,运用统计方法,对风浪的统计性质进行了分析研究.就其外观而言,这种统计性质,主要由波面纵座标、波要素等的概率分布来描述,在把风浪作为一线性流体动力学模式来描述时,获得波面纵座标遵循正态分布律.     

云南金平白马寨含矿镁铁-超镁铁岩体岩石地球化学

云南金平白马寨铜镍硫化物矿床含矿岩体为侵位在奥陶系砂页岩的镁铁-超镁铁环状杂岩体。从岩体核心到边缘依次出现橄榄岩—橄榄辉石岩—辉石岩—辉长岩的岩相分带。该岩体的主量元素显示拉斑玄武岩岩浆分异演化的趋势。REE显示富集LREE的配分模式,具明显的Eu异常。微量元素蛛网图显示明显的Ta、Nb、Ti及P的负异常。具有高(87Sr/86Sr)i(0.710974~0.722667)和低εNd(t)(-13.17~-12.09)的特征。微量元素和同位素地球化学证据表明,岩浆源于俯冲地壳物质改造的富集地幔,岩浆上升过程中遭受了一定的地壳物质混染。岩体可能是在弧后拉张的构造环境中形成。     

广州市美丽乡村空间分异特征及其影响因素

以广州市已公布的4批美丽乡村建设试点数据为基础，通过最邻近指数、基于Riple’s函数的多距离空间聚类分析、核密度分析和叠置分析等方法，探讨了广州市美丽乡村的发展现状、空间分布格局及其影响因素。结果表明：1）自2013年起，广州市美丽乡村数量逐年递增且增长率呈现上升趋势；2）广州市美丽乡村空间分布呈明显的集聚型分布；3）Ripley’s函数分析表明美丽乡村要素点空间分布格局随距离变化略有不同，在0.14 km处集聚强度达到最大；4）核密度分析显示美丽乡村高密度区域主要分布在广州南部和西北部，包括番禺－南沙1个热点主核心区和从化、花都－白云2个热点副核心区，密度分布呈现多核心不均衡特点；5）乡村的地形水文、人文历史、交通区位和政策规划为美丽乡村空间分布的主要影响因素，其中，政策规划因素对“美丽乡村群”空间格局的形成起决定性影响。空间分布特征总体反映出广州市美丽乡村规划建设初见成效，并逐步形成以热点核心区为基础的“美丽乡村群”。最后，在乡村选点、空间优化、价值提升以及乡村治理等方面提出若干建议。     

Modeling 3D thermal fracture propagation by transient cooling using virtual multidimensional internal bonds

Thermal fracturing can play an important role in development of unconventional petroleum and geothermal resources. Thermal fractures can result from the nonlinear deformation of the rock in response to thermal stress related to cold water injection as well as heating. Before the rock reaches the final failure stage, material softening and bulk modulus degradation can cause changes in the thermo‐mechanical properties of the solid. In order to capture this aspect of the rock fracture, a virtual multidimensional internal bond‐based thermo‐mechanical model is derived to track elastic, softening, and the failure stages of the rock in response to the temporal changes of its temperature field. The variations in thermo‐mechanical properties of the rock are derived from a nonlinear constitutive model. To represent the thermo‐mechanical behavior of pre‐existing fractures, the element partition method is employed. Using the model, numerical simulation of 3D thermal fracture propagation in brittle rock is carried out. Results of numerical simulations provide evidence of model verification and illustrate nonlinear thermal response and fracture development in rock under uniform cooling. In addition, fracture coalescence in a cluster of fractures under thermal stress is illustrated, and the process of thermal fracturing from a wellbore is captured. Results underscore the importance of thermal stress in reservoir stimulation and show the effectiveness of the model to predict 3D thermal fracturing. Copyright © 2016 John Wiley & Sons, Ltd.     

华北平原冀中坳陷东部SFQ1钻孔磁性地层年代学及其地质意义

可靠的地层年代标尺对于研究华北平原晚上新世以来沉积物记录的沉积环境演化、新构造运动及古气候演化具有重要意义.本文通过测定冀中坳陷东部的SFQ1钻孔岩芯古地磁,建立高分辨率磁性地层年代框架,并探讨其地质意义.结果表明:SFQ1孔中更新统底界埋深为71.0 m(布容期B/松山期M界线),下更新统底界埋深为197.8 m(松...     

Investigations on variations of the subtropical high in the Western Pacific during historic times

In this paper the 500 mb circulation field over East Asia was reconstructed by means of a stepwise regression technique, based on the relationship between summer (June to August) rainfall in China and 500 mb level heights. As a result of this study, three indices for the subtropical high, the longitude of the west border, and the latitude of the north border and intensity for the period AD 1471–1980 were extracted from reconstructed 500 mb level heights.The power spectrum analysis was carried out to investigate the variation of subtropical high indices for last 500 yr; it is shown that the prominent cycles are 22-, 36-, 55-yr and the quasi-biennial oscillation (QBO), among these the latter is more significant.The long-term variations of the 10 yr average 500 mb level heights and subtropical high indices are examined in relation to climate change; it was determined that the longitudinal variation of subtropical high plays an important role in the wetness variations over China.     

The Impact of Urbanization on Groundwater Quantity,Quality,Hydrothermal Changes and Its Countermeasures

Groundwater, as a drinking water source for nearly one third of the world’s urban population, plays a strategic role in the development of urbanization. The object of this study is urban areas with the largest demand for water resources, the heaviest load of groundwater pollution and the most intense development of underground projects. This study sorted out the eco-hydrological problems such as the variation of the groundwater hydrological process, the groundwater pollution, and the urban heat island of groundwater in urban areas under the background of urbanization. Furthermore, the mechanism of changes in the quantity, quality and heat of groundwater was also systematically analyzed, and the intrinsic interaction among these three factors was revealed. The study showed that changes in land use and land cover caused by the urbanization are the main reasons for the variation of groundwater hydrological process. The pollution load of urbanization construction and domestic production waste has aggravated the deterioration of groundwater quality. The increase in vertical heat flux caused by urbanization gives rise to the warming of groundwater. By summarizing the eco-hydrological problems and causes of groundwater in urbanized areas, several suggestions were proposed: \mathrm{①} Establishing the evaluation method and system of urban groundwater resources; \mathrm{②} Speeding up the technological breakthroughs of groundwater pollution control; \mathrm{③} Improving the regional control strategies for groundwater pollution; \mathrm{④} Optimizing the allocation of groundwater resources. This study will provide the theoretical basis and technical support for ensuring urban water safety, building ecological civilized cities and further promoting the sustainable development of economy and society.