南海西南海盆构造演化的热模拟研究   总被引：17，自引：6，他引：11       下载免费PDF全文

张健  宋海斌  李家彪 《地球物理学报》2005,48(6):1357-1365

南海西南海盆的张裂和海底扩张是白垩纪末至中始新世南海形成过程中最重要的构造事件.本文采用三维有限单元法对该区的热演化过程进行了模拟计算.通过对变形、温度结构的计算,研究了西南海盆张裂变形、海底扩张持续时间、地幔物质上升、地壳岩墙沿扩张中心的挤入扩张活力、岩浆活动等.计算结果表明：由于其深部动力学条件不足,海盆一次扩张持续时间在10～15Ma之间,其后地幔物质的上升活动逐渐停止,地壳失去扩张动力,使得扩张中心成为残留扩张中心的死亡裂谷,而未构成中脊或中隆带.虽然该处地幔物质上升的潜力不足,但伴随局部的断裂,尤其是盆、缘边界的拆离拉张,仍能产生相当强烈的岩浆喷溢活动,导致此区海盆成型之后的海山崛起.  相似文献   

川东北地区异常高压形成的地温场背景   总被引：33，自引：6，他引：27       下载免费PDF全文

卢庆治  胡圣标  郭彤楼  李忠平 《地球物理学报》2005,48(5):1110-1116

利用四川东北地区现有的钻井测温数据及测定的岩石样品热导率数据,计算了12口钻井的大地热流值. 结果表明,川东北地区现今地温梯度为18～25 ℃/km,平均21 ℃/km,大地热流值介于41～57 mW/m2之间,平均为49 mW/m2. 在此基础上,利用镜质体反射率(Ro)资料对研究区热史进行了恢复,认为研究区在255Ma左右古热流达到最高值(62～70 mW/m2),此后热流持续降低直到现今;研究区中-新生界不整合面的剥蚀厚度最大,可达约2100 m;异常高压是在低热流的地温场背景下形成的.  相似文献   

Determining the circulation depth of thermal springs in the southern Rocky Mountain Trench, south-eastern British Columbia, Canada using geothermometry and borehole temperature logs   总被引：1，自引：1，他引：0  

D. M. Allen  S. E. Grasby  D. A. Voormeij 《Hydrogeology Journal》2006,14(1-2):159-172

Geochemical data for thermal spring waters along the southern Rocky Mountain Trench in British Columbia, Canada were examined. The range of equilibration temperatures for the thermal springs is between 24 and 59°C, assuming that there is minimal mixing with colder shallow waters that might lead to a lowering of the calculated equilibration temperature. The chalcedony geothermometer is found to be the most appropriate given the carbonate host rocks. Temperature logs from 11 boreholes in the vicinity were used to calculate representative geothermal gradients, which range from 23.8 to 55.7°C/km with an average of 24.8±8.0°C/km. Using the average gradient and the range of equilibration temperatures calculated for each spring, the minimum range for the depth of origin of the thermal waters is 0.9–2.2 km. Heat flow values range from 90.3 to 155 mW/m², with an average of 109.1±21.0 mW/m². The moderate to high heat flow and heat generation result in generally higher temperatures at shallow depths, thus offering an explanation for the occurrence of thermal springs. The alignment of the thermal springs likely relates to the preferred northwest–southeast orientation for major thrust faults along the Rocky Mountain Trench, and with waters routed from depth along deep faults.

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Resumen Se examinan datos geoquímicos de aguas de fuentes termales a lo largo de la Trinchera sur de las Montañas Rocosas en Columbia Británica, Canadá. El rango de temperaturas de equilibrio para las fuentes termales se encuentra entre 24 y 59°C, asumiendo que existe mezcla mínima con aguas someras más frías que podrían conducir a un descenso de la temperatura de equilibrio calculada. El geotermómetro de calcedonia se ha encontrado que es el más apropiado debido a las rocas encajonantes carbonatadas. Se utilizaron los registros de temperatura de 11 pozos de la zona para calcular gradientes geotermales representativos, los cuales varían de 23.8 a 55.7°C/km con un promedio de 24.8±8.0°C/km. Utilizando el gradiente promedio y el rango de temperaturas de equilibrio calculadas para cada manantial, se estimó que el rango mínimo para la profundidad de origen de las aguas termales varía de 0.9 a 2.2 km. Los valores de flujo de calor varían de 90.3 a 155 mW/m², con un promedio de 109.1±21.0 mW/m². El flujo de calor moderado a alto y la generación de calor resultan en temperaturas generalmente más altas a profundidades someras ofreciendo de este modo una explicación para la ocurrencia de fuentes termales. El alineamiento de fuentes termales posiblemente se relaciona con la orientación preferida noroeste-sureste de fallas inversas principales a lo largo de la Trinchera de las Montañas Rocosas, y con aguas ascendentes profundas que se mueven a lo largo de fallas profundas.

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Résumé Les données géothermiques de sources thermales le long de la partie sud du fossé des Montagnes Rocheuses en Colombie Britannique, Canada, sont étudiées. Léchelle des températures déquilibre des sources thermales se situe entre 24 et 59°C, en assumant quil y a un mélange minimum avec les eaux froides de surface, ce qui conduit à une sous-évaluation de la température déquilibre. La calcédoine apparaît être le géothermomètre le plus approprié vu les roches hôtes carbonatées. Les diagraphies de température provenant de 11 forages proches ont été utilisées pour calculer le gradient géothermique représentatif, gradient compris entre 23.8 et 55.7°/km avec une moyenne de 24.8°/km. En utilisant le gradient moyen et les valeurs de température déquilibre calculées pour chaque source, la profondeur minimum des eaux thermales se situerait entre 0.9 et 2.2 km. Les flux de chaleur sont évalués entre 90.3 et 155 mW/m, avec une moyenne de 109.1±21.0 mW/m. Le transfert moyen de chaleur et la génération de chaleur résulte en températures ordinairement plus élevées aux faibles profondeurs, qui ainsi offre une explication à loccurrence de sources thermales. Les alignements de sources thermales sont vraisemblablement en relation avec lorientation Nord-Sud des principales failles-vraies le long du fossé des Montagnes Rocheuses, et avec lécoulement des eaux des profondeurs le long des failles.

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Application of the Energy-Casimir Method to the Study of Mesoscale Disturbance Stability          下载免费PDF全文

RAN Lingkun  CHU Yanli  GAO Shouting 《Acta Meteorologica Sinica》2010,24(3):297-306

Taking into account the effect of moisture, we derive a three-dimensional pseudoenergy wave-activity relation for moist atmosphere from the primitive zonal momentum and total energy equations in Cartesian coordinates by using the energy-Casimir method. In the derivation, a Casimir function is introduced, which is a single-wlue function of virtual potential temperature. Since the pseudoenergy wave-activity relation is constructed in the ageostrophic and nonhydrostatic dynamical framework, it may be applicable to diagnosing the stability of mesoscale disturbance systems in a steady-stratified atmosphere. The theoretical analysis shows that the wave-activity relation takes a nonconservative form in which the pseudoenergy wave-activity density is composed of perturbation kinetic energy, available potential energy, and buoyant energy. The local change of pseudoenergy wave-activity density depends on the combined effects of zonal basic flow shear, Coriolis force work and wave-activity source or sink as well as wave-activity flux divergence. The diagnosis shows that horizontal distribution and temporal trend of pseudoenergy wave-activity density are similar to those of the observed 6-h accumulated surface rainfall. This suggests that the pseudoenergy wave-activity density is capable of representing the dynamical and thermodynamic features of mesoscale precipitable systems in the mid-lower troposphere, so it is closely related to the observed surface rainfall. The calculation of the terms in the wave-activity relation reveals that the wave-activity flux divergence shares a similar temporal trend with the local change of pseudoenergy wave-activity density and the observed surface rainfall. Although the terms of zonal basic flow shear and Coriolis force contribute to the local change of pseudoenergy wave-activity density, the contribution from the wave-activity flux divergence is much more significant.  相似文献   

热气候指数在人体舒适度预报中的适用性   总被引：5，自引：0，他引：5       下载免费PDF全文

郑有飞  尹继福  吴荣军  叶殿秀 《应用气象学报》2010,21(6):709-715

为进一步提高夏季舒适度预报质量,该文根据国际生物气象研究学会制定的体感指标计算软件和国内现行指标的计算方法,引进并修正了热气候指数(UTCI),根据对2009年8月21—25日在南京信息工程大学205名军训大学生开展的问卷调查资料,对比验证了国内外多种指标,结果表明:国内指标基本能够表征人体热感觉,但仍需进一步完善;热气候指数较其他体感指标能更好地表达人体实际热舒适度,结合天气数值预报结果和SolAlt模型预报的太阳辐射,非常适宜作为南京市人体舒适度的预报指标。热气候指数的建立,提高了南京市的公共气象服务质量。  相似文献   

青藏高原热力异常对四川省及周边区域气象要素影响分析     

陈贝  吴涧 《四川气象》2010,(3):1-11

利用方差统计方法分析了前期高原大气热源异常时四川及其周边区域的主汛期的位势场、相对湿度场、垂直速度场以及风场的变化。结果表明,当前期高原大气热源异常时,次年汛期四川及其周边区域的各要素场会出现显著变化。当前期高原加热场异常偏强,在次年的5-6月东北冷涡异常偏强、7-9月青藏高压显著偏强,而副热带高压的位置明显偏东;当前期高原加热场异常偏弱时,次年河套西风槽则异常偏强,青藏高压明显偏弱。其次当前期高原加热场异常时在次年汛期比湿场、垂直速度以及风场变率上都有异常。分析结果对于进一步理解青藏高原对四川及周边地区的天气及气候变化具有一定的意义。  相似文献   

湖南特大冰冻灾害的云物理特征与人工影响技术探讨   总被引：1，自引：0，他引：1  

樊志超  高继林 《气象》2009,35(11):84-92

我国南方2008年初的持续低温雨雪冰冻灾害造成了重大社会影响,湖南等省损失巨大.利用常规气象资料分析天气成因,利用长沙高空气象探测站的L波段探空数据和地面气象观测资料分析湖南雨凇天气的大气层结特征,利用人工增雨云系模式模拟其微物理过程.结果表明:当锋面逆温具有较厚的融化层(或温度较高)和较薄的冷却层(或气温不太低)构成"雨凇层结"时,就可形成雨凇天气;混合云降水是这次冻雨的主要降水机制,"三层模型"和"雨凇层结"可以完整和全面地解释冻雨形成的机制与过程.在此基础上根据冰晶效应和爆炸效应进一步对人工防冻雨的可行性进行了技术探讨.  相似文献   

一次罕见冬季强浓雾天气成因分析   总被引：6，自引：1，他引：5  

雷正翠  夏文梅  周霖华  钱玮  张端禹 《气象科技》2010,38(3):289-294

利用加密观测资料和NCEP/NCAR 1°×1°的6 h再分析资料,对2006年12月25~27日发生在我国中东部地区的一次罕见强浓雾天气过程从大尺度背景、动力和热力机制等方面进行了诊断分析。结果表明:①本次过程大雾发生阶段近地面风速很小,在0.3~2.9 m/s之间变化;浓雾发生阶段风速在0.3~2.4 m/s之间变化;15 m能见度维持阶段风速在0.8~1.1 m/s之间变化;②虽然浓雾发生前的很长一段时间内水汽条件差,而且后期西风槽影响时也无降水,但是槽前西南气流的持续水汽输送使得强浓雾形成所必须的水汽条件得到满足;③在大雾发生前,稳定层结逐渐建立并在大雾期间稳定维持,稳定层结的建立和维持对浓雾的形成、持续有重要作用;日出后首先在较高层出现不稳定层结,继而下传到底层,稳定层结被破坏,大雾减轻或消散;④第1阶段(25日夜里至26日上午)强浓雾出现前,能见度出现多次急速大幅振荡,在第2阶段(26日傍晚至27日上午)则未出现类似现象。  相似文献   

Modelling Near-Surface Low Winds over Land under Stable Conditions: Sensitivity Tests,Flux-Gradient Relationships,and Stability Parameters   总被引：1，自引：1，他引：0  

Ashok K. Luhar  Peter J. Hurley  Ken N. Rayner 《Boundary-Layer Meteorology》2009,130(2):249-274

Low or weak wind-speed conditions, roughly defined as the periods when the mean wind speed at 10 m above the ground is 2 ms⁻¹ or less, are of considerable practical interest. However, they are not readily amenable to treatment within prognostic meteorological models and, consequently, difficult to predict, especially when the ambient stability is strong. In this paper, we apply an E − ε prognostic meteorological model to simulate near-surface meteorology and, focusing on low wind speeds, compare the predictions with measurements from two independent datasets. A sensitivity analysis is performed to investigate the possible reasons for the relatively inferior model performance for low winds when the atmosphere is stably stratified. A comprehensive data analysis is carried out to study low wind stable conditions, concentrating on the validity of various forms of flux–gradient relationships for momentum and heat within the framework of the Monin-Obukhov similarity theory, which models employ for calculating surface fluxes. The observed behaviour of various stability parameters, such as the Richardson number, is investigated. The results point to inadequacies of the current flux–gradient relationships, especially regarding momentum, under strongly stable conditions as being a dominant reason for the poor low wind predictions. The modelling issues identified are not just restricted to the present model, but are general in nature. The use of an alternative stability function for momentum under strongly stable conditions is explored. It results in improved model performance for low winds; however, further research is needed to better understand strongly stable flows in the lower atmosphere and to develop methods that can translate that understanding to operational meteorological modelling.  相似文献   

Estimation of the Friction Velocity in Stably Stratified Boundary-Layer Flows Over Hills     

José Luis Argaín  Pedro M. A. Miranda  Miguel A. C. Teixeira 《Boundary-Layer Meteorology》2009,130(1):15-28

A method is suggested for the calculation of the friction velocity for stable turbulent boundary-layer flow over hills. The method is tested using a continuous upstream mean velocity profile compatible with the propagation of gravity waves, and is incorporated into the linear model of Hunt, Leibovich and Richards with the modification proposed by Hunt, Richards and Brighton to include the effects of stability, and the reformulated solution of Weng for the near-surface region. Those theoretical results are compared with results from simulations using a non-hydrostatic microscale-mesoscale two-dimensional numerical model, and with field observations for different values of stability. These comparisons show a considerable improvement in the behaviour of the theoretical model when the friction velocity is calculated using the method proposed here, leading to a consistent variation of the boundary-layer structure with stability, and better agreement with observational and numerical data.  相似文献