地幔对流及其对地壳表层拉张盆地的影响   总被引：4，自引：0，他引：4  

陆现彩  顾连兴 《地学前缘》1998,(Z1)

回顾近十年来在地幔对流方面的最新研究进展,阐述了板块俯冲后在地幔中的演化特征,以及地幔上升流即地幔柱的驱动机制和地质效应。特别介绍了地幔柱对地壳表层拉张盆地形成和充填过程的影响。进一步探讨了地幔柱活动在济阳坳陷的地质表现及其引发的火山岩浆活动、碎屑充填特征。认为盆地演化的阶段性间接反映了地幔对流的阶段性。  相似文献   

Evolutionary sequences for Nova V1974 Cygni using new nuclear reaction rates and opacities     

S. Starrfield  J. W. Truran  M. C. Wiescher  & W. M. Sparks 《Monthly notices of the Royal Astronomical Society》1998,296(3):502-522

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Geothermal resource assessment of the United States     

L. J. Patrick Muffler  Robert L. Christiansen 《Pure and Applied Geophysics》1978,117(1-2):160-171

Geothermal resource assessment is the broadly based appraisal of the quantities of heat that might be extracted from the earth and used economically at some reasonable future time. In the United States, the Geological Survey is responsible for preparing geothermal assessments based on the best available data and interpretations. Updates are required every few years owing to increasing knowledge, enlarging data base, improving technology, and changing economics. Because geothermal understanding is incomplete and rapidly evolving, the USGS complements its assessments with a broad program of geothermal research that includes (1) study of geothermal processes on crustal and local scales, (2) regional evaluations, (3) intensive study of type systems before and during exploitation (4) improvement of exploration techniques, and (5) investigation of geoenvironmental constraints.  相似文献   

NATURE OF PRECIPITATION AND ACTIVITY OF CUMULUS CONVECTION DURING THE 1991 MEIYU SEASON OF CHANGJIANG-HUAIHE RIVER BASIN^*     

Lu Er  Ding Yihui  Masato Murakami  Kiyotoshi Takahashi 《Acta Meteorologica Sinica》1998,12(1):75-91

Seasonal variability regarding the nature of precipitation and the activity of cumulus convection during the 1991 Meiyu season of Changjiang-Huaihe River Basin(Jianghuai)has been investigated by calculating apparent heat source/apparent moisture sink and analyzing TBB(cloud-top blackody radiation temperature)data.It is found that three periods of strong ascending motion during the Meiyu season lead to three episodes of heavy rain,and the latent heat due to the precipitation is of the sole heat source of the atmosphere.The nature of precipitation shows distinct seasonal variability,from frontal precipitation of the first episode to the extremely strong convective precipitation of the third episode.TBB field of East Asia may well reflect not only the intensity of convection and rainfall,but also the movement of rain belt and convection belt.In the whole Meiyu season.convection belt mainly stays in Jianghuai.but may shift within the domain of East Asia.Its locating in Jianghuai or not determines the maintenance or break of Meiyu.In the third episode,the narrow convection belt over Jianghuai is mainly caused by southwest monsoon which takes moist and convective atmosphere from tropical ocean.  相似文献   

包含局地自由对流的Monin—Obukhov相似性函数     

张强 《气象科学》1998,18(1):1-9

本文从湍流产生和发展的本质出发,以湍流动能和湍流混合长为湍流输送的决定因子,用因次分析的方法得到了一套可包括局地自由对流在内的不稳定大气近地层Monin－Obukhov相似性函数。这套相似性函数不仅有较充分的理论依据,而且还有较明确的物理含意。它能在极端情况下自动蜕化出局地自由对流相似性预测形式。  相似文献   

九江地区一次强对流暴雨天气过程分析     

王维健 《气象与减灾研究》1998,(2)

从天气形势出发,结合物理量场、卫星云图和雷达回波等演变特征,分析洞庭湖附近生成的两个气旋波东移过程中在九江地区引起的强对流、暴雨天气。  相似文献   

Transitions in the style of mantle convection at high Rayleigh numbers     

Dayanthie Weeraratne  Michael Manga   《Earth and Planetary Science Letters》1998,160(3-4):563-568

The pattern and style of mantle convection govern the thermal evolution, internal dynamics, and large-scale surface deformation of the terrestrial planets. In order to characterize the nature of heat transport and convective behaviour at Rayleigh numbers, Ra, appropriate for planetary mantles (between 10⁴ and 10⁸), we perform a set of laboratory experiments. Convection is driven by a temperature gradient imposed between two rigid surfaces, and there is no internal heating. As the Rayleigh number is increased, two transitions in convective behaviour occur. First we observe a change from steady to time-dependent convection at Ra≈10⁵. A second transition occurs at higher Rayleigh numbers, Ra≈5×10⁶, with large-scale time-dependent flow being replaced by isolated rising and sinking plumes. Corresponding to the latter transition, the exponent β in the power law relating the Nusselt number Nu to the Rayleigh number (NuRa^β) is reduced. Both rising and sinking plumes always consist of plume heads followed by tails. There is no characteristic frequency for the formation of plumes.  相似文献   

On a Physically Realistic Fast Dynamo     

Kim  Eun-Jin  Hughes  D. W.  Soward  A. M. 《Studia Geophysica et Geodaetica》1998,42(3):335-342

As a step towards a physically realistic model of a fast dynamo, we study numerically a kinematic dynamo driven by convection in a rapidly rotating cylindrical annulus. Convection maintains the quasi-geostrophic balance whilst developing more complicated time-dependence as the Rayleigh number is increased. We incorporate the effects of Ekman suction and investigate dynamo action resulting from a chaotic flow obtained in this manner. We examine the growth rate as a function of magnetic Prandtl number Pm, which is proportional to the magnetic Reynolds number. Even for the largest value of Pm considered, a clearly identifiable asymptotic behaviour is not established. Nevertheless the available evidence strongly suggests a fast dynamo process.  相似文献   

On the effects of coherent structures on higher order moments in models of solar and stellar surface convection     

F. Kupka  F. J. Robinson 《Monthly notices of the Royal Astronomical Society》2007,374(1):305-322

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2013年7月1日河北宁晋极端短时强降水成因研究     

王丛梅  俞小鼎 《湖北气象》2015,(2):105-116

2013年7月1日午后至夜间,华北出现一次区域性暴雨和局地大暴雨过程。局地极端降水出现在河北省邢台市宁晋县四芝兰镇,过程雨量409 mm,其中当日17—19时连续2 h雨量超过100 mm。利用常规高空和地面观测资料、NCEP再分析资料和石家庄新一代天气雷达资料,探讨了宁晋极端短时强降水的形成原因。主要结论是:(1)低槽、冷锋、副热带高压及其外围低涡切变线为其主要影响系统,海南附近台风远距离影响加强了水汽自南向北的输送,半定常的地面辐合切变线对新生对流的触发和已有对流的维持及加强起到重要作用;(2)宁晋最强降水期间,其上空具有较强的垂直风切变,有利于高度组织化的对流系统发展;(3)对流系统的后向传播使回波主体移动缓慢、持续时间长,而回波强度大和雨强很强,则导致四芝兰镇极端强降水,此外,具有弱中气旋的超级单体相对较长时间的影响使其对四芝兰镇强降水具有重要贡献;(4)产生极端降水的对流系统属于高质心发展强烈的大陆强对流型,而非更易导致强降水的低质心系统。同时,针对众多学者研究北京"7.21"特大暴雨得到的一些结论进行了进一步探讨和验证。  相似文献