论浙江火山岩区金银矿床的成矿物质来源   总被引：2，自引：0，他引：2  

徐国风 《地球科学》1987,(4)

稳定同位素和地质特征的研究,结果表明浙江火山岩区金银矿床的成矿物质系多元来源。金属和挥发性组分来源于岩石圈深部(下地壳或上地幔)和上地壳,成矿流体是大量大气水和少量岩浆水的混合溶液.金银矿化与板块运动及地热流体对流体系有关.  相似文献   

A Note on the Mixing Length Theory and Massive Star Evolution     

Li－CaiDeng  Da－RunXiong 《中国天文和天体物理学报》2001,1(1):50-56

1 INTRODUCTIONThe mixing length theory (MLT) for stellar convection originally developed by Vitense(1953, 1958) has been the most popularly used local convection theory in the studies of stellarstructure and evolution. The theory was later modified and revised by many investigators,who suggested some different expressions. In fact, MLT is not a real hydrodynamic theory,rather, it is a simple "ballistic" theory which traces the motion of imaginary convective elements. In reality j stell…  相似文献   

On determining the noon polar cap boundary from SuperDARN HF radar backscatter characteristics     

M. Pinnock  A. S. Rodger 《Annales Geophysicae》2001,18(12):1523-1530

Previous work has shown that ionospheric HF radar backscatter in the noon sector can be used to locate the footprint of the magnetospheric cusp particle precipitation. This has enabled the radar data to be used as a proxy for the location of the polar cap boundary, and hence measure the flow of plasma across it to derive the reconnection electric field in the ionosphere. This work used only single radar data sets with a field of view limited to 2 h of local time. In this case study using four of the SuperDARN radars, we examine the boundary determined over 6 h of magnetic local time around the noon sector and its relationship to the convection pattern. The variation with longitude of the latitude of the radar scatter with cusp characteristics shows a bay-like feature. It is shown that this feature is shaped by the variation with longitude of the poleward flow component of the ionospheric plasma and may be understood in terms of cusp ion time-of-flight effects. Using this interpretation, we derive the time-of-flight of the cusp ions and find that it is consistent with approximately 1 keV ions injected from a subsolar reconnection site. A method for deriving a more accurate estimate of the location of the open-closed field line boundary from HF radar data is described.  相似文献   

Slab dehydration and fluid migration at the base of the upper mantle: implications for deep earthquake mechanisms     

Guillaume Richard  Marc Monnereau  Michel Rabinowicz 《Geophysical Journal International》2007,168(3):1291-1304

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Mantle lateral variations and elastogravitational deformations – II. Possible effects of a superplume on body tides     

L. Métivier  M. Greff-Lefftz  M. Diament 《Geophysical Journal International》2007,168(3):897-903

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Variability of Convective Activity over the North Indian Ocean and its Associations with Monsoon Rainfall over India     

D. R. Pattanaik 《Pure and Applied Geophysics》2007,164(8-9):1527-1545

The present study is an attempt to examine the variability of convective activity over the north Indian Ocean (Bay of Bengal and Arabian Sea) on interannual and longer time scale and its association with the rainfall activity over the four different homogeneous regions of India (viz., northeast India, northwest India, central India and south peninsular India) during the monsoon season from June to September (JJAS) for the 26 year period (1979 to 2004). The monthly mean Outgoing Long-wave Radiation (OLR) data obtained from National Oceanic and Atmospheric Administration (NOAA) polar orbiting spacecraft are used in this study and the 26-year period has been divided into two periods of 13 years each with period-i from 1979 to 1991 and period -ii from 1992 to 2004. It is ascertained that the convective activity increases over the Arabian Sea and the Bay of Bengal in the recent period (period -ii; 1992 to 2004) compared to that of the former period (period -i; 1979 to 1991) during JJAS and is associated with a significantly increasing trend (at 95% level) of convective activity over the north Bay of Bengal (NBAY). On a monthly scale, July and August also show increase in convective activity over the Arabian Sea and the Bay of Bengal during the recent period and this is associated with slight changes in the monsoon activity cycle over India. The increase in convective activity particularly over the Arabian Sea during the recent period of June is basically associated with about three days early onset of the monsoon over Delhi and relatively faster progress of the monsoon northward from the southern tip of India. Over the homogeneous regions of India the correlation coefficient (CC) of OLR anomalies over the south Arabian Sea (SARA) is highly significant with the rainfall over central India, south peninsular India and northwest India, and for the north Arabian Sea (NARA), it is significant with northwest India rainfall and south peninsular rainfall. Similarly, the OLR anomalies over the south Bay of Bengal (SBAY) have significant CC with northwest India and south peninsular rainfall, whereas the most active convective region of the NBAY is not significantly correlated with rainfall over India. It is also found that the region over northeastern parts of India and its surroundings has a negative correlation with the OLR anomalies over the NARA and is associated with an anomalous sinking (rising) motion over the northeastern parts of India during the years of increase (decrease) of convective activity over the NARA.  相似文献   

中纬度夏季一次深厚对流过程的数值模拟研究:高空热力层结和风切变影响   总被引：1，自引：0，他引：1       下载免费PDF全文

陈泽宇  吕达仁  刘锦丽 《大气科学》2002,26(6):744-750

针对一次发生在中纬度夏季的深厚对流过程进行的数值模拟研究的结果,引入一个较详细描述深厚对流状态下云微物理过程的参数化方案,对一个有限差分三维非静力弹性大气数值模式进行了改进.数值模拟得到了与天气雷达观测一致的结果.结果还显示,对于这次穿透高度超过了对流层顶的深厚对流过程,与高空斜压扰动有关的上对流层弱稳定热力层结对系统的维持起到了重要的作用.另外,还发现强烈的对流发展到对流层顶的高度时,受上曳体的驱动,在对流层顶附近的稳定层结中产生浮力性的扰动;它们与风切变相结合,进而对系统的水平移动产生控制作用.  相似文献   

一维积云模式初始参数优化的研究   总被引：2，自引：0，他引：2  

郑淑真  曾光平  隋平  张长安  何观芳 《气象》2002,28(2):13-16

福建省人工增雨指挥系统在预报积云降水和评估增雨效果中曾采用一维时变积云模式。关于该模式初始场的确定 ,考虑到不同天气类型对模式初始参数的影响 ,并采用了以确定敏感参数为主 ,综合考虑其他影响参数为辅的方法。经分类调试 ,证明了一维模式初始场确实与天气类型有关 ,并得到旱期降水预报率大于 75%和可预报积云云顶高度的结果。通过对模拟云和实测云高度的线性回归分析 ,以及经拟合敏感参数初始扰动温度与平均地面最高气温 ,均存在较好的相关。  相似文献   

1998年我国东部大陆夏季风特征研究   总被引：4，自引：1，他引：4  

徐国强  朱乾根 《气象》2002,28(3):8-13

利用NCEP／NCAR再分析资料和OLR资料，研究了1998年我国东部大陆夏季风的特征。结果指出，1998年夏季副高脊线的平均位置偏南，华南地区和长江流域的夏季风较强，强对流维持时间长；华北地区的夏季风较弱，对流比常年偏弱；我国东部大陆夏季风存在明显的低频振荡现象。  相似文献   

环境大气对积云发展的影响     

李珊 《气象研究与应用》2001,22(3):46-48

为了能更实际客观地模拟天气的发展变化，在胡志晋教授的一维时变积云数值模式的基础上考虑了环境大气与积云群的发生、发展及降水之间的相互作用，保留了原模式所有的微物理过程，建立了一维积云时变套柱模式。此模式不仅能模拟积云，还可以模拟积云在层状云中发展变化，以及模拟环境大气具有辐合辐散场时积云的发展。  相似文献