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51.
慕士塔格冰芯钻孔温度测量结果   总被引:1,自引:2,他引:1  
2002年8月对慕士塔格冰川累积区海拔6300m左右的两根冰芯钻孔(其中—根达到冰川底部基岩)进行了温度测量,揭示了该处冰川的温度分布特征.结果表明:慕士塔格冰芯的冰温是目前中低纬地区山地冰川中最低的,达-21.79℃,该最低温度出现的位置在35m以下;冰床底部的温度为-20.76℃,也远低于其它山地冰川的冰床温度,极低的温度对成冰过程有重要影响,并有利于获得可靠的冰芯记录。  相似文献   
52.
A daily rainfall dataset and the corresponding rainfall maps have been produced by objective analysis of rainfall data. The satellite estimate of rainfall and the raingauge values are merged to form the final analysis. Associated with epochs of monsoon these rainfall maps are able to show the rainfall activities over India and the Bay of Bengal region during the BOBMEX period. The intra-seasonal variations of rainfall during BOBMEX are also seen using these data. This dataset over the oceanic region compares well with other available popular datasets like GPCP and CMAP. Over land this dataset brings out the features of monsoon in more detail due to the availability of more local raingauge stations.  相似文献   
53.
The numerical models of mantle convection agree to depict avalanches behaviour according to the level of endothermicity of the spinel → perovskite phase change. Their potential effects on the global thermal and dynamical states of the mantle have been computed thanks to a numerical code, which takes into account both the 400-km exothermic and the 660-km endothermic phase changes. The cycle followed by the avalanches is: local layering, destabilization of the 660-km thermal layer, travelling and spreading on the core, and reappearing of the local layering. Therefore, mantle convection is characterized by quiet periods of partial layering embedded in catastrophic events. During the avalanche, the amplitude of the surface velocity is multiplied by two, which would imply an enhanced plate tectonic and ridge activities. The global thermal effects of the avalanche are compatible with a high mantle temperature and an acceleration of Earth's rotation during the Cretaceous. They also offer a coherent explanation to locate the origin of mantle plumes both within the CMB and just below the transition zone.  相似文献   
54.
Soaring migrants such as storks, pelicans and large birds of prey rely on thermal convection during migration. The convection model ALPTHERM was designed to predict the onset, strength, duration and depth of thermal convection for varying topographies for glider pilots, based on atmospheric conditions at midnight. We tested ALPTHERM predictions as configured for two topographies of central Israel, the Coastal Plains and the Judean and Samarian Mountains in order to predict altitudes of migrating white storks (Ciconia ciconia). Migrating flocks of white storks were tracked with a motorized glider, to measure maximum altitudes of migration during spring 2000. A significant positive correlation was found between the maximum daily altitudes of migration measured and the predicted upper boundary of thermal convection for the Coastal Plains and Samarian Mountains. Thirty-minute predictions for the Coastal Plains and Samarian Mountains correlated positively with measured maximum migration altitudes per thermal. ALPTHERM forecasts can be used to alter flight altitudes in both civil and especially military aviation and reduce the hazard of serious aircraft collisions with soaring migrants.  相似文献   
55.
上地幔变黏度小尺度对流的数值研究   总被引:6,自引:4,他引:6       下载免费PDF全文
基于二维模型,利用有限元方法,研究上地幔-岩石圈系统的变黏度小尺度对流. 考虑该系统的黏度随温度以指数形式变化,数值结果表明,当黏度随温度变化较剧烈时,由于低温高黏度,系统的最上部物质不参与对流,系统发育形成一个类似于岩石圈的静止盖层. 计算表面热流、地形起伏及重力异常与对流格局有较好的相关性,高热流、上升地形对应于对流的上升区,反之低热流、下降地形与对流的下降区对应.  相似文献   
56.
利用地震层析成像数据计算地幔对流新模型的探讨   总被引:5,自引:3,他引:5       下载免费PDF全文
假设地幔地震层析成像数据对应的地幔横向不均匀结构是地幔热对流的结果. 将地震层析成像数据转化为地幔温度(或密度)不均匀分布,考虑热流体动力学的三个基本方程,顾及热输运方程中的非线性项,直接将地震层析成像转化的地幔温度不均匀分布作为内部荷载引入基本方程, 反演计算地幔对流. 本文在利用地震层析成像数据计算地幔对流模型的新理论和方法的基础上,用SH12WM13地震层析成像模型数据,计算了全球地幔对流格局. 结果表明,对流格局不仅依赖地震层析成像数据,而且在很大程度上受地幔动力学框架、热动力参数和边界条件的所确定的系统响应函数的影响. 显示了地幔中复杂的对流格局,特别是区域性层状对流以及多层对流环可能在地幔中存在的现象.  相似文献   
57.
The Remote Sensing Core Curriculum (RSCC) was initiated in 1993 to meet the demands for a college-level set of resources to enhance the quality of education across national and international campuses. The American Society of Photogrammetry and Remote Sensing adopted the RSCC in 1996 to sustain support of this educational initiative for its membership and collegiate community. A series of volumes, containing lectures, exercises, and data, is being created by expert contributors to address the different technical fields of remote sensing. The RSCC program is designed to operate on the Internet taking full advantage of the World Wide Web (WWW) technology for distance learning. The issues of curriculum development related to the educational setting, with demands on faculty, students, and facilities, is considered to understand the new paradigms for WW-influenced computer-aided learning. The WWW is shown to be especially appropriate for facilitating remote sensing education with requirements for addressing image data sets and multimedia learning tools. The RSCC is located at http://www.umbc.edu/rscc  相似文献   
58.
三维重力内波和对流云街的启动机制   总被引:1,自引:0,他引:1       下载免费PDF全文
在一个下部为弱不稳定层、上部为稳定层的二层模式中,求解线性化的大气动力—热力学方程组,表明一个孤立山丘所引发的重力内波,在向下游传播过程中与边界层中对流相互作用,形成大气低层的涡漩活动,其图象与观测到的对流云街结构相似。  相似文献   
59.
60.
The geomagnetic field intensity during Archaean times is evaluated from a palaeomagnetic and chronological study of a dolerite dyke intruded into the 3000 Ma Nuuk Gneisses at Nuuk (64.2°N, 51.7°W), west Greenland. Plagioclase from the dolerite dyke yields a mean K-Ar age of 2752 Ma. Palaeomagnetic directions after thermal demagnetization of the dyke and the gneiss reveal a positive baked-contact test, indicating that the high-temperature-component magnetization of the dyke is primary. Thellier experiments on 12 dyke specimens yield a palaeointensity value of 13.5±4.4 μT. The virtual dipole moment at ca. 2.8 Ga is 1.9±0.6 × 1022 Am2, which is about one-quarter of the present value. The present study and other available data imply that the Earth's magnetic field at 2.7 ∼ 2.8 Ga was characterized by a weak dipole moment and that a fairly strong geomagnetic field similar to the present intensity followed the weak field after ca. 2.6 Ga.  相似文献   
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