乌鲁木齐地磁台环境磁场测量及分析

本文根据乌鲁木齐地磁台1988、1989两年的环境磁场测量结果,就地磁院内的环境磁场分布情况进行了讨论分析。并对该台如何保持长期不受环境磁场污染提出了建议。     

地球基本磁场的形成与变化的探讨

本文在铁磁体假说的基础上，探讨地球基本磁场的形成与变化的原因.地球的偶极磁场是由于地球的回转和内核中特殊的磁化环境，使内核中心形成的饱和磁化的永磁球体（即磁核）产生的，磁核的大小和温度负相关.地球的非偶极磁场，由外核内几个可确定的磁偶极子产生，这些磁偶极子，是外核中液态金属的流动，切割磁核的磁场而产生的涡流形成的.     

乌鲁木齐地磁台环境磁场梯度测量及分析

使用高灵敏度的Ｇ８５６,ＤＴＺ－２型核子旋进式磁力仪,对乌鲁木齐地磁台１９９个测点的磁场梯度进行了复测,经过严格的数据校正处理,重新作出了ΔＦ等磁力线图,并分析讨论了台站院内环境磁场的变化特征,测量结果表明;乌鲁木齐地磁台仍处于磁场正常区,工作环境符合《地磁台站观测规范》要求。     

海南省(岛)1988.0年代地磁图的绘制及琼中台址磁场区域代表性研究

本文通过对海南省(岛)地磁图绘制及其有关资料的分析,讨论了琼中地磁台地面磁场梯度分布,台地附近磁性环境变化特征,区域的地理位置、地质构造、磁场背景与台站观测值的关系。从而提出了琼中地磁台址磁场区城代表性的问题。     

低轨磁测卫星干扰磁场标定方法研究

为了提高空间磁场探测精度,磁测卫星一般将磁强计安装在长伸杆的顶端,同时通过整星磁洁净控制,来减小磁强计安装位置的磁场干扰量.针对低轨磁测卫星的特点,提出零磁场环境下卫星极弱干扰磁场的高精度测量方法,模拟在轨地磁场环境下卫星感应磁场的标定方法,以及磁力矩器剩磁不确定量的处理方法.通过以上方法对卫星本体产生的干扰磁场实施严格的标定和数据修正,可有效减小其影响,极大提升空间磁场探测精度.该方法已应用于电磁监测卫星,将整星的磁场干扰不确定量降低一个量级,达到优于0.3 nT的水平.     

地磁绝对子夜均值异常识别方法研究

地磁绝对子夜均值数据,即台站地方时00～03时期间的地磁场绝对数据是地球主磁场和地壳磁场变化研究中常用的基础数据.该均值中基本去除了电离层电流体系的影响,但仍不可避免地存在着主磁场的变化和磁层磁场的变化,可能会存在与地震孕育有关的地壳磁场的变化、因台站观测环境干扰或绝对观测错误产生的不可弥补的错误数据以及因数据处理错误产生的可修正的错误数据.     

广州地磁台环境干扰的监测与研究

通过对广州地磁台环境干扰源的监测，计算与分析得到：（1）不同时期产生的二个干扰源对地磁台1号墩磁场总强度测值的迭加影响为－25nT，与多台资料对比结果一致。（2）地磁台1号和5 ，1号与干扰源场区外Ⅰ号比测墩测得的磁场总强度、水平强度及垂直强度之差随时间的变化不明显，故认为广州地磁台环境干扰源目前尚属稳定。     

广州台环境磁场梯度测定

广州地磁台1956年建成至今三十多年,其环境发生了很大变化。木文通过对建台以来五次台站环境磁场梯度测定方法的总结和分析结果表明:建筑物对地磁台环境磁场分布的影响,主要与距离及建筑材料有关;也与建筑物之走向有一定关系;钢筋混凝土楼房(七层以下)建筑与地磁台最小距离不得少于160m。     

台湾花莲地震前电磁辐射异常分析

1 台站基本情况及仪器性能 杭州地震台建于1980年，位于杭州市植物园内，地处偏僻，地形开阔，环境幽静。台站距公路2.5 km，周围无高压线、变电所和工业干扰源，观测环境较好。根据浙江省地震局“十五”前兆台站数字改造要求，杭州地震台于2002年2月架设了地震电磁辐射仪（EMAOS-L）。 超低频数字地震电磁辐射仪（EMAOS-L），频率范围0.01～10 Hz。传感器由电极和磁探头两部分组成。它们分别接收地下电场和磁场信号，测量电场和磁场的扰动变化。埋地电极的材料是1铬18镍9钛优质不锈钢，有较好的防腐和导电性能。其埋设深度为6 m。埋…     

日冕磁场测量

磁场把太阳的各层大气耦合在一起,并主导着其中的各种物理过程,磁场的演化引发包括太阳爆发在内的活动现象,进而影响着地球的空间环境和人类的生存条件.要理解发生在太阳大气中的各种活动现象,离不开对其磁场的完整认知.然而目前对太阳高层大气尤其是日冕的磁场测量仍然严重缺失,这大大限制了人类对太阳活动的研究,制约了太阳物理和空间天...     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.