Planetary Wave Periods in <Emphasis Type="Italic">foF</Emphasis>2 Time Variations Based on Winter Data from Kaliningrad Station in 2008−2010     

Yu. N. Koren’kov  F. S. Bessarab  N. A. Koren’kova  V. S. Leshchenko 《Geomagnetism and Aeronomy》2018,58(3):420-429

The study presents the results of the analysis of the F2-layer critical frequency variations obtained for the winter periods of 2008–2010, during which sudden stratospheric warmings were observed. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) with the Parus digital ionosonde in standard sounding mode. The mean daily foF2 values were used in the analysis. The results of spectral analysis based on continuous wavelet transform showed that, during all of the warmings that occurred in 2008–2010, the foF2 time variations demonstrated the presence of wave processes with periods of approximately 5?6 days, as well as more extended processes with periods of ~10?13 and 23?30 days. These periods coincide with the characteristic periods of planetary waves observed in the mesosphere during sudden stratospheric warmings, while the 13- and 30-day periods can be conditioned by the influence of the Sun.  相似文献   

One-step solution to local tie vector determination at co-located GNSS/VLBI sites     

Xiaping Ma  Kegen Yu  Jean-Philippe Montillet  Xiaoxing He 《Studia Geophysica et Geodaetica》2018,62(4):535-561

The local tie vector, which connects the different space geodetic techniques at a co-located site, plays an important role in the realization of the International Terrestrial Reference Frame (ITRF). This paper presents a new method to determine the tie vector between the GNSS and very long baseline interferometry tracking points. The parameters of the local tie vector and the axes offsets are introduced into constraint equations. The parameters are then resolved using the 3D constrained least squares adjustment. With the surveying data collected at two different sites (Kunming and Urumqi) in China, the proposed method can precisely determine the local tie vectors in a geocentric frame. The root mean square error (RMSE) is (1.2, 2.3 and 1.5 mm) and (1.0, 1.5 and 1.4 mm) for the three coordinate components at the sites in Kunming and Urumqi, respectively. The offset between the primary and secondary axes of the VLBI telescopes is estimated to be 7.5 mm in Kunming’s site and 4.0 mm in Urumqi’s site, and the corresponding RMSE is 1.8 mm and 2.0 mm for the two sites, respectively.  相似文献   

C-RESPONSE OF GEOMAGNETIC DEPTH SOUNDING ON A 1D THIN SHELL MODEL     

LI Shi-wen  WENG Ai-hua  TANG Yu  ZHANG Yan-hui  LI Jian-ping  YANG Yue 《地震地质》2018,40(2):337-348

This paper tries to formulate the C-response of geomagnetic depth sounding(GDS)on an Earth model with finite electrical conductivity. The computation is performed in a spherical coordinate system. The Earth is divided into a series of thin spherical shells. The source is approximated by a single spherical harmonic P₁⁰ due to the spatial structure of electrical currents in the magnetosphere. The whole solution space is separated into inner and external parts by the Earth surface. Omitting displacement current, the magnetic field in the external space obeys Laplacian equation, while in the inner part, due to the finite conductivity, the electromagnetic fields obey Helmholtz equation. To connect the magnetic fields in the inner and external space, the continuity condition of magnetic fields is used on the Earth surface. The external magnetic fields are expressed by the inner and external source coefficients, from which a new parameter called C-response is computed from the inner coefficient divided by the external coefficient, thus normalizing the actual source strength. The inner magnetic fields in each layer can be recursively derived by the continuity boundary condition of both normal and tangential components of the magnetic field from the initial boundary condition at core-mantle-boundary. The consistency of our C-responses with that from a typical 1-D global model validates the accuracy of the proposed algorithm. Numerical results also show that the C-response estimated from the geomagnetic transfer function method will deviate exceeding 5%from the actual response at longer periods than about 10⁶s, which means that ignoring the curvature of the Earth at extreme long periods will make inversion result unreliable. Therefore, an accurate C-response should be computed in order to lay a solid foundation for reliable inversion.  相似文献   

The Hydrochemical Evolution of Water in Lake Karymskii during 1996‒2015 after an Underwater Eruption in Kamchatka     

A. G. Nikolaeva  G. A. Karpov  A. Yu. Bychkov 《Journal of Volcanology and Seismology》2018,12(2):109-127

This study considers variations in the physical and chemical characteristics of water in Lake Karymskii for the period from January 1996, when a phreatomagmatic eruption occurred in the lake, until 2015. Our monitoring revealed two characteristic sets of components whose behavior characterizes the hydrochemical evolution of lake water: a comparatively rapid exponential decay of the concentrations of SO₄, Ca, and Mg and a slow decrease in the concentrations of Cl, Na, and K. We arrived at the conclusion that two components of the fluid flow (a fumarolic and a hydrothermal component proper) simultaneously occurred during the eruption and thus had an effect on the lake water. We adduce evidence to show that the water balance and the chemical composition of Lake Karymskii stabilized toward 2015.  相似文献   

Variation in soil saturated hydraulic conductivity along the hillslope of collapsing granite gullies   总被引：2，自引：0，他引：2  

Xiaoqian Duan  Yusong Deng  Yu Tao  Yangbo He  Lirong Lin 《水文科学杂志》2018,63(5):803-817

Saturated hydraulic conductivity (K_s) affects the soil hydrological process and is influenced by many factors that exhibit strong spatial variations. To accurately measure K_s and its scale, spatial variability and relationship with collapsing gullies, we analysed four double-ring infiltrometer diameters in three soil layers during in situ experiments designed to measure K_s in two typical collapsing gullies (three slope sites) in Tongcheng County of China. The results showed that K_s increased with increasing inner ring diameter, but no significant difference existed between inner diameters of 30 and 40 cm. The K_s in red soil layers was higher than that in sandy soil layers, the transition layers had the lowest values. K_s also varied with slope position, gradually decreasing with distance from the gully head. The suggestion is that the spatial variation in K_s is affected not only by the intrinsic soil properties but also by the interaction with the collapsing gully.  相似文献   

一种自然邻近关系查询的空间索引结构     

张思佳  王瑜  刘鹏  张文靖  李佳田  肖怡 《地理信息世界》2018,(1):32-38

自然邻近关系在空间数据库管理系统中具有十分重要的地位。为了克服Voronoi图受空间目标位置的影响,本文采用约束Delaunay三角网,针对在二维欧式空间中离散面目标的自然邻近关系查询问题。首先对离散面进行三角剖分,然后将代表相同邻近关系的三角形合并成一个union,进而建立面目标自然邻近关系表达结构-Unions Delaunay。通过与Unions Delaunay相结合建立空间索引结构-R-tree Gridfile来实现对空间目标自然邻居完备的候选集提取以及索引结构的更新。对比实验结果表明R-tree Gridfile索引结构能够有效支持空间目标的自然邻近关系查询。  相似文献   

高海况下无人水下航行器的横摇运动分析          下载免费PDF全文

张钰  刘忠乐  张志强 《数字海洋与水下攻防》2018,1(2):50-54

为明确高海况下海况等级对无人水下航行器横摇运动的影响,得出满足某型无人水下航行器安全回收的海况条件,对高海况下无人水下航行器的横摇运动进行分析。运用频率响应法,分别在4级、5级和6级海况下，根据海浪谱密度函数和该型航行器的横摇频率响应函数,求得其横摇运动谱密度函数。再运用公式推导,得到其横摇运动的时域函数。使用MATLAB仿真软件对该型航行器进行横摇运动仿真,得到3种海况条件下，其横摇运动的时域函数图像,并验证仿真结果的准确性。仿真结论:高海况下的海况等级对无人水下航行器的横摇幅度有较大影响,满足其安全回收的海况条件为5级海况。  相似文献   

Atmospheric environmental capacity and urban atmospheric load in mainland China     

XU DaHai  WANG Yu  ZHU Rong 《中国科学:地球科学(英文版)》2018,(1)

Daily and annual average atmospheric environmental capacity coefficient(A-value) sequences for mainland China are calculated from hourly data recorded at 378 ground stations over 1975–2014. A-values at different recurrence intervals are calculated by fitting the sequences to Pearson type III distribution curves. Based on these A-values and source-sink balance(reference concentration 100 μg m~(-3)), atmospheric environmental capacities at the recurrence intervals are calculated for all of mainland China and each provincial administrative region. The climate average atmospheric environmental capacity reference value for the entire mainland is 2.169×10~7 t yr~(-1). An urban atmospheric load index is defined for analyses of the impact of population density on the urban atmospheric environment. Analyses suggest that this index is also useful for differentiating whether air quality changes are attributable to varying meteorological conditions or variations of artificial emission rate.Equations guiding the control of unorganized emission sources are derived for preventing air quality deterioration during urban expansion and population concentration.  相似文献   

海南省连片贫困地区农户致贫风险分析   总被引：4，自引：1，他引：3  

张金萍  宋伟  林丹  余珍鑫  李庭筠  罗邱戈  程叶青 《地理科学》2020,40(4):608-616

农村贫困与减贫是世界性难题,也是中国各级政府高度重视并着力解决的重大民生问题。基于农户及致贫风险的文献梳理,从区位、社会和劳动力3个要素维度构建了农户致贫风险分析的二元Logistic回归模型。采用484户农户问卷调查数据,分析了海南省连片贫困地区农户的致贫风险,提出有效减贫和持续发展对策。研究发现:① 海南连片贫困地区生态环境良好但贫困发生率较高,家庭劳动力较充裕但受教育水平较低,子女教育支出负担重,因病因残致贫比例较高,女性务工人口较多,农户自身脱贫致富的发展动力不足。② 海拔高度200 m以下、男性户主、拥有残疾或患病成员、务工人口比例低、女性务工人员占比高、以及单位劳动力供养学生数高的农户具有更大的致贫风险。③ 研究未发现女性户主、少数民族、低受教育水平户主、大型规模家庭有更高的致贫风险,女性成员比例、抚养比等因素对农户贫困影响较小。激发农户内生动力、大力发展特色化和规模化农业、增加农户就业机会、加强针对农民工、女性务工人员和病残群体的社会保障等减贫政策制定实施是实现脱贫攻坚目标的重要途径。  相似文献   

敦煌-格尔木铁路沿线风动力环境特征     

鱼燕萍  张克存  安志山  张余 《中国沙漠》2020,40(1):41-48

敦煌-格尔木铁路沿线地形复杂、起沙因素多变、沙源丰富，沙害问题日益严重。目前对其风沙活动规律还未有研究，不利于防沙工作的开展。为此，通过对自北向南的5个观测点（S1、S2、S3、S4、S5）风速和风向的观测、计算和分析，利用平均风速、起沙风况及输沙势对敦格铁路沿线的风动力环境特征进行研究。结果表明：S5、S4和S3的风况对铁路风沙灾害防治意义较大。S5年平均风速、起沙风频率和输沙势最大，春季风沙活动最为强烈，且风向单一、风力强劲，风沙运动方向基本与铁路垂直，沙粒易在铁路附近堆积。S4夏季风沙活动最为强烈；S3春季风沙活动最为强烈，且风向单一，S4和S3的风沙运动方向与铁路夹角小于90°，附近沙源广阔，铁路易受风沙侵蚀，阻碍交通运营。  相似文献