Analysis on the noises from continuously monitoring GPS sites

In this paper,we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered bythe Crustal Movement Observation Network of China over the whole country.The data are obtained in the periodfrom the beginning of the observation to the November of 2005.On the basis of data processing,we analyze thepower spectrum density of coordinate component noise at each site and calculate the spectral indexes manifestingthe noise property of each component.The spectral indexes indicate that for most sites,the noise of time series ofeach coordinate component can be addressed by the model of white noise flicker noise;and for a small amountof sites,it can be described by the model of white noise flicker noise random walk noise.We also quantita-tively estimate each noise component in the model by using the criterion of maximum likelihood estimation.Theresult shows that the white noise in the time series of GPS site coordinates does not constitute the main part ofnoise.Therefore,the error estimation of site movement parameters is usually too small,or too optimistic if weconsider the white noise only.Correspondingly,if this factor is not fully considered in explaining these movementparameters,it might mislead the readers.     

Soil organic carbon storage and soil CO<Subscript>2</Subscript> flux in the alpine meadow ecosystem

High-resolution sampling, measurements of organic carbon contents and ¹⁴C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of ¹⁴C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO₂ flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×10⁴ kg C hm⁻² to 30.75×10⁴ kg C hm⁻² in the alpine meadow ecosystems, with an average of 26.86×10⁴ kg C hm⁻². Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO₂ flux ranges from 103.24 g C m⁻² a⁻¹ to 254.93 gC m⁻² a⁻¹, with an average of 191.23 g C m⁻² a⁻¹. The CO₂ efflux produced from microbial decomposition of organic matter varies from 73.3 g C m⁻² a⁻¹ to 181 g C m⁻² a⁻¹. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%281.23% of total CO₂ emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research. Supported by the National Natural Science Foundation of China (Grant Nos. 40231015, 40471120 and 40473002) and the Guangdong Provincial Natural Science Foundation of China (Grant No. 06300102)     

直流激电测深二维反演的若干问题研究

目前,激电数据的二维反演主要针对高密度激电数据,而对于常规的激电测深则很少涉及.据此,针对常规激电测深二维反演所涉及到的一些技术难点进行探讨.在正演过程中,根据实测数据实现有限元网格自动剖分,并采用双网格系统,用相邻节点电导率双线性连续进行有限元模拟,并对模拟的误差进行校正.在反演过程中,利用互换原理和Broyden的方法计算偏导数矩阵;采用与奇异值分解算法精度相当的共轭梯度算法求解偏导数矩阵方程.最后通过对模拟数据和实测数据进行反演试算,验证本计算方法是可行的.     

TSP的应用及其与SEG-2数据文件格式间的转换

TSP超前地质预报系统目前在我国已得到了比较广泛的应用,但厂家未提供其数据文件存储格式.为此,在举例说明TSP的应用效果后,笔者采用UltraEdit软件对多个TSP数据文件进行分析,弄清了其原始数据的总体存储结构.另外,还简单介绍了国际标准地震数据SEG-2文件的存储格式,并在Matlab语言环境下编制了读取SEG-2数据文件与TSP数据文件的程序,实现了将SEG-2文件转换成TSP数据文件的功能.因此,在今后的工作中可直接应用TSP的数据处理软件包TSPwin来处理国产的超前地震数据.     

3D structure of the Earth's crust beneath the northern part of the Bohemian Massif

The SUDETES 2003 wide-angle refraction/reflection experiment covered the area of the south-western Poland and the northern Bohemian Massif. The good quality data that were gathered combined with the data from previous experiments (POLONAISE'97, CELEBRATION 2000) allowed us to prepare a 3D seismic model of the crust and uppermost mantle for this area. We inverted travel times of both refracted and reflected P waves using the JIVE3D package. This allowed us to obtain a model of P-wave velocity distribution as well as the shape of major boundaries in the crust. We also present a detailed uncertainty analysis for both the boundary depths and the velocity field. In doing the uncertainty analysis we found an interesting, strong dependence between uncertainty and inversion scheme (order of used phases). We also compared the model with surface geology and found good correlation between velocity inhomogeneities in the uppermost crust (down to 2 km) and major geological units. The higher velocity lower crust (6.9–7.2 km/s) could result from remelting of the lower crust or magmatic underplating.     

A coupling of mixed and continuous Galerkin finite element methods for poroelasticity I: the continuous in time case

In this paper, we formulate a finite element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. Here, we approximate the pressure by a mixed finite element method and the displacements by a Galerkin method. Theoretical convergence error estimates are derived in a continuous in-time setting for a strictly positive constrained specific storage coefficient. Of particular interest is the case when the lowest-order Raviart–Thomas approximating space or cell-centered finite differences are used in the mixed formulation, and continuous piecewise linear approximations are used for displacements. This approach appears to be the one most frequently applied to existing reservoir engineering simulators.     

A Network Model for Dispersion of Communicable Diseases

The spread of communicable diseases through a population is an intrinsic spatial and temporal process. This paper presents an individual‐based analytical framework for modeling the spatial and temporal heterogeneity in the disease transmission. The framework specifies a network model structure and six associated parameters. These parameters describe the properties of nodes, the properties of links, and the topology of the network. Through this model structure and associated parameters, this framework allows the representation of discrete individuals, individualized interactions, and interaction patterns in a network of human contact. The explicit representation of the spatial distribution and mobility of individuals in particular facilitates the modeling of spatial heterogeneity in the disease transmission.     

MM5对末次盛冰期中国气候的模拟研究Ⅰ:CO2和地球轨道参数的影响

通过模式结果与实况资料和地质记录对比,表明模式系统可以较好地模拟现代气候状况和末次盛冰期气候的变化,特别是降水的变化与地质记录符合得较好。在末次盛冰期和现代气候状况下地球轨道参数的变化对中国地区年平均温度的影响很小,但对不同季节温度变化的作用不同。冬季气温的变化比较显著,不能忽略。CO2浓度在末次盛冰期最低,其混合比为200×10-6,这使得气温降低。CO2的作用也存在明显的季节和区域特征。冬季其影响最大;但夏季其作用较小,甚至出现CO2浓度减少温度增加的现象。产生增温现象的原因是云量发生了变化,使到达地面的太阳辐射增加。这个结果表明云在气候变化中,可能起着非常重要的作用,甚至可以影响某时段和区域温度等要素变化的方向。青藏高原地区对这两个辐射因子变化的响应与中国其他地区相比偏小,原因是该地区的云量高于其他地区。相对现代气候,末次盛冰期地球轨道参数变化对气候的影响小于CO2的作用。但相对于末次盛冰期气候的变化,这两个因子的贡献都是比较小的。CO2对末次盛冰期年平均温度变化的贡献大约为3%—10%。此外,现代和末次盛冰期气候背景下,CO2的作用相同。     

2005年登陆我国热带气旋特征分析

热带气旋是影响我国沿海的主要灾害性天气系统之一, 它产生的狂风、暴雨、巨浪和风暴潮, 给沿岸地区人民生命和国家财产安全带来严重威胁。而严重的台风灾害, 往往是台风登陆引起的。为进一步研究登陆热带气旋的活动规律, 总结了2005年登陆我国热带气旋的特点, 结果表明:2005年登陆我国热带气旋具有登陆季节短、登陆地点分布异常、台风比例异常偏高、灾害损失极为严重的特点。同时, 还讨论了2005年登陆我国热带气旋异常的气候原因, 并指出未来几年登陆热带气旋和台风的年频数处在上升趋势中。     

FY-2C积雪判识方法研究

介绍了利用FY-2C资料进行积雪判识的原理,在阈值法基础上的辅助因子函数积雪判识方法以及相应的FY-2C积雪判识结果精度验证分析等。一般较为常用的卫星遥感积雪判识方法为简单阈值法,由于其带有一定的随机性,很难客观反映下垫面条件差异对阈值选取的影响。以阈值法为基础,将所使用的主要变量以函数形式表达,以海拔高度、地理位置、季节、土地覆盖类型等作为阈值函数的变量,通过大量采样建立起多种阈值函数,从而实现随时空特点变化的阈值实时计算。该方法用于FY-2C积雪判识,较好地解决了FY-2C全圆盘范围内广大区域不同下垫面类型下的实时积雪监测。通过与NOAA-17人机交互积雪判识结果对比分析,该方法的积雪判识精度可达85%左右。