【作者】 李英冰；

【导师】 徐绍铨； 郭俊义；

【作者基本信息】 武汉大学 ， 大地测量学与测量工程， 2003， 博士

【摘要】 大气负荷、内陆水负荷、海洋潮汐和非潮汐海洋负荷变化使得地表物质重新分布,从而使地表位移、重力、地倾斜和应变等发生变化,同时也会引起地心、大地水准面和地球自转的变化。环境变化引起的地表垂直位移可达几十mm,对水平位移的影响为垂直位移的1/3～1/10,对重力的间接效应可达几十μgal。在利用现代大地测量技术监测地表构造性运动时,必须将环境负荷效应从观测值中剔除,否则会严重污染测量的结果。同时,环境负荷引起的形变也可用现代空间大地测量和地面重力测量进行探测。 论文主要研究了固体地球环境变化响应的物理机制和计算方法,编写了相应的计算软件,利用气象数据和卫星测高数据进行了实际计算,对计算结果进行了相关分析,并与GPS测站坐标的时间序列进行比较,对GPS精密测量中的环境负荷改正进行了讨论。本文主要研究成果和结论为: (1) 系统地总结了环境负荷变化造成地表形变的计算理论和探测方法。将计算理论归纳为三类:线性模型趋近、球谐函数趋近、格林函数趋近。线性模型趋近是将地球形变归因于当地环境变化,建立局部地区环境负荷变化与形变量关系:球谐函数趋近是将环境负荷进行球谐展开,然后结合负荷勒夫数进行计算;负荷格林函数趋近是将环境荷量与负荷格林函数进行卷积积分,得到测站在环境负荷作用下的形变。其中线性模型趋近方法简单,主要用于计算大气负荷引起的地表垂直位移和重力变化,并且计算精度不高,后两种方法可以计算各种环境负荷变化引起的地表形变,计算精度较高。综述了地表位移、重力变化的探测方法。 (2) 综述了温度变化引起地壳位移和应变变化的计算方法,编写了相应的计算程序,进行了实例计算。计算结果表明:温度变化引起的地表垂直位移的最大值不超过±0.5mm,应变的最大值为±0.4nstrain。 (3) 在经典的负荷理论基础上,从运动方程着手,定义了大气引力勒夫数,推导了高阶引力勒夫数、大气引力造成的地表位移、重力、地倾斜、应变等格林函数表达式,编写程序计算了引力勒夫数和大气引力负荷格林函数的理论值。定义了大气压强勒夫数,推导了大气压强格林函数的计算公式,编写程序并计算了大气压强负荷勒夫数和大气压强负荷格林函数。 (4) 基于理想大气模型,推导了空间大气密度与地面压强的关系,将大气引力格林函数转化为只依赖于地表大气压强的形式,结合大气压强负荷格林函数,得到了大气格林函数的实用计算公式和数值结果。将该数值结果同海洋负荷格林函数进行比较,发现二更多还原

【Abstract】 Mass above Earth’s surface are redistributed due to temporal variations of atmospheric, continental hydrologic and oceanic loading. Mass redistribution causes variation of Earth’s surface displacement, gravity, tilt and strain, as well as geocenter, geoid and Earth’s rotation. Vertical displacement of Earth’s surface due to environmental loading can reach several centimeters, and horizontal displacements have amplitudes of several millimeters with accompanying gravity variation of several tens u gal. These deformations may add noise to geodetic observations, so the effect of environmental variation can not be ignored for modem geodesy. In many instances, the deformation is large enough to be detected with space based geodetic techniques as well as terrestrial gravity observations.This dissertation focuses on physical mechanism and computing method of solid Earth response to environmental variation. Software for computing environmental variation effect is developed. Some cases are investigated using weather and altimetry data, and related analyses are done. The main products and conclusions of this dissertation are:(1)Theory and computing method of environmental effect on Earth’s surface are addressed. The computing methods can be divided into three kinds: linear model approach, spherical harmonic function approach and Green’s functions approach. Principles of each kind of methods are put forward, advantages and disadvantages of each kind of methods are evaluated. Detection methods of displacement and gravity variation are summarized.(2)Computing method for crust’s displacement and strain variation caused by temperature variation are presented, some related software are developed, and some instances have been investigated. From the results, we can see that the maximum value of vertical displacement variation does not exceed 0.5mm and that of strain does not exceed 0.4nstrain.(3)Atmospheric gravitational load Love numbers (AGLLN) are defined and a set of asymptotic equations of AGLLN are put forward. Green’s functions of atmospheric gravitational loading, describing the Earth deformation which includes horizontal and vertical displacements, horizontal and vertical accelerations and strain tensor, are derived out by evaluating the properly weighted sums of AGLLN. Atmospheric pressure loads Love numbers (APLLN) are defined and the formulas of Green’s functions for pressure are deduced. Some related programs are developed and the numerical values of Green’s function are computed using the preliminary reference Earth model (PREM).(4)Based on ideal atmospheric model, relationship between atmospheric density fluctuation in the air and pressure fluctuation at the Earth’s surface is established. Formula and numerical values of gravitation Green’s function only depending on pressure are presented. Together with Green’s function for atmospheric pressure, we get the practical form of atmospheric Green’s function. There is no observable difference between Green’s function of atmospheric loading and the corresponding one of ocean loading. The effects of terrain, temperature variation and atmospheric model are discussed.(5)For computing the quantities describing Earth’s deformation caused by atmospheric loading, it needs to be evaluated convolutions of the Green’s function with the fluctuant pressure. In practical computation, we always adopt the pressure data at certain grid at certain time interval provided by various organizations, so we can transfer integral operation into operation of sum. The inner zone should be specially treated because the Green’s function generally has larger absolute value with smaller angular distance. High-resolution land-sea data base is one of the important factors for the accurate loading estimation, especially for adjacent-sea sites. Details of process and computing flow chart are addressed, and related C++ programs for computing the deformation due to atmospheric loading are developed. Deformation time series of 40 GPS sites due to atmospheric loading, from Jan 1, 1952 to Jul. 6, 2003, are computed using atmospheric pressure data from National Center for Environmental Prediction (NCEP). Inverted barometer (IB) hypothesis and non-inverted barometer (NEB) hypothesis, as the oceanic response to pressure forcing, are investigated. From the results, we can see that the amplitude of vertical displacement due to atmospheric loading can reach ±20mm, the amplitude of horizontal displacement is about ± 5mm, and the amplitude of gravity variation is about ± 50 u gal. The power spectrum, time-frequency distribution, annual period and semi-annual period of the deformation series are analyzed. We have computed differences of deformations for different Green’s function numerical results and different land-sea database as well as different atmospheric response models. The admittance factors are computed by least square estimation, and most of results are between -0.1 and -0.8 mm/mbar.(6)Continental water models are presented, and numerical recipes for computing the deformation due to Continental water variation are addressed. The programs for computing the deformation due to snow loading and soil moisture changes have be developed. Displacement and gravitation variation series due to continental water loading are computed using the about 50 years data from NCEP. It is shown that the amplitude of vertical displacement due to snow loading can reach ±8mm, the amplitude of horizontal displacement is about ±2mm, and the amplitudeof gravity variation is about ±10fj,gal. It also shown that the amplitude of vertical displacement due to soil moist variation can reach rtlOmm, the amplitude of horizontal displacement is about ±3mm, and the amplitude of gravity variation is about ±20figal .The power spectrum, time-frequency distribution ,annual period and semi-annual period of the deformation are analyzed. We have computed differences of deformations for different Green’s function numerical results and different land-sea database as well as different data sources.(7)The modern global tide models can be categorized into three groups: hydrodynamical model, empirical model and assimilation model. Main ocean tide models are evaluated, and numerical recipes for computing Earth deformation due to ocean tide loading are addressed. The C++ programs for computing the effect of ocean tide loading are developed, and displacements of 40 sites response to M2, S2, N2, K2, K^,O\, Pi, Qi,MF, MM, and ssa are computed. M2, S2, N3, Ki,Oi and Pi have important effect on Earth’s surface , even for island and adjacent-sea sites.(8)Deformation series of 40 sites, due to sea level anomalies of nearly 10 year’s Topex/Poseidon and ERS1/2 altimetry data from Centre National d’Etudes Spatiales(CNES), are computed. From the results we can see that the maximum value of vertical displacement due to sea level anomalies can reach ±5mm, and that of horizontal displacement is about ±2mm. From power spectrum analysis, it is shown that annual term is the main period in displacement series. As the trend of sea level rising, The trend is also existed in the displacement series of each site. The trend for horizontal displacement is less than ±0.15mm/yr, and that of vertical displacement is about ±0.35mm/yr.(9)Load moment of atmospheric loading, continental hydrologic loading and sea level anomalies are computed. Potential and vertical displacement, due to environmental variation of every 2 months in 2000, are computed using the theory of Blewitt(2001). It is shown that the potential variation is about l~3gal and the vertical displacement is about lmm.(lO)Geoid variation, which is caused by environmental variation, can be computed by spherical harmonic function approach . Geoid variations, due to environmental variation of Feb. 1, Mar. 29, May 31, Aug. 2, Oct. 4, and Nov. 29 in 2000, are computed. From the results, we can see that maximum value of Geoid variation can reach 25mm.(1 l)Power spectrum and periods of pole motion(PM) and of length of day(LOD) variation, from geodesy and from effect of environmental variation (inverted barometer,wind and continental water), are computed. From the results, we know that the main periods are annual termand semi-annual term, and the amplitudes of annual term and semi-annual term are reduced after removing environmental effect.(12)Vertical annual and semi-annual terms of 40 IGS GPS sites are analyzed. The amplitudes of annual and semi-annual terms are deduced after pole tide, ocean tide loading, atmosphere, notidal ocean, snow, and soil wetness corrections. So environmental loading corrections should be added to time series of GPS coordinate.(13)GPS baseline time series of "GNS-JIAN" , "GNS-CTK" and "WUHN-GNS" are computed. The corrections of tide and environmental effect for vertical component of those baselines are investigated. From the results,we know that the corrections of tide and environmental effect should be considered when the length of baseline is much longer and accuracy is required higher.(14)The software SEREV 0.1 (Solid Earth Response to Environmental Variation, Version 0.1) is developed. The Earth’s deformation due to environmental effect and tide can be computed using SEREV 0.1. It can compute power spectrum, time-frequency distribution and period. SEREV 0.1 also provide utility for coordinate transferred and data formats changed.更多还原