Study On The Loading Effects Of The Atmospheric Pressure

With the development of the modern geodesy technologies and the techniques of the data analysis, it is necessary to take account of the loading effects of the atmospheric pressure on the surface-based observations of various geophysical fields. The loading effects of the atmosphere are the sum of the direct effect, which comes from its Newtonian attraction to any point on the surface or within the interior of the Earth, and the indirect effects, which is induced by the Earth's deformation and additional gravitational potential arising from redistribution of the mass because it can be regarded as the surface loads. They are traditionally expressed as the convolution integration of the atmospheric Green's function, which is virtually the sum of the elastic and gravitational Green's functions, and the measured values of the barometric pressure on the Earth's surface over the globe. Based on the response theory of an elastic Earth to surface loads and the model of the standard atmosphere, the characteristics of changes in the loading effects with time, space and frequency are comprehensively investigated in this dissertation. The numerical results obtained in this study can provide accurate atmospheric correction models for high-precision continuous measurements of the geophysical fields such as gravity, tilt, displacement and strain on the Earth's surface. The main results are listed as following:In chapter 1, the background of this study is briefly introduced. Based on the analysis of the development and achievement of the loading theory of the atmospheric pressure, the method and research routine, adopted in this study, are chosen.In chapter 2, the meteorological knowledge, data and the methods of the data processing, related to the study on the atmospheric loads, are simply presented. The model for the perfect gas constant, describes by the relative moisture, is developed. The influences of the variation in the vapor component in the atmosphere on the perfect gas constant are evaluated by using the changing characteristics of the temperature on the surface, its spatial gradient and the barometric pressure. The surface-based pressure recordings, obtained in China and is adjacent region, are pre-processed and grided.In chapter 3, we briefly present the fundamental theory of the elastic response of a spherical Earth to the surface loads and the treatment to the loading effects of the barometric pressure. The expression of the atmospheric gravity and tilt Green's functions is finally deduced.In chapter 4, the influences of the Earth's models on the elastic Green's function, aswell as on the atmospheric loading effects, are discussed using the numerical techniques. The attraction Green's function is solved out based on the state equations of the ideal gas and the hydrostatic equilibrium equation. The influences of various factors upon the gravity and tilt Green's functions, as well as upon the gravity and tilt, are considered in detail. The station-dependent gravity and tilt Green's functions at Wuchang are obtained, based on the spherically symmetric Earth model.In chapter 5, the numerical results of the atmospheric effects on various geophysical field observations are obtained. The temporal series of the atmospheric loading effects are obtained using the ground-based measurements of the temperature and pressure. The temporal, spatial and frequency-field characteristics are discussed. The validity of the corresponding empiric formula is analyzed and the atmospheric effects and correction method are investigated in the data analysis of the ground-based observations. The atmospheric effects on the gravity observations are analyzed and detected using the gravity data recorded with the superconducting gravimeters at the Global Geodynamic Project (GGP) stations. The possibility of the atmospheric correction to the displacement measurements at the International GPS Service (IGS) stations is discussed.In chapter 5, using the mathematic theory of statistics, the errors of the convolution technique, u...