Applications of the Fictitious Compress Recovery Approach in Physical Geodesy

The fictitious compress recovery approach is introduced, which could be applied to the estab-lishment of the Runge-Krarup theorem, the determination of the Bjerhammar's fictitious gravity anomaly, the solution of the "downward continuation" problem of the gravity field, the confirmation of the convergence of the spherical harmonic expansion series of the Earth's potential field, and the gravity field determination in three cases: gravitational potential case, gravitation case, and gravitational gradient case. Several tests using simulation experiments show that the fictitious compress recovery approach shows promise in physical ge-odesy applications.

Design of Geodetic SVLBI Satellite Orbit and Its Tracking Network

SVLBI (空间很长的基线干涉量度) 在测地学和地球动力学有一些重要潜在的应用，为哪个最困难的任务是精确决定一颗 SVLBI 卫星的轨道。这个工作学习将可能能决定一颗空间 VLBI 卫星的轨道的几种技术。然后，根据为测地学的学习和 GNSS 的几何学的卫星和要求的类型和特征(GPS，伽利略) 追踪空间 VLBI 卫星的卫星， SVLBI 卫星(TEST-SVLBI ) 的六个 Keplerian 元素被决定。一个程序被设计由网络，追踪的网络 ofTEST-SVLBI 与被设计的车站分析不同高度的空格的范围区域。由网络追踪 TEST-SVLBI 的效率被学习，并且结果被介绍。

Global spectral model of the geoid

The coefficients of the Global Gravitational Models （GGMs） define the external gravitational field of the Earth. In many geoscience applications and gravity interpretations these coefficients are routinely used to represent the geoid surface and related gravitational field quantities without taking into consideration the internal convergence domain for computing the gravitational field inside the Earth＇s masses. In this study we discuss this issue and present the numerical approach for computing the gravitational field quantities on the geoid. The proposed numerical approach utilizes spectral expressions for the gravi- metric forward modelling of topographic mass density distribution and the indirect gravimetric modelling of mass density heterogeneities inside the geoid. In the numerical realization we demonstrate that for precise applications the differences between the potential values computed at the topographic surface and on the geoid should be taken into consideration especially in mountainous regions with complex geology as well as in polar regions, where these differences in absolute values reach 40 m2 s-2 （or more）, which translates into vertical displacements between the geoid and the quasigeoid of about 4m,

Spatiotemporal estimation of hourly 2-km ground-level ozone over China based on Himawari-8 using a self-adaptive geospatially local model

Ground-level ozone(O_(3))is a primary air pollutant,which can greatly harm human health and ecosystems.At present,data fusion frameworks only provided ground-level O_(3) concentrations at coarse spatial(e.g.,10 km)or temporal(e.g.,daily)resolutions.As photochemical pollution continues increasing over China in the last few years,a high-spatial–temporal-resolution product is required to enhance the comprehension of ground-level O_(3) formation mechanisms.To address this issue,our study creatively explores a brand-new framework for estimating hourly 2-km ground-level O_(3) concentrations across China(except Xinjiang and Tibet)using the brightness temperature at multiple thermal infrared bands.Considering the spatial heterogeneity of ground-level O_(3),a novel Self-adaptive Geospatially Local scheme based on Categorical boosting(SGLboost)is developed to train the estimation models.Validation results show that SGLboost performs well in the study area,with the R2 s/RMSEs of 0.85/19.041 lg/m^(3) and 0.72/25.112 lg/m^(3) for the space-based cross-validation(CV)(2017–2019)and historical space-based CV(2019),respectively.Meanwhile,SGLboost achieves distinctly better metrics than those of some widely used machine learning methods,such as e Xtreme Gradient boosting and Random Forest.Compared to recent related works over China,the performance of SGLboost is also more desired.Regarding the spatial distribution,the estimated results present continuous spatial patterns without a significantly partitioned boundary effect.In addition,accurate hourly and seasonal variations of ground-level O_(3) concentrations can be observed in the estimated results over the study area.It is believed that the hourly 2-km results estimated by SGLboost will help further understand the formation mechanisms of ground-level O_(3) in China.

GPS-derived horizontal ice flow velocities along the traverse route from Zhongshan Station to Dome-A, East Antarctica

The traverse route from Zhongshan Station to Dome A is one of the most important expedition routes of ITASE Project. China carried out 3 inland traverses during the 1996/1997, 1997/1998, 1998/1999 austral summer field seasons. The field team reached inland 300 km, 500 km and 1100 km away from Zhongshan Station respectively. Some ice motion stakes were set up, occupied and reoccupied along the route by GPS technology. It showed that the ice along the traverse route flowed with an 8 25 ma -1 velocity to the northwest, the direction of the bottom of Lambert Glacier Basin. They coincide with the results along the eastern section from LGB59 70 of the LGB route deduced by Australia in both values and directions. Furthermore, the directions of the horizontal flow are perpendicular to the surface topography contour. The much larger velocity at the point of LT980 with an approximate value of 100 ma -1 was probed. It was caused by a 15 km wide trough on the bed beneath this point.

Influence of Uneven Trace Spacing on Rayleigh Wave Dispersion

Rayleigh wave dispersion signals are significant to underground investigation.Tradition-ally,uniformed trace spacing is employed in surface wave surveys.In some cases,however,uneven trace spacing is often encountered because of the limitations of the site condition.In order to study the influence of uneven trace spacing on the dispersion data construction of Rayleigh waves,data acquisi-tion is performed based on a 2.5D field layout with a linear array of geophones fixed and a mobile source.The observation direction controls the trace spacing of the measurement.The final results demonstrate that the trace nonuniformity has significant influence on the Rayleigh wave dispersion feature constructed.When the observation angle is over 45o,the dispersion image will be too distorted to extract dispersion data correctly.

Effective Dispersion Curve and Pseudo Multimode Dispersion Curves for Rayleigh Wave

The hi-energy bands in the dispersion image are usually interpreted as the true dispersion phase velocities.However,the multiple dispersion modes of Rayleigh wave in layered media stack in space,producing the effective dispersion curve and the pseudo multimode dispersion curves in disper-sion image.The effective dispersion curve has the maximum energy with lower phase velocities than pseudo dispersion phase velocities,and thus is often misunderstood as the fundamental mode.Within the tolerable misfit,the effective dispersion curve can approach the true fundamental mode.Different from the true multimode dispersion curves,the pseudo multimode dispersion curves are related to the effective dispersion curve.A numerical model is adapted to simulate the true dispersion curves,effec-tive dispersion curve,and pseudo multimode dispersion curves.Their differences and mutual relations are demonstrated.