高精度GPS观测中的负荷效应

讨论了高精度GPS观测中的负荷效应问题。根据地表质量负荷理论的Green函数方法，计算了地球表面质量负荷（包括大气、非潮汐海洋和陆地水）对中国部分IGS台站垂直位移的影响。其中，大气负荷对各台站的影响比较一致，变化幅度约为20 mm，非潮汐海洋对沿海台站的负荷影响显著，其变化幅度达到10 mm，水负荷对各台站的影响差异较大，最大的变化幅度约20 mm；总的负荷效应达到厘米量级，与GPS观测结果的比较说明在高精度的GPS观测的时间序列中，存在明显的季节性变化，而该变化与表面负荷有着直接的关系。特别是对于房山和乌鲁木齐2个台站，GPS观测的垂直变化中的季节项基本上就是来自于地球表面的质量负荷；而昆明和拉萨这2个台站尽管位于板块运动活跃区域，垂直季节性变化也主要源于地表负荷。因此扣除这些负荷影响的GPS观测资料将更有利于研究地壳的运动特征。

Loading Effect on High Precision GPS Observations

The problem of loading effect on high precision GPS observations is discussed in this paper. According to the Green's approach in theory of mass load on Earth's surface, the vertical displacements at some Chinese IGS stations due to mass load, including atmosphere, non tidal ocean and land water, are estimated. The atmosphere loading effects on different stations are of the similar characteristic, which has the magnitude of 20mm; the non tide ocean loading effects are accountable only at the costal stations, which have magnitude of 10mm; and the land water loading effects are various at different stations, which have magnitude of 20mm. And the total effects of the three sources have obvious seasonal variation with magnitudes of the order of centimeter, which are corresponding to the mass load and comparable with the observations obtained by GPS. Especially for stations of Fangshan and Wulumuqi, the seasonal variations in GPS time series primarily result from mass load. Furthermore, although the stations of Kunming and Lasha locate in active plate motion area, the seasonal variations mostly attribute to surface mass load. Therefore, the GPS observations with the loading effect excluded will contribute more to investigation on the characteristic of crustal movement.