大气负载效应对不同纬度IGS测站的影响

Effects of atmospheric loading on IGS stations in different latitude zones

针对目前大气负载效应明显的纬度分布特性未得到重视,大部分GPS坐标时间序列均未加入大气负载修正,导致忽略了中高纬地区测站受大气负载的显著影响这一问题,该文从测站位置纬度分布的角度,着重计算分析由大气负载效应引起的国际GNSS服务测站位移,分析大气负载效应对GPS坐标时间序列的影响,以及因纬度差异导致的国际GNSS服务测站受大气负载效应影响存在的差异。通过计算修正前后GPS坐标时间序列均方根值和加权均方根值,评估对GPS坐标时间序列进行大气负载效应修正的重要性。分析结果表明,大气负载对测站影响的分布与纬度位置有明显关联,中高纬地区其效果显著,而低纬地区受其影响相对较小。在北斗全球坐标框架的建立中,若考虑大气负载效应的影响,精度上将有毫米级的提高。

Based on information of the evenly distributed IGS stations which are selected to build the international terrestrial reference frame 2008（ITRF2008）, this paper selected 150 healthy international GNSS service（IGS）stations distributed in different latitude zones. Then, displacements of IGS stations caused by atmospheric loading were calcu- lated using grids provided by the global geophysical fluids center （GGFC）, results of which were analyzed to interpret the differences of effects of atmospheric loading on stations in different latitude zones. Finally, the calculated displace- ments were used to correct IGS station time series provided by scripps orbit and permanent array center （SOPAC）. Analysis indicated a strong correlation between the location of a station and atmospheric loading effects on it, with the effects on stations more significant in mid-and high-latitude zones than that on stations in low latitude zone. After the atmospheric loading correction applied, RMS of about 71% of GPS height time series were reduced, with maximum reduction of 2.1mm. Furthermore, by comparing WRMS difference and latitude location of stations, a general trend of increasing WRMS difference along with the increase of latitude could be found, which indicated better correction ef- ficiency in high latitude zones; also, of all the selected sites distributed on different plates, Eurasian plate was the most affected and showed better improvements in RMS of height time series, commonly ranged from 1.5 to 2mm. As a result, in order to build a more precise BeiDou coordinate frame, it was suggested that atmospheric loading should be taken into consideration, which would improve the frame by millimeter level.