南极和格陵兰岛GPS连续台站背景噪声时空特性

基于GPS观测数据获取的陆地垂向运动对研究现今两极区域的冰川质量变化具有重要的科学意义.受地表环境负荷对GPS时间序列中背景噪声空间异质性的影响, 在利用GPS时间序列获取垂向速度场时, 估计结果存在较大不确定度.本文针对南极和格陵兰岛区域的GPS连续观测时间序列中背景噪声的空间特性对速度场及其不确定度的影响问题, 利用地表环境负荷模型(包括大气、非潮汐海洋和水文负荷)和重力卫星GRACE/GRACE-FO观测数据反演的地表弹性形变对GPS时间序列进行了改正.通过对改正前后的数据进行背景噪声特性分析, 揭示出修正环境负荷形变能够有效降低极区GPS时间序列背景噪声幅度, 但是大气和非潮汐海洋负荷改正造成了大多数台站背景噪声谱指数的减小, 南极和格陵兰岛分别约为其GPS台站总数的46.1%和84.6%, 直接导致了对GPS速度不确定度估计的改善效果不明显.对背景噪声空间异质性的研究结果表明, 极区台站的背景噪声参数主要表现为随纬度变化的空间特性.

Spatio-temporal characteristics of background noise of GPS continuous stations over Antarctica and Greenland

The vertical land motion from GPS observation is of great significance for studying the changes in glacier mass in polar regions. However, there is significant uncertainty when using GPS to derive the vertical velocity field due to the spatial variability of background noise within GPS time series, which may be induced by surface environmental loads. In this study, we evaluate the influence of the spatial characteristics of background noise on the velocity field and its uncertainty in the GPS continuous observations of Antarctica and Greenland. GPS time series are corrected using surface environmental loading models including atmospheric, non-tidal ocean, and hydrological loads. Additionally, the surface elastic deformation is modeled using gravity satellite observations from GRACE/GRACE-FO. Through the analysis of background noise characteristics in the GPS time series before and after correction, it is concluded that the correction of environmental load deformation can effectively reduce the background noise in GPS time series. The correction of atmospheric and non-tidal oceanic loads resulted in a reduction of the background noise spectrum index at most stations, with approximately 46.1% and 84.6% of the total GPS stations in Antarctica and Greenland, respectively. We find that the improvement in GPS velocity uncertainty estimation is not obvious. In addition, we analyze the spatial heterogeneity of background noise, which reveals that the spatial characteristics of background noise parameters and velocity uncertainties vary with latitude.