Analysis of the Temporal and Spatial Variability of the Wet Troposphere at a Local Scale by High-rate PPP Using a Dense GNSS Network

The objective of this work is to study and characterize the temporal and spatial variability of water vapor at a local scale, i.e. less than 10 km, by analyzing wet tropospheric delays estimated by a dense GNSS network. Experiments using high-rate (30 s and 5 s) observations are conducted in order to investigate also the short periodic refractivity fluctuations induced by turbulence, expected to be in the range of minutes to seconds. The effects induced by interpolation errors of satellite clocks with high-rate observations are investigated. The GPS-derived precipitable water vapor (PWV) is validated by comparison with the PWV measured by radiosondes and a radiometer, obtaining differences of about 2 mm in RMS. The distribution of PWV is studied by geostatistics (kriging) and turbulence analyses. Spatial and temporal structure functions are computed for both zenith wet delays and show power-law behaviors varying between 5/3 and 2/3, consistently with the Treuhaft-Lanyi model (i.e. a long baseline approximation for Kolmogorov turbulence theory). Power-law behaviors in temporal structure functions result both for long-term variations, with correlation lengths depending on the weather conditions, and for short-term fluctuations, until about 10 seconds; for shorter time lags the structure functions decorrelate into noise.

这项工作的目的是通过分析由密集的全球导航卫星系统（GNSS）网络估算的湿对流层延迟，在局部尺度（即小于10千米）上研究和描述水汽的时空变异性。为了也研究由湍流引起的短周期折射率波动（预计在分钟到秒的范围内），进行了使用高采样率（30秒和5秒）观测的实验。研究了高采样率观测下卫星钟插值误差所引起的影响。通过与无线电探空仪和辐射计测量的可降水量水汽（PWV）进行比较，对全球定位系统（GPS）导出的PWV进行了验证，均方根（RMS）差异约为2毫米。通过地质统计学（克里金法）和湍流分析研究了PWV的分布。计算了天顶湿延迟的时空结构函数，它们呈现出在5/3和2/3之间变化的幂律行为，这与特鲁哈夫特 - 兰尼模型（即柯尔莫哥洛夫湍流理论的长基线近似）一致。在时间结构函数中的幂律行为既出现在长期变化中（相关长度取决于天气条件），也出现在短期波动中（直到约10秒）；对于更短的时间滞后，结构函数去相关为噪声。