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 decon-elate into noise.