Atmospheric water-vapor signals in GPS data: synergies, correlations, signals and errors

I explore the-statistics of integrated water-vapor (IWV) and the ability of GPS to provide information that reflects large-scale weather systems. I de monstrate that the power spectral density (PSD) is a much more robust estim ator of IWV statistics than the structure function is for long time scales. I then use the PSD to investigate the IWV statistics of simulated atmosphe res. I use a random walk to approximate the Kolmogorov behavior of local at mospheric turbulence. The atmospheres I simulate contain the turbulent beha vior sumperimposed on systematic changes to the IWV that might be associate d with the passage of fronts. I demonstrate that the PSD associated with su ch frontal systems might be quite similar to those for pure turbulent behav ior This result may explain why many previous studies that examined PSDs of IWV over a site concluded that the spectra was Kolmogorov. I also derive t he first cross-power spectrum of IWV using GPS sites separated by similar t o 500 km. At this separation, the local turbulence may be assumed to have b ecome decorrelated. I find that even this long wavelength signal consists o f components at a wide range of temporal frequencies. The IWV cross power s pectrum contains significant energy even at temporal frequencies of 2-4 cyc les per hour. (C) 2001 Elsevier Science Ltd. All rights reserved.