Analysis of the Effect Upon GPS Measurements Arising From Deviations From Hydrostatic Equilibrium in Areas Affected by Severe Weather

Francesca Sciro Scappuzzo, Beat Buerki, Hans-Gert Kahle, Bruce T. Anderson

Abstract:	"We have developed a modified model of the Dry Zenith Delay for GPS measurements acquired at stations located on mountain areas affected by severe weather. This new model takes into account the non-hydrostatic conditions associated with the orographic wind as it relates to the particular topography of the mountain. This correction term is computed modeling the mountain waves or lee waves dynamics using a linear analysis of the steady flow over a mountain, where the linear approximation permits analytically exact solutions. We mathematically modeled the pressure deviation from hydrostatic equilibrium, and we derived an estimate of the Dry Zenith Delay error associated with this pressure deviation, both locally and remotely, using actual atmospheric parameters recoded on Mount Washington, NH, USA, during different seasons in 2004. According to our proposed model, non-negligible nonhydrostatic conditions exist on Mount Washington more than 50 % of the time during winter months. Preliminary results indicate that the error in the estimate of the Dry Zenith Delay can be much higher than found in previous literature (assumed to be up to 20 mm/1000 mbar). According to our model, the error in the estimate of the Dry Zenith Delay derived from non-hydrostatic contribution can be 20 to 40 mm/1000 mbar and can even exceed 60 mm /1000 mbar for exceptionally high winds in winter (over 180 km/h). For the typical nonhydrostatic effect associated with dynamic flow over topography, we observed an error in the PW estimate of 3 to 4 mm; during severe weather conditions this error can be as high as 11 mm for wind peak gusts of 180 km/h."
Published in:	Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005) June 27 - 29, 2005 Royal Sonesta Hotel Cambridge, MA
Pages:	440 - 448
Cite this article:	Scappuzzo, Francesca Sciro, Buerki, Beat, Kahle, Hans-Gert, Anderson, Bruce T., "Analysis of the Effect Upon GPS Measurements Arising From Deviations From Hydrostatic Equilibrium in Areas Affected by Severe Weather," Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005), Cambridge, MA, June 2005, pp. 440-448.
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