| One source of error for GPS signals received on the Earth is due to the delay caused by propagation through the troposphere. If a receiver's coordinates are known and surface pressure measurements are available, the positioning problem can be inverted such that the wet delay in the signal can be used to derive water vapour content in the atmosphere through a tomographic, 4-D model.; Local radiosonde observations, monthly-averaged climate data and GPS occultation-derived wet refractivity measurements were assimilated into a tomography model which originally used ground-based GPS data over southern Alberta. Improvements were made to the estimation of vertical profiles of water vapour, and improvements in the integrated domain were on the order of ∼0.5 cm for the assimilation of radiosonde data. The best results were obtained by assimilating radiosonde observations. Occultation measurement assimilation resulted in improvements in the integrated domain of up to 0.5 cm. |
