Abstract
Abstract. Tomographic techniques are successfully applied to obtain 4D images of the tropospheric refractivity in a local dense network of global positioning system (GPS) receivers. We show here how GPS data are processed to obtain the tropospheric slant wet delays and discuss the validity of the processing. These slant wet delays are the observables in the tomographic processing. We then discuss the inverse problem in 4D tropospheric tomography making extensive use of simulations to test the system and define the resolution and the impact of noise. Finally, we use data from the Kilauea network in Hawaii for February 1, 1997, and a local 4×4×40 voxel grid on a region of 400 km2 and 15 km in height to produce the corresponding 4D wet refractivity fields, which are then validated using forecast analysis from the European Center for Medium Range Weather Forecast (ECMWF). We conclude that tomographic techniques can be used to monitor the troposphere in time and space.Key words: Radio science (remote sensing; instruments and techniques)
Highlights
Tomographic techniques aim to obtain a solution ®eld from integrated measurements along dierent ray paths.They have been successfully applied, for instance, in seismic and oceanographic studies, using earthquake and accoustic sensing; two dimensional images of the ionosphere using radio signals from polar orbiting satellites and dedicated receivers have been described
Flores positioning system (GPS) globally and continuously transmits radio signals, which are aected by the presence of the atmosphere and carry information on its state
Flores et al.: 4D tropospheric tomography using GPS slant wet delays pressure in mbar, T is the atmospheric temperature in K
Summary
Tomographic techniques aim to obtain a solution ®eld from integrated measurements along dierent ray paths They have been successfully applied, for instance, in seismic and oceanographic studies, using earthquake and accoustic sensing; two dimensional images of the ionosphere using radio signals from polar orbiting satellites and dedicated receivers have been described A. Flores et al.: 4D tropospheric tomography using GPS slant wet delays pressure in mbar, T is the atmospheric temperature in K (Smith and Weintraub, 1953; Thayer, 1974), and W is the liquid water vapour in the atmosphere. Flores et al.: 4D tropospheric tomography using GPS slant wet delays pressure in mbar, T is the atmospheric temperature in K (Smith and Weintraub, 1953; Thayer, 1974), and W is the liquid water vapour in the atmosphere The latter term is generally neglected (Kursinski, 1997). We take GPS data measured in this network for one particular day (1 February, 1997) and apply the described techniques to yield wet refractivity
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