Towards an independent and autonomous meteorological service based on GNSS earth limb sounding technique?
Benedetto, C. ; Vespe, F. ; Pacione, R.
Jan - 2002
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type: Conference Proceedings
Abstract
In the last decade the use of GPS radio occultations technique (GPS RO) has been deeply and widely investigated for retrieving physical and chemical parameters of Earth atmosphere. The technique proved to be particularly precise in retrieving temperature profiles with an high vertical resolution (<1 Km). Temperature profiles are obtained for dry part of atmosphere solving for the system of 2 equations (Smith \&Weintraub equation for refractivity and state equation o gasses) in 2 unknownf (hydrostatic dry pressure P and temperature T). The System cannot be solved for lower troposphere because the water vapour pressure is not negligible. So we are forced to include some other informations such as the humidity computed by the models (ECMWF or NCEP) or adding another observable in the system as the zenith troposphere delays estimated by the GPS ground stations. Recently it has been proposed by the authors a new approach able to retrieve water vapour content without using external data. In the new proposed approach the humidity profiles are extracted differentiating the refractivity retrieved by the GPS RO with that obtained by fitting the outer layers refractivity with a dry atmosphere model (Hopfield). The present work can be considered a follow on activity in which we use directly the bending angles: i.e. before Abell inversion. Furthermore the results of validation activities using zenith tropospheric delays estimated by a ground GPS network are shown. Finally it is proposed a method for the refinement of the temperature and water vapour content profiles retrieved by the GPS RO.
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