Retrieval of Key Climate Variables Using Occultation Geometry of a Mountain top GPS Receiver.

Ashraf Mousa and T. Tsuda

Abstract:	Radio Occultation measurements using GPS and a receiver on a Low Earth Orbit (LEO) have recently been shown to produce accurate profiles of Atmospheric refractivity with high vertical resolution. While GPSLEO occultation has the advantage of being global, the sampling in any region is relatively sparse without a large number of orbiting receivers. By contrast, a receiver located inside the atmosphere (such as on a mountain top) can be used to provide dense data over specific areas of interest. Current study introduces a least squares generalized raytracing inversion method for retrieval of refractivity profile from the mountain top GPS receiver data. Spherical symmetry is assumed for the atmosphere and the refractivity is modelled as a piecewise exponential, with a scale height changing from one atmospheric layer to the next. Additional refractivity data derived from a model is introduced as constraints. Refractivity parameters are determined using least squares method by minimizing the difference between measured bending angle and model refractivity and those calculated from the exponential model and ray tracing. The result shows that GPS receiver inside the atmosphere can produce accurate refractivity vertical profile with high resolution.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	1117 - 1126
Cite this article:	Mousa, Ashraf, Tsuda, T., "Retrieval of Key Climate Variables Using Occultation Geometry of a Mountain top GPS Receiver.," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 1117-1126.
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