Open AccessDerivation of the Water Vapor Content from the GNSS Radio Occultations Observations
Author(s) -
F. Vespe,
Teresa Persia
Publication year - 2006
Publication title -
journal of atmospheric and oceanic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.774
H-Index - 124
eISSN - 1520-0426
pISSN - 0739-0572
DOI - 10.1175/jtech1891.1
Subject(s) - radio occultation , troposphere , gnss applications , humidity , remote sensing , water vapor , global positioning system , environmental science , atmosphere (unit) , bending , inversion (geology) , meteorology , geodesy , computer science , geology , physics , telecommunications , paleontology , structural basin , thermodynamics
The present work investigates the possibility of retrieving humidity using the bending angle data obtained from radio occultation of GPS signals without additional external information. In particular, with the proposed approach, the dry pressure profiles are obtained by fitting the bending angles of the outer-troposphere layers (from h = h250K up to the stratopause) using the Hopfield dry atmosphere model. The ground pressure and temperature are the parameters of the model to be estimated. In the second step the humidity profiles are extracted by subtracting the contribution resulting from the dry atmosphere from the measured bending angles. Such derivation implies a complex mathematical treatment of the relationship between the bending angle and the refractivity, which is fully explained herein. Furthermore, the method was applied on Challenging Minisatellite Payload (CHAMP) profiles. The CHAMP profiles are achieved by applying heuristic retrieval algorithms based on the canonical transform. The algorithms are applied to minimize the negative refractivity bias that is observed for low-latitude GNSS RO. Thus, the results are shown and discussed in the second part of the paper. Finally, it is widely discussed how the proposed method is able to retrieve refractivity profiles without using the Abel inversion.