Special Issue: Application of GPS and other space geodetic techniques to Earth Sciences (2)
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Initial results of combining GPS occultations with ECMWF global analyses within a 1DVar framework
Earth, Planets and Space volume 52, pages 885–892 (2000)
Abstract
We present results of combining occultation refractivity profiles from GPS/MET with ECMWF global analyses in a 1DVar framework in order to separate the wet and dry contributions to refractivity and assess their impact on the analyzed temperature, surface pressure and specific humidity fields. We find significant zonal mean temperature, surface pressure and humidity differences between the 1DVar solutions and the ECMWF analyses reflecting biases between the GPS refractivities and ECMWF analyses. Large profile-to-profile temperature discrepancies in the tropical lower stratosphere are due to waves not represented in the analyses. The 1DVar solution is generally drier than ECMWF particularly in the southern subtropics. Lack of moisture above 300 hPa in the present model caused the solution to make large adjustments in low latitude surface pressure and tropospheric temperatures to increase upper troposphere densities and compensate for the missing upper level moisture. The discrepancies between the solution and the background and observational data sets represent roughly a 2-sigma level of agreement rather than the 1-sigma level desired in a 1DVar solution. Given the simplicity of our error covariances, our results are promising as a first step. In the future, the error covariances need to be refined and, in particular, to vary with location.
References
Fjeldbo, G. F., V. R. Eshleman, and A. J. Kliore, The neutral atmosphere of Venus as studied with the Mariner V radio occultation experiments, Astron. J., 76, 123–140, 1971.
Gadd, A. J., B. R. Barwell, S. J. Cox, and R. J. Renshaw, Global processing of satellite sounding radiances in a numerical weather prediction system, Q. J. Roy. Met. Soc., 121, 615–630, 1995.
Healy, S. B. and J. R. Eyre, Retrieving temperature, water vapour and surface pressure information from refractive index profiles derived by radio occultation: a simulation study, Q. J. Roy. Met. Soc., 2000 (in press).
Karayel, E. T. and D. P. Hinson, Sub-Fresnel-scale vertical resolution in atmospheric profiles from radio occultation, Radio Sci., 32(2), 411–423, 1997.
Kursinski, E. R., The GPS radio occultation concept: theoretical performance and initial results, Ph.D. thesis, Calif. Inst. of Technol., Pasadena, 1997.
Kursinski, E. R. and G. A. Hajj, A comparison of water vapor derived from GPS occultations and global weather analyses, J. Geophys. Res., 2000a (in press).
Kursinski, E. R. and G. A. Hajj, Zonal variability and accuracy of water vapor estimated from GPS and global weather analyses, J. Geophys. Res., 2000b (submitted).
Kursinski, E. R., G. A. Hajj, K. R. Hardy, L. J. Romans, and J. T. Schofield, Observing tropospheric water vapor by radio occultation using the Global Positioning System, Geophys. Res. Lett., 22, 2365–2368, 1995.
Kursinski, E. R., G. A. Hajj, W. I. Bertiger, S. S. Leroy, T. K. Meehan, L. J. Romans, J. T. Schofield, D. J. McCleese, W. G. Melbourne, C. L. Thornton, T. P. Yunck, J. R. Eyre, and R. N. Nagatani, Initial results of radio occultation observations of Earth’s atmosphere using the Global Positioning System, Science, 271, 1107–1110, 1996.
Kursinski, E. R., G. A. Hajj, K. R. Hardy, J. T. Schofield, and R. Linfield, Observing Earth’s atmosphere with radio occultation measurements using GPS, J. Geophys. Res., 102(D19), 23429–23465, 1997.
Kursinski, E. R., G. A. Hajj, S. S. Leroy, and B. Herman, The GPS radio occultation technique, Terrestrial, Atmopsheric and Oceanic Sciences (TAO), 11, 53–114, 2000.
Leroy, S. S., Measurement of geopotential heights by GPS radio occultation, J. Geophys. Res., 102, 6971–6986, 1997.
Rocken, C., R. Anthes, M. Exner, D. Hunt, S. Sokolovskiy, R. Ware, M. Gorbunov, W. Schreiner, D. Feng, B. Herman, Y.-H. Kuo, and X. Zou, Analysis and validation of GPS/MET data in the neutral atmosphere, J. Geophys. Res., 102, 29849–29866, 1997.
Tsuda, T., M. Nishida, C. Rocken, and R. H. Ware, A Global Morphology of Gravity Wave Activity in the stratosphere revealed by the GPS occultation data (GPS/MET), J. Geophys. Res., 1999 (submitted).
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Kursinski, E.R., Healy, S.B. & Romans, L.J. Initial results of combining GPS occultations with ECMWF global analyses within a 1DVar framework. Earth Planet Sp 52, 885–892 (2000). https://doi.org/10.1186/BF03352301
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DOI: https://doi.org/10.1186/BF03352301