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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 32, issue 8
Ann. Geophys., 32, 911–923, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 32, 911–923, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 06 Aug 2014

Regular paper | 06 Aug 2014

Near real-time water vapor tomography using ground-based GPS and meteorological data: long-term experiment in Hong Kong

P. Jiang1, S. R. Ye1, Y. Y. Liu1, J. J. Zhang2, and P. F. Xia1 P. Jiang et al.
  • 1GNSS Research Center, Wuhan University, Wuhan, 430079, China
  • 2CMA, Institute of Urban Meteorology, Beijing, 100089, China

Abstract. Water vapor tomography is a promising technique for reconstructing the 4-D moisture field, which is important to the weather forecasting and nowcasting as well as to the numerical weather prediction. A near real-time 4-D water vapor tomographic system is developed in this study. GPS slant water vapor (SWV) observations are derived by a sliding time window strategy using double-difference model and predicted orbits. Besides GPS SWV, surface water vapor measurements are also assimilated as real time observations into the tomographic system in order to improve the distribution of observations in the lowest layers of tomographic grid. A 1-year term experiment in Hong Kong was carried out. The feasibility of the GPS data processing strategy is demonstrated by the good agreement between the time series of GPS-derived Precipitable Water Vapor (PWV) and radio-sounding-derived PWV with a bias of 0.04 mm and a root-mean-square error (RMSE) of 1.75 mm. Using surface humidity observations in the tomographic system, the bias and RMSE between tomography and radiosonde data are decreased by half in the ground level, but such improved effects weaken gradually with the rise of altitude until becoming adverse above 4000 m. The overall bias is decreased from 0.17 to 0.13 g m−3 and RMSE is reduced from 1.43 to 1.28 g m−3. By taking the correlation coefficient and RMSE between tomography and radiosonde individual profile as the statistical measures, quality of individual profile is also improved as the success rate of tomographic solution is increased from 44.44 to 63.82% while the failure rate is reduced from 55.56 to 36.18%.

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