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Volume 10, issue 8 | Copyright

Special issue: Advanced Global Navigation Satellite Systems tropospheric...

Atmos. Meas. Tech., 10, 2807-2820, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Aug 2017

Research article | 07 Aug 2017

Determination of zenith hydrostatic delay and its impact on GNSS-derived integrated water vapor

Xiaoming Wang1,2, Kefei Zhang2,3, Suqin Wu2, Changyong He2, Yingyan Cheng4, and Xingxing Li5 Xiaoming Wang et al.
  • 1Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing 100094, China
  • 2Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, School of Science, Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia
  • 3School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou, China
  • 4Institute of Geodesy and Geodynamics, Chinese Academy of Surveying and Mapping, Beijing, China
  • 5Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Brandenburg, Germany

Abstract. Surface pressure is a necessary meteorological variable for the accurate determination of integrated water vapor (IWV) using Global Navigation Satellite System (GNSS). The lack of pressure observations is a big issue for the conversion of historical GNSS observations, which is a relatively new area of GNSS applications in climatology. Hence the use of the surface pressure derived from either a blind model (e.g., Global Pressure and Temperature 2 wet, GPT2w) or a global atmospheric reanalysis (e.g., ERA-Interim) becomes an important alternative solution. In this study, pressure derived from these two methods is compared against the pressure observed at 108 global GNSS stations at four epochs (00:00, 06:00, 12:00 and 18:00UTC) each day for the period 2000–2013. Results show that a good accuracy is achieved from the GPT2w-derived pressure in the latitude band between −30 and 30° and the average value of 6h root-mean-square errors (RMSEs) across all the stations in this region is 2.5hPa. Correspondingly, an error of 5.8mm and 0.9kgm−2 in its resultant zenith hydrostatic delay (ZHD) and IWV is expected. However, for the stations located in the mid-latitude bands between −30 and −60° and between 30 and 60°, the mean value of the RMSEs is 7.3hPa, and for the stations located in the high-latitude bands from −60 to −90° and from 60 to 90°, the mean value of the RMSEs is 9.9hPa. The mean of the RMSEs of the ERA-Interim-derived pressure across at the selected 100 stations is 0.9hPa, which will lead to an equivalent error of 2.1mm and 0.3kgm−2 in the ZHD and IWV, respectively, determined from this ERA-Interim-derived pressure. Results also show that the monthly IWV determined using pressure from ERA-Interim has a good accuracy − with a relative error of better than 3% on a global scale; thus, the monthly IWV resulting from ERA-Interim-derived pressure has the potential to be used for climate studies, whilst the monthly IWV resulting from GPT2w-derived pressure has a relative error of 6.7% in the mid-latitude regions and even reaches 20.8% in the high-latitude regions. The comparison between GPT2w and seasonal models of pressure–ZHD derived from ERA-Interim and pressure observations indicates that GPT2w captures the seasonal variations in pressure–ZHD very well.

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Short summary
Accurate knowledge of water vapor (WV) is vital for global climate studies. The Global Navigation Satellite System (GNSS) has been used as an emerging tool for sensing integrated WV (IWV). In the determination of PWV, surface pressure is required. However, few GNSS stations were installed with meteorological sensors back in the 1990s. Our research indicates that the ERA-Interim-derived pressure has the potential to be used to obtain high-accuracy IWV on a global scale for climate studies.
Accurate knowledge of water vapor (WV) is vital for global climate studies. The Global...