An inter-comparison study to estimate zenith wet delays using VLBI, GPS, and NWP models

Abstract

Water vapour is a key variable in atmospheric processes and plays a crucial role in atmospheric motions on a wide range of scales in space and time. The water vapour content is approximately proportional to the zenith wet delay (ZWD) which, in turn, constitutes a crucial parameter in geodetic microwave space techniques (VLBI and GPS). Apart from being determined by measurement techniques, the ZWD can also be derived from numerical weather prediction (NWP) models such as the non-hydrostatic MM5 model and the hydrostatic HIRLAM model. At the station Robledo de Chavela (Madrid) ZWD values were derived from VLBI, GPS, MM5, and HIRLAM for the beginning of December 1996. The results of the different techniques agree to the sub-centimetre level with correlation values of 0.87 (GPS vs. MM5), 0.81 (GPS vs. HIRLAM), and 0.84 (MM5 vs. HIRLAM). The correlation VLBI vs. MM5 of 0.78 is based on a short VLBI time series and should be considered preliminary. Further studies with longer time series are necessary to confirm this value. The bias and RMS difference values are all contained in the margin provided by the internal errors.

Multi-technique comparison of troposphere zenith delays and gradients during CONT08

“…Behrend et al (2000Behrend et al ( , 2002 between ZTDs from GPS and VLBI was rather good (see Table 7); DORIS was fairly compatible with GPS and VLBI, but the agreement for WVR and ECMWF with ZTDs estimated from spacegeodetic techniques was rather low. To get detailed information on comparisons of troposphere parameters, readers are referred to, e.g.…”

“…To get detailed information on comparisons of troposphere parameters, readers are referred to, e.g. MacMillan and Ma (1994), Chen and Herring (1997), Emardson et al (1998), Haas et al (1999), Behrend et al (2000Behrend et al ( , 2002, Cucurull et al (2000), Gradinarsky et al (2000), Niell et al (2001), or Schuh and Böhm (2003).…”

Strain accumulation in and around Ou Backbone Range, northeastern Japan as observed by a dense GPS network

“…Collected data are analyzed using a precise point positioning (PPP) strategy of GIPSY/OASIS-II (Zumberge et al, 1997), which has been used in many geodetical and geophysical applications (e.g. Ohtani et al, 2000;Shoji et al, 2000;Behrend et al, 2000;Gradinarsky et al, 2000;Becker et al, 2000;Aonashi et al, 2000;Takiguchi et al, 2000;Cardellach et al, 2000). Figure 3 shows an example of time series of ITRF97 coordinates derived at station AKT0.…”

Combination methods of tropospheric time series

“…Comparisons between GPS and VLBI-derived tropospheric zenith delays have been performed by many authors (e.g., Behrend et al, 2000;Gradinarsky et al, 2002;Niell et al, 2001;Pacione et al, 2002;Snajdrova et al, 2006;Steigenberger et al, 2007).…”