Troposphere Modeling in a Regional GPS Network

S. Skone, V. Hoyle

Department of Geomatics Engineering, University of Calgary, 2500 University Dr. N.W., T2N 1N4 Calgary, Canada.

DOI:                 

Abstract

By using a regional network of Global Positioning System (GPS) reference stations, it is possible to recover estimates of the slant wet delay (SWD) to all GPS satellites in view. SWD observations can then be used to model the vertical and horizontal structure of water vapor over a local area, using a tomographic approach. The University of Calgary currently operates a regional GPS real-time network of 14 sites in southern Alberta. This network provides an excellent opportunity to study severe weather conditions (e.g. thunderstorms, hail, and tornados) which develop in the foothills of the Rockies near Calgary. In this paper, a 4-D tomographic water vapor model is tested using the regional GPS network. A field campaign was conducted during July 2003 to derive an extensive set of truth data from radiosonde soundings. Accuracies of tomographic water vapor retrieval techniques are evaluated for 1) using only ground-based GPS input, and 2) using a ground-based GPS solution augmented with vertical wet refractivity profiles derived from radiosondes released within the GPS network. Zenith wet delays (ZWD) are computed for both cases, by integrating through the 4-D tomography predictions, and these values are compared with truth ZWD derived from independent radiosonde measurements. Results indicate that ZWD may be modeled with accuracies at the sub-centimeter level using a ground-based GPS network augmented with vertical profile information. This represents an improvement over the GPS-only approach.

Keywords

troposphere, water vapor, tomography, GPS, positioning, atmospheric errors Ionosphere, WADGPS, WAAS

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Bar-Sever Y E.; Kroger P M. (1998): Estimating horizontal gradients of tropospheric path delay with a single GPS receiver, Journal of Geophysical Research, 103(B3):5019-5035
[2]	Bevis M S.; Businger S.; Herring T A.; Rocken C.; Anthes R A.; Ware R H. (1992): GPS meteorology: remote sensing of atmospheric water vapor using the Global Positioning System, Journal of Geophysical Research, 97(D14):15787-15801
[3]	Braun J.; Rocken C. (2003): Water vapor tomography within the planetary boundary layer using GPS, International Workshop on GPS Meteorology, Tsukuba, Japan, 14-17January, http://dbx.cr.chiba-u.jp/Gps_Met/gpsmet
[4]	Brunner F K.; Gu M. (1991): An improved model for the dual frequency ionospheric correction of GPS observations, Manuscripta Geodaetica, 16:205-214
[5]	Flores A.; Ruffini G.; Ruis A. (2000): 4D tropospheric tomography using GPS slant wet delays, Annales Geophysicae, 18:223-234
[6]	Gelb A. (1974): Applied Optimal Estimation, Cambridge, Mass.: MIT Press
[7]	Gradinarsky L.; Jarlemark P. (2002): GPS tomography using the permanent network in Goteborg: simulations, Proceedings of IEEE Positioning, Location and Navigation Symposium, Palm Springs, CA, 15-18 April, 128-133
[8]	Gregorius T.; Blewitt G. (1998): The effect of weather fronts on GPS measurements, GPS World, May:52-60
[9]	Hugentobler U.; Schaer S.; Fridez P. (2001): Bernese GPS Software Version 4.2 Manual, Astronomical Institute University of Berne, February
[10]	Institute of Information and Computing Science (ICS) Web Site (2004), Temp, humidity and dew-point ONA, http://www.cs.uu.nl/wais/html/na-dir/meteorology/tempdewpoint. html, Accessed: August 10
[11]	Niell A E. (1996): Global mapping functions for theatmosphere delay at radio wavelengths, Journal of Geophysical Research, 101(B2):3227-3246
[12]	Skone S.; Shrestha S. (2003): 4-D modeling of water vapor using a regional GPS network, Proceedings of the ION National Technical Meeting, Anaheim, CA, 22-24 January
[13]	Vaisala (2004): RS80 Spec Sheet, http://www.vaisala.com/DynaGen_Attachments/Att2743/2 743.pdf, Accessed August 13
[14]	Ware R.; Alber C.; Rocken C.; Solheim F. (1997): Sensing integrated water vapour along GPS ray paths, Geophysical Research Letters, 24:417-420
[15]	Wickert J.; Reigber C.; Beyerle G.; K?nig R.; Marquardt C.; Schmidt T.; Grunwaldt L.; Galas R.; Meehan T. Melbourne W.; Hocke K (2001): Atmosphere sounding by GPS radio occultation: first results from CHAMP, Geophysical Research Letters, 28:3263-3266