Quantitative assessment of meteorological and tropospheric Zenith Hydrostatic Delay models

Abstract Tropospheric delay has always been an important issue in GNSS/DORIS/VLBI/InSAR processing. Most commonly used empirical models for the determination of tropospheric Zenith Hydrostatic Delay (ZHD), including three meteorological models and two empirical ZHD models, are carefully analyzed in this paper. Meteorological models refer to UNB3m, GPT2 and GPT2w, while ZHD models include Hopfield and Saastamoinen. By reference to in-situ meteorological measurements and ray-traced ZHD values of 91 globally distributed radiosonde sites, over a four-years period from 2010 to 2013, it is found that there is strong correlation between errors of model-derived values and latitudes. Specifically, the Saastamoinen model shows a systematic error of about −3 mm. Therefore a modified Saastamoinen model is developed based on the “best average” refractivity constant, and is validated by radiosonde data. Among different models, the GPT2w and the modified Saastamoinen model perform the best. ZHD values derived from their combination have a mean bias of −0.1 mm and a mean RMS of 13.9 mm. Limitations of the present models are discussed and suggestions for further improvements are given.

[1]  J. Johansson,et al.  A Microwave Radiometer Comparison and Its Implication for the Accuracy of Wet Delays , 2013 .

[2]  Y. Bar-Sever,et al.  DORIS Tropospheric Estimation at IGN: Current Strategies, GPS Intercomparisons and Perspectives , 2014 .

[3]  Richard B. Langley,et al.  UNB3m_pack: a neutral atmosphere delay package for radiometric space techniques , 2008 .

[4]  Calibration of zenith hydrostatic delay model for local GPS applications , 2000 .

[5]  I. Shapiro,et al.  Geodesy by radio interferometry: Effects of atmospheric modeling errors on estimates of baseline length , 1985 .

[6]  R. Dach,et al.  Bernese GNSS Software Version 5.2 , 2015 .

[7]  Development of a site-specific ZHD model using radiosonde data , 2012, Acta Geodaetica et Geophysica Hungarica.

[8]  H. Schuh,et al.  Short Note: A global model of pressure and temperature for geodetic applications , 2007 .

[9]  Yang Gao,et al.  Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation , 2015, Journal of Geodesy.

[10]  T. Nilsson,et al.  GPT2: Empirical slant delay model for radio space geodetic techniques , 2013, Geophysical research letters.

[11]  Robert Weber,et al.  Development of an improved empirical model for slant delays in the troposphere (GPT2w) , 2015, GPS Solutions.

[12]  S. Rózsa.  Uncertainty Considerations for the Comparison of Water Vapour Derived from Radiosondes and GNSS , 2014 .

[13]  Pascal Willis,et al.  A high‐quality, homogenized, global, long‐term (1993–2008) DORIS precipitable water data set for climate monitoring and model verification , 2014 .

[14]  T. Herring,et al.  GPS Meteorology: Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System , 1992 .

[15]  Daniel MacMillan,et al.  Tropospheric delay ray tracing applied in VLBI analysis , 2014 .

[16]  J. Barnett,et al.  Monthly mean global climatology of temperature, wind, geopotential height, and pressure for 0 - 120 km , 1990 .

[17]  G. D. Thayer,et al.  An improved equation for the radio refractive index of air , 1974 .

[18]  Ahmed El-Mowafy,et al.  Performance evaluation of different troposphere delay models and mapping functions , 2013 .

[19]  Michael Bevis,et al.  GPS meteorology: Reducing systematic errors in geodetic estimates for zenith delay , 1998 .

[20]  V. Mendes,et al.  Modeling the neutral-atmosphere propagation delay in radiometric space techniques , 1998 .

[21]  Study of tropospheric delay over Indian region from MODIS, NCEP/NCAR data and ground based water vapor measurements at Kolkata , 2015 .

[22]  H. S. Hopfield.  Tropospheric refraction effects on satellite range measurements. , 1972 .

[23]  H. Schuh,et al.  Atmospheric Effects in Space Geodesy , 2013 .

[24]  Richard B. Langley,et al.  A web-based package for ray tracing the neutral atmosphere radiometric path delay , 2009, Comput. Geosci..

[25]  Witold Rohm,et al.  Ground-based GNSS ZTD/IWV estimation system for numerical weather prediction in challenging weather conditions , 2014 .

[26]  J. Thepaut,et al.  The ERA‐Interim reanalysis: configuration and performance of the data assimilation system , 2011 .

[27]  Thomas A. Herring,et al.  Impact of a priori zenith hydrostatic delay errors on GPS estimates of station heights and zenith total delays , 2006 .

[28]  J. Saastamoinen.  Atmospheric Correction for the Troposphere and Stratosphere in Radio Ranging Satellites , 2013 .

[29]  Harald Schuh,et al.  Comparison of Ray-Tracing Packages for Troposphere Delays , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[30]  Ernest K. Smith,et al.  The Constants in the Equation for Atmospheric Refractive Index at Radio Frequencies , 1953, Proceedings of the IRE.

[31]  Jean M. Rüeger,et al.  Refractive Index Formulae for Radio Waves , 2002 .

[32]  H. S. Hopfield.  Two- quartic tropospheric refractivity profile for correcting satellite data , 1969 .

[33]  Yibin Yao,et al.  A New Method to Accelerate PPP Convergence Time by using a Global Zenith Troposphere Delay Estimate Model , 2014, Journal of Navigation.