Multi-technique comparison of troposphere zenith delays and gradients during CONT08
Journal article, 2011

CONT08 was a 15 days campaign of continuous Very Long Baseline Interferometry (VLBI) sessions during the second half of August 2008 carried out by the International VLBI Service for Geodesy and Astrometry (IVS). In this study, VLBI estimates of troposphere zenith total delays (ZTD) and gradients during CONT08 were compared with those derived from observations with the Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and water vapor radiometers (WVR) co-located with the VLBI radio telescopes. Similar geophysical models were used for the analysis of the space geodetic data, whereas the parameterization for the least-squares adjustment of the space geodetic techniques was optimized for each technique. In addition to space geodetic techniques and WVR, ZTD and gradients from numerical weather models (NWM) were used from the European Centre for Medium-Range Weather Forecasts (ECMWF) (all sites), the Japan Meteorological Agency (JMA) and Cloud Resolving Storm Simulator (CReSS) (Tsukuba), and the High Resolution Limited Area Model (HIRLAM) (European sites). Biases, standard deviations, and correlation coefficients were computed between the troposphere estimates of the various techniques for all eleven CONT08 co-located sites. ZTD from space geodetic techniques generally agree at the sub-centimetre level during CONT08, and-as expected-the best agreement is found for intra-technique comparisons: between the Vienna VLBI Software and the combined IVS solutions as well as between the Center for Orbit Determination (CODE) solution and an IGS PPP time series; both intra-technique comparisons are with standard deviations of about 3-6 mm. The best inter space geodetic technique agreement of ZTD during CONT08 is found between the combined IVS and the IGS solutions with a mean standard deviation of about 6 mm over all sites, whereas the agreement with numerical weather models is between 6 and 20 mm. The standard deviations are generally larger at low latitude sites because of higher humidity, and the latter is also the reason why the standard deviations are larger at northern hemisphere stations during CONT08 in comparison to CONT02 which was observed in October 2002. The assessment of the troposphere gradients from the different techniques is not as clear because of different time intervals, different estimation properties, or different observables. However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.2 and 0.7 mm.





Troposphere zenith

path delay

gps data

base-line interferometry

Numerical weather models

atmospheric modeling errors

long time-series


gnss service

Horizontal troposphere gradients



Space geodetic techniques


K. Teke

Vienna University of Technology

Hacettepe University

Johannes Böhm

Vienna University of Technology

T. Nilsson

Vienna University of Technology

H. Schuh

Vienna University of Technology

P. Steigenberger

Technical University of Munich

R. Dach

University of Bern

R. Heinkelmann

Deutsches Geodätisches Forschungsinstitut (DGFI)

P. Willis

Sorbonne University

IGN Institut Geographique National

Institut de Physique du Globe de Paris

Rüdiger Haas

Chalmers, Earth and Space Sciences, Space Geodesy and Geodynamics

Susana García Espada

Chalmers, Earth and Space Sciences, Space Geodesy and Geodynamics

Thomas Hobiger

Japan National Institute of Information and Communications Technology

R. Ichikawa

Japan National Institute of Information and Communications Technology

S. Shimizu

National Research Institute for Earth Science and Disaster Prevention (NIED)

Journal of Geodesy

0949-7714 (ISSN) 1432-1394 (eISSN)

Vol. 85 7 395-413

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