Multi-technique comparison of troposphere zenith delays and gradients during CONT08
Artikel i vetenskaplig tidskrift, 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.

Numerical weather models




atmospheric modeling errors

Space geodetic techniques


path delay

gps data

Troposphere zenith

base-line interferometry



Horizontal troposphere gradients

gnss service


long time-series


K. Teke

Hacettepe Universitesi

Technische Universität Wien

Johannes Böhm

Technische Universität Wien

T. Nilsson

Technische Universität Wien

H. Schuh

Technische Universität Wien

P. Steigenberger

Technische Universität München

R. Dach

Universität Bern

R. Heinkelmann

Deutsches Geodätisches Forschungsinstitut (DGFI)

P. Willis

Universite Paris Sorbonne - Paris IV

Institut de Physique du Globe de Paris

IGN Institut Geographique National

Rüdiger Haas

Chalmers, Rymd- och geovetenskap, Rymdgeodesi och geodynamik

Susana García Espada

Chalmers, Rymd- och geovetenskap, Rymdgeodesi och geodynamik

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. 85 395-413


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