Article (Scientific journals)
Statistical significance of trends in Zenith Wet Delay from re-processed GPS solutions
Klos, Anna; Hunegnaw, Addisu; Teferle, Felix Norman et al.
2018In GPS Solutions
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Keywords :
Global Positioning System; Zenith Wet Delay; Statistical Significance; Autoregressive Noise
Abstract :
[en] Long series of Zenith Wet Delay (ZWD) obtained as part of a homogeneous re-processing of Global Positioning System solutions constitute a reliable set of data to be assimilated into climate models. The correct stochastic properties, i.e. the noise model of these data, have to be identified to assess the real value of ZWD trend uncertainties since assuming an inappropriate noise model may lead to over- or underestimated error bounds leading to statistically insignificant trends. We present the ZWD time series for 1995–2017 for 120 selected globally distributed stations. The deterministic model in the form of a trend and significant seasonal signals were removed prior to the noise analysis. We examined different stochastic models and compared them to widely assumed white noise (WN). A combination of the autoregressive process of first-order plus WN (AR(1) + WN) was proven to be the preferred stochastic representation of the ZWD time series over the generally assumed white-noise-only approach. We found that for 103 out of 120 considered stations, the AR(1) process contributed to the AR(1) + WN model in more than 50% with noise amplitudes between 9 and 68 mm. As soon as the AR(1) + WN model was employed, 43 trend estimates became statistically insignificant, compared to 5 insignificant trend estimates for a white-noise-only model. We also found that the ZWD trend uncertainty may be underestimated by 5–14 times with median value of 8 using the white-noise-only assumption. Therefore, we recommend that AR(1) + WN model is employed before tropospheric trends are to be determined with the greatest reliability.
Research center :
ULHPC - University of Luxembourg: High Performance Computing
Disciplines :
Earth sciences & physical geography
Author, co-author :
Klos, Anna
Hunegnaw, Addisu  ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit
Teferle, Felix Norman ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit
Abraha, Kibrom Ebuy ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit
Ahmed, Furqan ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit
Bogusz, Janusz
External co-authors :
yes
Language :
English
Title :
Statistical significance of trends in Zenith Wet Delay from re-processed GPS solutions
Publication date :
02 March 2018
Journal title :
GPS Solutions
ISSN :
1521-1886
Publisher :
Springer, Heidelberg, Germany
Peer reviewed :
Peer Reviewed verified by ORBi
Focus Area :
Computational Sciences
FnR Project :
FNR6835562 - Multi-gnss Benefits To Long-term Monitoring Applications In The Geosciences, 2013 (01/05/2014-30/04/2018) - Kibrom Ebuy Abraha
Name of the research project :
R-AGR-0376 - IRP15 - SGSL (20150501-20170430) - TEFERLE Felix Norman
Funders :
Polish National Science Centre grant UMO-2016/21/B/ST10/02353
COST ES1206
Fonds National de la Recherche, Luxembourg (Reference No. 6835562)
Available on ORBilu :
since 13 November 2018

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