Effect of antenna snow intrusion on vertical GPS position time series in Antarctica
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ORIGINAL ARTICLE
Effect of antenna snow intrusion on vertical GPS position time series in Antarctica A. Koulali1
· P. J. Clarke1
Received: 22 January 2020 / Accepted: 17 July 2020 © The Author(s) 2020
Abstract Vertical surface displacements from continuous Global Positioning System (GPS) stations often show strong seasonal signals, which in some cases may be associated with surface mass loading, including hydrological, and non-tidal oceanic and atmospheric loading. In Antarctica, many GPS stations show vertical motions in phase with seasonal snow accumulation changes, but these variations cannot be fully explained with snow load variations between seasons. Instead we show, for many sites in Antarctica, that a significant component of the annual cycle in vertical GPS coordinates time series may be related to snow/ice inside antennas causing as an artefact apparent seasonal variation, with amplitudes of up to 4 mm. We present a method based on the Empirical Mode Decomposition (EMD) algorithm to remove this artefact signal. The corrected GPS time series show an improvement in the agreement with displacements predicted by elastic modelling using GRACE-derived surface mass loads. Keywords Monumentation effect · Antenna · Radome · Snow · Antarctica
1 Introduction Surface displacement time series, derived from the Global Positioning System (GPS), contain signatures of multiple geophysical phenomena, ranging from global tectonic plate motions (Feigl et al. 1993) to local climatic effects (Davis et al. 2004). While horizontal components of displacements are widely used, vertical displacements were historically less favourable due to their sensitivity to errors in orbital modelling, monument instabilities, tropospheric modelling errors and other reference frame factors (e.g. Herring et al. 2016). However, during recent years numerous improvements have been made in the analysis of GPS data (e.g. Boehm et al. 2006; Steigenberger et al. 2009; Tregoning and Watson 2009). Time series of vertical displacements are now derived with better precision allowing their usage for studying the Earth’s response to various loading effects, including Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00190-020-01403-6) contains supplementary material, which is available to authorized users.
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A. Koulali [email protected] Geospatial Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
Global Isostatic Adjustment (GIA) (e.g. King et al. 2010), hydrology (e.g. Borsa et al. 2014) and sea level (e.g. Wöppelmann et al. 2009). Vertical GPS time series often show seasonal variations dominated by yearly and half-yearly periods (van Dam et al. 2007). These variations are mainly associated with the Earth’s response to surface hydrological and atmospheric loading caused by the water transfer between continents and oceans. These displacements could in principle be predicted if the Earth’s rheology and the load are known. Therefore, retrieving accurately the annual signal from verti
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