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Evaluation of Spatial and Temporal Characteristics of GNSS-Derived ZTD Estimates in Nigeria (8552)

Olalekan Isioye (Nigeria), Ludwig Combrinck and Joel Botai (South Africa)
Mr Olalekan Adekunle Isioye
PhD Student
University of Pretoria
South Africa
Department of Geography Geoinformatics and Meteoro
University of Pretoria
Pretoria
South Africa
 
Corresponding author Mr Olalekan Adekunle Isioye (email: lekkyside4u[at]yahoo.com, tel.: +2348036055824)
 

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Published on the web 2017-03-10
Received 2016-10-01 / Accepted 2017-02-01
This paper is one of selection of papers published for the FIG Working Week 2017 in Helsinki, Finland and has undergone the FIG Peer Review Process.

FIG Working Week 2017
ISBN 978-87-92853-61-5 (Online) ISBN 978-87-92853-62-2 (Printed)
ISSN 2307-4086
URL n/a

Abstract

Précis This study presents an in depth analysis to comprehend the spatial and temporal variability of Zenith Tropospheric Delay (ZTD) over Nigeria during the period 2010–2014 using estimates from Global Navigation Satellite Systems (GNSS) data. GNSS data addresses the drawbacks in traditional techniques (e.g., radiosondes) of observing periodicities in ZTD. The ZTD estimates show weak spatial dependence among the stations, though this can be attributed to the density of stations in the network. Tidal oscillations are noticed at the GNSS stations. These oscillations are of the diurnal and semi diurnal components. The diurnal components as seen from the ZTD are the principal source of the oscillations. This upshot may perhaps be ascribed to temporal variations in atmospheric water vapour on a diurnal scale. Additionally, the diurnal ZTD cycles exhibited noteworthy seasonal dependence, with larger amplitudes in the rainy (wet) season and smaller ones in the Harmattan (dry) season. Notably, the stations in the northern part of the country reached very high amplitudes in the months of June, July and August at the peak of the wet season, characterized by very high rain fall. This is pinpointing the fact that with the little amount of atmospheric water vapour in the atmosphere usually around ten percent, its variations greatly influence the corresponding diurnal and seasonal discrepancies of ZTD. This study further affirms the prospective relevance of ground-based GNSS data to atmospheric studies. As such, GNSS data analysis is recommended as a tool for future exploration of Nigerian weather and climate.
 
Keywords: Geoinformation/GI; GNSS/GPS; Remote sensing

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