Abstract
Considerable efforts are being made worldwide to upgrade tide gauge networks using new technologies. Because of the unique location of the Kerguelen Islands, the measurement of sea level there has received particular attention, with up to four systems equipped with modern sensors functioning simultaneously (two pressure tide gauges, a radar tide gauge, and a GPS-equipped buoy). We analysed and compared the sea level data obtained with these systems from 2003 to 2010, together with a time series of tide pole observations. This is the first time that a multi-comparison study with tide gauges has been undertaken over such a long time span and that the stability of modern radar tide gauges has been examined. The multi-comparison enabled us to evaluate the performance of the tide gauges in several frequency ranges, identify errors and estimate their magnitude. The drift of the pressure sensors (up to 8.0 mm/yr) was found to be one of the most relevant sources of systematic error. Other sources of difference such as clock drift, scale error and different locations of the instruments were also detected. After correcting the time series of sea level for these errors we estimated an upper bound for the radar instrumental error in field condition at ~0.3 cm.
Highlights
The performance of tide gauges has been given considerable attention over the last decades, in particular in the context of the Global Sea Level ObservingSystem (GLOSS) programme (IOC 1997, Merrifield et al 2010)
After correcting the time series of sea level for these errors we estimated an upper bound for the radar instrumental error in field condition at ~0.3 cm
The results from the comparisons undertaken in the previous section can be used to estimate an upper bound for the radar instrumental error in field conditions
Summary
The performance of tide gauges has been given considerable attention over the last decades, in particular in the context of the Global Sea Level ObservingSystem (GLOSS) programme (IOC 1997, Merrifield et al 2010). As a result of the increasing interest in greater-quality, higher-frequency sea level data, tide gauge networks have been upgraded and traditional mechanical float gauges have been progressively replaced by electronic tide gauges equipped with acoustic, pressure and (more recently) radar sensors During this process, comparison experiments have been undertaken and the results have been published (Woodworth and Smith 2003, Martin et al 2005, Martin Miguez et al 2008b, Blasi 2009). Radar tides gauges in particular stood out as a promising option in terms of accuracy and ease of operation (Martin Miguez et al 2008a) As a result, this technology was chosen for the upgrading of many national networks and in the GLOSS and ODINAfrica programmes (Woodworth et al 2007, 2009, Martin Miguez et al 2008a). This interest is apparent on the UNESCO/IOC website (www.ioc-sealevelmonitoring.org), on which 25% of the displayed tide gauges use radar technology
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