scholarly journals Validation of recent altimeter missions at non-dedicated tide gauge stations in the Southeastern North Sea

2021 ◽  
Author(s):  
Saskia Esselborn ◽  
Julia Illigner ◽  
Tilo Schöne ◽  
Robert Weiß ◽  
Thomas Artz ◽  
...  
Keyword(s):  
North Sea ◽  
Tide Gauge ◽  
Sea Surface ◽  
Time Shift ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Gauge Data ◽  
Sea Surface Heights ◽  
The Absolute ◽  
Rms Errors

<p>The absolute and relative accuracy of sea surface heights derived from six altimeter missions (Jason-1/2/3, Envisat, Saral, Sentinel-3A) is evaluated at five GNSS-controlled tide gauge stations in the German Bight (SE North Sea). The precision of the total water level envelope (TWLE) is assessed for the period 2000 to 2019 based on RMS errors and explained variances. The comparison is based on TWLE instead of dealiased sea level data since the tidal and barotropic dynamic is not known with sufficient accuracy in this area. The tide gauges are partly located at the open sea, partly at the coast close to mudflats. The tide gauge data is available every minute, the 20 Hz level 2 altimetry data is interpolated to virtual stations at distances between 2 and 15 km to the tide gauges. The altimeter data is based on standard retrackers, the correction models are adjusted to coastal applications and exclude the corrections for ocean tides and dynamic atmosphere to allow a direct comparison to the tide gauge data. To account for slight differences of the tidal dynamics between gauge and altimetry an optimal time shift and scale between each pair of locations is estimated and applied. This tidal correction improves the RMS errors by 15-75%. The explained variances are excellent at all stations (> 96%). The resultant RMS errors are mainly between 2-5 cm depending on location and mission. The RMS errors rise up to 10 cm where coastal dynamics play a dominant role or the altimeter approaches the land very closely (<7 km). The accuracy of the absolute biases is strongly dependent on the knowledge of the mean sea surface heights in the region.</p>

scholarly journals A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

2017 ◽  
Vol 34 (2) ◽  
pp. 295-307 ◽  
Author(s):  
Kristine M. Larson ◽  
Richard D. Ray ◽  
Simon D. P. Williams
Keyword(s):  
Tide Gauge ◽  
Signal Propagation ◽  
Propagation Delay ◽  
Terrestrial Reference Frame ◽  
Water Levels ◽  
Sea Surface ◽  
Ocean Tide ◽  
Gps Receiver ◽  
Tide Gauge Data ◽  
Gauge Data

AbstractA standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years of water levels estimated from GPS sea surface reflections. The GPS results are improved by accounting for (tidal) motion of the reflecting sea surface and for signal propagation delay by the troposphere. The RMS error of individual GPS water level estimates is about 12 cm. Lower water levels are measured slightly more accurately than higher water levels. Forming daily mean sea levels reduces the RMS difference with the tide gauge data to approximately 2 cm. For monthly means, the RMS difference is 1.3 cm. The GPS elevations, of course, can be automatically placed into a well-defined terrestrial reference frame. Ocean tide coefficients, determined from both the GPS and tide gauge data, are in good agreement, with absolute differences below 1 cm for all constituents save K1 and S1. The latter constituent is especially anomalous, probably owing to daily temperature-induced errors in the Aquatrak tide gauge.

Review and Assessment of gap-filling methods from tide-gauges: Maxima missing at the Esbjerg, Denmark station, before 1910.

2020 ◽  
Author(s):  
Peter Thejll
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Model Fit ◽  
Tide Gauges ◽  
Harmonic Model ◽  
Gap Filling ◽  
Tide Gauge Data ◽  
Tide Gauge Record ◽  
Long Baseline ◽  
Gauge Data

<p>Information on extremes of the sea-level is obtained from tide-gauge<br>records.  Such records may have gaps.</p><p>Estimates of potential changes in the size and/or frequency of sea-level<br>extremes are hampered by long gaps, or when just the high extremes are<br>missing due, e.g. to equipment failure.</p><p>Methods used for filling such gaps can be based on having multiple<br>records from gauges near each other; but what to do if there is<br>only one record? This problem can typically occur when old tide-gauge<br>records are used -- the use of multiple recorders at the same place is<br>more wide-spread today. However, especially older and therefore longer<br>records hold the key to obtaining long-baseline insights into the temporal<br>evolution of extreme tides and thus impacts of e.g. climate change.</p><p>In this work, we review and assess methods for gap filling. We asses using<br>the 'known truth' method, i.e. by applying realistic gaps to complete<br>gauge records and reconstructing and then comparing errors calculated as<br>the diffrence between modelled and actual values.  We compare a simple<br>harmonic model fit method to various spline methods as well as Neural<br>network and deep learning approches.  We also test a hybrid method<br>which uses not just tide-gauge data but also air pressure readings<br>from a meteorological station near the tide-gauge.</p><p>We then attempt to fill in the missing maxima of the Esbjerg, Denmark<br>hourly tide-gauge record since 1889. Particularly, before 1910 the maxima<br>above 300 cm are missing (Bijl, et al., 1999), and we try to fill these in.</p>

scholarly journals Measuring rates of present-day relative sea-level rise in low-elevation coastal zones: A critical evaluation

2018 ◽  
Author(s):  
Molly E. Keogh ◽  
Torbjörn E. Törnqvist
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Land Surface ◽  
Tide Gauge ◽  
Tide Gauges ◽  
Coastal Zones ◽  
Tide Gauge Data ◽  
Relative Sea Level ◽  
Gauge Data ◽  
Coastal Louisiana

Abstract. Although tide gauges are the primary source of data used to calculate multi-decadal to century-scale rates of relative sea-level change, we question the reliability of tide-gauge data in rapidly subsiding low-elevation coastal zones (LECZs). Tide gauges measure relative sea-level rise (RSLR) with respect to the base of associated benchmarks. Focusing on coastal Louisiana, the largest LECZ in the United States, we find that these benchmarks (n = 35) are anchored an average of 21.5 m below the land surface. Because at least 60 % of subsidence occurs in the top 5–10 m of the sediment column in this area, tide gauges in coastal Louisiana do not capture the primary contributor to RSLR. Similarly, GPS stations (n = 10) are anchored an average of > 14.3 m below the land surface and therefore also do not capture shallow subsidence. As a result, tide gauges and GPS stations in coastal Louisiana, and likely in LECZs worldwide, systematically underestimate rates of RSLR as experienced at the land surface. We present an alternative approach that explicitly measures RSLR in LECZs with respect to the land surface and eliminates the need for tide-gauge data. Shallow subsidence is measured by rod surface-elevation table‒marker horizons (RSET-MHs) and added to measurements of deep subsidence from GPS data, plus sea-level rise from satellite altimetry. We show that for a LECZ the size of coastal Louisiana (25,000–30,000 km2), about 40 RSET-MH instruments suffice to collect useful data. Rates of RSLR obtained from this approach are substantially higher than rates as inferred from tide-gauge data. We therefore conclude that LECZs may be at higher risk of flooding, and within a shorter time horizon, than previously assumed.

scholarly journals Why We Must Tie Satellite Positioning to Tide Gauge Data

Eos ◽  
2017 ◽  
Author(s):  
P. Woodworth ◽  
G. Wöppelmann ◽  
M. Marcos ◽  
M. Gravelle ◽  
R. Bingley
Keyword(s):  
Tide Gauge ◽  
Positioning System ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Satellite Positioning ◽  
Gauge Data

Accurate measurements of changes in sea and land levels with location and time require making precise, repeated geodetic ties between tide gauges and satellite positioning system equipment.

scholarly journals Reconstruction and Projection of Sea Level Around the Korean Peninsula Using Cyclostationary Empirical Orthogonal Functions

2017 ◽  
Author(s):  
Se-Hyeon Cheon ◽  
Benjamin D. Hamlington ◽  
Kyung-Duck Suh
Keyword(s):  
Sea Level ◽  
Satellite Data ◽  
Korean Peninsula ◽  
Tide Gauge ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Satellite Altimeter ◽  
Reconstruction Process ◽  
The Past ◽  
Gauge Data

Abstract. Since the advent of the modern satellite altimeter era, the understanding of the sea level has increased dramatically. The satellite altimeter record, however, dates back only to the 1990s. The tide gauge record, on the other hand, extends through the 20th century, but with poor spatial coverage when compared to the satellites. Many studies have been conducted to extend the spatial resolution of the satellite data into the past by finding novel ways to combine the satellite data and tide gauge data in what are known as sea level reconstructions. However, most of the reconstructions of sea level were conducted on a global scale, leading to reduced accuracy on regional levels, particularly where there are relatively few tide gauges. The sea around the Korean Peninsula is one such area with few tide gauges prior to 1960. In this study, new methods are proposed to reconstruct the past sea level and project the future sea level around the Korean Peninsula. Using spatial patterns obtained from a cyclo-stationary empirical orthogonal function decomposition of satellite data, we reconstruct sea level over the time period from 1900 to 2014. Sea surface temperature data and altimeter data are used simultaneously in the reconstruction process, leading to an elimination of reliance on tide gauge data. Although the tide gauge data was not used in the reconstruction process, the reconstructed results showed better agreement with the tide gauge observations in the region than previous studies that incorporated the TG data. This study demonstrates a reconstruction technique that can be used on regional levels, with particular emphasis on areas with poor tide gauge coverage.

scholarly journals Caspian Sea Tidal Modelling Using Coastal Tide Gauge Data

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Mahmoud Pirooznia ◽  
Seyyed Rouhollah Emadi ◽  
Mehdi Najafi Alamdari
Keyword(s):  
Caspian Sea ◽  
Tide Gauge ◽  
The Other ◽  
Analysis Method ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
The Caspian Sea ◽  
Gauge Data ◽  
Harmonic Analysis Method ◽  
Using Data

The purpose of this paper is to model tidal conditions in the Caspian Sea using data from coastal tide gauges of Anzali, Noshahr, and Neka Ports. Harmonic analysis method was used to identify and examine 40 tidal components. The results illustrate that the annual (Sa) and semiannual solar (Ssa) components on all of the ports listed have the highest range in comparison with the other components which are, respectively, 16 cm, 18 cm, and 15 cm for annual components and 2.8 cm, 5.4 cm, and 3.7 cm for semiannual components.

scholarly journals Reconstruction of sea level around the Korean Peninsula using cyclostationary empirical orthogonal functions

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 959-970 ◽  
Author(s):  
Se-Hyeon Cheon ◽  
Benjamin D. Hamlington ◽  
Kyung-Duck Suh
Keyword(s):  
Sea Level ◽  
Satellite Data ◽  
Korean Peninsula ◽  
Tide Gauge ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Satellite Altimeter ◽  
Reconstruction Process ◽  
Spatial Coverage ◽  
Gauge Data

Abstract. Since the advent of the modern satellite altimeter era, the understanding of the sea level has increased dramatically. The satellite altimeter record, however, dates back only to the 1990s. The tide gauge record, on the other hand, extends through the 20th century but with poor spatial coverage when compared to the satellites. Many studies have been conducted to create a dataset with the spatial coverage of the satellite datasets and the temporal length of the tide gauge records by finding novel ways to combine the satellite data and tide gauge data in what is known as sea level reconstruction. However, most of the reconstructions of sea level were conducted on a global scale, leading to reduced accuracy on regional levels, especially when there are relatively few tide gauges. The seas around the Korean Peninsula are one such area with few tide gauges before 1960. In this study, new methods are proposed to reconstruct past sea level around the Korean Peninsula. Using spatial patterns obtained from a cyclostationary empirical orthogonal function decomposition of satellite data, we reconstruct sea level over the period from 1900 to 2014. Sea surface temperature data and altimeter data are used simultaneously in the reconstruction process, leading to an elimination of reliance on tide gauge data. Although we did not use the tide gauge data in the reconstruction process, the reconstructed sea level has a better agreement with the tide gauge observations in the region than previous studies that incorporated the tide gauge data. This study demonstrates a reconstruction technique that can potentially be used at regional levels, with particular emphasis on areas with poor tide gauge coverage.

Tide gauge data archaeology provides natural subsidence rates along the coasts of the Po Plain and of the Veneto-Friuli Plain, Italy

2020 ◽  
Author(s):  
S Zerbini ◽  
S Bruni ◽  
F Raicich
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Tide Gauge ◽  
Anthropogenic Activities ◽  
Reliable Estimate ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Northern Adriatic ◽  
Po Plain ◽  
Gauge Data

Summary In Northern Italy, natural subsidence affects the Po and Veneto-Friuli Plains. Anthropogenic activities which started during the 1930s enhanced the natural rates considerably. Information on land lowering can be obtained not only by geodetic or geological data, but also analyzing and comparing sea-level time series of neighboring tide gauges. In the Northern Adriatic, several tide gauge stations were operational before the onset of the anthropogenic activities. We analyzed data spanning the period 1873–1922 from Marina di Ravenna, Venice and Trieste, in Italy. The 1897–1922 data of Pula, Croatia, were also considered for the analysis, but this time series was finally discarded because too short. Trieste, located in a relatively stable area, is characterized by a sea-level rate of 1.21 ± 0.35 mm/yr (1875–1922) that can be assumed to be a reliable estimate of the local sea-level rise during the period of interest. We compared the rate observed at Trieste with those obtained at Marina di Ravenna, 3.09 ± 0.31 mm/yr (1873–1922), and Venice, 2.05 ± 0.22 mm/yr (1873–1922). This comparison shows that the natural subsidence rate decreases from Marina di Ravenna to Venice and Trieste, turning out to be 1.88 ± 0.47 mm/yr and 0.84 ± 0.41 mm/yr at Marina di Ravenna and Venice, respectively.

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