Current Applications for an Array of Water Level Gauge Stations

Marine Geodesy, 1996

2011

Sea level change (SLC) real-time monitoring has being developed and improved for the Portuguese tide gauge, based in FTP access to the internet server of the Portuguese geographical institute. A software application, named MareVB and in development since 2008, gets a 3 minute stream input of sea level height and a 10 minute stream input of air-pressure. Based on a predicted tide model, the sea level height is compared and analyzed, and storm-surge amplitude is determined, as well as the high frequency oscillation (seichas) due to the storm and tsunami waves. Using such real-time SLC data analysis, the application is now running as a coastal hazard warning system, emailing automatic warnings in real-time to national authorities and to other institutions and coworkers, where the levels of coastal hazards of SLC are considered. A post-processing monitoring of SLC is also performed and a time series is evaluated and actualized. Such SLC time series enables the statistics of storm-surges and the determination of the sea level rise rate associated to the global climate change and other regional phenomena. The computational methodology, the application for real-time monitoring and the statistics of storm-surges at Cascais for the period of last 10 years are presented here.

2007

Small sea level oscillations (amplitude ~ 0.1 feet = 3 cm) with time scales between 1.6 and 1.9 hours, and an average period (frequency) of 1.84 hours (13 CPD), have been recorded by two tide gauges located in two small harbors at Eastern Puerto Rico. The two harbors are connected by a shallow shelf with an average depth of 10 meters. The oscillation period is shorter than the twelfth-diurnal tidal constituents – with periods from 2.03 to 2.09 hours – and longer than the sixteen-diurnal harmonic (8M2 or M16; period of 1.55 hours). It is possible that the period of the 1.8-hour oscillation is determined by the basin geometry and depth. In addition, it is an intermittent signal in the water-level record. The duration of the larger amplitude oscillations is less than 0.5 days. Maximum amplitudes reached up to 0.2 feet.

Measurement, 2018

Understanding noise and possible bias in tide-gauge sensors is important for determining the mean sea level, its fluctuations and their climatic, geophysical and engineering implications, but not an easy task. In the past, this problem has been examined through comparison of different sensors in the laboratory, or through correlations of neighbouring sensors. In this study we identified and studied 10 cases of harbours with fully collocated sensors. Transient differences were found between collocated records. Pressure gauges were found significantly more sensitive to noise than radar-type sensors, and with higher chances of long-term transient bias. The amplitude of the observed bias is important, of the same order of magnitude with tsunami waves in the open sea and with seismic ground displacements. Only 9% of the sensors analysed were found to satisfy the 1 cm accuracy criterion imposed by the Permanent Service for Mean Sea Level (PSMSL).

Frontiers in Marine Science

Natural Hazards, 2020

The progressive upgrade of tide gauges to match tsunami warning requirements, tied with an upgrade of tide gauges with 1-min or less sampling and latency, has led to a huge amount of data available worldwide for studies of coastal hazards related to high-frequency sea level oscillations. This upgrade in the observation network poses a challenge in matching the operational data flow, quality control and processing, as well as an opportunity for a more immediate evaluation and understanding of the physical phenomena contained in the raw data, such as meteotsunamis and infragravity waves. The main purpose of this study is to present a new operational tool that enables, for the first time, user-friendly and fast exploitation of an up to now hidden information on high-frequency sea level oscillations. Developed and implemented for 40 tide gauges at the main ports of the Spanish coast, the new tool is based on the automatic analysis of 2-Hz raw data and the online publication of relevant products in near real time. It includes an event detection algorithm and a display calendar to select and review historical events, resulting in a revolutionary advanced toolbox, a new window to phenomena that affects ports operations and infrastructures. This toolbox, combined with the open dataset, provides the first steps for considering HFSLO in the definition of operational risk management. Dealing with these raw data in near real time requires careful selection of appropriate algorithms and quality control procedures, with therefore additional difficulties, that are discussed in this paper.

2003

Changes in mean sea (MSL) level recorded relative to tide gauge benchmarks (TGBM) are corrupted by vertical land movements. Accurate estimates of changes in absolute sea level, require these MSL records to be corrected for ground level changes at tide gauge sites.

Revista Brasileira de Geofísica, 2012

Meteorological events cause pronounced low-frequency sea level variations along the Mid-Atlantic coast of South America. Spectral analysis of hourlysea level data during 1983 from tide gauges at Puerto Madryn and Mar del Plata, Argentina, and Cananeia and Ilha Fiscal, Brazil, yielded energetic variance peaks withperiods between 2 and 28 days, with good coherence among the four gauges. These results suggest that coherent low-frequency sea level disturbances may propagatealong the Mid-Atlantic coast of South America towards the northeast, mostly as barotropic shelf waves. The principal long waves were identified with heights up to 1 m,periods of 7.8 and 9.0 days, with variances of 2.5-5.4 m2 and coherences in the order of 0.88 to 0.98. These long waves recur every 5-16 days, propagate towards theequator with an average phase speed of 11 m/s, and require 77 hours to travel the 3,010 km distance from Puerto Madryn to Ilha Fiscal.

Environmental Geology, 2008

A considerable proportion of the world population lives and works on or near coasts. Therefore, knowledge of the physical processes which affect the coast is very important. These include the tides of the sea and the oceanic and meteorological circulation patterns that cause variations of the sea level and generate waves. The sea level is measured by tide-gauges, while the height of waves may be determined by a variety of special devices. Radar systems have been applied for the sea level and wave measurements since the late 1990s. This paper presents results from a field test or such a radar application and aims to give the reader help and support in the selection of an appropriate radargauge system to measure sea level and sea state. The underlying physical principles of radar and its application in distance measurements are not subjects of this paper.