Seasonal and interannual variability in the Gulf of Cadiz: Validation of gridded altimeter products

Gómez-Enri, Jesús; Aboitiz, A.; Tejedor, B.; Villares, P.

doi:10.1016/j.ecss.2011.10.013

Cited by 9 publications

(9 citation statements)

References 24 publications

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“…The study area has been also used in the past for the validation of conventional radar altimeter data near the shore. Gómez-Enri et al (2012) and Laiz et al (2013) used weekly maps of SLA from AVISO (Archiving, Validation and Interpretation of Satellite data in Oceanography) to validate time series of SLA, finding high and significant correlations (r > 0.85) with in-situ tide gauge sea level data at monthly time scales. August 2010 to December 2014.…”

Section: Study Areamentioning

confidence: 99%

Validation of CryoSat-2 SIRAL sea level data in the eastern continental shelf of the Gulf of Cadiz (Spain)

Gómez-Enri

Vignudelli

Cipollini

et al. 2018

Advances in Space Research

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We present the validation of sea level measurements taken over the eastern shelf of the Gulf of Cadiz (southwestern Iberian Peninsula) by the European Space Agency CryoSat-2 satellite's SIRAL altimeter in SAR mode. Time series of sea level anomaly (SLA) at 20-Hz posting rate (corresponding to approximately 350 m along the satellite track) are compared against sea level measurements from two tide gauge stations located along the Spanish coast of the study area. Due to the long repeat cycle of CryoSat-2 (369 days), data selection is performed by including all the tracks falling in a radius of 50 km from the location of the tide gauge stations. Then, time series of SLA are formed during the observational time period (August 2010-December 2014) by taking the altimeter measurements located at growing distances from the coast (1, 3, 5, 10, 15 and 20 km) as well as around four isobaths (10, 25, 50 and 75 m). The validation of AltiKa's SARAL altimeter 20-Hz data, using its two 35-day-repeat ground tracks available in the area is also presented. Overall, CryoSat-2 20-Hz SLAs selected in the coastal strip from 3 to 20 km agree well with data from the western station (Huelva) with rmse ranging from 11.4 to 6.4 cm. The analysis at the eastern station (Bonanza) yields rmse ranging from 16.8 to 14.6 cm. The comparisons made with CryoSat-2 20-Hz SLAs are in agreement with the rmse estimated using AltiKa 20-Hz SLAs at distances to the coast higher than 5 km, and much better in the 1-5 coastal band. The differences in quantity of SAR mode data observed at the two stations and in their agreement with the tide gauges can be explained by (1) the more complex coastal morphology around Bonanza station with the altimetry tracks almost parallel to the coast; (2) the noisier hydrodynamics around Bonanza station due to the presence of the estuary mouth of the Guadalquivir River; and (3) residual (uncorrected) tidal signals in the Bonanza gauge record. We conclude that the quality of SAR altimetry is comparable or even slightly better than conventional altimetry, thus qualifying SAR data for exploitation in oceanographic studies and sea level monitoring. An example is the analysis made of the surface signal due to a heavy Guadalquivir River discharge event.

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Section: Study Areamentioning

confidence: 99%

Validation of CryoSat-2 SIRAL sea level data in the eastern continental shelf of the Gulf of Cadiz (Spain)

Gómez-Enri

Vignudelli

Cipollini

et al. 2018

Advances in Space Research

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“…Both above‐cited studies agree that there are some regions where a poor performance of the altimeter is due to local phenomena. At regional scales, altimetry data were successfully used to characterize the seasonal variability in regions such as Gulf of Cadiz [ Gomez‐Enri et al ., ; Laiz et al ., ], Nordic Seas [ Volkov and Pujol , ], Baltic Sea [ Passaro et al ., ] and the Río de la Plata (RdP) estuary [ Saraceno et al ., ; Strub et al ., ], among others. In particular, in the RdP estuary (Figure ), that is part of the SWACS, the observed pattern of seasonal SLA variations is due to a combination of solar radiation and wind forcing [ Saraceno et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Sea level anomaly on the Patagonian continental shelf: Trends, annual patterns and geostrophic flows

et al. 2016

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We study the annual patterns and linear trend of satellite sea level anomaly (SLA) over the southwest South Atlantic continental shelf (SWACS) between 54ºS and 36ºS. Results show that south of 42°S the thermal steric effect explains nearly 100% of the annual amplitude of the SLA, while north of 42°S it explains less than 60%. This difference is due to the halosteric contribution. The annual wind variability plays a minor role over the whole continental shelf. The temporal linear trend in SLA ranges between 1 and 5 mm/yr (95% confidence level). The largest linear trends are found north of 39°S, at 42°S and at 50°S. We propose that in the northern region the large positive linear trends are associated with local changes in the density field caused by advective effects in response to a southward displacement of the South Atlantic High. The causes of the relative large SLA trends in two southern coastal regions are discussed as a function meridional wind stress and river discharge. Finally, we combined the annual cycle of SLA with the mean dynamic topography to estimate the absolute geostrophic velocities. This approach provides the first comprehensive description of the seasonal component of SWACS circulation based on satellite observations. The general circulation of the SWACS is northeastward with stronger/weaker geostrophic currents in austral summer/winter. At all latitudes, geostrophic velocities are larger (up to 20 cm/s) close to the shelf‐break and decrease toward the coast. This spatio‐temporal pattern is more intense north of 45°S.

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“…In particular, Gó mez-Enri et al (2012) analyzed the effect of sporadic and heavy Guadalquivir River discharges in the sea level of the eastern continental shelf of the Gulf of Cadiz. They concluded that these events could explain up to 50% of the variance of the daily mean sea level recorded by a tide gauge in the estuary mouth.…”

Section: Introductionmentioning

confidence: 99%

“…Low-resolution (LR, hereinafter) (1/3°Â 1/3°) gridded weekly maps of SLA routinely produced by AVISO (Archiving, Validation, and Interpretation of Satellite Oceanographic data, http://www.aviso.oceanobs.com/) have been used in the past to study the sea-level variability over continental shelves at different time scales (Volkov et al, 2007;Saraceno et al, 2008;Gó mez-Enri et al, 2012;Laiz et al, 2013;Caballero et al, 2014). In particular, Gó mez-Enri et al (2012) analyzed the effect of sporadic and heavy Guadalquivir River discharges in the sea level of the eastern continental shelf of the Gulf of Cadiz.…”

Section: Introductionmentioning

confidence: 99%

Heavy Guadalquivir River discharge detection with satellite altimetry: The case of the eastern continental shelf of the Gulf of Cadiz (Iberian Peninsula)

Gómez-Enri

Escudier

Pascual

et al. 2015

Advances in Space Research

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In situ water levels in the Guadalquivir River estuary mouth show the effect of strong river freshwater discharges on the monthly means of the sea level on a yearly basis. Accurate altimeter products oriented toward coastal zones are increasing the number of potential applications at different spatiotemporal scales. The present work is focused on the analysis of the sea-level variability in the eastern shelf of the Gulf of Cadiz (between North Africa and the southwestern side of the Iberian Peninsula), adjacent to the Guadalquivir River estuary. Sixteen years (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)) of along-track and standard AVISO maps of sea-level anomalies (SLAs) have been used to generate a new high-resolution product with increased spatiotemporal resolution. The use of a bathymetry constraint and smaller correlation scales in the methodology developed to generate high-resolution altimeter products improves the characterization of the mesoscale signals in the coastal strip adjacent to the estuary due to strong river freshwater discharges. This has been confirmed by the analysis of along-track SLA data in the vicinity of the estuary. The daily evolution (2 weeks) of the sea level obtained in the event of December 2009 might be related to the river plume extension observed by optical Moderate Resolution Imaging Spectrometer (MODIS) images. The spatiotemporal distribution of the altimeter tracks available in the study area might compromise the mapping capabilities to capture coastal and fine-scale features.

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Seasonal and interannual variability in the Gulf of Cadiz: Validation of gridded altimeter products

Cited by 9 publications

References 24 publications

Validation of CryoSat-2 SIRAL sea level data in the eastern continental shelf of the Gulf of Cadiz (Spain)

Validation of CryoSat-2 SIRAL sea level data in the eastern continental shelf of the Gulf of Cadiz (Spain)

Sea level anomaly on the Patagonian continental shelf: Trends, annual patterns and geostrophic flows

Heavy Guadalquivir River discharge detection with satellite altimetry: The case of the eastern continental shelf of the Gulf of Cadiz (Iberian Peninsula)

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