Improved satellite altimeter mapped sea level anomalies in the Mediterranean Sea: A comparison with tide gauges

Marcos, Marta; Pascual, Ananda; Pujol, Isabelle

doi:10.1016/j.asr.2015.04.027

Cited by 19 publications

(14 citation statements)

References 20 publications

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“…As for the global products, mapping was also improved at regional scales, with a positive impact in coastal areas, as presented by Marcos et al (2015) and Juza et al (2016) in the Mediterranean Sea.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, as long as the MDT is combined with the SLA in order to estimate the absolute dynamic topography (ADT), the reference period the MDT refers to must be coherent with the reference period that the SLA refers to. The latest MDT_CNES/CLS 2013 (Mulet et al, 2013) available from Aviso is based on a 20-year reference period, consistent with the DT2014 SLA products.…”

Section: Reference Period and Sla Reference Conventionmentioning

confidence: 99%

“…The MDT used in the DT2014 reprocessing is the MDT CNES/CLS 2013 (Mulet et al, 2013), corrected to be consistent with the 20-year reference period used for the SLA.…”

Section: Derived Product Generationmentioning

confidence: 99%

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DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years

et al. 2016

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Abstract. The new DUACS DT2014 reprocessed products have been available since April 2014. Numerous innovative changes have been introduced at each step of an extensively revised data processing protocol. The use of a new 20-year altimeter reference period in place of the previous 7-year reference significantly changes the sea level anomaly (SLA) patterns and thus has a strong user impact. The use of upto-date altimeter standards and geophysical corrections, reduced smoothing of the along-track data, and refined mapping parameters, including spatial and temporal correlationscale refinement and measurement errors, all contribute to an improved high-quality DT2014 SLA data set. Although all of the DUACS products have been upgraded, this paper focuses on the enhancements to the gridded SLA products over the global ocean. As part of this exercise, 21 years of data have been homogenized, allowing us to retrieve accurate large-scale climate signals such as global and regional MSL trends, interannual signals, and better refined mesoscale features.An extensive assessment exercise has been carried out on this data set, which allows us to establish a consolidated error budget. The errors at mesoscale are about 1.4 cm 2 in lowvariability areas, increase to an average of 8.9 cm 2 in coastal regions, and reach nearly 32.5 cm 2 in high mesoscale activity areas. The DT2014 products, compared to the previous DT2010 version, retain signals for wavelengths lower than ∼ 250 km, inducing SLA variance and mean EKE increases of, respectively, +5.1 and +15 %. Comparisons with independent measurements highlight the improved mesoscale representation within this new data set. The error reduction at the mesoscale reaches nearly 10 % of the error observed with DT2010. DT2014 also presents an improved coastal signal with a nearly 2 to 4 % mean error reduction. High-latitude areas are also more accurately represented in DT2014, with an improved consistency between spatial coverage and sea ice edge position. An error budget is used to highlight the limitations of the new gridded products, with notable errors in areas with strong internal tides.

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Section: Discussionmentioning

confidence: 99%

Section: Reference Period and Sla Reference Conventionmentioning

confidence: 99%

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DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years

et al. 2016

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“…The improvement in the coastal areas of the Mediterranean Sea has recently been demonstrated by Marcos et al (2015). A reasonable agreement between tide gauge records and near-coast SLAs in the Black Sea has also been documented (Volkov and Landerer, 2015;Korotaev et al, 1998;Stanev et al, 2000Goryachkin et al, 2003;Avsar et al, 2015).…”

Section: Methodsmentioning

confidence: 80%

Quantifying the impact of basin dynamics on the regional sea level rise in the Black Sea

2017

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Abstract. Satellite altimetry measurements show that the magnitude of the Black Sea sea level trends is spatially uneven. While the basin-mean sea level rise from 1993 to 2014 was about 3.15 mm yr −1 , the local rates of sea level rise varied from 1.5-2.5 mm yr −1 in the central part to 3.5-3.8 mm yr −1 at the basin periphery and over the northwestern shelf and to 5 mm yr −1 in the southeastern part of the sea. We show that the observed spatial differences in the dynamic sea level (anomaly relative to the basin-mean) are caused by changes in the large-and mesoscale dynamics of the Black Sea. First, a long-term intensification of the cyclonic wind curl over the Black Sea, observed in 1993-2014, strengthened divergence in the center of the basin and led to the rise of the sea level in coastal and shelf areas and a lowering in the basin's interior. Second, an extension of the Batumi anticyclone to the west resulted in ∼ 1.2 mm yr −1 higher rates of sea level rise in the southeastern part of the sea. Further, we demonstrate that the large-scale dynamic sea level variability in the Black Sea can be successfully reconstructed using the wind curl obtained from an atmospheric reanalysis. This allows for the correction of historical tide gauge records for dynamic effects in order to derive more accurate estimates of the basin-mean sea level change in the past, prior to the satellite altimetry era.

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“…Second, altimetry measurements are not available near the coast, and their accuracy in the vicinity of the coast falls down due to inaccurate atmospheric and geophysical corrections [26]. This includes the decrease of quality of the wet tropospheric correction, mapping procedure, mean dynamic topography, and difficulties in the description of barotropic sea level variability [2,[27][28][29][30]. Third, altimetry-derived velocities are geostrophic and represent only a part, also very important, of the current velocity [31].…”

Section: Introductionmentioning

confidence: 99%

Reconstructing Large- and Mesoscale Dynamics in the Black Sea Region from Satellite Imagery and Altimetry Data—A Comparison of Two Methods

2018

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Two remote sensing methods, satellite altimetry and 4D-Var assimilation of satellite imagery, are used to compute surface velocity fields in the Black Sea region. Surface currents derived from the two methods are compared for several cases with intense mesoscale and large-scale dynamics during low wind conditions. Comparison shows that the obtained results coincide well quantitatively and qualitatively. However, satellite imagery provides more reasonable results on the spatial variability of coastal dynamics than altimetry data. In particular, this is related to the reconstruction of eddy coastal dynamics, such as Black Sea near-shore anticyclones. Current streamlines in these eddies are not closed near the coast in altimetry data, which we relate to the extrapolation during mapping procedure in the absence of coastal along-track measurements. On the other hand, in offshore areas, imagery-derived currents can be underestimated due to the absence of thermal contrasts and smoothing during the procedure of the 4D-Var assimilation. Wind drift currents are another source of inconsistency, as their impact is directly observed in satellite imagery but absent in altimetry data. The advantage of the 4D-Var method for reconstructing coastal dynamics is used to compute surface currents in the Marmara Sea on the base of 250 m resolution Modis optical data. The results reveal the very complex dynamics of the basin, with a large number of mesoscale and sub-mesoscale eddies. 4D-Var assimilation of Modis imagery is used to obtain information about dynamic characteristics of these small eddies with radiuses of 4-10 km.

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Improved satellite altimeter mapped sea level anomalies in the Mediterranean Sea: A comparison with tide gauges

Cited by 19 publications

References 20 publications

DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years

DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years

Quantifying the impact of basin dynamics on the regional sea level rise in the Black Sea

Reconstructing Large- and Mesoscale Dynamics in the Black Sea Region from Satellite Imagery and Altimetry Data—A Comparison of Two Methods

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