scholarly journals A coastally improved global dataset of wet tropospheric corrections for satellite altimetry

2019 ◽  
Author(s):  
Clara Lázaro ◽  
Maria Joana Fernandes ◽  
Telmo Vieira ◽  
Eliana Vieira
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Coastal Zone ◽  
Satellite Altimetry ◽  
Microwave Radiometer ◽  
Satellite Orbit ◽  
Time Variability ◽  
Path Delay ◽  
Coastal Regions

Abstract. Global mean sea level is a valuable proxy to understand climate change and how it operates, since it includes the response from various components of the climate system. Global sea level rise is accelerating, which is a concern for coastal areas management from medium to long-term time scales. Satellite radar altimetry (RA) has been providing us information regarding the sea level anomaly (SLA) field and its space-time variability since the early 90s. As satellite orbit determination, reference surfaces (e.g., mean sea surface) and instrumental, range and geophysical corrections improved over the decades, the data from past missions were reprocessed subsequently, leading to an SLA dataset over open ocean accurate to the centimetre-level. The accuracy of satellite altimetry is known to deteriorate towards the coastal regions due to several reasons, amongst which the improper account for the wet path delay (WPD) can be pointed out. The most accurate WPDs for RA are derived from the on-board microwave radiometer (MWR) radiance measurements, acquired simultaneously as the altimeter ranges. In the coastal zone, however, the signal coming from the surrounding land contaminates these measurements and the water vapour retrieval from the MWR fails. As meteorological models do not handle coastal atmospheric variability correctly yet, the altimeter measurements are rejected whenever MWR observations are absent or invalid. The need to solve this altimetry issue in the coastal zone, simultaneously responding to the growing demand of data in these regions, motivated the development of the GNSS-derived Path Delay (GPD) algorithm. The GPD combines WPD from several sources through objective analysis (OA) to estimate the WPD or the corresponding RA correction accounting for this effect, the wet tropospheric correction (WTC), for all along-track altimeter points for which this correction has been set as invalid or is absent. The current GPD version (GPD Plus, GPD+) uses as data sources WPD from coastal and island GNSS stations, from satellites carrying microwave radiometers, and from valid on-board MWR measurements. The GPD+ has been tuned to be applied to all, past and operational, RA missions, with or without an on-board MWR. The long-term stability of the WTC dataset is ensured by its inter-calibration with respect to the Special Sensor Microwave Imager (SSM/I) and SSMI/I Sounder (SSM/IS). The dataset is available for TOPEX/Poseidon (T/P), Jason-1 and Jason-2 (NASA/CNES), Jason-3 (NASA/EUMETSAT), ERS 1, ERS-2, Envisat and CryoSat-2 (ESA), SARAL/AltiKa (ISRO/CNES) and GFO (U.S. Navy) RA missions. The GPD+ WTC for Sentinel-3 shall be released soon. The present paper describes the GPD+ database and its independent validation through statistical analyses of SLA. Overall, results show that the GPD+ WTC is the most effective in reducing the SLA variance in the coastal regions, in particular for the ESA missions. Moreover, GPD+ recovers a significant number of measurements, which otherwise would be rejected due to land, rain and ice contamination and instrument malfunctioning. Consequently, GPD+ database has been chosen as reference WTC in the Sea Level Climate Change Initiative (CCI) products; the GPD+ has also been adopted as reference in CryoSat-2 Level 2 Geophysical Ocean Products (GOP). Strategies to further improve the methodology, therefore enhancing the quality of the database, are also discussed. The GPD+ dataset is archived on the homepage of the Satellite Altimetry Group, University of Porto, publicly available at the repository https://doi.org/10.23831/FCUP_UPORTO_GPDPlus_v1.0 (Fernandes et al., 2019).

scholarly journals A coastally improved global dataset of wet tropospheric corrections for satellite altimetry

2020 ◽  
Vol 12 (4) ◽  
pp. 3205-3228
Author(s):  
Clara Lázaro ◽  
Maria Joana Fernandes ◽  
Telmo Vieira ◽  
Eliana Vieira
Keyword(s):  
Sea Level ◽  
Coastal Zone ◽  
North American ◽  
Satellite Altimetry ◽  
Microwave Radiometer ◽  
Satellite System ◽  
Path Delay ◽  
Coastal Zones ◽  
The North ◽  
Along Track

Abstract. The accuracy of satellite radar altimetry (RA) is known to deteriorate towards the coastal regions due to several reasons, amongst which the improper account for the wet path delay (WPD) can be pointed out. The most accurate WPDs for RA are derived from the on-board microwave radiometer (MWR) radiance measurements, acquired simultaneously as the altimeter ranges. In the coastal zone, however, the signal coming from the surrounding land contaminates these measurements and the water vapour retrieval from the MWR fails. As meteorological models do not handle coastal atmospheric variability correctly yet, the altimeter measurements are rejected whenever MWR observations are absent or invalid. The need to solve this RA issue in the coastal zone, simultaneously responding to the growing demand for data in these regions, motivated the development of the GNSS (Global Navigation Satellite System) derived Path Delay (GPD) algorithm. GPD combines WPD from several sources through objective analysis (OA) to estimate the WPD or the corresponding RA correction accounting for this effect, the wet tropospheric correction (WTC), for all along-track altimeter points for which this correction has been set as invalid or is not defined. The current GPD version (GPD Plus, GPD+) uses as data sources WPD from coastal and island GNSS stations, from satellites carrying microwave radiometers, and from valid on-board MWR measurements. GPD+ has been tuned to be applied to all, past and operational, RA missions, with or without an on-board MWR. The long-term stability of the WTC dataset is ensured by its inter-calibration with respect to the Special Sensor Microwave Imager (SSM/I) and SSM/I Sounder (SSMIS). The dataset is available for the TOPEX/Poseidon (T/P); Jason-1 and Jason-2 (NASA and CNES); Jason-3 (NASA and EUMETSAT); ERS-1, ERS-2, Envisat and CryoSat-2 (ESA); SARAL/AltiKa (ISRO and CNES); and GFO (US Navy) RA missions. The GPD+ WTC for Sentinel-3 (ESA and EUMETSAT) shall be released soon. The present paper describes the GPD+ database and its assessment through statistical analyses of sea level anomaly (SLA) datasets, calculated with GPD+, the ECMWF Reanalysis Interim (ERA-Interim) model or MWR-derived WTCs. Global results, as well as results for three regions (the North American and European coasts and the Indonesia region), are presented for ESA's recent Envisat Full Mission Reprocessing (FMR) V3.0. Global results show that the GPD+ WTC leads to a reduction in the SLA variance of 1–2 cm2 in the coastal zones, when used instead of the ERA WTC, which is one of the WTCs available in these products and can be adopted when the MWR-derived WTC is absent or invalid. The improvement of the GPD+ WTC over the ERA WTC is maximal over the tropical oceans, particularly in the Pacific Ocean, showing that the model-derived WTC is not able to capture the full variability in the WPD field yet. The statistical assessment of GPD+ for the North American coast shows a reduction in SLA variance, when compared to the use of the ERA-derived WTC, of 1.2 cm2, on average, for the whole range of distances from the coast considered (0–200 km). Similar results are obtained for the European coasts. For the Indonesia region, the use of the GPD+ WTC instead of that from ERA leads to an improvement, on average, on the order of 2.2 cm2 for distances from the coast of up to 100 km. Similar results have been obtained for the remaining missions, particularly for those from ESA. Additionally, GPD+ recovers the WTC for a significant number of along-track altimeter points with missing or invalid MWR-derived WTCs, due to land, rain and ice contamination and instrument malfunctioning, which otherwise would be rejected. Consequently, the GPD+ database has been chosen as the reference WTC in the Sea Level Climate Change Initiative (CCI) products; GPD+ has also been adopted as the reference in CryoSat-2 Level-2 Geophysical Ocean Products (GOP). Strategies to further improve the methodology, therefore enhancing the quality of the database, are also discussed. The GPD+ dataset is archived on the home page of the Satellite Altimetry Group, University of Porto, publicly available at the repository https://doi.org/10.23831/FCUP_UPORTO_GPDPlus_v1.0 (Fernandes et al., 2019).

Estimating Vertical Land Motion in Northern Adriatic Sea with Coastal Altimetry and In Situ Observations

2020 ◽  
Author(s):  
Francesco De Biasio ◽  
Stefano Vignudelli ◽  
Giorgio Baldin
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Coastal Zone ◽  
Satellite Altimetry ◽  
Data Sets ◽  
Tide Gauges ◽  
The Mediterranean

<p align="justify"><span>The European Space Agency, in the framework of the Sea Level Climate Change Initiative (SL_CCI), is developing consistent and long-term satellite-based data-sets to study climate-scale variations of sea level globally and in the coastal zone. Two altimetry data-sets were recently produced. The first product is generated over a grid of 0.25x0.25 degrees, merging and homogenizing the various satellite altimetry missions. The second product that is still experimental is along track over a grid of 0.35 km. An operational production of climate-oriented altimeter sea level products has just started in the framework of the European Copernicus Climate Change Service (C3S) and a daily-mean product is now available over a grid of 0.125x0.125 degrees covering the global ocean since 1993 to present.</span></p><p align="justify"><span>We made a comparison of the SL_CCI satellite altimetry dataset with sea level time series at selected tide gauges in the Mediterranean Sea, focusing on Venice and Trieste. There, the coast is densely covered by civil settlements and industrial areas with a strongly rooted seaside tourism, and tides and storm-related surges reach higher levels than in most of the Mediterranean Sea, causing damages and casualties as in the recent storm of November 12th, 2019: the second higher water registered in Venice since 1872. Moreover, in the Venice area the ground displacements exhibit clear negative trends which deepen the effects of the absolute sea level rise.</span></p><p align="justify"><span>Several authors have pointed out the synergy between satellite altimetry and tide gauges to corroborate evidences of ground displacements. Our contribution aims at understanding the role played by subsidence, estimated by the diffence between coastal altimetry and in situ measurements, on the local sea level rise. A partial validation of these estimates has been made against GPS-derived values, in order to distinguish the contributions of subsidence and eustatism. This work will contribute to identify problems and challenges to extend the sea level climate record to the coastal zone with quality comparable to the open ocean, and also to assess the suitability of altimeter-derived absolute sea levels as a tool to estimate subsidence from tide gauge measurement in places where permanent GPS receivers are not available.</span></p>

scholarly journals Improved sea level record over the satellite altimetry era (1993–2010) from the Climate Change Initiative project

Ocean Science ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 67-82 ◽  
Author(s):  
M. Ablain ◽  
A. Cazenave ◽  
G. Larnicol ◽  
M. Balmaseda ◽  
P. Cipollini ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Climate Model ◽  
Atmospheric Correction ◽  
European Space Agency ◽  
Processing System ◽  
Change Initiative ◽  
Global Mean

Abstract. Sea level is one of the 50 Essential Climate Variables (ECVs) listed by the Global Climate Observing System (GCOS) in climate change monitoring. In the past two decades, sea level has been routinely measured from space using satellite altimetry techniques. In order to address a number of important scientific questions such as "Is sea level rise accelerating?", "Can we close the sea level budget?", "What are the causes of the regional and interannual variability?", "Can we already detect the anthropogenic forcing signature and separate it from the internal/natural climate variability?", and "What are the coastal impacts of sea level rise?", the accuracy of altimetry-based sea level records at global and regional scales needs to be significantly improved. For example, the global mean and regional sea level trend uncertainty should become better than 0.3 and 0.5 mm year−1, respectively (currently 0.6 and 1–2 mm year−1). Similarly, interannual global mean sea level variations (currently uncertain to 2–3 mm) need to be monitored with better accuracy. In this paper, we present various data improvements achieved within the European Space Agency (ESA) Climate Change Initiative (ESA CCI) project on "Sea Level" during its first phase (2010–2013), using multi-mission satellite altimetry data over the 1993–2010 time span. In a first step, using a new processing system with dedicated algorithms and adapted data processing strategies, an improved set of sea level products has been produced. The main improvements include: reduction of orbit errors and wet/dry atmospheric correction errors, reduction of instrumental drifts and bias, intercalibration biases, intercalibration between missions and combination of the different sea level data sets, and an improvement of the reference mean sea surface. We also present preliminary independent validations of the SL_cci products, based on tide gauges comparison and a sea level budget closure approach, as well as comparisons with ocean reanalyses and climate model outputs.

scholarly journals Crossover comparison of climate-change adaptation measures taken in the Gdansk (Baltic-sea) and Rotterdam (Nord-sea) deltas.

2021 ◽  
Vol 1 ◽  
pp. 9
Author(s):  
Fred Sanders ◽  
Hugo Sanders ◽  
Karen Jonkers
Keyword(s):  
Climate Change ◽  
The Netherlands ◽  
Baltic Sea ◽  
Sea Level ◽  
Climate Change Impacts ◽  
Adaptation Measures ◽  
Change Trend ◽  
Vistula Delta ◽  
Crossover Comparison

Gdansk in Poland and the Netherlands share a long-term relationship that started with the establishment of Dutch Mennonites in the Vistula delta in the 16th Century. Climate-change figures show that both the Polish Gdansk and DutchRotterdam deltas will suffer flooding due to sea level rise, with accumulating severe rainfall accompanied by high river levels; reasons that led to a comparison of the adaptation measures taken. On the basis of the crossover comparison studied, it can be concluded that Poland and the Netherlands have a virtually identical approach when it comes to climate-change impacts on their current situation. With regard to the long-term climate-change trend, the Netherlands in exploring for the future more ‘anticipatory’ measures with the development of new scenarios for the protection of land and cities. In the Netherlands the use of Hackathon approach is thereby used more often to explore such scenarios. The interaction between the experts and stakeholders of different expertise in this methodology show to lead to creative and new perspectives. This approach may also be recommended for the situation in Gdansk.

scholarly journals Hazardous phenomena in the slides zone of the Ukrainian section in Azov sea

2021 ◽  
Keyword(s):  
Sea Level ◽  
Coastal Zone ◽  
Residential Buildings ◽  
Engineering Structures ◽  
Temperature And Precipitation ◽  
Azov Sea ◽  
Coastal Sea ◽  
Landslide Processes ◽  
High Degree

Formulation of the problem. According long- term data analyses under the slides zone in Ukrainian part of the Azov sea sustainable processes had been marked. Landslides are most active in autumn and spring. The activation of landslides occurs under the influence of man-made and natural factors. The most significant factor is coastal abrasion. Review of previous publications. It was established that the air temperature and precipitation, the temperature and salinity of sea waters and the hydrometeorological regime of the coastal zone and the water balance of the Black and Azov seas as well depends on climatic changes. The rising of the sea level has intensified over the past decades. These changes found a response in the coastal zone that reacted to them and acquired corresponding trends. Purpose is to determine the reasons for the formation of dynamically unstable sectors and the possibility of protecting the shores on the Ukrainian coast in the Azov Sea, the subject is landslide processes, as the result of the abrasion of the shores, the object is the variability of the natural and anthropogenic conditions of the Ukrainian coast of the Azov Sea in the area of interaction between the sea and land. Methods. Analyses of images space and temporal dynamic of Earth remote sensing satellites by DigitalGlobe, USGS LandLook and Sentinel were used and also retrospective long term of hydrometeorological data and standard statistical methods. Results. The places (areas) with pronounced coastal dynamic processes on the Ukrainian coast of the Azov Sea were identified, that require special attention: two in the Kherson region, five in the Zaporozhye region and four in Donetsk. In the coastal zone of the Azov Sea the rate of abrasion from 1 to 4 m per year (in exceptional cases up to 15 m per year) was marked. In a period of significant level rises, the flooding of ports, berths, the destruction of hydraulic engineering structures, storage facilities, and residential buildings is possible. Also, during the period of the significant decreasing of the sea level, the already limited depth of the approach channels decreases again, that disrupts the operation of the fleet. Conclusions. Investigations of the current state of the Ukrainian coastal zone of the Azov Sea, that is significant importance for the sustainable the economy development, the recreational region’s potential and the social level of the population. It has been established that in the eastern regions of the Azov coast of Ukraine there are a deficit of sediments and a high degree of variability of the abrasion form of the coastal-sea relief is noted, and an excess of sediments are formed in the western and northwestern regions.

scholarly journals Evaluating on flooding area and tidal beach change in Quang Ninh coastal zone due to sea level rise

2020 ◽  
Vol 3 (SI3) ◽  
pp. First
Author(s):  
Van Manh Dinh ◽  
Thu Ha Tran ◽  
Manh Chien Truong
Keyword(s):  
Climate Change ◽  
Numerical Model ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Zone ◽  
Beach Erosion ◽  
Tidal Range ◽  
Climate Change Scenarios ◽  
Quang Ninh ◽  
Flooded Areas

Viet Nam is considered one of countries most affected by climate change and sea-level rise. It results in many negative effects, such as flooding, saline intrusion and beach erosion occurred in the coastal zones. Quang Ninh with more than 250 km coastline, located in the northeastern part of Vietnam, is one of the vulnerable coastal provinces under the heavily affected due to the sea level rise. In order to evaluate the changes of flooded areas and tidal beaches due to the sea level rise in Quang Ninh coastal zone a 2D numerical model is set up, using the 3-grids nesting technique. The numerical model is calibrated by using the harmonic constants of 8 tidal constituents at Hon Dau tide station and validated with the observed data. On the basis of the climate change scenarios (RCP4.5, RCP8.5) in the period from 2020 to 2100, the corresponding sea level values are used in the numerical modeling to calculate the changes of flooded areas and tidal beaches due to the sea level rise. The obtained results on changing of the flooded area and tidal beach in Quang Ninh coastal zone are not only statically by changing water sea levels but also due to changing of the tidal range in this area. The calculated results point out that districts under the most affected of the sea level rise are Quang Yen, Tien Yen, Hai Ha, Mong Cai.

Climate Change Impacts on a Mediterranean Coastal Wetland due to Sea Level Rise (L’Albufera de Valencia, Spain)

2021 ◽  
Author(s):  
Clara E Estrela Segrelles ◽  
Miguel Ángel Pérez Martín ◽  
Gabriel Gómez Martínez
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Water Volume ◽  
Lake Ecosystem ◽  
Lake Levels ◽  
Short Term

<p>Sea level rise produced by climate change severely affects coastal ecosystems. The increase in the area below sea level facilitates the penetration of the marine wedge and causes an increase in soil salinity. Coastal wetlands are areas of great ecological importance due to the richness of flora and fauna that inhabit them. A change in salinity conditions could lead to a reduction or loss of habitat for the wetland biota. Based on RCP4.5 and RCP8.5 CMIP5 multimodel scenarios, in the Western Mediterranean coast, the sea level will rise 0.16 m in the short term (2026 - 2045) and 0.79 m in 2100. Also, high-end scenarios indicate that sea level will rise between 1.35 m and 1.92 m in the long term.</p><p>A sea level rise analysis has been developed in the coastal wetlands of Júcar River Basin District (JRBD). The results show that coastal wetlands are the mainly area affected in the JRBD, so the 90% of the area under the sea level are wetlands. L’Albufera de Valencia is the main wetland in this basin and, also the main wetland affected. It is an anthropized humid zone, regulated by users through gates to preserve the adequate water level for agricultural and environmental purposes such as rice cultivation around the lake and bird habitats conservation, especially in winter. The outcome of the study shows a significative increase in the area below the sea from 507 ha and 4.2 hm<sup>3</sup> of water volume at present to 3,244 ha that represents 42.6 hm<sup>3</sup> of water volume in the short term. In the long term, the area below the sea is 7,253 ha which means 118.4 hm<sup>3</sup> of water volume in the percentile 50 scenario and, in the worst extreme scenario, it is 13,896 ha that represents 289.7 hm<sup>3</sup> of water volume. This leads to a redefinition of the lake management levels as a climate change adaptation measure to prevent the lake salinization and severe impacts in the lake ecosystem. L’Albufera lake levels need to be increased in the next years to avoid the sea water penetration, related to the sea level rise. Thus, in the short term the lake levels must be increased around 0.16 m and, in the long term, L’Albufera levels must be increased around 0.8 m.</p>

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