Improvements in Precise Orbits of Altimetry Satellites and Their Impact on Mean Sea Level Monitoring

Rudenko, Sergei; Neumayer, Karl Hans; Dettmering, D; Esselborn, Saskia; Schöne, Tilo; Raimondo, J. C.

doi:10.1109/tgrs.2017.2670061

Cited by 33 publications

(28 citation statements)

References 31 publications

(43 reference statements)

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“…The amplitude of the annual cycle of the sea level difference computed against predominantly coastal in situ data reaches 2.4 mm with the v1.1 ECV and is reduced to 1.6 mm with the v2.0 ECV, suggesting that the annual signal is better retrieved with the reprocessed dataset. This observed difference is related to the changes in the level 2 altimeter standards involved in the ECV production, the main contributors being the orbit solutions (Couhert et al, 2015;Rudenko et al, 2017) and the GPD+ wet troposphere correction (Fernandes and Lázaro, 2016) used for the different altimeter missions . The new pole tide correction also affects the amplitude of the annual cycle.…”

Section: Seasonal Cyclementioning

confidence: 99%

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

Legeais

Ablain

Zawadzki

et al. 2018

Earth Syst. Sci. Data

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183

135

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Abstract. Sea level is a very sensitive index of climate change since it integrates the impacts of ocean warming and ice mass loss from glaciers and the ice sheets. Sea level has been listed as an essential climate variable (ECV) by the Global Climate Observing System (GCOS). During the past 25 years, the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed to provide an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the project (2010)(2011)(2012)(2013), an initial version (v1.1) of the sea level ECV was made available to users . During the second phase of the project (2014-2017), improved altimeter standards were selected to produce new sea level products (called SL_cci v2.0) based on nine altimeter missions for the period 1993-2015 (https://doi.org/10.5270/esa-sea_level_cci-1993_2015-v_2.0-201612; Legeais and the ESA SL_cci team, 2016c). Corresponding orbit solutions, geophysical corrections and altimeter standards used in this v2.0 dataset are described in detail in Quartly et al. (2017). The present paper focuses on the description of the SL_cci v2.0 ECV and associated uncertainty and discusses how it has been validated. Various approaches have been used for the quality assessment such as internal validation, comparisons with sea level records from other groups and with in situ measurements, sea level budget closure analyses and comparisons with model outputs. Compared with the previous version of the sea level ECV, we show that use of improved geophysical corrections, careful bias reduction between missions and inclusion of new altimeter missions lead to improved sea level products with reduced uncertainties on different spatial and temporal scales. However, there is still room for improvementPublished by Copernicus Publications. 282J.-F. Legeais et al.: An improved and homogeneous altimeter sea level record from the ESA since the uncertainties remain larger than the GCOS requirements (GCOS, 2011). Perspectives on subsequent evolution are also discussed.

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Section: Seasonal Cyclementioning

confidence: 99%

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

Legeais

Ablain

Zawadzki

et al. 2018

Earth Syst. Sci. Data

Self Cite

183

135

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“…We use SLR and DORIS observations for all three satellites. To derive the satellite orbits, we use the same models, procedures, and parameterization as described in Rudenko et al (2017) but use two different ITRF realizations -ITRF2008 and ITRF2014.…”

Section: Itrf Realizations Used For Precise Orbit Determinationmentioning

confidence: 99%

“…The main models used for orbit determination are given in Table 2. For the details on the models and procedures used for the POD, the reader is referred to Rudenko et al (2014) and Rudenko et al (2017). The orbits of these satellites derived using ITRF2008 and ITRF2014 are called VER11 (version 11) and VER13 (version 13) orbits, respectively.…”

Section: Itrf Realizations Used For Precise Orbit Determinationmentioning

confidence: 99%

Impact of terrestrial reference frame realizations on altimetry satellite orbit quality and global and regional sea level trends: a switch from ITRF2008 to ITRF2014

Rudenko¹,

Esselborn

Schöne

et al. 2019

Solid Earth

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Abstract. A terrestrial reference frame (TRF) is a basis for precise orbit determination of Earth-orbiting satellites, since it defines positions and velocities of stations, the tracking data of which are used to derive satellite positions. In this paper, we investigate the impact of the International Terrestrial Reference Frame realization ITRF2014, as compared to its predecessor ITRF2008, on the quality of orbits, namely, on root-mean-square (rms) fits of observations and orbital arc overlaps of three altimetry satellites (TOPEX/Poseidon, Jason-1, and Jason-2) in the time interval from August 1992 to April 2015 and on altimetry products computed using these orbits, such as single-satellite altimeter crossover differences, radial and geographically correlated mean sea surface height (SSH) errors and regional and global mean sea level trends. The satellite orbits are computed using satellite laser ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) observations of a global network of stations. We have found that using ITRF2014 generally improves the orbit quality as compared to using ITRF2008. Thus, the mean values of the rms fits of SLR observations decreased (improved) by 2.4 % and 8.8 % for Jason-1 and Jason-2, respectively, but are almost not impacted for TOPEX/Poseidon when using ITRF2014 instead of ITRF2008. The internal orbit consistency in the radial direction (as derived from arc overlaps) is reduced (improved) by 6.6 %, 2.3 %, and 5.9 % for TOPEX/Poseidon, Jason-1, and Jason-2, respectively. Single-satellite altimetry crossover analyses indicate reduction (improvement) in the absolute mean crossover differences by 0.2 mm (8.1 %) for TOPEX, 0.4 mm (17.7 %) for Jason-1, and 0.6 mm (30.9 %) for Jason-2 with ITRF2014 instead of ITRF2008. The major improvement of the mean values of the rms of crossover differences (0.13 mm; 0.3 %) has been found for Jason-2. Multi-mission crossover analysis shows slight improvements in the standard deviations of radial errors: 0.1 %, 0.2 %, and 1.6 % for TOPEX, Jason-1, and Jason-2, respectively. The standard deviations of geographically correlated mean SSH errors improved by 1.1 % for Jason-1 and 5.4 % for Jason-2 and degraded by 1.3 % for TOPEX. The change from ITRF2008 to ITRF2014 orbits only has minor effects on the estimation of regional and global sea level trends over the 22-year time series from 1993 to 2015. However, on interannual timescales (3–8 years) large-scale coherent trend patterns are observed that seem to be connected to drifts between the origins of the tracking station networks. This leads to the changes in interannual global mean sea level of up to 0.06 mm yr−1 for TOPEX, 0.05 mm yr−1 for Jason-1, and up to 0.12 mm yr−1 for Jason-2, i.e., up to 4 % of the corresponding sea level signal based on altimetry for timescales of 3 to 8 years. The respective changes in the regional sea level trend on these timescales are up to 0.4 mm yr−1 in the time span from April 1993 to July 2008 and up to 1.0 mm yr−1 in the time span from July 2008 to April 2015.

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“…The associated round robin data packages (RRDP) showing the impact 25 analysis of each standard and the output of the meeting are available on the SL_cci website (http://www.esa-sealevelcci.org/PublicDocuments), with a synopsis of the comparisons given in Quartly et al (2017). Many of the applied corrections have been revised, in particular modeled orbits due to time-variable gravity (Rudenko et al, 2014;Couhert et al, 2015, Rudenko et al, 2016, satellite attitude, macromodels and tropospheric correction models for DORIS observations (Rudenko et al, 2017), modifications to the wet tropospheric correction based on combined GNSS and radiometer data sets 30 (Fernandes et al, 2015) and the latest changes in ocean tide (FES2014) and "pole tide" .…”

Section: Input Data and Altimeter Standardsmentioning

confidence: 99%

“…The amplitude of the annual cycle of the sea level difference with in-situ data reaches 2.4 mm with the v1.1 ECV and is reduced to 1.6 mm with the v2.0 ECV, suggesting that the annual signal is better retrieved with the reprocessed dataset. This observed difference is related to the changes in the level 2 altimeter standards involved in the ECV production, the main contributors being the orbit solutions (Couhert et al, 2015;Rudenko et al, 2017) and the GPD+ wet troposphere correction (Fernandes and Lázaro, 2016) used for the different altimeter missions (Quartly et al, 30 2017). The new pole tide correction also affects the amplitude of the annual cycle.…”

Section: Seasonal Cyclementioning

confidence: 99%

An Accurate and Homogeneous Altimeter Sea Level Record from the ESA Climate Change Initiative

Legeais¹,

Ablain²,

Zawadzki³

et al. 2017

Preprint

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Sea Level is a very sensitive index of climate change since it integrates the impacts of ocean warming and ice mass loss from 25 glaciers and the ice sheets. Sea Level has been listed as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). During the past 25 years, the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed at providing an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the 30 project (2010)(2011)(2012)(2013), an initial version (v1.1) of the sea level ECV has been made available to users . During the second phase (2014-2017), improved altimeter standards have been selected to produce new sea level products (called SL_cci v2.0) based on 9 altimeter missions for the period 1993-2015 (https://doi.org/10.5270/esa-sea_level_cci-1993_2015-v_2.0-201612). Corresponding orbit solutions, geophysical corrections and altimeter standards used in this v2.0 dataset are described in details in Quartly et al. (2017). The present paper focuses on the description of the SL_cci v2.0 ECV 35and associated uncertainty and discusses how it has been validated. Various approaches have been used for the quality assessment such as internal validation, comparisons with sea level records from other groups and with in-situ measurements, Earth Syst. Sci. Data Discuss., https://doi.2 sea level budget closure analyses and comparisons with model outputs. Compared to the previous version of the sea level ECV, we show that use of improved geophysical corrections, careful bias reduction between missions and inclusion of new altimeter missions lead to improved sea level products with reduced uncertainties at different spatial and temporal scales.However, there is still room for improvement since the uncertainties remain larger than the GCOS requirements.Perspectives for subsequent evolutions are also discussed. 5 IntroductionPresent-day Global Mean Sea Level (MSL) rise primarily reflects the amount of heat added in the ocean and land ice melt in response to anthropogenic global warming (e.g. IPCC, 2013;von Schuckmann et al., 2016). Accurate monitoring of the sea level is required to better understand its variability and distinguish between natural and anthropogenic forcing factors at the origin of observed changes. It also allows validation of the climate models developed for projecting future changes, as the 10 models are supposed to correctly reproduce present-day and recent-past changes. Since 1993, satellite altimetry missions deliver accurate sea level measurements, allowing the monitoring of sea level variations at different spatial and temporal scales (Pujol et al., 2016; Escudier et al., 2017). About a decade ago, the Global Climate Observing System (GCOS) defined a list of key parameters of the Earth ...

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Improvements in Precise Orbits of Altimetry Satellites and Their Impact on Mean Sea Level Monitoring

Cited by 33 publications

References 31 publications

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

Impact of terrestrial reference frame realizations on altimetry satellite orbit quality and global and regional sea level trends: a switch from ITRF2008 to ITRF2014

An Accurate and Homogeneous Altimeter Sea Level Record from the ESA Climate Change Initiative

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