main results of sea-level cci...
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CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
ESA’s Sea Level Climate Change Initiative
M Ablain1 , G. Larnicol1, A. Cazenave2, Y Faugère1, J. Johannessen3, D. Stammer4, G. Timms5, P. Knudsen6, P. Cipolini7, M. Roca8, S. Rudenko9, J.
Fernandes10, M. Balmaseda11, T. Guinle12, J. Benveniste13
1 CLS, 2LEGOS, 3 NERSC, 4University of Hamburg, 5 LOGICA,6 DTU, 7 NOCS,8IsardSat,
9GFZ, 10 University of Porto, 11 ECMWF, 12 CNES, 13ESA
Main results of Sea-Level CCI phase-1
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• Objectives of this presentation is to answer the two following questions :
1. Which improvements have been done during phase 1 ?
2. Why do we have to continue on phase 2 ?
1) Development and selection of new algorithms
2) Sea Level ECV products and assessment
3) Definition of user requirements and description of error budget
Outlines
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
1) Development and selection of new algorithms
• The Altimetric system is complex : it integrates other sub-systems as complex as the altimetric system itself.
Altimetry System : Altimeter, radiometer
Precise Orbit Determination
Geodetic fields and processes (Geoïd, MSS ,
GIA, ..) Oceanic processes
(Tides, Sea state, …)
Atmospheric fields (pressure, wind, wet
troposphere)
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
1) Development and selection of new algorithms
Precise Orbit Determination
• The consequences are : ⇒ The Sea-level calculation is composed of many components : ⇒ Several standards exist for each component
∑=
−−=N
iiCorrectionRangeOrbitSSH
0
The evaluation of sea-level calculation performances needs to evaluate a lot of algorithms/corrections
Altimetry System : Altimeter, radiometer
Oceanic processes (Tides, Sea state, …)
Atmospheric fields (pressure, wind, wet
troposphere)
Geodetic fields and processes (Geoïd, MSS ,
GIA, ..)
• The Altimetric system is complex : it itegrates other sub-systems as complex as the altimetric system itself.
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• News algorithms and altimeter corrections have been developed and tested: - they come from Sea Level CCI partners but also from external projects or studies
SL-CCI new algo/corrections: - New Orbit solutions (GFZ) -New instrumental corrections (CLS/isardSAT) -New wet Tropo corrections (University of Porto) -New atmosphercical correction with ERA-interim (CLS) - New ionospheric corrections (CLS) -New algorithms to merge altimeter mission together (CLS)
External projects and studies: - Jason-2 reprocessing (SALP project / CNES) - Envisat reprocessing (FPAC/ESA/CNES) : - New orbit solutions (POD group) - New tidal models (R.Ray, CNES/LEGOS/CLS) - Mean Sea Surface (DTU, CNES/CLS) - ERS-1/ERS-2 reprocessing (REAPER project / ESA)
Validated within the
SL-CCI project
1) Development and selection of new algorithms
42 RRDP reports were produced
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• lt consists in comparing the new algorithms with the reference ones : - using a common set of validation diagnoses for all the algorithms
- using validation diagnoses dedicated for climate scales
- using the same altimeter data base
- producing validation reports separating the spatial and temporal climate scales
1) Development and selection of new algorithms
A formal validation protocol was developed within the SLCCI project in order to validate and estimate the performances of new altimeter standards at climate scales.
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Impact of new SL-CCI correction in SSH calculation in comparison with the reference one (AVISO standards,…)
Climate
Applications Temporal Scales For 1 mission (Envisat, ERS,
Jason, T/P,…)
Global Mean Sea Level
Long-term evolution (trend)
Inter annual signals (> 1 year)
Annual and semi-annual Signals
Regional Mean Sea Level
Long-term evolution (trend)
Annual and semi-annual Signals
Mesoscale Signals < 2 months
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Impact of new SL-CCI in SSH calculation in comparison with AVISO standards
Climate
Applications Temporal Scales For 1 mission (Envisat, ERS,
Jason, T/P,…)
Global Mean Sea Level
Long-term evolution (trend) NO IMPACT
Inter annual signals (> 1 year) LOW IMPACT
Annual and semi-annual Signals STRONG IMPACT
Regional Mean Sea Level
Long-term evolution (trend)
Annual and semi-annual Signals
Mesoscale Signals < 2 months
Definition of the indicator value
Significant impact Low impact No impact detected
Trend >0.15 mm/yr Trend> 0.05 mm/yr Trend< 0.05 mm/yr
Amplitude> 0.5 mm Amplitude> 0.2 mm Amplitude< 0.2 mm
Amplitude> 1 mm Amplitude> 0.2 mm Amplitude< 0.2 mm
Trend > 0.5 mm/yr Trend> 0.1 mm/yr Trend< 0.1 mm/yr
Amplitude> 5 mm Amplitude> 0.5 mm Amplitude< 0.5 mm
Crossovers Variance differences > 1 cm²
Crossovers Variance differences > 0.2
cm²
Crossovers Variance differences < 0.2
cm²
+ -
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
ERS-1 ERS-2 EN T/P J1 J2 GFO
Orbit Reaper Reaper GDRD GDRD GDRD Major Instrumental correction
PTR
Sea State Bias 2007
Ionosphere Reaper Rep.
Wet troposphere
GPS-based
GPS-based
GPS-based
GPS-based
GPS-based
GPS-based
Dry troposphere Era Interim based
Combined atmospheric correction
Era Interim based
Ocean tide GOT 4.8 Solid Earth tide
Pole tide MSS DTU10 Merging algorithms New regional biases and monthly OI
Selection meeting outputs
Discussions & recommendations available on the SL CCI web site
New algo/corr applied in SL CCI
No change with respect to reference (AVISO products)
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
ERS-1 ERS-2 EN T/P J1 J2 GFO
Orbit Reaper Reaper GDRD GDRD GDRD Major Instrumental correction
PTR
Sea State Bias 2007
Ionosphere Reaper Rep.
Wet troposphere
GPS-based
GPS-based
GPS-based
GPS-based
GPS-based
GPS-based
Dry troposphere Era Interim based
Combined atmospheric correction
Era Interim based
Ocean tide GOT 4.8 Solid Earth tide
Pole tide MSS DTU10 Merging algorithms New regional biases and monthly OI
Selection meeting outputs
Discussions & recommendations available on the SL CCI web site
New algo/corr applied in SL CCI
No change with respect to reference (AVISO products)
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Atmospheric corrections derived from ECMWF reanalysis (ERA-Interim): ⇒ very strong improvement on early altimetry years (1993-2000) : T/P, ERS1-ERS-2
Climate
Applications
Temporal Scales
For TOPEX, ER1 and ERS-2
Global Mean Sea
Level
Long-term evolution (trend)
Inter annual signals (> 1
year) Annual and semi-annual
Signals
Regional Mean Sea
Level
Long-term evolution (trend)
Annual and semi-annual
Signals
Mesoscale Signals < 2 months
+
+
Evolution of the SSH error reduction thanks to the new DAC corrections
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Climate
Applications
Temporal Scales
For TOPEX, ER1 and ERS-2
Global Mean Sea
Level
Long-term evolution (trend)
Inter annual signals (> 1
year) Annual and semi-annual
Signals
Regional Mean Sea
Level
Long-term evolution (trend)
Annual and semi-annual
Signals
Mesoscale Signals < 2 months
+
+
Impact of the new DAC correction on the regional MSL trends between 1993 and 2005
Atmospheric corrections derived from ECMWF reanalysis (ERA-Interim): : ⇒ very strong improvement on early altimetry years (1993-2000) : T/P, ER1-ERS-2
1) Development and selection of new algorithms
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Input data acquisi-on
Pre Processing Orbit, Instrum & Geophysical corr,
including CCI correc.ons
Mul-mission calibra-on Orbit / Long Wave Lenght Error
including the new CCI methodology
Mapping including including the new CCI methodology
Level 2 product
Indicators computa-on
• 7 missions (re)processed: (T/P, Jason1/2, ERS-1/2, ENVISAT & GFO) • Period: [1993-2010]
• 50 years of data (re)processed
• Based on SSALTO/DUACS infrastucture
2) Sea Level ECV products and assessment
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
2) Sea Level ECV products and assessment
¼° Gridded Monthly mean
Global MSL evolution SLCCI ECV release : V1.1 available via: http://www.esa-sealevel-cci.org/
Please contact us: info-sealevel@esa-sealevel-cci.org
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
2) Sea Level ECV products and assessment
SLCCI ECV release : V1.1 available via: http://www.esa-sealevel-cci.org/
Please contact us: info-sealevel@esa-sealevel-cci.org
¼° Gridded Monthly mean
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
2) Sea Level ECV products and assessment
• External users have also uploaded the SL-CCI products :
⇒ NASA Earth Observatory (USA), U. Colorado (USA), University of Edinburgh (UK), Mercator Océan (France), IMEDEA (Spain), …
• Products are used by the climate modelling group:
⇒ UoH (D.Stammer) : assimilation of sea-level ECV in model (along-track product) ⇒ ECMWF (M. Balmaseda) : assimilation of sea-level ECV in model (along-track product) and also the Global MSL indicator ⇒ NERSC (J. Johannessen) : comparison of sea-level ECV (grids) with model outputs ⇒ LEGOS (A. Cazenave) : use of sea-level ECV (grids + indicator) for closure budget studies
• In phase 2, the objective is to increase the user number
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• The regional Mean Sea Level trends have been significantly improved : ⇒ differences in the range +/- 2 mm/yr at local scales ⇒ these differences are significant since regional Mean Sea Level trends are ranging between +/- 10 mm/yr from 1993 onwards
Improvements of SLCCI project on regional MSL trends
Regional MSL trends from SLCCI project
1993-2010
2) Sea Level ECV products and assessment
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• Interesting results of SL-CCI ECV products via sea level budget studies (LEGOS) at inter-annual scales :
⇒ Differences between other international groups have been analyzed ⇒ Better coherence between the SLCCI GMSL and the mass + steric components
2) Sea Level ECV products and assessment
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
• ECV assessment by climate users:
- Validation of SL-CCI ECV products with models => performed by D. Stammer (University of Hamburg), M. Balmaseda (ECMWF), J. Johannessen (NERSC)
ECV CCI V1.0 – Ref (AVISO) Orca 1 Model - Ref (AVISO)
By M. Balmaseda (ECMWF)
-5 mm/yr + 5 mm/yr -10 mm/yr + 10 mm/yr
2) Sea Level ECV products and assessment
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Spatial Scales Temporal Scales User Requirements
Global Mean Sea Level
(10-day averaging)
Long-term evolution (> 10 years )
0.3 mm/yr
Inter annual signals (< 5 years)
0.5 mm over 1 year
Periodic signals (Annual, 60-days,…)
Regional Mean Sea Level
(2x2 deg boxes and 10-day averaging)
Long-term evolution (trend)
1 mm/yr
Inter annual signals (> 1 year) Periodic signals (Annual, 60-days,…)
• Users requirements have defined separating spatial and temporal scales
3) Definition of user requirements and description of error budget
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Spatial Scales Temporal Scales User Requirements
Global Mean Sea Level
(10-day averaging)
Long-term evolution (> 10 years )
0.3 mm/yr
Inter annual signals (< 5 years)
0.5 mm over 1 year
Periodic signals (Annual, 60-days,…)
Not defined
Regional Mean Sea Level
(2x2 deg boxes and 10-day averaging)
Long-term evolution (trend)
1 mm/yr
Inter annual signals (> 1 year)
Not Defined
Periodic signals (Annual, 60-days,…)
Not Defined
• Users requirements have defined separating spatial and temporal scales
3) Definition of user requirements and description of error budget
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Spatial Scales Temporal Scales User Requirements Altimetry errors
Global Mean Sea Level
(10-day averaging)
Long-term evolution (> 10 years )
0.3 mm/yr < 0.5 mm/yr
Inter annual signals (< 5 years)
0.5 mm over 1 year < 2 mm
over 1 year
Periodic signals (Annual, 60-days,…)
Not defined Annual < 1 mm 60-day < 5 mm
Regional Mean Sea Level
(2x2 deg boxes and 10-day averaging)
Long-term evolution (trend)
1 mm/yr < 3 mm/yr
Inter annual signals (> 1 year)
Not Defined
Periodic signals (Annual, 60-days,…)
Not Defined Annual < 1mm 60-day < 5 mm
• Error characterisation of altimetry measurements at climate scales (Ablain et al, 2012)
3) Definition of user requirements and description of error budget
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
Spatial Scales Temporal Scales User Requirements Altimetry errors
Global Mean Sea Level
(10-day averaging)
Long-term evolution (> 10 years )
0.3 mm/yr < 0.5 mm/yr
Inter annual signals (< 5 years)
0.5 mm over 1 year < 2 mm
over 1 year
Periodic signals (Annual, 60-days,…)
Not defined Annual < 1 mm 60-day < 5 mm
Regional Mean Sea Level
(2x2 deg boxes and 10-day averaging)
Long-term evolution (trend)
1 mm/yr < 3 mm/yr
Inter annual signals (> 1 year)
Not Defined Not evaluated
Periodic signals (Annual, 60-days,…)
Not Defined Annual < 1mm 60-day < 5 mm
• Error characterisation of altimetry measurements at climate scales (Ablain et al, 2012)
3) Definition of user requirements and description of error budget
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
4) Conclusions
• Although ECV sea-level is a mature variable, a lot of improvements were made : ⇒ Improvement of user requirements for Sea Level at climate scales
⇒ homogenization of altimetry databases for all the altimeter missions
⇒ reduction of altimetry errors at climate scales
⇒ development of a formal validation protocol to select the best altimeter corrections ⇒ better characterisation of altimetry errors at climate scales
⇒ assessment of Sea-Level ECV products by climate users
⇒ publication of several peer-review papers
1. Which improvements have been done during phase 1?
CCI Collocation meeting | 4-6 Feb 2014, ESRIN, Frascati, Italy
4) Conclusions
• Although a lot of improvements were made, the user requirements are not reached
⇒ Many external corrections still must be evaluated (altimetry system is complex)
⇒ Continue to improve the algorithms/corrections within the CCI project : e.g. : Arctic area and coastal areas could be improved.
⇒ Refine the user requirements at climate scales
⇒ Continue to better describe the altimetry errors
⇒ Increase the length of time series and provide ECV products more regularly (to reduce the gap with the present date)
⇒ Integrate new altimeter missions (Cryosat-2, Sentinel-3, SARAL/Altika, Jason-3)
⇒ Improve the link with users
2. Why do we have to continue on phase 2 ?
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