GOVST III, Paris Nov 2011 ECMWF ECMWF Report Magdalena Alonso Balmaseda Kristian Mogensen...
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Transcript of GOVST III, Paris Nov 2011 ECMWF ECMWF Report Magdalena Alonso Balmaseda Kristian Mogensen...
GOVST III, Paris Nov 2011 ECMWF
ECMWF Report
Magdalena Alonso BalmasedaKristian Mogensen
• Operational Implementation of NEMO/NEMOVAR
• ORAS4: Ocean ReAnalysis System 4
• Some lessons learnt during preparation
• Evaluation process
• Plans
GOVST III, Paris Nov 2011 ECMWF
Delayed Ocean Re-Analysis ~ORAS4 (NEMOVAR)
Real Time Ocean Analysis
ECMWF:
Forecasting Systems
ECMWF:
Forecasting Systems
Medium-Range (10-day)Partial coupling
Medium-Range (10-day)Partial coupling
Seasonal ForecastsFully coupled
Seasonal ForecastsFully coupled
Extended + Monthly Fully coupled
Extended + Monthly Fully coupled
Ocean model
Atmospheric model
Wave model
Atmospheric model
Ocean model
Wave model
Oce
an Init
ial
Condit
ions
GOVST III, Paris Nov 2011 ECMWF
• ECMWF has a implemented new operational ocean re-analysis system.
http://www.ecmwf.int/products/forecasts/d/charts/oras4/reanalysis/
• It implies the transition to NEMO/NEMOVAR from HOPE/OI
• It consists of 5 ensemble members, covering the period 1958-Present, continuously updated.
• It is used for the initialization of the operational monthly and seasonal forecasts.
• It is also used to initialize the CMIP5 decadal forecasts (EC-Earth …)
• It is a valuable resource for climate variability studies.
• Documentation in preparation: Mogensen et al 2011, Balmaseda et al 2011
ECMWF: Operational Ocean Changes in 2011. ORAS4
GOVST III, Paris Nov 2011 ECMWF
Ocean Model: NEMO V3.0 ORCA1 and 42 levels (ocean)
Data Assimilation: NEMOVAR (3D-var FGAT).
Data: Temperature and Salinity Profiles (EN3-XBT corrected and GTS), SST (HADISST/ OIv21x1 /OSTIA), along track Altimeter Sea Level (AVISO). See figure below
Forcing: ERA40/ERA-INTERIM/ECMWF NWP (see figure below)
Bias Correction: In T/S and P gradient. Seasonal prescribed (from Argo+Alti) + Adaptive on line
Ensemble Generation: wind perturbations, observation coverage, spin-up. 5 ensemble members
ORAS4 Main Ingredients
GOVST III, Paris Nov 2011 ECMWF
What have we learned in the preparation process?
• Which SST product to use?• Which products are available? Criteria for evaluation
• Assimilation of altimeter: variational implementation of Cooper and Haines in 3Dvar. Non trivial. Sorted.
• Coastal Covariances: Impact of Assimilation in the Atlantic MOC.
• Bias correction scheme: estimation of the offline term from Argo period. (Not a problem, a success; It affects the results)
• How to evaluate ocean reanalyses?
GOVST III, Paris Nov 2011 ECMWF
Which SST product to use?
Options for Re-analysisOIV2_1x1: (weekly)~1982 onwardsOIV2_025_AVHRR(daily)~1982 onwardsOIV2_O25_AVHR+AMSR:~2002 onwardsOptions for Real-Time: As before +OSTIA (from 2008 onwards): Consistency with atmospheric analysis
OIV2_025_AVHRR: bias cold in the global mean (regional differences)
Bias decreases with time. OSTIA in beween (not shown)
Weaker interannual variability
Fit to insitu Temperature: bias cold in tropics, better in mid latitudes,.
Not clear impact on Seasonal Forecasts
DECISION: OIV2_1x1 until 2010, OSTIA thereafter.
GOVST III, Paris Nov 2011 ECMWF
Multivariate balance for AltimeterIN NEMOVAR the balance is between sea level and steric height
(1) )( :form lincrementain or ,00
zrefzref
dzzdz
Original formulation of NEMOVAR
αref and βref are calculated by linearizing the equation of estate using the background T/S values as reference. Comments:
i) zref=1500m is arbitrary. An attempt to take into account that baroclinicity is low below this level. Can we account for the vertical stratification more universally?
ii) this can lead to increments in model levels with large dz
SandT
STmz
refref
refref
refref
ref
(2) 1500
GOVST III, Paris Nov 2011 ECMWF
anom GLOBAL
1994 1996 1998 2000 2002 2004 2006 2008Time
0.00
0.02
0.04
0.06
0.08
0.10
0.12
AVISOCONTROLAssim: TSAltimeter+MDTcontrol
But Impact on Steric Height not realistic:
This problem not so apparent if assimilating T/S and
altimeter, but it is still there. Why?
SO10 _T3_P50_L320_Z0_V1:bckintSO10 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 1.3e-12, Max= 1.7e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO14 _T3_P50_L320_Z0_V1:bckintSO14 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 1.3e-10, Max= 1.5e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO8 _T3_P50_L320_Z0_V1:bckintSO8 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.6e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO30 _T3_P50_L320_Z0_V1:bckintSO30 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.8e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO25 _T3_P50_L320_Z0_V1:bckintSO25 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.8e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
Single Obs Experiments: T increment
The temperature increment is applied to the thickest model
levels
GOVST III, Paris Nov 2011 ECMWF
Modifications
A):Weighting based on stratification. Use BV frequency to calculate αN and βN instead of equation of state
B) Do not double-count balance-salinity corrections
2 2 2 2;
z zN N z N T N S
z T S
2
2
ref ref ref ref
ref ref
T S S TN
z z T z
z S T zN T T
T T z T
GOVST III, Paris Nov 2011 ECMWF
anom GLOBAL
1994 1996 1998 2000 2002 2004 2006 2008Time
0.00
0.02
0.04
0.06
0.08
0.10
0.12
AVISOCONTROLAssim: TSAltimeter+MDTcontrol
New Balance formulation:
anom GLOBAL
1994 1996 1998 2000 2002 2004 2006 2008Time
0.00
0.01
0.02
0.03
0.04
AVISOCONTROLAssim:TSAlti+MDTcontrol(Modified)Sea Level Altimeter (AVISO)
CONTROLASSIM: TS
CONTROL+ALTIASSIM: TS + ALTI
Problem with Steric Height Solved
Problem with deep T increments Solved
SO10 _T3_P50_L320_Z0_V1:bckintSO10 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 1.3e-12, Max= 1.7e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO14 _T3_P50_L320_Z0_V1:bckintSO14 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 1.3e-10, Max= 1.5e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO8 _T3_P50_L320_Z0_V1:bckintSO8 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.6e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO30 _T3_P50_L320_Z0_V1:bckintSO30 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.8e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
SO25 _T3_P50_L320_Z0_V1:bckintSO25 _T3_P50_L320_Z0_V1:bckint
latitudes in [49.0, 51.0] - (4 points) (): Min= 0.0e+00, Max= 1.8e-02, Int= 1.0e-03
80W 60W 40W 20W 0ELongitude
50004000300020001000300250200150100500
Depth
(m
)
0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02
Old New
anom GLOBAL
1994 1996 1998 2000 2002 2004 2006 2008Time
0.00
0.01
0.02
0.03
0.04
AVISOCONTROLAssim:TSAlti+MDTcontrol(Modified)TS+Alti
GOVST III, Paris Nov 2011 ECMWF
rms EQ2 Potential Temperature
0.0 0.5 1.0 1.5 2.0 2.5rms EQ2 Potential Temperature
-500
-400
-300
-200
-100
0
Depth
(m
)
rms EQIND Potential Temperature
0.0 0.5 1.0 1.5 2.0rms EQIND Potential Temperature
-500
-400
-300
-200
-100
0
Depth
(m
)
rms TRPAC Potential Temperature
0.4 0.6 0.8 1.0 1.2 1.4rms TRPAC Potential Temperature
-500
-400
-300
-200
-100
0
Depth
(m
)
rms GLOBAL Potential Temperature
0.6 0.8 1.0 1.2 1.4 1.6rms GLOBAL Potential Temperature
-500
-400
-300
-200
-100
0
Depth
(m
)
CONTROL ASSIM: T+S ASSIM: T+S+Alti
EQ Central Pacific EQ Indian Ocean
TROPICAL Pacific GLOBAL
Altimeter Improves the fit to InSitu Temperature Data
RMSE of 10 days forecast
GOVST III, Paris Nov 2011 ECMWF
Assessment of the ORA-S4 re-analysis
Choose a baseline: the CONTROL (e.i., no data assim)
1. Assim Intrinsic Metrics
• Fit to obs (first-guess minus obs): Bias, RMS
• Error growth (An-obs versus FG-obs)
• Consistency: Prescribed/Diagnosed B and R
This is insufficient to assess a Reanalysis product
2. Spatial/temporal consistency: long time series and spatial maps
• Time correlation with Mooring currents
• Correlation with altimeter/Oscar currents
• Transports (MOC and RAPID): short time series
Quite limited records. Not always independent data
3. Skill of Seasonal Forecasts
Expensive. Model error can be a problem.
4. Observing System Experiments
GOVST III, Paris Nov 2011 ECMWF
Assimilation Statistics: Incremental Analysis Update
GLOBAL RMSE Temperature
0.4 0.6 0.8 1.0 1.2-1000
-800
-600
-400
-200
0
Dep
th (m
)
RMSE ANRMSE FGRMSE MIN
GOVST III, Paris Nov 2011 ECMWF
Fit To Obs
• Bias thin lines
• RMSE thick lines
• Assimilation improves over the
control everywhere. A large part
of the improvements comes
from the reduction of bias.
• Note large errors in Extratropics
come from WBC and coastal
areas, where obs are given little
weight
EQUA Potential Temperature
-0.5 0.0 0.5 1.0 1.5 2.0 2.5-1000
-800
-600
-400
-200
0
Depth
(m
)
TROP Potential Temperature
-0.5 0.0 0.5 1.0 1.5 2.0-1000
-800
-600
-400
-200
0
Depth
(m
)
NXTRP Potential Temperature
-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0-1000
-800
-600
-400
-200
0
Depth
(m
)
SXTRP Potential Temperature
-0.5 0.0 0.5 1.0 1.5 2.0-1000
-800
-600
-400
-200
0
Depth
(m
)
GLOBAL Potential Temperature
-0.5 0.0 0.5 1.0 1.5 2.0 2.5-1000
-800
-600
-400
-200
0
Depth
(m
)
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
Bias ANBias FGBias CNTLRMSE ANRMSE FGRMSE CNTL
GOVST III, Paris Nov 2011 ECMWF
TROP Potential Temperature Depth= 200.0 meters
1960 1970 1980 1990 2000 2010Time
0.0
0.5
1.0
1.5
2.0Bias ORAS4
Bias CNTLRMSE ORAS4
RMSE CNTL
TROP Salinity Depth= 200.0 meters
1960 1970 1980 1990 2000 2010Time
0.00
0.05
0.10
0.15
0.20
0.25
0.30Bias ORAS4
Bias CNTLRMSE ORAS4
RMSE CNTL
Fit to Obs
ORAS4 shows reduced RMSE and bias respect the CNTL, in both T and S
The bias is ORAS4 is more stable in time
Fit improves with time, both ORAS4 and CNTL :Not only more subsurface obs, but better surface forcing and SST data?.
GOVST III, Paris Nov 2011 ECMWF
Fit to ADCP mooring data
• Some improvement of the Pacific and Atlantic undercurrents, which are still on the weak side.
T0N165E
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
T0N170W
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
T0N140W
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
P0N23W
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
R0N90E
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
R0N90E
-0.5 0.0 0.5 1.0Zonal current (m/s)
-300
-200
-100
0
Dep
th (m
)
ADCP
ORAS4CNTL
GOVST III, Paris Nov 2011 ECMWF
NEMOVAR re-an: verif. against altimeter data
correl (1): fe5x sossheig ( 1993-2008 ) correl (1): fe5x sossheig ( 1993-2008 )
(ndim): Min= -0.37, Max= 1.00, Int= 0.02
100E 160W 60WLongitude
60S
40S
20S
0
20N
40N
60N
Latitud
e
0.40 0.44 0.48 0.52 0.56 0.60 0.64 0.68 0.72 0.76 0.80 0.84 0.88 0.92 0.96 1.00
RMSE (1): fe5x sossheig (1993-2008) RMSE (1): fe5x sossheig (1993-2008)
(m): Min= 0.01, Max= 0.15, Int= 0.01
100E 160W 60WLongitude
60S
40S
20S
0
20N
40N
60N
Latitud
e
0.02 0.04 0.06 0.08 0.10
rms/signal(1): fe5x sossheig (1993-2008) rms/signal(1): fe5x sossheig (1993-2008)
(N/A): Min= 0.10, Max= 3.18, Int= 0.20
100E 160W 60WLongitude
60S
40S
20S
0
20N
40N
60N
Latitud
e
0.00 0.40 0.80 1.20 1.60 2.00
sdv_fe5x/sdv_aviso (1): sossheig (1993-2008) sdv_fe5x/sdv_aviso (1): sossheig (1993-2008)
(N/A): Min= 0.22, Max= 2.74, Int= 0.20
100E 160W 60WLongitude
60S
40S
20S
0
20N
40N
60N
Latitud
e
0.00 0.40 0.80 1.20 1.60 2.00
fa9p_oref_19932008_1_sossheig_stats.ps) Aug 4 2010
NEMOVAR T+S
ORA-S4: NEMOVAR T+S+Alti
CNTL NEMO NoObs
GOVST III, Paris Nov 2011 ECMWF
Comparison with RAPID derived transports
MOC
2002 2004 2006 2008 2010 20120
10
20
30Ekman
2002 2004 2006 2008 2010 2012-10
-5
0
5
10
MOC-Ekman
2002 2004 2006 2008 2010 20120
10
20
30ORAS4RAPID
Atlantic MOC at 26N
Short time seriesORAS4 underestimates the MOCNote the large minima in 2010 and 2011!!
GOVST III, Paris Nov 2011 ECMWF
More MOC diagnostics
MOC
1960 1970 1980 1990 2000 2010 20200
10
20
30MidOcean
1960 1970 1980 1990 2000 2010 2020-40
-30
-20
-10
0
Ekman
1960 1970 1980 1990 2000 2010 2020-10
-5
0
5
10
RAPIDCNTLORAS4
FST
1960 1970 1980 1990 2000 2010 202010
20
30
40
RAPIDORAS4CNTL
• In low res model the Florida Strait transport is not so well defined.
• Assimilation reduction of the FST is proportional to the weight is given to the obs (not shown)
• Ocean model tends to produce too strong and shallow AABW cell
MOC profile
GOVST III, Paris Nov 2011 ECMWF
Impact on Of ORAS4 in SST Seasonal ForecastsAnomaly correlation: ORAS4 CNTL Persistence
GOVST III, Paris Nov 2011 ECMWF
ERA+
ASMER
A ASM
-6
-4
-2
0
2
4
6
GLOBAL HEAT BUDGET
1960 1970 1980 1990 2000Time
-10
-5
0
5
10 ERA+ASM 0.23 W/m2ERA 4.99 W/m2ASM -4.76 W/m2
El ChichonPinatubo
Global Surface Heat Fluxes from Reanalysis
GOVST III, Paris Nov 2011 ECMWF
Meridional Heat Transport ATL 195801:200912Meridional Heat Transport ATL 195801:200912
20S 0 20N 40N 60N0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Meridional Heat Transport ATL 195801:200912
ORA-S4GW2000
Meridional Heat Transport INP0 195801:200912Meridional Heat Transport INP0 195801:200912
20S 0 20N 40N 60N-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5Meridional Heat Transport INP0 195801:200912
ORA-S4GW2000
Meridional Heat Transport GLO 195801:200912Meridional Heat Transport GLO 195801:200912
20S 0 20N 40N 60N-2
-1
0
1
2
3Meridional Heat Transport GLO 195801:200912
ORA-S4GW2000
drag) Oct 18 2011
Mean and time variability of ORAS4 oceanic heat transport.
(GW2000: Ganachaud and Wunsch 2000)
ORAS4 HEAT contributions (1.e22 J)
1970 1980 1990 2000Time
-5
0
5
10
15
Ocean Heat content 0.00Total=Surface+Relax+Assim+BiasC+Geothermal 5050.99ERA+ASSIM heat flux integral
ORAS4 total (whole depth) heat content
The time integral of the ERA+ASM surface heat flux
results in the evolution of the total ocean heat content
Climate Applications
GOVST III, Paris Nov 2011 ECMWF
Summary
• Operational implementation of NEMO/NEMOVAR in forecasting systems and ocean reanalysis • Transition from HOPE/OI• ORAS4: new Ocean Reanalysis with NEMOVAR• Still climate resolution: approx 1x1 degree.
• Some lessons learns in the preparation process• Choice of SST product for reanalysis not trivial. Next is to try OSTIA reanalysis• Balance relationship between altimeter and T/S not solved problem. Not trivial. Still room for
improvement• Improved covariance needed for the assimilation of observations near the coast.
• How to evaluate an ocean assimilation system and ocean reanalyses product?
• Evaluation of the ocean reanalysis is a pre-requisite for the interpretation of climate signals• Standard assimilation statistics needed but not sufficient for the reanalyses• Need information about time variability: sustained time series are very important:
(altimeter, moorings, RAPID, other?)• Impact on seasonal forecast is a test and a result.
• What is next?• Document system, web pages, papers• Higher resolution ocean model and reanalysis(ORCA 025)• Sea-Ice model in monthly, seasonal forecast and reanalyses• Improved coupling (bulk formula, wave effects, ocean mixed layer)• Increased coupling (forecast and analysis)