#newfcsystem
#newfcsystem
Description of upgrade
The fifth generation of the ECMWF seasonal forecasting system, in short SEAS5, will be introduced in the autumn of 2017, replacing System 4, which was released in 2011. SEAS5 includes updated versions of the atmospheric (IFS) and interactive ocean (NEMO) models and adds the interactive sea ice model LIM2. The IFS uses a new grid and horizontal resolution has been increased (details below). Ocean horizontal and vertical resolution have also been increased. Ocean and land initial conditions have been updated, and the re-forecast ensemble size has been increased from 15 to 25. While re-forecasts span 1981 to 2016, the re-forecast period used to calibrate the forecasts when creating products will use the more recent period 1993 to 2016. SEAS5 highlights include a marked improvement in SST drift, especially in the tropical Pacific, and improvements in the prediction skill of Arctic sea ice.
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The page will be updated as required. It was last changed on 0304.10.2017
For a record of changes made to this page please refer to Document versions.
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Timetable for implementation
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The planned timetable for the implementation of SEAS5 is as follows:
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We acknowledge the contribution of the Copernicus Climate Change Service (C3S) in the production of SEAS5. C3S provided the computer time for the generation of the re-forecasts for SEAS5 and for the production of the ocean reanalysis (ORAS5), used as initial conditions for the SEAS5 re-forecasts. SEAS5 will be the ECMWF contribution to the C3S multi-model seasonal forecast products, see paragraph 'SEAS5 and Copernicus services'.
Current Status
Latest news
4/10/2017: The re-archiving of the problematic SEAS6 pressure level derived fields has completed last night and we have validated the data this morning.
3/10/2017: We have identified a problem with some archived pressure level fields for some derived fields associated with the real-time forecasts. The fields affected are type=hcmean from stream msmm, and types fcmean and em from stream mmsa. Pressure level fields from 925 hPa up to 1 hPa are affected, for dates from January to September 2017. Surface fields and 1000hPa pressure level fields are not affected.
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Note that the main monthly mean fields (stream=msmm, type=fcmean) are *not* affected. We will begin re-archiving the affected pressure level fields in MARS at 14:30UTC on the 3rd October, to correct the problem, and will confirm on this page when the re-archiving is complete. Please accept our apologies for any inconvenience caused.
Current Status
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SEAS5 has now entered release candidate testing. The re-forecast data are fully available in MARS and Forecast data are also available in MARS and through dissemination. Graphical products will shortly be made available on our website
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New release day for SEAS5 data
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We are pleased to announce that the SEAS5 products (data and charts) will be released 3 days earlier, on the 5th of each month at 12UTC. System 4 products are currently released on the 8th of each month.
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Summary description of SEAS5
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With a few exceptions, SEAS5 is configured to be identical to the extended part of the ENS, as implemented with IFS Cycle 43r1. In particular, the same resolution is used for both the monthly and seasonal forecast ranges. However, while the ENS will be regularly upgraded over the next few years with each new cycle of the IFS, the SEAS5 will remain fixed at IFS Cycle 43r1. Previous seasonal forecast systems have had a lifetime of about 5 years, and although future upgrades of SEAS may happen more often there is not yet a planned date for the introduction of SEAS6.
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The table below summarizes the upgrades in model components and initialization for SEAS5.
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Meteorological content of SEAS5
Atmosphere model
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The IFS has been upgraded from cycle 36r4 to 43r1. In this time many changes have been made to model physics (surface drag, boundary layer entrainment, shallow convection, vertical diffusion, orographic drag, surface climate fields, CO2/CH4 climatologies, convective detrainment, cloud scheme physical processes, introduction of a lake model, radiation-surface interactions, solar zenith angle calculations, freezing rain physics, cloud erosion, CAMS O3 climatology, boundary layer cloud) and to model numerics (revised semi-Lagrangian extrapolation, revised interpolation of moist variables, cubic truncation and octahedral grid, semi-lagrangian departure point iterations, spectral viscosity). Further details can be found in the documentation of the evolution of the IFS.
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Ocean model: higher resolution and wave interaction
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As for System 4, SEAS5 uses the NEMO (Nucleus for European Modelling of the Ocean) ocean model (Madec 2008), but with upgrades in the model version, ocean physics and resolution. The resolution has been increased from 1 degree and 42 layers in SEAS4 to 0.25 degrees and 75 layers in SEAS5. The vertical resolution is particularly refined in the uppermost part of the ocean, with an increase in the number of levels in the first 50 metres from 5 to 18. The increase in horizontal resolution improves the representation of sharp fronts and ocean transports. The vertical resolution increase means that the diurnal cycle of sea-surface temperatures (SST) is much better captured, with a 1-metre top level in the new configuration compared to the previous 10-metre top level.
The ocean model configuration is based on that developed by the DRAKKAR for the NEMO version V3.4 (SEAS4 used V3.2), and contains upgrades introduced at ECMWF regarding aspects of ocean-surface wave interaction (Breivik et al. 2015). These aspects include a momentum flux estimated from the dissipation term (accounting for the intensity of breaking waves) ; the surface boundary condition of the turbulent kinetic energy equation, which now account for the energy flux from breaking waves (Craig and Banner 1994); and the Coriolis-Stokes forcing term is introduced in the momentum equation
Prognostic Sea Ice model
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The interactive sea-ice model LIM2, the Louvain-la-Neuve Sea Ice Model developed at the Belgian Université Catholique de Louvain, has been implemented in SEAS5. LIM2 is part of the NEMO modelling framework also used at ECMWF to model the ocean. This is the first time that the ECMWF seasonal system includes a prognostic sea-ice model. In SEAS4, the sea-ice was prescribed by sampling the recent history of sea-ice occurrences. The prognostic sea-ice model allows sea-ice cover to respond to changes in the atmosphere and ocean states, and intends to capture inter-annual variability and trends in the sea-ice over. Therefore SEAS5 should be able to provide seasonal outlooks of sea-ice cover, which is a product of interest for users.
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Ocean Initial conditions: ensemble of ocean reanalyses
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SEAS5 ocean and sea-ice initial conditions are provided by the new ocean analysis and reanalysis ensemble (ORAS5). ORAS5 uses the same ocean model and sea-ice as the couple forecasts in SEAS5, and consists on 5 ensemble members covering the period 1975 to the present. Compared to its predecessor ORAS4 (Balmaseda et al 2013), used to initialized SEAS4, ORAS5 has higher resolution, updated data assimilation and observational data sets, and most importantly, provides sea-ice initial conditions by assimilating sea-ice concentration.
ORAS5 has been developed based on Ocean Reanalysis Pilot 5 (ORAP5) (Zuo et al. 2015; Tietsche et al. 2015), using updated observational data sets. The ocean in-situ temperature and salinity comes from the recent quality-controlled EN4 (Good et al. 2013), which has higher vertical resolution and fuller spatial coverage than the previous version EN3 - used in ORAP5 and ORAS4. The altimeter sea-level data have also been updated to the latest version (DUACS2014) from CMEMS (Copernicus Marine Environmental Monitoring Services). The underlying SST analysis before 2008 has also been changed in ORAS5: it comes from the HadISST2 dataset, the same used in the currently ERA5 reanalysis. From 2008 onwards the SST and sea-ice are given by the OSTIA product, which is also used in the ECMWF NWP operational analysis.
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The perturbation scheme used to generate the ensemble of reanalyses has also been modified. The scheme consists of two distinct elements: perturbations to the assimilated observations, both profiles and surface, and perturbations to the surface forcing fields. For details see Zuo et al 2017, Technical Memorandum 795).
Meteorological impact of SEAS5
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Pre-implementation testing showed that the model version planned for SEAS5 gives substantial improvements in SST bias in the tropical Pacific, with consequent improvements in ENSO forecast skill. A more comprehensive assessment of the meteorological impact based on analysis of the full set of SEAS5 re-forecasts is being made and will be given shortly. Assessments of mid-latitude forecast skill are subject to considerable sampling error, and the limited sample sizes available from pre-implementation testing are not considered reliable predictors of the eventual outcome of the SEAS5 re-forecast dataset.
The graphical products for SEAS5 show anomalies with respect to a 1993-2016 base period, whereas System 4 used a 1981-2010 base period. Due to global warming, the use of a more recent base period results in significant changes to the plotted anomalies, particularly for temperature and geopotential height. Thus although the actual (calibrated) temperature forecast may be very similar, the plotted anomaly can look quite different. Users are encouraged to calibrate the forecasts according to their own needs by using the re-forecast data available in MARS. Re-forecasts cover 1981-2016 to maximize the data available for skill estimation and calibration.
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Changes to GRIB encoding
Model identifiers
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The GRIB model identifiers (generating process identification number) for SEAS5 will be changed as follows:
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| GRIB 1 Section 1 Octets | GRIB 2 (only for SEAS5) Octets | grib_api/ecCodes key name | Component | Model ID | |
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| System 4 | SEAS5 | ||||
| 6 | 14 (in Section 4) | generatingProcessIdentifier | Atmospheric model | 139 | 147 |
| Ocean wave model | 107 | 112
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| 52-53 | 18-19 (in Section 2) | systemNumber | 4 | 5 | |
GRIB 2 data
SEAS5 model level data is coded in GRIB 2, compared to GRIB 1 for System 4. The change to GRIB 2 for model level data was introduced in IFS Cycle 37r2 in 2011. See under User impact below for more information.
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Use of the octahedral reduced Gaussian grid
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SEAS5 introduces a new form of the reduced Gaussian grid, the octahedral grid, for the atmospheric (mostly) single level data. See Introducing the octahedral reduced Gaussian grid for further details.
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Surface parameters added
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Several new parameters have been added related to the lake model, 6h instantaneous stresses have been added to help user applications such as wave modelling, and top incoming solar radiation has been added with a 24 hour output frequency. Note also that surface and sub-surface runoff are now fully available (in System 4, these parameters were available for the real-time forecasts, but only a limited number of the re-forecasts).
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| paramId | name | frequency |
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| 26 | Lake cover | Step 0 only |
| 228007 | Lake depth | Step 0 only |
| 228008 | Lake mixed layer temperature | 24 hour |
| 228014 | Lake ice depth | 24 hour |
| 229 | Instantaneous eastward turbulent surface stress | 6h |
| 230 | Instantaneous northward turbulent surface stress | 6h |
| 212 | Top incoming solar radiation | 24h |
| 8 | Surface runoff | 24h |
| 9 | Sub-surface runoff | 24h |
Surface fields output at additional timesteps
Some surface fields previously archived every 24 hours are now archived every 6 hours. As well as increased availability of synoptic data, this also changes the monthly means for the instantaneous fields such as SST and soil temperature. These are now calculated from 6 hourly data, and no longer have the diurnal cycle aliased into them. (For accumulated fields, the monthly mean rate of accumulation is independent of whether synoptic data is written at 6 or 24h intervals).
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| paramId | name | frequency |
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| 34 | Sea surface temperature | 6 hr |
| 144 | Snowfall | 6 hr |
| 139 | Soil temperature level 1 | 6 hr |
| 169 | Surface solar radiation downwards | 6 hr |
| 175 | Surface thermal radiation downwards | 6 hr |
| 228 | Total precipitation | 6 hr |
Model level data
SEAS5 model level data are now produced to 6 months instead of 5 months for System 4.
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Ocean waves parameters added
All fields are output every 24 hours
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Impact of SEAS5 on users
Software
EMOSLIB version 443, GRIB API version 1.17.0 or ecCodes version 2.0.0 are the minimum versions recommended to manipulate all SEAS5 fields.
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| Note |
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ecCodes has now replaced GRIB API on the ECMWF platforms. GRIBEX is no longer available and cannot decode GRB 2 data. |
Increased field sizes
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The size of the fields archived have increased by a factor 2 to 4. When retrieving data via MARS or dissemination, if no spectral truncation or grid resolutions are specified, fields are provided at the model resolution.
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In particular, users should be aware of the increase in memory and CPU time needed to process the increased resolution fields and adjust their programs and batch scripts appropriately.
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Re-forecast data in MARS
The SEAS5 re-forecast data can be accessed in MARS from:
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Only registered users with access to MARS will be able to access the re-forecast data sets.
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The re-forecast data for all 12 months in the year have been released.
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Test SEAS5 Forecast data in MARS
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SEAS5 technical test data are available in MARS with experiment version 9001 (MARS keyword EXPVER=9001) for the runs of May, June and July 2017 at 00UTC. The data can be accessed in MARS from:
- Atmospheric forecasts (class=od, stream=mmsf, expver=9001, system=5, method=1)
- Wave forecasts (class=od, stream=wasf, expver=9001, system=5, method=1)
- Atmospheric monthly means (class=od, stream=msmm, expver=9001)
- Wave monthly means (class=od, stream=swmm, expver=9001)
Seasonal forecast monthly anomalies (class=od, stream=mmsa, expver=9001)
The SEAS5 Forecast beta release data are intended for testing technical aspects and should not be used for operational forecasting. Please report any problems you find with these data to User Support.
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Release candidate SEAS5 data have been archived in MARS from January 2017 onwards with experiment version 0001:
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- Atmospheric forecasts (class=od, stream=mmsf, expver=001, system=5, method=1)
- Wave forecasts (class=od, stream=wasf, expver=001, system=5, method=1)
- Atmospheric monthly means (class=od, stream=msmm, expver=001)
- Wave monthly means (class=od, stream=swmm, expver=001)
Seasonal forecast monthly anomalies (class=od, stream=mmsa, expver=001)
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Test real-time SEAS5 data in dissemination
SEAS5 test data are now available in dissemination for the run of August 2017 onwards. SEAS5 test dissemination files are queued into ECPDS in delayed (standby) mode. Users can trigger the transmission of wanted test products at their convenience by logging into the test ECPDS system at https://ecpds-xmonitor.ecmwf.int/ in the usual manner. Users can find the SEAS5 by selecting all the datesin the interface. In order to receive the test products, users will have to open their firewall to the relevant ECPDS Data Movers:
Internet transfers: 193.61.196.104 (ecpds-xma.ecmwf.int) 193.61.196.105 (ecpds-xmb.ecmwf.int)
RMDCN transfers: 136.156.8.132 (mspds-dm4.ecmwf.int)
SEAS5 test dissemination file names will have EXPVER '9001' as the last part of the file name, e.g. ALL0801000010______9001, to distinguish with the operational file names ending with '1', e.g. ALL0801000010______1. Note however that the GRIB messages in the SEAS5 test dissemination data will contain the key expver=0001. GRIB headers fully reflect the generating process (systemNumber=5, methodNumber=1).
At the moment, SEAS5 test data are generated based on the current (SYSTEM=4) dissemination requirements. Users wishing to test new SEAS5 products or to request fields at a higher resolution can change their requirements at https://ecaccess.ecmwf.int:7443/do/product/requirements. Note that the SEAS5 requirements now include the directive 'SYSTEM=5'. Any changes made will be effective with the next run of SEAS5.
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SEAS5 T319/O320 products can be requested in their original representation as well as in the previously supported representations in System 4. Supported latitude/longitude resolutions in the System 5 are:
multiplies of 0.4/0.4 degrees (as the third leg of the monthly forecast)
multiplies of 0.75/0.75 degrees, to provide seamless transition from the Seasonal System 4 (current resolution)
Where possible, we would advise users to request the native (Octahedral) resolutions.
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Parallel run of System 4 and SEAS5
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SEAS5 has run for May, June, July 2017 in beta testing (experiment=9001). SEAS5 will run in near real-time from September onwards. SEAS5 data will then become available shortly after the System 4 data have been released.
On the switch-over date, presently expected to be for the November run, SEAS5 will become the operational system. The SEAS5 dissemination file names will then end with EXPVER '1'. System 4 will continue to be run as a near real-time system, for a limited period of time. Data from System 4 will be available from MARS and, for those interested, through dissemination on request. Those interested should contact Data Services at ECMWF. On the implementation date of SEAS5, users who requested to keep getting System 4 data though dissemination will receive both the SEAS5 and System 4 files via ECPDS, with the System4 file names including EXPVER '9004', e.g. ALL1101000010______9004.
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| Note |
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| The release date of these '9004' files in ECPDS will remain the 8th of each month at 12UTC. |
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We intend to stop running System 4 before March 2018. Users are advised to make sure that all their applications are switched to using SEAS5 data as soon as possible after the implementation.
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Graphical display of SEAS5 test forecasts
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Graphical products from the seasonal forecast system are displayed on the Forecast Charts pages of the ECMWF website. We will make the SEAS5 graphical products available on the ECMWF website as soon as possible.
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Time-critical applications
Member State users of the "Simple time-critical jobs" framework can test that their scripts will work with the SEAS5 test data by using the new 'event' set up.
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| Event ID | Event name | Description |
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| 1763 | seasonal5_fc | At this stage, the system 5 Seasonal Forecast real time products have been updated. |
Users are reminded to change the directive 'SYSTEM=5' in their MARS requests.
SEAS5 in EUROSIP
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EUROSIP, the Multi-model seasonal forecast, will use SEAS5 data as soon as SEAS5 will have been implemented in operations.
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SEAS5 and Copernicus services
The C3S is currently in a proof-of-concept phase and the data services for the Copernicus users are being developed. At the moment, for seasonal forecasts, graphical products only are available on the C3S web site (https://climate.copernicus.eu/seasonal-forecasts). In early 2018, it is expected that SEAS5 data on a 1-degree resolution grid will be freely available for download from C3S on the 10th of each month, 5 days after the SEAS5 products are available through the normal ECMWF dissemination mechanisms.
References
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- Madec G (2008) NEMO ocean engine. Tech. rep., Institut Pierre-Simon Laplace (IPSL), URL https://www.nemo-ocean.eu/doc/
Good, S. A., M. J. M., and R. N. A., 2013: EN4: Quality controlled ocean temperature and salinity profiles and monthly objective analyses with uncertainty estimates. J. Phys. Oceanogr.,118, 6704–6716, doi:10.1002/2013JC009067.
Fichefet T,Maqueda MAM (1997) Sensitivity of a global sea ice model to the treatment of ice thermodynamics and dynamics. Journal of Geophysical Research 102(C6):12,609–12,646, DOI 10.1029/97JC00480,URL http://doi.wiley.com/10.1029/97JC00480
Balmaseda MA, Mogensen K, Weaver AT (2013) Evaluation of the ECMWF ocean reanalysis system ORAS4. Quarterly Journal of the Royal Meteorological Society 139(674):1132{1161
Steffen Tietsche, Magdalena a. Balmaseda, Hao Zuo, and Kristian Mogensen. Arctic sea ice in the global eddy-permitting ocean reanalysis ORAP5. Climate Dynamics, jun 2015. ISSN 0930-7575. doi: 10.1007/s00382-015-2673-3. URL http://link.springer.com/10.1007/s00382-015-2673-3.
Hao Zuo, Magdalena A Balmaseda, and Kristian Mogensen. The new eddy-permitting ORAP5 ocean reanalysis: description, evaluation and uncertainties in climate signals. Climate Dynamics, 2015. doi: 10.1007/s00382-015-2675-1. URL http://link.springer.com/article/10.1007/s00382-015-2675-1.
Zuo, H., M.A. Balmaseda, E. Boisseson and S. Hirahara, 2017: A new ensemble generation method for ocean reanalyses. ECMWF Technical Memorandum 795.
Zuo et al 2018 (in preparation)
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| Date | Reason for update |
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| 05.07.2017 |
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| 31.08.2017 |
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| 08.09.2017 |
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| 03.10.2017 |
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| 04.10.2017 |
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