#newfcsystem
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This page is used only to draft changes for review prior to publishing in the Forecast User space and is accessible by ECMWF staff only. The publicly accessible page can be viewed in the Forecast User space. |
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 planned timetable for the implementation of SEAS5 is as follows:
| Date | Event |
|---|---|
| 05 July 2017 | Initial announcement. Data available in MARS |
| mid September 2017 | Availability of test data in dissemination |
| early November 2017 | Expected date of implementation |
The timetable represents current expectations and may change in light of actual progress made.
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The table below summarizes the upgrades in model components and initialization for SEAS5.
| System 4 | SEAS5 | |
|---|---|---|
| IFS Cycle | 36r4 | 43r1 |
| IFS horizontal resolution | TL255 | TCO319 |
| IFS Gaussian grid | N128 (80 km) | O320 (35 km) |
| IFS vertical resolution (TOA) | L91 (0.01 hPa) | L91 (0.01 hPa) |
| IFS model stochastic physics | 3-lev SPPT and SPBS | 3-lev SPPT and SPBS |
| Ocean model | NEMO v3.0 | NEMO v3.4 |
| Ocean horizontal resolution | ORCA 1.0 | ORCA 0.25 |
| Ocean vertical resolution | L42 | L75 |
| Sea ice model | Sampled climatology | LIM2 |
| Atmosphere initialization (Re-forecast/Forecast) | ERA-Interim/Operations | ERA-Interim/Operations |
Land Initialization | ERA-Interim land (32r3)/Operations | ERA-Interim land (43r1)/Operations |
| Ocean initialization | ORA-S4 | ORS-S5 |
| Forecast ensemble size | 51 (0-7m) 15 (8-13m) | 51 (0-7m) 15 (8-13m) |
| Re-forecast years | 30 (1981-2010) | 36 (1981-2016) |
| Re-forecast ensemble size | 15 (0-7m) 15 (8-13m) | 25 (0-7m) 15 (8-13m) |
| Calibration period | 1981-2010 | 1993-2016 |
Meteorological content of SEAS5
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The GRIB model identifiers (generating process identification number) for SEAS5 will be changed as follows:
| GRIB 1 Section 1 Octets | GRIB 2 (only for SEAS5) Octets | grib_api/ecCodes key name | Component | Model ID | |
|---|---|---|---|---|---|
| System 4 | SEAS5 | ||||
| 6 | 14 (in Section 4) | generatingProcessIdentifier | Atmospheric model | 139 | 147 |
| Ocean wave model | 107 | 112
| |||
| 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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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).
| paramId | name | frequency |
|---|---|---|
| 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).
| paramId | name | frequency |
|---|---|---|
| 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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All fields are output every 24 hours
| paramId | name |
|---|---|
| 140220 | Mean wave period based on the first moment |
| 140221 | Mean wave period based on the second moment |
| 140244 | Mean square slope of waves |
| 140249 | 10 m wind direction (no calculation of monthly mean/max/min/SD) |
Impact 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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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)
Document versions
| Date | Reason for update |
|---|---|
| 05.07.2017 |
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