| Basic Comparison of ECMWF ERA-Interim and ERA5 Reanalyses | ||
|---|---|---|
| Based in part on Core-Climax Workshop, Brussels, January 15-16, 2015, and "ECMWF – Computing and Forecast System", iCAS 2015, Annecy, France, September 2015 (Isabella Weger) | ||
| Category | ERA-Interim | ERA5 |
| Start of Production | August 2006 IFS1 Cy31r2 | June 2015 IFS1 Cy41r2 |
| Model Input | As in operations (inconsistent SST) | Appropriate for Climate (CMIP52, HadISST.23) |
| Model Horizontal Grid | Reduced Gaussian and spectral coefficients | Reduced Gaussian and spectral coefficients |
| Model Horizontal Resolution | Nominally 78 km global (0.703125°) ECMWF T255 N128 (∼512 x 256) | Nominally 31 km global (0.28125°) ECMWF T639 N320 (∼1280 x 640) |
| Model Vertical Resolution | 60 levels to 10 Pa (hybrid σ-p coordinate) | 137 levels to 1 Pa (hybrid σ-p coordinate) |
| Standard Pressure Levels | 37 levels† | Identical to ERA-Interim |
| Time Period | 1979 to present time | 1979 to present time Extension back to ∼1950 |
| Dissemination | Monthly (up to 3 month lag at NCAR) | Monthly (up to 3 month lag at NCAR) (Daily for ERA5T) |
| Observations | Primarily ERA-40, GTS4 | Various reprocessed CDR5s |
| Radiative Transfer | RTTOV67 | RTTOV611 |
| Analysis Method | 4D-Var7 1D + 4D-Var for rain | 10-member ensemble 4D-VAR (EDA8) All-sky microwave |
| Variational Bias Correction | Satellite radiances | Satellite radiances, ozone, aircraft, surface pressure, radiosondes |
| Maximum Volume | 50 TB | 5.0 PB (1.5 PB for core atmospheric analysis and forecast groups) |
| 1IFS, Integrated Forecast System 2CMIP5, Coupled Model Intercomparison Project Phase 5 3HadISST.2, Hadley Centre Sea Ice and Sea Surface Temperature data set version 2 4GTS, Global Telecommunication System 5CDR, Climate Data Record 6RTTOV, Radiative Transfer for TOVS, TOVS being TIROS Operational Vertical Sounder (originally hosting the Microvave Sounding Unit – MSU, the High Resolution Infrared Radiation Sounder – HIRS, and the Stratospheric Sounding Unit – SSU) 74D-Var, 4-Dimensional Variational Data Assimilation 8EDA, Ensemble Data Assimilation †The 37 standard pressure levels (in mb, or hPa) are: 1 2 3 5 7 10 20 30 50 70 100 125 150 175 200 225 250 300 350 400 450 500 550 600 650 700 750 775 800 825 850 875 900 925 950 975 1000 | ||