Comparison table
This table highlights major differences between ERA-Interim, ERA5 and ERA5-Land. There are many additional differences, in particular changes to the computation of individual atmospheric parameters (due to the change in the assimilation system from 31r2 to 41r2) are not listed here.
| ERA-Interim | ERA5 | ERA5-Land | |
|---|---|---|---|
| Period covered | 1979 - present | 1940 - present | 1950 - present |
| Production Period | August 2006 – 31st August 2019 | Jan 2016 – end 2017, then continued in near real-time | May 2018-July 2019 [1981-2019], then continued with 2-3 months delay wrt real time & Jan-Dec 2020 [1950-1980] |
| Model version | IFS Cycle 31r2 | IFS Cycle 41r2 | Tiled ECMWF Scheme for Surface Exchanges over Land incorporating land surface hydrology (H-TESSEL) IFS Cycle 45r1 |
| Assimilation system | IFS Cycle 31r2 4D-Var | IFS Cycle 41r2 4D-Var | n/a |
| Spatial resolution | 79 km globally, 60 levels to 0.1 hPa | 31 km globally, 62km for the Ensemble of Data Assimilations (EDA), 137 levels to 0.01 hPa | 9km globally, 62 km from ERA5 EDA equivalent surface fields |
| Output frequency (temporal resolution) | 6-hourly analysis fields Forecast fields on surface and pressure levels 3-hourly up to 24 hours, with reduced frequency up to 10 days | Hourly analysis fields, 3-hourly for the Ensemble of Data Assimilations (EDA) Hourly forecast fields, 3-hourly for the Ensemble of Data Assimilations (EDA), up to 18 hours, with reduced frequency up to 10 days (not in initial release) | Hourly fields for all variables |
| Uncertainty estimates | None | From a 10-member Ensemble of Data Assimilations (EDA) at 63 km resolution | From ERA5-equivalent variables 10-member Ensemble of Data Assimilations (EDA) at 63 km resolution. |
| Model input | As in operations (inconsistent SST) | Appropriate for climate (e.g. CMIP5 greenhouse gases, volcanic eruptions, SST and sea-ice cover) | Atmospheric forcing of ERA5 with additional lapse-rate correction |
| Input observations | As in ERA-40 and from Global Telecommunication System | In addition, various newly reprocessed datasets and recent instruments that could not be ingested in ERA-Interim | Observations indirectly influence the simulation through the atmospheric forcing from ERA5. This forcing drives the ERA5-Land single simulation and it has been obtained by assimilating observations through a 4D-VAR data assimilation system and a Simplified Extended Kalman Filter |
| Variational bias scheme | Satellite radiances | Also ozone, aircraft and surface pressure data | n/a |
| Satellite data | RTTOV-7, clear-sky, 1D-VAR rainy radiances | RTTOV-11, all-sky for various components | n/a |
| New parameters | ERA-Interim contains about 100 parameters on surface and single level alone, plus parameters on other level types. | ERA5 contains over 240 parameters on surface and single level alone, plus parameters on other level types. For specific parameters please compare the technical documentation linked below. | ERA5-Land contains finer-scale information of land surface component than ERA5, plus specific evaporation parameters. For specific parameters please compare the technical documentation linked below. |
| Parameters removed | A few parameters present in ERA-Interim are not available in ERA5. For availability of specific parameters please see the technical documentation linked below. | Most of the atmospheric parameters and all the wave parameters present in ERA-5 are not available in ERA5-Land. For availability of specific parameters please see the technical documentation linked below. | |
| Handling of accumulated parameters | Accumulated from the beginning of the forecast | Accumulated from previous post-processing | Accumulated from the beginning of the forecast |
| Product main page | https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-interim | http://climate.copernicus.eu/climate-reanalysis | http://climate.copernicus.eu/climate-reanalysis |
| Technical documentation | Berrisford et al 2011: The ERA-Interim archive Version 2.0 | ERA5 data documentation | ERA5-Land: data documentation |
| Additional innovations | Long-term evolution of CO2 in RTTOV, cell-pressure correction SSU, improved bias correction for radiosondes, EDA perturbations for sea-ice cover |
