## Introduction

Here we document the ERA5 dataset, which, eventually, will cover the period January 1950 to near real time (NRT). ERA5 data released so far covers the period from 1979 to 2-3 months before the present.

ERA5 was produced using 4D-Var data assimilation in CY41R2 of ECMWF’s Integrated Forecast System (IFS), with 137 hybrid sigma/pressure (model) levels in the vertical, with the top level at 0.01 hPa. Atmospheric data are available on these levels and they are also interpolated to 37 pressure, 16 potential temperature and 1 potential vorticity level(s). "Surface or single level" data are also available, containing 2D parameters such as precipitation, 2m temperature, top of atmosphere radiation and vertical integrals over the entire atmosphere. The IFS is coupled to a soil model, the parameters of which are also designated as surface parameters, and an ocean wave model.

The ERA5 dataset contains one (31 km) high resolution realisation (HRES) and a reduced resolution ten member ensemble (EDA). Generally, the data are available at a sub-daily and monthly frequency and consist of analyses and short (18 hour) forecasts, initialised twice daily from analyses at 06 and 18 UTC. Most analysed parameters are also available from the forecasts. There are a number of forecast parameters, e.g. mean rates and accumulations, that are not available from the analyses.

## How to download ERA5

The data are archived in the ECMWF data archive (MARS) and a pertinent sub-set of the data, interpolated to a regular latitude/longitude grid, has been copied to the Climate Data Store (CDS) disks.

Documentation is available on how to download ERA5 data. (Member State users can access the data directly from MARS, in the usual manner.) Data can be downloaded either from the relevant CDS download page or, for larger data volumes, using the CDS API.

## The IFS and data assimilation

The model documentation for CY41R2 is at https://www.ecmwf.int/en/publications/search/?solrsort=sort_label%20asc&secondary_title=%22IFS%20Documentation%20CY41R2%22

The 4D-Var data assimilation uses 12 hour windows from 09 UTC to 21 UTC and 21 UTC to 09 UTC (the following day).

The model time step is 12 minutes for the HRES and 20 minutes for the EDA, though occasionally these numbers are adjusted to cope with instabilities.

## Data organisation

The data can be accessed from MARS using the keywords class=ea and expver=0001. Subdivisions of the data are labelled using stream, type and levtype.

**Stream:**

- oper: HRES sub-daily
- wave: HRES waves sub-daily
- mnth: HRES synoptic monthly means
- moda: HRES monthly means of daily means
- wamo: HRES waves synoptic monthly means
- wamd: HRES waves monthly means of daily means
- enda: EDA sub-daily
- ewda: EDA waves sub-daily
- edmm: EDA synoptic monthly means
- edmo: EDA monthly means of daily means
- ewmm: EDA waves synoptic monthly means
- ewmo: EDA waves monthly means of daily means

**Type:**

- an: analyses
- fc: forecasts
- em: ensemble mean
- es: ensemble standard deviation

**Levtype:**

- sfc: surface or single level
- pl: pressure levels
- pt: potential temperature levels
- pv: potential vorticity level
- ml: model levels

**In MARS:** the date and time of the data is specified with three MARS keywords, date, time and step. For analyses, step=0 hours so that date and time specify the analysis time. For forecasts, date and time specify the forecast start time and step specifies the number of hours since that start time. The combination of date, time and forecast step defines the validity time. For analyses, the validity time is equal to the analysis time.

**In the CDS:** analyses are provided rather than forecasts, unless the parameter is only available from the forecasts. The date and time of the data is specified using the validity date/time, so step does not need to be specified. For forecasts, steps between 1 and 12 hours have been used to provide data for all the validity times in 24 hours, see Table 0 below.

Table 0: the mapping, for forecasts, between MARS date, time and step and the CDS date and time

CDS date time | MARS date time step | CDS date time | MARS date time step | |
---|---|---|---|---|

date 00 | date-1 18 06 | date 12 | date 06 06 | |

date 01 | date-1 18 07 | date 13 | date 06 07 | |

date 02 | date-1 18 08 | date 14 | date 06 08 | |

date 03 | date-1 18 09 | date 15 | date 06 09 | |

date 04 | date-1 18 10 | date 16 | date 06 10 | |

date 05 | date-1 18 11 | date 17 | date 06 11 | |

date 06 | date-1 18 12 | date 18 | date 06 12 | |

date 07 | date 06 01 | date 19 | date 18 01 | |

date 08 | date 06 02 | date 20 | date 18 02 | |

date 09 | date 06 03 | date 21 | date 18 03 | |

date 10 | date 06 04 | date 22 | date 18 04 | |

date 11 | date 06 05 | date 23 | date 18 05 |

## Spatial grid

The ERA5 HRES atmospheric data has a resolution of 31km, 0.28125 degrees, and the EDA has a resolution of 62km, 0.5625 degrees. (Depending on the parameter, the data are archived either as spectral coefficients with a triangular truncation of T639 (HRES) and T319 (EDA) or on a reduced Gaussian grid with a resolution of N320 (HRES) and N160 (EDA). These grids are so called "linear grids", sometimes referred to as TL639 (HRES) and TL319 (EDA).)

The wave data are produced and archived on a different grid to that of the atmospheric model, namely a reduced latitude/longitude grid with a resolution of 0.36 degrees (HRES) and 1.0 degrees (EDA).

ERA5 data available from the CDS disks has been pre-interpolated to a regular latitude/longitude grid appropriate for that data.

The article Model grid box and time step might be useful.

## Temporal frequency

For sub-daily data for the HRES (stream=oper/wave) the analyses (type=an) are available hourly. The short forecasts, run from 06 and 18 UTC, have hourly steps from 0 to 18 hours. For the EDA, the sub-daily non-wave data (stream=enda) are available every 3 hours but the sub-daily wave data (stream=ewda) are available hourly.

## Wave spectra

The ERA5 wave model uses wave spectra with 24 directions and 30 frequencies (see "2D wave spectra (single)", Table 7), for more information see the article About ERA wave spectra.

## Mean rates and accumulations

The accumulations in the short forecasts (from 06 and 18 UTC) of ERA5 are treated **differently** compared with those in ERA-Interim (where they are from the beginning of the forecast to the forecast step). In the short forecasts of ERA5 the accumulations are since the previous post processing (archiving), so for:

- HRES: accumulations are over the hour ending at the forecast step
- EDA: accumulations are over the 3 hours ending at the forecast step
- Monthly means of daily means (stream=moda/edmo): accumulations have been scaled to have units that include "per day", see section Monthly means

Mean rate parameters in ERA5 are similar to accumulations except that the accumulations have been divided by the length of the processing period in seconds to produce temporally averaged rates, so the units include "per second". For "surface or single level" parameters, the mean rates (Table 4) provide similar information to the accumulations (Table 3), but with the different units.

Note that:

- For the CDS time, or validity time, of 00 UTC, the mean rates and accumulations are over the hour (3 hours for the EDA) ending at 00 UTC i.e. the mean or accumulation is during the previous day.
- Mean rates and accumulations are not available from the analyses.
- Mean rates and accumulations at step=0 have values of zero because the length of the processing period is zero.

## Minimum/maximum since the previous post processing

The short forecasts of ERA5 contain some surface and single level parameters that are the minimum or maximum value since the previous post processing (archiving), see Table 5 below. So, for:

- HRES: the minimum or maximum values are in the hour ending at the forecast step
- EDA: the minimum or maximum values are in the 3 hours ending at the forecast step

## Monthly means

In addition to the sub-daily data, most parameters are also available as monthly means. For the surface and single level parameters, there are some exceptions which are listed in Table 8.

Monthly means are available in two forms:

- Synoptic monthly means, for each particular time and forecast step (stream=mnth/wamo/edmm/ewmm) - in the CDS, referred to as "monthly averaged by hour of day".
- Monthly means of daily means, for the month as a whole (stream=moda/wamd/edmo/ewmo) - in the CDS, referred to as "monthly averaged". These monthly means are created from the hourly data for the reanalysis (HRES) and 3 hourly data for the ensemble members (EDA).

Monthly means for:

- forecast parameters are created using the first 12 hours of the twice daily short forecasts (beginning at 06 and 18 UTC).
- analysis and instantaneous forecast parameters are created from data with a valid time in the month, between 00 and 23 UTC, which excludes the time 00 UTC on the first day of the following month.
- accumulation and mean rate forecast parameters are created from data with a forecast period falling within the month. Therefore, monthly means of daily means for accumulations and mean rates are created from contiguous data with forecast periods spanning from 00 UTC on the first day of the month to 00 UTC on the first day of the following month.

The accumulations in monthly means of daily means (stream=moda/edmo) have been scaled to have units that include "per day", so for accumulations in these streams:

- The hydrological parameters are in units of "m of water per day" and so they should be multiplied by 1000 to convert to kgm
^{-2}day^{-1}or mmday^{-1}. - The energy (turbulent and radiative) and momentum fluxes should be divided by 86400 seconds (24 hours) to convert to the commonly used units of Wm
^{-2}and Nm^{-2}, respectively.

## Ensemble means and standard deviations

For the EDA sub-daily data (stream=enda/ewda), compared with HRES sub-daily data (stream=oper/wave), there are also ensemble means and standard deviations (type=em/es).

Ensemble standard deviation is often referred to as ensemble spread and is calculated as the standard deviation of the 10-members in the ensemble (i.e., including the control). It is not the sample stdv, so we divide by 10 rather than 9 (N-1).

Ensemble means and standard deviations contain analysed parameters when step=0, otherwise they contain forecast parameters. However, only surface and pressure level data (levtype=sfc/pl) contain forecast steps beyond 3 hours. There are no monthly means for ensemble means and standard deviations.

## Data format

Model level fields are in GRIB2 format. All other fields are in GRIB1, unless otherwise indicated.

## Level listings

Pressure levels: 1000/975/950/925/900/875/850/825/800/775/750/700/650/600/550/500/450/400/350/300/250/225/200/175/150/125/100/70/50/30/20/10/7/5/3/2/1

Potential temperature levels: 265/275/285/300/315/320/330/350/370/395/430/475/530/600/700/850

Potential vorticity level: 2000

Model levels: 1/to/137, which are described at https://www.ecmwf.int/en/forecasts/documentation-and-support/137-model-levels.

## Parameter listings

Tables 1-6 below describe the surface and single level parameters (levtype=sfc), Table 7 describes wave parameters, Table 8 describes the monthly mean exceptions for surface and single level and wave parameters and Tables 9-13 describe upper air parameters on various levtypes. Information on all ECMWF parameters is available from the ECMWF parameter database.

Parameters described as "instantaneous" below, are valid at the specified time.

Table 1: stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc: surface and single level parameters: invariants

count | name | units | shortName | paramId | an | fc |

1 | Lake cover | (0 - 1) | cl | 26 | x | x |

2 | Lake depth | m | dl | 228007 | x | x |

3 | Low vegetation cover | (0 - 1) | cvl | 27 | x | |

4 | High vegetation cover | (0 - 1) | cvh | 28 | x | |

5 | Type of low vegetation | ~ | tvl | 29 | x | |

6 | Type of high vegetation | ~ | tvh | 30 | x | |

7 | Soil type | ~ | slt | 43 | x | |

8 | Standard deviation of filtered subgrid orography | m | sdfor | 74 | x | |

9 | Geopotential | m**2 s**-2 | z | 129 | x | x |

10 | Standard deviation of orography | ~ | sdor | 160 | x | |

11 | Anisotropy of sub-gridscale orography | ~ | isor | 161 | x | |

12 | Angle of sub-gridscale orography | radians | anor | 162 | x | |

13 | Slope of sub-gridscale orography | ~ | slor | 163 | x | |

14 | Land-sea mask | (0 - 1) | lsm | 172 | x | x |

Table 2: stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc: surface and single level parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Convective inhibition | J kg**-1 | cin | 228001 | x | |

2 | Friction velocity | m s**-1 | zust | 228003 | x | |

3 | Lake mix-layer temperature | K | lmlt | 228008 | x | x |

4 | Lake mix-layer depth | m | lmld | 228009 | x | x |

5 | Lake bottom temperature | K | lblt | 228010 | x | x |

6 | Lake total layer temperature | K | ltlt | 228011 | x | x |

7 | Lake shape factor | dimensionless | lshf | 228012 | x | x |

8 | Lake ice temperature | K | lict | 228013 | x | x |

9 | Lake ice depth | m | licd | 228014 | x | x |

10 | UV visible albedo for direct radiation | (0 - 1) | aluvp | 15 | x | x |

11 | Minimum vertical gradient of refractivity inside trapping layer | m**-1 | dndzn | 228015 | x | |

12 | UV visible albedo for diffuse radiation | (0 - 1) | aluvd | 16 | x | x |

13 | Mean vertical gradient of refractivity inside trapping layer | m**-1 | dndza | 228016 | x | |

14 | Near IR albedo for direct radiation | (0 - 1) | alnip | 17 | x | x |

15 | Duct base height | m | dctb | 228017 | x | |

16 | Near IR albedo for diffuse radiation | (0 - 1) | alnid | 18 | x | x |

17 | Trapping layer base height | m | tplb | 228018 | x | |

18 | Trapping layer top height | m | tplt | 228019 | x | |

19 | Cloud base height | m | cbh | 228023 | x | |

20 | Zero degree level | m | deg0l | 228024 | x | |

21 | Instantaneous 10 metre wind gust | m s**-1 | i10fg | 228029 | x | |

22 | Sea ice area fraction | (0 - 1) | ci | 31 | x | x |

23 | Snow albedo | (0 - 1) | asn | 32 | x | x |

24 | Snow density | kg m**-3 | rsn | 33 | x | x |

25 | Sea surface temperature | K | sst | 34 | x | x |

26 | Ice temperature layer 1 | K | istl1 | 35 | x | x |

27 | Ice temperature layer 2 | K | istl2 | 36 | x | x |

28 | Ice temperature layer 3 | K | istl3 | 37 | x | x |

29 | Ice temperature layer 4 | K | istl4 | 38 | x | x |

30 | Volumetric soil water layer 1 | m**3 m**-3 | swvl1 | 39 | x | x |

31 | Volumetric soil water layer 2 | m**3 m**-3 | swvl2 | 40 | x | x |

32 | Volumetric soil water layer 3 | m**3 m**-3 | swvl3 | 41 | x | x |

33 | Volumetric soil water layer 4 | m**3 m**-3 | swvl4 | 42 | x | x |

34 | Convective available potential energy | J kg**-1 | cape | 59 | x | x |

35 | Leaf area index, low vegetation | m**2 m**-2 | lai_lv | 66 | x | x |

36 | Leaf area index, high vegetation | m**2 m**-2 | lai_hv | 67 | x | x |

37 | Neutral wind at 10 m u-component | m s**-1 | u10n | 228131 | x | x |

38 | Neutral wind at 10 m v-component | m s**-1 | v10n | 228132 | x | x |

39 | Surface pressure | Pa | sp | 134 | x | x |

40 | Soil temperature level 1 | K | stl1 | 139 | x | x |

41 | Snow depth | m of water equivalent | sd | 141 | x | x |

42 | Charnock | ~ | chnk | 148 | x | x |

43 | Mean sea level pressure | Pa | msl | 151 | x | x |

44 | Boundary layer height | m | blh | 159 | x | x |

45 | Total cloud cover | (0 - 1) | tcc | 164 | x | x |

46 | 10 metre U wind component | m s**-1 | 10u | 165 | x | x |

47 | 10 metre V wind component | m s**-1 | 10v | 166 | x | x |

48 | 2 metre temperature | K | 2t | 167 | x | x |

49 | 2 metre dewpoint temperature | K | 2d | 168 | x | x |

50 | Soil temperature level 2 | K | stl2 | 170 | x | x |

51 | Soil temperature level 3 | K | stl3 | 183 | x | x |

52 | Low cloud cover | (0 - 1) | lcc | 186 | x | x |

53 | Medium cloud cover | (0 - 1) | mcc | 187 | x | x |

54 | High cloud cover | (0 - 1) | hcc | 188 | x | x |

55 | Skin reservoir content | m of water equivalent | src | 198 | x | x |

56 | Instantaneous large-scale surface precipitation fraction | (0 - 1) | ilspf | 228217 | x | |

57 | Convective rain rate | kg m**-2 s**-1 | crr | 228218 | x | |

58 | Large scale rain rate | kg m**-2 s**-1 | lsrr | 228219 | x | |

59 | Convective snowfall rate water equivalent | kg m**-2 s**-1 | csfr | 228220 | x | |

60 | Large scale snowfall rate water equivalent | kg m**-2 s**-1 | lssfr | 228221 | x | |

61 | Instantaneous eastward turbulent surface stress | N m**-2 | iews | 229 | x | x |

62 | Instantaneous northward turbulent surface stress | N m**-2 | inss | 230 | x | x |

63 | Instantaneous surface sensible heat flux | W m**-2 | ishf | 231 | x | x |

64 | Instantaneous moisture flux | kg m**-2 s**-1 | ie | 232 | x | x |

65 | Skin temperature | K | skt | 235 | x | x |

66 | Soil temperature level 4 | K | stl4 | 236 | x | x |

67 | Temperature of snow layer | K | tsn | 238 | x | x |

68 | Forecast albedo | (0 - 1) | fal | 243 | x | x |

69 | Forecast surface roughness | m | fsr | 244 | x | x |

70 | Forecast logarithm of surface roughness for heat | ~ | flsr | 245 | x | x |

71 | 100 metre U wind component | m s**-1 | 100u | 228246 | x | x |

72 | 100 metre V wind component | m s**-1 | 100v | 228247 | x | x |

73 | Precipitation type | code table (4.201) | ptype | 260015* | x | |

74 | K index | K | kx | 260121* | x | |

75 | Total totals index | K | totalx | 260123* | x |

*GRIB2 format

Table 3: stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc: surface and single level parameters: accumulations

count | name | units | shortName | paramId | an | fc |

1 | Large-scale precipitation fraction | s | lspf | 50 | x | |

2 | Downward UV radiation at the surface | J m**-2 | uvb | 57 | x | |

3 | Boundary layer dissipation | J m**-2 | bld | 145 | x | |

4 | Surface sensible heat flux | J m**-2 | sshf | 146 | x | |

5 | Surface latent heat flux | J m**-2 | slhf | 147 | x | |

6 | Surface solar radiation downwards | J m**-2 | ssrd | 169 | x | |

7 | Surface thermal radiation downwards | J m**-2 | strd | 175 | x | |

8 | Surface net solar radiation | J m**-2 | ssr | 176 | x | |

9 | Surface net thermal radiation | J m**-2 | str | 177 | x | |

10 | Top net solar radiation | J m**-2 | tsr | 178 | x | |

11 | Top net thermal radiation | J m**-2 | ttr | 179 | x | |

12 | Eastward turbulent surface stress | N m**-2 s | ewss | 180 | x | |

13 | Northward turbulent surface stress | N m**-2 s | nsss | 181 | x | |

14 | Eastward gravity wave surface stress | N m**-2 s | lgws | 195 | x | |

15 | Northward gravity wave surface stress | N m**-2 s | mgws | 196 | x | |

16 | Gravity wave dissipation | J m**-2 | gwd | 197 | x | |

17 | Top net solar radiation, clear sky | J m**-2 | tsrc | 208 | x | |

18 | Top net thermal radiation, clear sky | J m**-2 | ttrc | 209 | x | |

19 | Surface net solar radiation, clear sky | J m**-2 | ssrc | 210 | x | |

20 | Surface net thermal radiation, clear sky | J m**-2 | strc | 211 | x | |

21 | TOA incident solar radiation | J m**-2 | tisr | 212 | x | |

22 | Vertically integrated moisture divergence | kg m**-2 | vimd | 213 | x | |

23 | Total sky direct solar radiation at surface | J m**-2 | fdir | 228021 | x | |

24 | Clear-sky direct solar radiation at surface | J m**-2 | cdir | 228022 | x | |

25 | Surface solar radiation downward clear-sky | J m**-2 | ssrdc | 228129 | x | |

26 | Surface thermal radiation downward clear-sky | J m**-2 | strdc | 228130 | x | |

27 | Surface runoff | m | sro | 8 | x | |

28 | Sub-surface runoff | m | ssro | 9 | x | |

29 | Snow evaporation | m of water equivalent | es | 44 | x | |

30 | Snowmelt | m of water equivalent | smlt | 45 | x | |

31 | Large-scale precipitation | m | lsp | 142 | x | |

32 | Convective precipitation | m | cp | 143 | x | |

33 | Snowfall | m of water equivalent | sf | 144 | x | |

34 | Evaporation | m of water equivalent | e | 182 | x | |

35 | Runoff | m | ro | 205 | x | |

36 | Total precipitation | m | tp | 228 | x | |

37 | Convective snowfall | m of water equivalent | csf | 239 | x | |

38 | Large-scale snowfall | m of water equivalent | lsf | 240 | x | |

39 | Potential evaporation | m | pev | 228251 | x |

Accumulations are described in section Mean rates and accumulations. The accumulations in monthly means of daily means (stream=moda/edmo) have been scaled to have units that include "per day", so for accumulations in these streams:

- The hydrological parameters are in units of "m of water per day" and so they should be multiplied by 1000 to convert to kg m
^{-2}day^{-1}or mm day^{-1}. - Energy (turbulent and radiative) and momentum fluxes should be divided by 86400 seconds (24 hours) to convert to the commonly used units of W m
^{-2}and N m^{-2}, respectively.

Table 4: stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc: surface and single level parameters: mean rates

count | name | units | shortName | paramId | an | fc |

1 | Mean surface runoff rate | kg m**-2 s**-1 | msror | 235020 | x | |

2 | Mean sub-surface runoff rate | kg m**-2 s**-1 | mssror | 235021 | x | |

3 | Mean snow evaporation rate | kg m**-2 s**-1 | mser | 235023 | x | |

4 | Mean snowmelt rate | kg m**-2 s**-1 | msmr | 235024 | x | |

5 | Mean large-scale precipitation fraction | Proportion | mlspf | 235026 | x | |

6 | Mean surface downward UV radiation flux | W m**-2 | msdwuvrf | 235027 | x | |

7 | Mean large-scale precipitation rate | kg m**-2 s**-1 | mlspr | 235029 | x | |

8 | Mean convective precipitation rate | kg m**-2 s**-1 | mcpr | 235030 | x | |

9 | Mean snowfall rate | kg m**-2 s**-1 | msr | 235031 | x | |

10 | Mean boundary layer dissipation | W m**-2 | mbld | 235032 | x | |

11 | Mean surface sensible heat flux | W m**-2 | msshf | 235033 | x | |

12 | Mean surface latent heat flux | W m**-2 | mslhf | 235034 | x | |

13 | Mean surface downward short-wave radiation flux | W m**-2 | msdwswrf | 235035 | x | |

14 | Mean surface downward long-wave radiation flux | W m**-2 | msdwlwrf | 235036 | x | |

15 | Mean surface net short-wave radiation flux | W m**-2 | msnswrf | 235037 | x | |

16 | Mean surface net long-wave radiation flux | W m**-2 | msnlwrf | 235038 | x | |

17 | Mean top net short-wave radiation flux | W m**-2 | mtnswrf | 235039 | x | |

18 | Mean top net long-wave radiation flux | W m**-2 | mtnlwrf | 235040 | x | |

19 | Mean eastward turbulent surface stress | N m**-2 | metss | 235041 | x | |

20 | Mean northward turbulent surface stress | N m**-2 | mntss | 235042 | x | |

21 | Mean evaporation rate | kg m**-2 s**-1 | mer | 235043 | x | |

22 | Mean eastward gravity wave surface stress | N m**-2 | megwss | 235045 | x | |

23 | Mean northward gravity wave surface stress | N m**-2 | mngwss | 235046 | x | |

24 | Mean gravity wave dissipation | W m**-2 | mgwd | 235047 | x | |

25 | Mean runoff rate | kg m**-2 s**-1 | mror | 235048 | x | |

26 | Mean top net short-wave radiation flux, clear sky | W m**-2 | mtnswrfcs | 235049 | x | |

27 | Mean top net long-wave radiation flux, clear sky | W m**-2 | mtnlwrfcs | 235050 | x | |

28 | Mean surface net short-wave radiation flux, clear sky | W m**-2 | msnswrfcs | 235051 | x | |

29 | Mean surface net long-wave radiation flux, clear sky | W m**-2 | msnlwrfcs | 235052 | x | |

30 | Mean top downward short-wave radiation flux | W m**-2 | mtdwswrf | 235053 | x | |

31 | Mean vertically integrated moisture divergence | kg m**-2 s**-1 | mvimd | 235054 | x | |

32 | Mean total precipitation rate | kg m**-2 s**-1 | mtpr | 235055 | x | |

33 | Mean convective snowfall rate | kg m**-2 s**-1 | mcsr | 235056 | x | |

34 | Mean large-scale snowfall rate | kg m**-2 s**-1 | mlssr | 235057 | x | |

35 | Mean surface direct short-wave radiation flux | W m**-2 | msdrswrf | 235058 | x | |

36 | Mean surface direct short-wave radiation flux, clear sky | W m**-2 | msdrswrfcs | 235059 | x | |

37 | Mean surface downward short-wave radiation flux, clear sky | W m**-2 | msdwswrfcs | 235068 | x | |

38 | Mean surface downward long-wave radiation flux, clear sky | W m**-2 | msdwlwrfcs | 235069 | x | |

39 | Mean potential evaporation rate | kg m**-2 s**-1 | mper | 235070 | x |

The mean rates in Table 4 provide similar information to the accumulations in Table 3, except that they are expressed as temporal averages instead of accumulations, and so have units of "per second". The hydrological parameters are in units of "kg m^{-2} s^{-1}" and so they can be multiplied by 86400 seconds (24 hours) to convert to kg m^{-2} day^{-1} or mm day^{-1}.

Table 5: stream=oper/enda, levtype=sfc: surface and single level parameters: minimum/maximum

count | name | units | shortName | paramId | an | fc |

1 | 10 metre wind gust since previous post-processing | m s**-1 | 10fg | 49 | x | |

2 | Maximum temperature at 2 metres since previous post-processing | K | mx2t | 201 | x | |

3 | Minimum temperature at 2 metres since previous post-processing | K | mn2t | 202 | x | |

4 | Maximum total precipitation rate since previous post-processing | kg m**-2 s**-1 | mxtpr | 228226 | x | |

5 | Minimum total precipitation rate since previous post-processing | kg m**-2 s**-1 | mntpr | 228227 | x |

Table 6: stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc: surface and single level parameters: vertical integrals (not available for type=em/es) and total column: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Vertical integral of mass of atmosphere | kg m**-2 | vima | 162053 | x | x |

2 | Vertical integral of temperature | K kg m**-2 | vit | 162054 | x | x |

3 | Vertical integral of kinetic energy | J m**-2 | vike | 162059 | x | x |

4 | Vertical integral of thermal energy | J m**-2 | vithe | 162060 | x | x |

5 | Vertical integral of potential+internal energy | J m**-2 | vipie | 162061 | x | x |

6 | Vertical integral of potential+internal+latent energy | J m**-2 | vipile | 162062 | x | x |

7 | Vertical integral of total energy | J m**-2 | vitoe | 162063 | x | x |

8 | Vertical integral of energy conversion | W m**-2 | viec | 162064 | x | x |

9 | Vertical integral of eastward mass flux | kg m**-1 s**-1 | vimae | 162065 | x | x |

10 | Vertical integral of northward mass flux | kg m**-1 s**-1 | viman | 162066 | x | x |

11 | Vertical integral of eastward kinetic energy flux | W m**-1 | vikee | 162067 | x | x |

12 | Vertical integral of northward kinetic energy flux | W m**-1 | viken | 162068 | x | x |

13 | Vertical integral of eastward heat flux | W m**-1 | vithee | 162069 | x | x |

14 | Vertical integral of northward heat flux | W m**-1 | vithen | 162070 | x | x |

15 | Vertical integral of eastward water vapour flux | kg m**-1 s**-1 | viwve | 162071 | x | x |

16 | Vertical integral of northward water vapour flux | kg m**-1 s**-1 | viwvn | 162072 | x | x |

17 | Vertical integral of eastward geopotential flux | W m**-1 | vige | 162073 | x | x |

18 | Vertical integral of northward geopotential flux | W m**-1 | vign | 162074 | x | x |

19 | Vertical integral of eastward total energy flux | W m**-1 | vitoee | 162075 | x | x |

20 | Vertical integral of northward total energy flux | W m**-1 | vitoen | 162076 | x | x |

21 | Vertical integral of eastward ozone flux | kg m**-1 s**-1 | vioze | 162077 | x | x |

22 | Vertical integral of northward ozone flux | kg m**-1 s**-1 | viozn | 162078 | x | x |

23 | Vertical integral of divergence of cloud liquid water flux | kg m**-2 s**-1 | vilwd | 162079 | x | x |

24 | Vertical integral of divergence of cloud frozen water flux | kg m**-2 s**-1 | viiwd | 162080 | x | x |

25 | Vertical integral of divergence of mass flux | kg m**-2 s**-1 | vimad | 162081 | x | x |

26 | Vertical integral of divergence of kinetic energy flux | W m**-2 | viked | 162082 | x | x |

27 | Vertical integral of divergence of thermal energy flux | W m**-2 | vithed | 162083 | x | x |

28 | Vertical integral of divergence of moisture flux | kg m**-2 s**-1 | viwvd | 162084 | x | x |

29 | Vertical integral of divergence of geopotential flux | W m**-2 | vigd | 162085 | x | x |

30 | Vertical integral of divergence of total energy flux | W m**-2 | vitoed | 162086 | x | x |

31 | Vertical integral of divergence of ozone flux | kg m**-2 s**-1 | viozd | 162087 | x | x |

32 | Vertical integral of eastward cloud liquid water flux | kg m**-1 s**-1 | vilwe | 162088 | x | x |

33 | Vertical integral of northward cloud liquid water flux | kg m**-1 s**-1 | vilwn | 162089 | x | x |

34 | Vertical integral of eastward cloud frozen water flux | kg m**-1 s**-1 | viiwe | 162090 | x | x |

35 | Vertical integral of northward cloud frozen water flux | kg m**-1 s**-1 | viiwn | 162091 | x | x |

36 | Vertical integral of mass tendency | kg m**-2 s**-1 | vimat | 162092 | x | |

37 | Total column cloud liquid water | kg m**-2 | tclw | 78 | x | x |

38 | Total column cloud ice water | kg m**-2 | tciw | 79 | x | x |

39 | Total column supercooled liquid water | kg m**-2 | tcslw | 228088 | x | |

40 | Total column rain water | kg m**-2 | tcrw | 228089 | x | x |

41 | Total column snow water | kg m**-2 | tcsw | 228090 | x | x |

42 | Total column water | kg m**-2 | tcw | 136 | x | x |

43 | Total column water vapour | kg m**-2 | tcwv | 137 | x | x |

44 | Total column ozone | kg m**-2 | tco3 | 206 | x | x |

Table 7: stream=wave/ewda/wamo/wamd/ewmm/ewmo: wave parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Significant wave height of first swell partition | m | swh1 | 140121 | x | x |

2 | Mean wave direction of first swell partition | degrees | mwd1 | 140122 | x | x |

3 | Mean wave period of first swell partition | s | mwp1 | 140123 | x | x |

4 | Significant wave height of second swell partition | m | swh2 | 140124 | x | x |

5 | Mean wave direction of second swell partition | degrees | mwd2 | 140125 | x | x |

6 | Mean wave period of second swell partition | s | mwp2 | 140126 | x | x |

7 | Significant wave height of third swell partition | m | swh3 | 140127 | x | x |

8 | Mean wave direction of third swell partition | degrees | mwd3 | 140128 | x | x |

9 | Mean wave period of third swell partition | s | mwp3 | 140129 | x | x |

10 | Wave Spectral Skewness | dimensionless | wss | 140207 | x | x |

11 | Free convective velocity over the oceans | m s**-1 | wstar | 140208 | x | x |

12 | Air density over the oceans | kg m**-3 | rhoao | 140209 | x | x |

13 | Normalized energy flux into waves | dimensionless | phiaw | 140211 | x | x |

14 | Normalized energy flux into ocean | dimensionless | phioc | 140212 | x | x |

15 | Normalized stress into ocean | dimensionless | tauoc | 140214 | x | x |

16 | U-component stokes drift | m s**-1 | ust | 140215 | x | x |

17 | V-component stokes drift | m s**-1 | vst | 140216 | x | x |

18 | Period corresponding to maximum individual wave height | s | tmax | 140217 | x | x |

19 | Maximum individual wave height | m | hmax | 140218 | x | x |

20 | Model bathymetry | m | wmb | 140219 | x | x |

21 | Mean wave period based on first moment | s | mp1 | 140220 | x | x |

22 | Mean wave period based on second moment | s | mp2 | 140221 | x | x |

23 | Wave spectral directional width | dimensionless | wdw | 140222 | x | x |

24 | Mean wave period based on first moment for wind waves | s | p1ww | 140223 | x | x |

25 | Mean wave period based on second moment for wind waves | s | p2ww | 140224 | x | x |

26 | Wave spectral directional width for wind waves | dimensionless | dwww | 140225 | x | x |

27 | Mean wave period based on first moment for swell | s | p1ps | 140226 | x | x |

28 | Mean wave period based on second moment for swell | s | p2ps | 140227 | x | x |

29 | Wave spectral directional width for swell | dimensionless | dwps | 140228 | x | x |

30 | Significant height of combined wind waves and swell | m | swh | 140229 | x | x |

31 | Mean wave direction | degrees | mwd | 140230 | x | x |

32 | Peak wave period | s | pp1d | 140231 | x | x |

33 | Mean wave period | s | mwp | 140232 | x | x |

34 | Coefficient of drag with waves | dimensionless | cdww | 140233 | x | x |

35 | Significant height of wind waves | m | shww | 140234 | x | x |

36 | Mean direction of wind waves | degrees | mdww | 140235 | x | x |

37 | Mean period of wind waves | s | mpww | 140236 | x | x |

38 | Significant height of total swell | m | shts | 140237 | x | x |

39 | Mean direction of total swell | degrees | mdts | 140238 | x | x |

40 | Mean period of total swell | s | mpts | 140239 | x | x |

41 | Mean square slope of waves | dimensionless | msqs | 140244 | x | x |

42 | 10 metre wind speed | m s**-1 | wind | 140245 | x | x |

43 | Altimeter wave height | m | awh | 140246 | x | |

44 | Altimeter corrected wave height | m | acwh | 140247 | x | |

45 | Altimeter range relative correction | ~ | arrc | 140248 | x | |

46 | 10 metre wind direction | degrees | dwi | 140249 | x | x |

47 | Wave spectral kurtosis | dimensionless | wsk | 140252 | x | x |

48 | Benjamin-Feir index | dimensionless | bfi | 140253 | x | x |

49 | Wave spectral peakedness | dimensionless | wsp | 140254 | x | x |

50 | 2D wave spectra (single) | m**2 s radian**-1 | 2dfd | 140251* | x |

*for 30 frequencies and 24 directions

count | name | units | shortName | paramId | an | fc |

1 | UV visible albedo for direct radiation | (0 - 1) | aluvp | 15 | x | no mean |

2 | UV visible albedo for diffuse radiation | (0 - 1) | aluvd | 16 | x | no mean |

3 | Near IR albedo for direct radiation | (0 - 1) | alnip | 17 | x | no mean |

4 | Near IR albedo for diffuse radiation | (0 - 1) | alnid | 18 | x | no mean |

5 | Magnitude of turbulent surface stress | N m**-2 s | magss | 48 | x | |

6 | Mean magnitude of turbulent surface stress | N m**-2 | mmtss | 235025 | x | |

7 | 10 metre wind gust since previous post-processing | m s**-1 | 10fg | 49 | no mean | |

8 | Maximum temperature at 2 metres since previous post-processing | K | mx2t | 201 | no mean | |

9 | Minimum temperature at 2 metres since previous post-processing | K | mn2t | 202 | no mean | |

10 | 10 metre wind speed | m s**-1 | 10si | 207 | x | x |

11 | Maximum total precipitation rate since previous post-processing | kg m**-2 s**-1 | mxtpr | 228226 | no mean | |

12 | Minimum total precipitation rate since previous post-processing | kg m**-2 s**-1 | mntpr | 228227 | no mean | |

13 | Altimeter wave height | m | awh | 140246 | no mean | |

14 | Altimeter corrected wave height | m | acwh | 140247 | no mean | |

15 | Altimeter range relative correction | ~ | arrc | 140248 | no mean | |

16 | 2D wave spectra (single) | m**2 s radian**-1 | 2dfd | 140251 | no mean |

Table 9: stream=oper/enda/mnth/moda/edmm/edmo, levtype=pl: pressure level parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Potential vorticity | K m**2 kg**-1 s**-1 | pv | 60 | x | x |

2 | Specific rain water content | kg kg**-1 | crwc | 75 | x | x |

3 | Specific snow water content | kg kg**-1 | cswc | 76 | x | x |

4 | Geopotential | m**2 s**-2 | z | 129 | x | x |

5 | Temperature | K | t | 130 | x | x |

6 | U component of wind | m s**-1 | u | 131 | x | x |

7 | V component of wind | m s**-1 | v | 132 | x | x |

8 | Specific humidity | kg kg**-1 | q | 133 | x | x |

9 | Vertical velocity | Pa s**-1 | w | 135 | x | x |

10 | Vorticity (relative) | s**-1 | vo | 138 | x | x |

11 | Divergence | s**-1 | d | 155 | x | x |

12 | Relative humidity | % | r | 157 | x | x |

13 | Ozone mass mixing ratio | kg kg**-1 | o3 | 203 | x | x |

14 | Specific cloud liquid water content | kg kg**-1 | clwc | 246 | x | x |

15 | Specific cloud ice water content | kg kg**-1 | ciwc | 247 | x | x |

16 | Fraction of cloud cover | (0 - 1) | cc | 248 | x | x |

Table 10: stream=oper/enda/mnth/moda/edmm/edmo, levtype=pt: potential temperature level parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Montgomery potential | m**2 s**-2 | mont | 53 | x | |

2 | Pressure | Pa | pres | 54 | x | |

3 | Potential vorticity | K m**2 kg**-1 s**-1 | pv | 60 | x | |

4 | U component of wind | m s**-1 | u | 131 | x | |

5 | V component of wind | m s**-1 | v | 132 | x | |

6 | Specific humidity | kg kg**-1 | q | 133 | x | |

7 | Vorticity (relative) | s**-1 | vo | 138 | x | |

8 | Divergence | s**-1 | d | 155 | x | |

9 | Ozone mass mixing ratio | kg kg**-1 | o3 | 203 | x |

Table 11: stream=oper/enda/mnth/moda/edmm/edmo, levtype=pv: potential vorticity level parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Potential temperature | K | pt | 3 | x | |

2 | Pressure | Pa | pres | 54 | x | |

3 | Geopotential | m**2 s**-2 | z | 129 | x | |

4 | U component of wind | m s**-1 | u | 131 | x | |

5 | V component of wind | m s**-1 | v | 132 | x | |

6 | Specific humidity | kg kg**-1 | q | 133 | x | |

7 | Ozone mass mixing ratio | kg kg**-1 | o3 | 203 | x |

Table 12: stream=oper/enda/mnth/moda/edmm/edmo, levtype=ml: model level parameters: instantaneous

count | name | units | shortName | paramId | an | fc |

1 | Specific rain water content | kg kg**-1 | crwc | 75 | x | x |

2 | Specific snow water content | kg kg**-1 | cswc | 76 | x | x |

3 | Eta-coordinate vertical velocity | s**-1 | etadot | 77 | x | x |

4 | Geopotential* | m**2 s**-2 | z | 129 | x | x |

5 | Temperature | K | t | 130 | x | x |

6 | U component of wind | m s**-1 | u | 131 | x | x |

7 | V component of wind | m s**-1 | v | 132 | x | x |

8 | Specific humidity | kg kg**-1 | q | 133 | x | x |

9 | Vertical velocity | Pa s**-1 | w | 135 | x | x |

10 | Vorticity (relative) | s**-1 | vo | 138 | x | x |

11 | Logarithm of surface pressure* | ~ | lnsp | 152 | x | x |

12 | Divergence | s**-1 | d | 155 | x | x |

13 | Ozone mass mixing ratio | kg kg**-1 | o3 | 203 | x | x |

14 | Specific cloud liquid water content | kg kg**-1 | clwc | 246 | x | x |

15 | Specific cloud ice water content | kg kg**-1 | ciwc | 247 | x | x |

16 | Fraction of cloud cover | (0 - 1) | cc | 248 | x | x |

*Only archived on level=1.

Table 13: stream=oper/enda/mnth/moda/edmm/edmo, levtype=ml: model level parameters: mean rates

count | name | units | shortName | paramId | an | fc |
---|---|---|---|---|---|---|

1 | Mean temperature tendency due to short-wave radiation | K s**-1 | mttswr | 235001 | x | |

2 | Mean temperature tendency due to long-wave radiation | K s**-1 | mttlwr | 235002 | x | |

3 | Mean temperature tendency due to short-wave radiation, clear sky | K s**-1 | mttswrcs | 235003 | x | |

4 | Mean temperature tendency due to long-wave radiation, clear sky | K s**-1 | mttlwrcs | 235004 | x | |

5 | Mean temperature tendency due to parametrisations | K s**-1 | mttpm | 235005 | x | |

6 | Mean specific humidity tendency due to parametrisations | kg kg**-1 s**-1 | mqtpm | 235006 | x | |

7 | Mean eastward wind tendency due to parametrisations | m s**-2 | mutpm | 235007 | x | |

8 | Mean northward wind tendency due to parametrisations | m s**-2 | mvtpm | 235008 | x | |

9 | Mean updraught mass flux* | kg m**-2 s**-1 | mumf | 235009 | x | |

10 | Mean downdraught mass flux* | kg m**-2 s**-1 | mdmf | 235010 | x | |

11 | Mean updraught detrainment rate | kg m**-3 s**-1 | mudr | 235011 | x | |

12 | Mean downdraught detrainment rate | kg m**-3 s**-1 | mddr | 235012 | x | |

13 | Mean total precipitation flux* | kg m**-2 s**-1 | mtpf | 235013 | x | |

14 | Mean turbulent diffusion coefficient for heat* | m**2 s**-1 | mtdch | 235014 | x |

*These parameters provide data for the model half levels, at the interfaces of the model layers.

## Observations

The observations (satellite and in-situ) used as input into ERA5 are listed below.

### Satellite Data

Sensor | Satellite | Satellite agency | Data provider+ | Measurement (sensitivities exploited in ERA5 / variables analysed) |
---|---|---|---|---|

Satellite radiances (infrared and microwave) | ||||

AIRS | AQUA | NASA | NOAA | BT (T, humidity and ozone) |

AMSR-2 | GCOM-W1* | JAXA | BT (column water vapour, cloud liquid water, precipitation and ocean surface wind speed) | |

AMSRE | AQUA* | JAXA | BT (column water vapour, cloud liquid water, precipitation and ocean surface wind speed) | |

AMSUA | NOAA-15/16/17/18/19, AQUA, METOP-A/B | NOAA,ESA,EUMETSAT | BT (T) | |

AMSUB | NOAA-15/16/17 | NOAA | BT (humidity) | |

ATMS | NPP | NOAA | BT (T and humidity) | |

CRIS | NPP | NOAA | BT (T, humidity and ozone) | |

HIRS | TIROS-N, NOAA-6 /7/8/9/11/14 | NOAA | BT (T, humidity and ozone) | |

IASI | METOP-A/B | EUMETSAT/ESA | EUMETSAT | BT (T, humidity and ozone) |

GMI | GPM | NASA/JAXA | BT (humidity, column water vapour, cloud liquid water, precipitation, ocean surface wind speed) | |

MHS | NOAA-18/19, METOP-A/B | NOAA, EUMETSAT/ESA | BT (humidity and precipitation) | |

MSU | TIROS-N, NOAA-6 to 12, NOAA-14 | BT (T) | ||

MWHS | FY-3-A/B | NRSCC | BT (humidity) | |

MWHS2 | FY-3-C | CMA | BT (T, humidity and precipitation) | |

MWTS | FY-3A/B | NRSCC | BT (T) | |

MWTS2 | FY-3C | CMA | BT (T) | |

SSM/I | DMSP-11*/13*/14*/15* | US Navy | NOAA,CMSAF* | BT (column water vapour, cloud liquid water, precipitation and ocean surface wind speed) |

SSMIS | DMSP-16/17/18 | US Navy | NOAA | BT (T, humidity, column water vapour, cloud liquid water, precipitation and ocean surface wind speed) |

SSU | TIROS-N, NOAA-6/7/8/9/11/14 | NOAA | BT (T) | |

TMI | TRMM | NASA/JAXA | BT (column water vapour, cloud liquid water, precipitation, ocean surface wind speed) | |

MVIRI | METEOSAT 5/7 | EUMETSAT/ESA | EUMETSAT | BT (water vapour, surface/cloud top T) |

SEVIRI | METEOSAT-8*/9*/10 | EUMETSAT/ESA | EUMETSAT | BT (water vapour, surface/cloud top T) |

GOES IMAGER | GOES-8/9/10/11/12/13/15 | NOAA | CIMMS,NESDIS | BT (water vapour, surface/cloud top T) |

MTSAT IMAGER | MTSAT-1R/MTSAT-2 | JMA | BT (water vapour, surface/cloud top T) | |

AHI | Himawari-8 | JMA | BT (water vapour, surface/cloud top T) | |

Satellite retrievals from radiance data | ||||

MVIRI | METEOSAT-2*/3*/4*/5*/7* | EUMETSAT/ESA | EUMETSAT | wind vector |

SEVIRI | METEOSAT-8*/9*/10 | EUMETSAT/ESA | EUMETSAT | wind vector |

GOES IMAGER | GOES-4-6/8*/9*/10*/11*/12*/13*/15* | NOAA | CIMMS*,NESDIS | wind vector |

GMS IMAGER | GMS-1*/2/3*/4*/5* | JMA | wind vector | |

MTSAT IMAGER | MTSAT-1R*/MTSAT2 | JMA | wind vector | |

AHI | Himawari-8 | JMA | JMA | wind vector |

AVHRR | NOAA-7 /9/10/11/12/14 to 18, METOP-A | NOAA | CIMMS,EUMETSAT | wind vector |

MODIS | AQUA/TERRA | NASA | NESDIS,CIMMS | wind vector |

GOME | ERS-2* | ESA | Ozone | |

GOME-2 | METOP*-A/B | ESA/EUMETSAT | Ozone | |

MIPAS | ENVISAT* | ESA | Ozone | |

MLS | EOS-AURA* | NASA | Ozone | |

OMI | EOS-AURA* | NASA | Ozone | |

SBUV,SBUV-2 | NIMBUS-7*,NOAA*9/11/14/16/17/18/19 | NOAA | NASA | Ozone |

SCIAMACHY | ENVISAT* | ESA | Ozone | |

TOMS | NIMBUS-7*,METEOR-3-5,ADEOS-1*,EARTH PROBE | NASA | Ozone | |

Satellite GPS-Radio Occultation data | ||||

BlackJack | CHAMP,GRACE*-A/B,SAC-C* | DLR,NASA/DLR,NASA/COMAE | GFZ,UCAR* | Bending angle |

GRAS | METOP-A/B | EUMETSAT/ESA | EUMETSAT | Bending angle |

IGOR | TerraSAR-X*, TanDEM-X, COSMIC*-1 to 6 | NSPO/NOAA | GFZ,UCAR* | Bending angle |

Satellite scatterometer data | ||||

AMI | ERS-1,ERS-2 | ESA | Backscatter sigma0, soil moisture | |

ASCAT | METOP-A/B* | EUMETSAT/ESA | EUMETSAT/TU Wien | Backscatter sigma0, soil moisture |

OSCAT | OCEANSAT-2 | ISRO | KNMI | Backscatter sigma0 |

SEAWINDS | QUIKSCAT | NASA | NASA | Backscatter sigma0 |

Satellite Altimeter data | ||||

RA | ERS-1*/2* | ESA | Wave Height | |

RA-2 | ENVISAT* | ESA | Wave Height | |

Poseidon-2 | JASON-1* | CNES/NASA | CNES | Wave Height |

Poseidon-3 | JASON-2 | CNES/NOAA/NASA/EUMETSAT | NOAA/EUMETSAT | Wave Height |

SIRAL | CRYOSAT-2 | ESA | Wave Height | |

AltiKa | SARAL | CNES/ISRO | EUMETSAT | Wave Height |

* reprocessed dataset

+ when different than the satellite agency

### In-situ data, provided by WMO WIS

Dataset name | Observation type | Measurement |
---|---|---|

SYNOP | Land station | Surface Pressure, Temperature, wind, humidity |

METAR | Land station | Surface Pressure, Temperature, wind,humidity |

DRIBU/DRIBU-BATHY/DRIBU-TESAC/BUFR Drifting Buoy | Drifting buoys | 10m-wind, Surface Pressure |

BUFR Moored Buoy | Moored buoys | 10m-wind, Surface Pressure |

SHIP | ship station | Surface Pressure, Temperature, wind, humidity |

Land/ship PILOT | Radiosondes | wind profiles |

American Wind Profiler | Radar | wind profiles |

European Wind Profiler | Radar | wind profiles |

Japanese Wind Profiler | Radar | wind profiles |

TEMP SHIP | Radiosondes | Temperature, wind, humidity profiles |

DROP Sonde | Aircraft-sondes | Temperature, wind profiles |

Land/Mobile TEMP | Radiosondes | Temperature, wind, humidity profiles |

AIREP | Aircraft data | Temperature, wind profiles |

AMDAR | Aircraft data | Temperature, wind profiles |

ACARS | Aircraft data | Temperature, wind profiles, humidity |

WIGOS AMDAR | Aircraft data | Temperature, wind profiles |

Ground based radar | Radar precipitation composites | Rain rates |

### Snow data

Dataset name | Observation type | Measurement |
---|---|---|

SYNOP | Land station | Snow depth |

Additional national reports | Land station | Snow depth |

NOAA/NESDIS IMS | Merged satellite | Snow cover (NH only) |

## Guidelines

The following advice is intended to help users understand particular features of the ERA5 data:

- Sea surface temperature and sea-ice cover (see Table 2 above) are available at the usual times, eg hourly for the HRES, but their content is only updated once daily.
- Mean rates and accumulations at step=0 have values of zero because the length of the processing period is zero.

## Known issues

Currently, we are aware of these issues with ERA5:

ERA5 suffers from an overly strong equatorial mesospheric jet, particularly in the transition seasons.

From 2000 to 2005, ERA5 has a poor fit to radiosonde temperatures in the stratosphere, with a cold bias in the lower stratosphere and a warm bias higher up.

ERA5 uncertainty: although small values of ensemble spread correctly mark more confident estimates than large values, numerical values are over confident. The spread does give an indication of the relative uncertainty in space and time.

- Discontinuities in ERA5: ERA5 is produced by several parallel experiments, each for a different period, which are then appended together to create the final product. This can create discontinuities at the transition points.
- The Potential Evaporation field (pev, parameter Id 228251) is largely underestimated over deserts and high-forested areas. This is due to a bug in the code that does not allow transpiration in case no low vegetation type is present.
- The hourly data reveals a mismatch in the analysed near surface wind speed between the end of one assimilation cycle and the beginning of the next (which occurs at 9:00 and 21:00 UTC). This problem mostly occurs in low latitude oceanic regions, though it can also be seen over Europe and the USA. The forecast near surface winds show much better agreement between the assimilation cycles, at least on average, so our advice would be to use the forecast winds. We cannot rectify the problem in the analyses.
- Wind values are far too low on pressure levels at the poles in the Climate Data Store (CDS)
- Prior to 2014, the SST was not used over the Great Lakes to nudge the lake model. Consequently, the 2 metre temperature has an annual cycle that is too strong, with temperatures being too cold in winter and too warm in summer.
- ERA5 large 10m winds: a few times per year, the analysed low level winds, eg 10m winds, become very large in a particular location, which varies amongst a few apparently preferred locations. The largest values seen so far are about 300 ms
^{-1}.

## Resolved issues

## How to cite ERA5

Please acknowledge the use of ERA5 as stated in the Copernicus C3S/CAMS License agreement:

"5.1.2 Where the Licensee communicates or distributes Copernicus Products to the public, the Licensee shall inform the recipients of the source by using the following or any similar notice:

5.1.3 Where the Licensee makes or contributes to a publication or distribution containing adapted or modified Copernicus Products, the Licensee shall provide the following or any similar notice:

5.1.3 Any such publication or distribution covered by clauses 5.1.1 and 5.1.2 shall state that neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus Information or Data it contains."

You may also cite the ERA5 dataset as follows:

**Dataset citable as:** Copernicus Climate Change Service (C3S) (2017): ERA5: Fifth generation of ECMWF atmospheric reanalyses of the global climate . Copernicus Climate Change Service Climate Data Store (CDS), *date of access*. https://cds.climate.copernicus.eu/cdsapp#!/home

## References

Operational global reanalysis: progress, future directions and synergies with NWP

Further ERA5 references are available from the ECMWF e-Library.

## Related articles