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All the analysed parameters and many of the forecast parameters are described as "instantaneous". For more information on what this means, see Parameters valid at the specified time.
Mean rates/fluxes and accumulations
The accumulations (over the processing period) in the short forecasts (from 06 and 18 UTC) of ERA5 are treated differently compared with those in ERA-Interim and operational data (where the accumulations are from the beginning of the forecast to the validity date/time). In the short forecasts of ERA5, the accumulations are since the previous post processing (archiving), so for:
- reanalysis: accumulations are over the hour (the processing period) ending at the validity date/time
- ensemble: accumulations are over the 3 hours (the processing period) ending at the validity date/time
- Monthly means (of daily means, stream=moda/edmo): accumulations have been scaled to have an "effective" processing period of one day, see section Monthly means
Mean rate/flux parameters in ERA5 (e.g. Table 4) provide similar information to accumulations (Table 3), except that they are expressed as temporal averages, over the same processing periods, instead of accumulations, and so have units of "per second".
- Mean rate/flux parameters are easier to deal with than accumulations because the units do not vary with the processing period.
- The mean rate hydrological parameters (e.g. the "Mean total precipitation rate") have units of "kg m-2 s-1", which are equivalent to "mm s-1". If you multiply by 86400 seconds (24 hours) you will produce the commonly used units of "mm day-1".
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- For the CDS time, or validity time, of 00 UTC, the mean rates/fluxes 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/fluxes and accumulations are not available from the analyses.
- Mean rates/fluxes and accumulations at step=0 have values of zero because the length of the processing period is zero.
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- Most hydrological parameters are in units of "m of water per day", so these 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.
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(stream=oper/enda/mnth/moda/edmm/edmo, levtype=sfc)
| count | name | units | Variable name in CDS | shortName | paramId | an | fc |
| 1 | kg m**-2 s**-1 | mean_surface_runoff_rate | msror | 235020 | x | ||
| 2 | kg m**-2 s**-1 | mean_sub_surface_runoff_rate | mssror | 235021 | x | ||
| 3 | kg m**-2 s**-1 | mean_snow_evaporation_rate | mser | 235023 | x | ||
| 4 | kg m**-2 s**-1 | mean_snowmelt_rate | msmr | 235024 | x | ||
| 5 | Proportion | mean_large_scale_precipitation_fraction | mlspf | 235026 | x | ||
| 6 | W m**-2 | mean_surface_downward_uv_radiation_flux | msdwuvrf | 235027 | x | ||
| 7 | kg m**-2 s**-1 | mean_large_scale_precipitation_rate | mlspr | 235029 | x | ||
| 8 | kg m**-2 s**-1 | mean_convective_precipitation_rate | mcpr | 235030 | x | ||
| 9 | kg m**-2 s**-1 | mean_snowfall_rate | msr | 235031 | x | ||
| 10 | W m**-2 | mean_boundary_layer_dissipation | mbld | 235032 | x | ||
| 11 | W m**-2 | mean_surface_sensible_heat_flux | msshf | 235033 | x | ||
| 12 | W m**-2 | mean_surface_latent_heat_flux | mslhf | 235034 | x | ||
| 13 | W m**-2 | mean_surface_downward_short_wave_radiation_flux | msdwswrf | 235035 | x | ||
| 14 | W m**-2 | mean_surface_downward_long_wave_radiation_flux | msdwlwrf | 235036 | x | ||
| 15 | W m**-2 | mean_surface_net_short_wave_radiation_flux | msnswrf | 235037 | x | ||
| 16 | W m**-2 | mean_surface_net_long_wave_radiation_flux | msnlwrf | 235038 | x | ||
| 17 | W m**-2 | mean_top_net_short_wave_radiation_flux | mtnswrf | 235039 | x | ||
| 18 | W m**-2 | mean_top_net_long_wave_radiation_flux | mtnlwrf | 235040 | x | ||
| 19 | N m**-2 | mean_eastward_turbulent_surface_stress | metss | 235041 | x | ||
| 20 | N m**-2 | mean_northward_turbulent_surface_stress | mntss | 235042 | x | ||
| 21 | kg m**-2 s**-1 | mean_evaporation_rate | mer | 235043 | x | ||
| 22 | N m**-2 | mean_eastward_gravity_wave_surface_stress | megwss | 235045 | x | ||
| 23 | N m**-2 | mean_northward_gravity_wave_surface_stress | mngwss | 235046 | x | ||
| 24 | W m**-2 | mean_gravity_wave_dissipation | mgwd | 235047 | x | ||
| 25 | kg m**-2 s**-1 | mean_runoff_rate | mror | 235048 | x | ||
| 26 | W m**-2 | mean_top_net_short_wave_radiation_flux_clear_sky | mtnswrfcs | 235049 | x | ||
| 27 | W m**-2 | mean_top_net_long_wave_radiation_flux_clear_sky | mtnlwrfcs | 235050 | x | ||
| 28 | W m**-2 | mean_surface_net_short_wave_radiation_flux_clear_sky | msnswrfcs | 235051 | x | ||
| 29 | W m**-2 | mean_surface_net_long_wave_radiation_flux_clear_sky | msnlwrfcs | 235052 | x | ||
| 30 | W m**-2 | mean_top_downward_short_wave_radiation_flux | mtdwswrf | 235053 | x | ||
| 31 | kg m**-2 s**-1 | mean_vertically_integrated_moisture_divergence | mvimd | 235054 | x | ||
| 32 | kg m**-2 s**-1 | mean_total_precipitation_rate | mtpr | 235055 | x | ||
| 33 | kg m**-2 s**-1 | mean_convective_snowfall_rate | mcsr | 235056 | x | ||
| 34 | kg m**-2 s**-1 | mean_large_scale_snowfall_rate | mlssr | 235057 | x | ||
| 35 | W m**-2 | mean_surface_direct_short_wave_radiation_flux | msdrswrf | 235058 | x | ||
| 36 | W m**-2 | mean_surface_direct_short_wave_radiation_flux_clear_sky | msdrswrfcs | 235059 | x | ||
| 37 | W m**-2 | mean_surface_downward_short_wave_radiation_flux_clear_sky | msdwswrfcs | 235068 | x | ||
| 38 | W m**-2 | mean_surface_downward_long_wave_radiation_flux_clear_sky | msdwlwrfcs | 235069 | x | ||
| 39 | kg m**-2 s**-1 | mean_potential_evaporation_rate | mper | 235070 | x |
The mean rates/fluxes 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.
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