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Major modification in progress for this article - please DO NOT UPDATE THIS PAGE or your edits will get overwritten when the new modified article will be published. Please edit the working copy of this page in the C3S Modified CKB articles section |
Introduction
Here we document the ERA5-Land dataset that, which in its consolidated version,covers the same period as ERA5, from January 1950 to 2-3 months before the present. In In addition, the facility to deliver ERA5-Land-T versiondelivers non-checked close to Near-Real-Time (NRT) updates is being implemented and it will be made available shortly. This daily updates. ERA5-Land NRT facility (hereafter called ERA5-LandT) will be synchronized with those of ERA5 -T is synchronized with the close to NRT daily updates provided by the ERA5 climate reanalysis (ERA5T).
ERA5-Land is a replay of the land component of the ERA5 climate reanalysis, forced by meteorological fields from ERA5. Note that ERA5-Land always uses forcing fields based on the final release of ERA5 (i.e., expver=0001). ERA5-Land comes with a series of improvements making it more accurate for all types of land applications. In particular, ERA5-Land runs at enhanced resolution (9 km vs 31 km in ERA5). The temporal frequency of the output is hourly and the fields are masked for all oceans, making them lighter to handle. Click this link here for comparison of the ERA5-Land features against other ECMWF reanalyses.
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Currently, the data can only be downloaded on a regular latitude/longitude grid of 0.1°x0.1° via the CDS catalogue. In the near future the data will also be made available Users with access to the ECMWF Meteorological Archival and Retrieval System (MARS) can also retrieve the data in the native grid.
NOTE: Please, note that since 1st Jan 2020 the new ECMWF Meteorological Interpolation and Regridding interpolation package (MIR) has been used to interpolate the atmospheric forcing of ERA5 into the ERA5-Land grid. While this change will be unnoticeable for the overwhelming majority of users, locally and under very limited conditions (some areas with high orography, some coastal points) some fields may suffer of a very small discontinuity this day.
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Data organisation and access
The The full ERA5-Land and ERA5-Land-T data are archived in the ECMWF data archive (MARS) and the data have been copied to the Climate Data Store (CDS). The ERA5-Land (or recent ERA5-Land-T) data should be downloaded using the using the CDS catalogue or the CDS API, which can obtain data from the CDS copy or from MARS (Member State users can access the data using MARS directly, in the usual manner). Documentation on how to use the CDS API to download ERA5-Land data can be found found here. The installation and downloading steps are similar to those of ERA5.
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For sub-daily data for the HRES (stream=oper) the parameters labelled as analyses (type=an) are available hourly. The once daily short forecasts, run from 00 UTC, also provide data hourly, with steps from 01 to 24. The uncertainty is currently provided by ERA5 EDA fields, which are available every 3 hours for the surface fields.
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Data update frequency
Initial release data, i.e. data with just a few days behind real time, is called ERA5-Land-T. Both for the CDS and MARS, daily updates for ERA5-Land-T are available about 5 days behind real time and monthly mean updates are available about 5 days after the end of the month.
The daily updates for ERA5-Land-T data on the CDS occur at no fixed time during the day.
For the CDS, ERA5-Land-T data for a month is overwritten by the final ERA5-Land data about two months after the month in question.
For MARS, the final ERA5-Land data are available about two months after the month in question. In addition, the last few months of data are kept online and can be accessed much quicker than older data on tape.
In the event that serious flaws are detected in ERA5-Land-T, the latter could be different to the final consolidated ERA5-Land data. Based on experience with the production of ERA5-Land so far, our expectation is that such an event would occur only when a flaw in the atmospheric forcing (from ERA5) is detected, and the expectation is that the latter occur only on rare occasions.
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Please, note that the convention for accumulations used in ERA5-Land differs with that for ERA5. The accumulations in the short forecasts of ERA5-Land (with hourly steps from 01 to 24) are treated the same as those in ERA-Interim or ERA-Interim/Land, i.e., they are accumulated from the beginning of the forecast to the end of the forecast step. For example, runoff at day=D, step=12 will provide runoff accumulated from day=D, time=0 to day=D, time=12. The maximum accumulation is over 24 hours, i.e., Please, note that the convention for accumulations used in ERA5-Land differs with that for ERA5. The accumulations in the short forecasts of ERA5-Land (with hourly steps from 01 to 24) are treated the same as those in ERA-Interim or ERA-Interim/Land, i.e., they are accumulated from the beginning of the forecast to the end of the forecast step. For example, runoff at day=D, step=12 will provide runoff accumulated from day=D, time=0 to day=D, time=12. The maximum accumulation is over 24 hours, i.e., from day=D, time=0 to day=D+1,time=0 (step=24).
- HRES: accumulations are from 00 UTC to the hour ending at the forecast step
- For the CDS time, or validity time, of 00 UTC, the accumulations are over the 24 hours ending at 00 UTC i.e. the accumulation is during the previous day
- Synoptic monthly means (stream=mnth): accumulations have units of "variable_units per forecast_step hours"
- Monthly means of daily means (stream=moda): accumulations have units that include "per day", see section Monthly means
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=D+1,time=0 (step=24).
- HRES: accumulations are from 00 UTC to the hour ending at the forecast step
- For the CDS time, or validity time, of 00 UTC, the accumulations are over the 24 hours ending at 00 UTC i.e. the accumulation is during the previous day
- Synoptic monthly means (stream=mnth): accumulations have units of "variable_units per forecast_step hours"
- Monthly means of daily means (stream=moda): accumulations have units that include "per day", see section Monthly means
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In addition to the sub-daily data, all ERA5-Land parameters are also available as monthly means. Monthly means are available in two forms:
- Synoptic monthly means, for each particular time and forecast step (stream=mnth) - 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) - in the CDS, referred to as "monthly averaged". These monthly means are created from the hourly data for the HRES.
Monthly means for:
- parameters labelled as analyses or instantaneous forecasts are created from data with a valid time in the month, between 00 and 23 UTC on each day of the month.
- accumulations are created from data with a forecast period falling within the month. Monthly means of daily means for accumulations are created from the last forecast step (24) of the forecasts for each day of the month.
The accumulations in monthly means of daily means (stream=moda) have units that include "per day". So for accumulations in this stream:
- The hydrological parameters are in units of "m of water equivalent per day" and so they should be multiplied by 1000 to convert to kgm-2day-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.
The accumulations in synoptic monthly means (stream=mnth) have units that include "variable_units per forecast_step hours
In addition to the sub-daily data, all ERA5-Land parameters are also available as monthly means. Monthly means are available in two forms:
- Synoptic monthly means, for each particular time and forecast step (stream=mnth) - 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) - in the CDS, referred to as "monthly averaged". These monthly means are created from the hourly data for the HRES.
Monthly means for:
- parameters labelled as analyses or instantaneous forecasts are created from data with a valid time in the month, between 00 and 23 UTC on each day of the month.
- accumulations are created from data with a forecast period falling within the month. Monthly means of daily means for accumulations are created from the last forecast step (24) of the forecasts for each day of the month.
The accumulations in monthly means of daily means (stream=moda) have units that include "per day". So for accumulations in this stream:
- The hydrological parameters are in units of "m of water equivalent per dayforecast_step hours" and so they should be multiplied by 1000 to convert to kgm-2day-1 or mmday-1 per forecast_step hours or mm per forecast_step hours.
- The energy (turbulent and radiative) and momentum fluxes should be divided by 86400 seconds (24 hours) 60 x 60 x fc_step to convert to the commonly used units of Wm-2 and Nm-2, respectively.
The accumulations in synoptic monthly means (stream=mnth) have units that include "variable_units per forecast_step hours". So for accumulations in this stream:
- The hydrological parameters are in units of "m of water equivalent per forecast_step hours" and so they should be multiplied by 1000 to convert to kgm-2 per forecast_step hours or mm per forecast_step hours.
- The energy (turbulent and radiative) and momentum fluxes should be divided by 60 x 60 x fc_step to convert to the units of Wm-2 and Nm-2, respectively.
Data format
Surface fields in ERA5-Land are encoded either in GRIB1 or GRIB2 format. Tables 1 and 2 indicate the format for all parameters in ERA5-Land. Note that the retrieval of the data in NetCDF format is still possible via the CDS.
Data format
Surface fields in ERA5-Land are encoded either in GRIB1 or GRIB2 format. Tables 1 and 2 indicate the format for all parameters in ERA5-Land. Note that the retrieval of the data in NetCDF format is still an option available via the CDS.
The article "What are GRIB files and how can I read them" might be helpful.
For GRIB format, ERA5-Land-T data can be identified by the key expver=0005 in the GRIB header. Consolidated ERA5-Land data is identified by the key expver=0001.
For netCDF data requests which return just ERA5-Land or just ERA5-Land-T data, there is no means of differentiating between ERA5-Land and ERA5-Land-T data in the resulting netCDF files.
For netCDF data requests which return a mixture of ERA5-Land and ERA5-Land-T data, the origin of the variables (1 or 5) will be identifiable in the resulting netCDF files. See this link for more details applied to ERA5 dataThe article "What are GRIB files and how can I read them" might be helpful.
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