ERA5(T) Rectangular Grid
Introduction
"ERA5(T) Rectangular Grid" is the most up-to date ERA5 data in windPRO, provided by a seamless merge of the ERA5 data and the preliminary ERA5(T) data. Both datasets hold a focused climate-data parameter subset of the ERA5 data with each dating back more than 20 years and the data available in windPRO are updated twice a month. For a general introduction to the ERA5 data in windPRO along with validation reports, please refer to our ERA5 Gaussian Grid wiki-page.
Why an additional "ERA5 Rectangular Grid" dataset in windPRO?
The first ERA5-based dataset in windPRO was released in summer 2017 and now named ERA5 Gaussian Grid. The original ERA5 data is based on model output from a reduced gaussian grid, which has been a recommended first choise for many modellers and analysts. Unfortuantely, the newly released ERA5(T) data from December 2019 (preliminary data, but updated with a shorter delay) is currently unavailable for the reduced gaussian grid. As such, ERA5(T) data is currently only offered by ECMWF on an interpolated, rectangular geographical grid in a 0.25x0.25 degree resolution. From our understanding, it is due to current technical limitations in the data-distribution systems at ECMWF and CDS. The windPRO "ERA5(T) Rectangular Grid" dataset is created in order to provide the most recent and up-to date data in windPRO - with both ERA5 data and ERA5(T) included.
Performance: "ERA5 Gaussian Grid" vs "ERA5(T) Rectangular Grid
EMD has benchmarked the two datasets: the native "ERA5 Gaussian Grid" and the interpolated "ERA5(T) Rectangular Grid" to investigate any performance differences in the two quite similar datasets. The benchmark is made against high-quality wind-speed data from more than 300 tall meteorological masts with a global distribution. As the evaluation-metrics, we consider the wind-speed corelation (R2) at different averaging times: hourly, daily and monthly. Our benchmark shows, that the two datasets correlate equaly well against the local meteorological mast data, with a slight advantage to the interpolated "ERA5(T) Rectangular Grid" dataset - see the table below. Since small differences are seen, we do not recommend to mix ERA5 data originating from different grids as inconsistencies then might occur.
Dataset Overview
- Content:: Renewable energy focused data subset of ERA5 and ERA5(T). ERA5(T) data is flagged - see the paramateter list below.
- Spatial Resolution: The dataset grid derived from an interpolated, regular geographical (lat/lon) grid at 0.25x0.25 resolution (around 27.8 km).
- Temporal Resolution: Hourly values.
- Coverage: Coverage is global for land-areas and coastal regions. In windPRO, offshore coverage is at a distance of approximately 300 km from any known coastlines.
- Period: 30+ years. The EMD databases will hold data back to 1988.
- Update schedule:
- Currently, EMD plans to update the dataset twice a month - with data being aviailable with a one week delay from real-time. The first update will be around the 8th of a month - here all data from the previous month will be available. The second update will be around the 23rd of a month - here the first half of the month will be available.
- Once the final ERA5 data becomes available (after 2-3 months) the dataset will be updated with that data. According to ECMWF they do not expect changes to happen very often - and in the event that it does happen - it will be communicated to users. At EMD we will communicate any such changes to the windPRO users as well.
Data Parameters
EMD extracts a focused subset of climate-parameters from the ERA5 datasets - with special emphasis on renewable energy and wind-energy modelling. When the data have been processed at EMD, then the following parameters are available from within the online-data services within windPRO.
| Parameter | Unit | Description |
|---|---|---|
| time | UTC time stamp | |
| wSpeed.10 | m/s | Wind speed @ 10m |
| wDir.10 | deg | Wind direction @ 10m |
| wSpeed.100 | m/s | Wind speed @ 100m |
| wDir.100 | deg | Wind direction @ 100m |
| temperature.2 | deg.celcius | Temperature @ 2m |
| dewPointTemp.2 | deg.celcius | Dew point temperature @ 2m |
| rh.2 | % | Relative humidity @ 2m |
| psfc | pa | Surface pressure |
| msl | pa | Mean sea-level pressure |
| blh | m | Boundary layer height |
| tcc | % | Total cloud cover |
| heatFlux | w/m2 | Instantaneous surface sensible heat flux |
| zust | m/s | Friction velocity |
| cbh | m | Cloud base height |
| ssrdAcc | w/m2 | Surface solar radiation downwards |
| era5t | 0/1 | Binary variable indicating whether the sample is ERA5T data |
Required Modules/Licenses
To access the ERA5 reanalysis data from within windPRO - the following licenses/modules are required in your windPRO setup:
- Basis
- METEO
When the license fee is paid, you then have access to the full dataset without further cost. Downloading of data is unrestricted for licenced users with an active service subscription, however, a "fair use" policy applies. Visit EMD online ordering to purchase the needed licences.
Attribution
If data from this dataset is used within any private or public disseminations, then EMD and its data providers must be acknowledged.
Source: ERA5(T) Rectangular Grid. Distribution through EMD and windPRO - EMD International A/S, 2020. This dataset uses ERA5 and ERA5T which is being developed through the Copernicus Climate Change Service (C3S). Data processing and distribution for ERA5 is carried out by ECMWF.