ERA5(T) Rectangular Grid

Winds @ 100m

Introduction

"ERA5(T) Rectangular Grid" provides the most up-to date ERA5 data in windPRO - and it includes the preliminary ERA5T data. This dataset is a part of the ERA5 data offerings in windPRO - now with two datasets on two different geographical grids - rectangular and gaussian. Both datasets hold a focused climate-data parameter subset of the ERA5 data with each dating back more than 20 years. "ERA5(T) Rectangular Grid" data provides a seamless merge of the ERA5 and ERA5T, with ERA5T being preliminary data for ERA5. Data available in windPRO are updated two times 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; this dataset is now named ERA5 Gaussian Grid. These original, first ERA5 data is based on model output from a reduced gaussian grid. This grid has been a recommended, first choise for many modellers and analysts. Unfortuantely, the newly released ERA5T data from december 2019 (preliminary data, but updated with a shorter delay), is currently unavailable for the reduced gaussian grid. As such, ERA5T data is currently only offered by ECMWF on an interpolated, rectangular geographical grid in a 0.25x0.25 degree resolution. As we undertand it, this is due to current technical limitations in the data-distribution systems at ECMWF and CDS. The windPRO "ERA(T) Rectangular Grid" dataset is created in order to provide the most recent and up-to-date data windPRO - with both ERA5T data and ERA5 included.

Performance: "ERA5 Gaussian Grid" vs "ERA5(T) Rectangular Grid
EMD has benchmarked the two datasets: the native "ERA5 Gaussian Grid" and the interpolated "ERA5/5T (Rectangular Grid)" to investigate any performance differences in the two quite simmilar 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 show, that the two datasets correlate equaly well against the local meteorological mast data - with a very slight advantage to the interpolated "ERA5(5) 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 ERA5T. ERA5T 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.

Table: Overview of the windPRO subset of ERA5 parameters.

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: 
ERA5/5T (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.

External Links

• ECMWF - What is ERA5 - https://software.ecmwf.int/wiki/display/CKB/What+is+ERA5
• ERA5 Data Documentation at ECMWF - https://software.ecmwf.int/wiki/display/CKB/ERA5+data+documentation
• Copernicus Climate Change Service - ERA5 Page - https://climate.copernicus.eu/products/climate-reanalysis
• Release note for ERA5T data - https://confluence.ecmwf.int/display/CUSF/Release+of+ERA5T