...
| Info | ||||
|---|---|---|---|---|
| ||||
|
| Note |
|---|
To generate this ERA5 hourly time series dataset, homogenisation conventions have been applied to the ERA5 source GRIB data to ensure consistency, usability, and alignment across chosen variables and time steps. The processed data were then written to an ARCO Zarr archive, enabling efficient cloud-optimised access and scalable data retrieval. Please see details below. The dataset presented here is a subset of selected parameters from the full CDS ERA5 pressure levels hourly dataset. Requirements for additional parameters may be considered. Please raise your request with ECMWF Support here. |
Introduction
...
Introduction
ERA5 is the fifth generation ECMWF reanalysis for the global climate and weather and currently covers the past 80 years. It covers the period from January 1940 to the present with hourly sampling and continues to be extended forward
...
with
...
5 days behind real time.
The
...
ERA5 Analysis Ready Cloud Optimised (ARCO) data on pressure levels presented here is a 6-hourly subset
...
of some parameters and pressure levels of the full Climate Data Store (CDS) ERA5 pressure levels hourly dataset on 0.25 degrees resolution and is stored
...
in a ARCO format. It allows direct access to a subset of the pressures variables (see below) without downloading individual files, enabling efficient and scalable data access and retrieval. The ARCO format has a dual-chunking approach which means that data access can be optimised for retrieving long-time periods for a limited area (geo-chunked) or short-time period for large areas (time-chunked).
Methodology
...
| Excerpt |
|---|
The process to generate this dataset involves:
|
Data organization and access
The ARCO data is stored as Zarr datacubes to provide efficient access to time-chunked and geo-chunked ERA5 single level hourly data:
| Variable set (Item) | Chunking strategy (Asset) | URL for Zarr datacube |
|---|---|---|
Pressure levels (Table 1) | Geo-chunked | https://arco. |
...
| Info | ||
|---|---|---|
| ||
Access to ARCO data is programmatic; therefore, users of these resources and this documentation are expected to have some relevant programming experience. |
The Zarr datacubes can now be accessed using your CDS API key. Below is a simple plug-and-play code snippet and a more detailed Jupyter Notebook example. For more detailed and advanced access examples, please refer to the main Analysis Ready Cloud Optimised (ARCO) Data.
| Code Block | ||||
|---|---|---|---|---|
| ||||
import xarray as xr
# Geo-chunked data for access optimised along the time dimension (e.g. for time-series at a single point)
# Pressure
pressure_geo_url = "https://arco.datastores.ecmwf.int/cadl-arco-geo-048/arco/reanalysis_era5_pressure_levels/pl/geoChunked.zarr"
# Time-chunked data for access optimised along the time dimension (e.g. for time-series at a single point)
# Pressure
pressure_time_url = "https://arco.datastores.ecmwf.int/cadl-arco-time-048/arco/reanalysis_era5_pressure_levels/pl/timeChunked.zarr"
# Open one of the Zarr objects with xarray, the default example opens the geo-chunked surface variables
ds = xr.open_zarr(
surface_geo_url,
consolidated=True,
storage_options={
"headers": {"Authorization": f"Bearer <CDS-API-KEY>"}
}
)
# Inspect the variables
print(ds) |
| Expand | ||||||
|---|---|---|---|---|---|---|
| ||||||
|
Time-series access via the CDS
The ERA5
The data is now available from the Climate Data Store (CDS), either interactively through its download web form or programmatically using the CDS API service:
ERA5 hourly time-series data on pressure levels from 1940 to present catalogue entry allows users to download long time series for a single-point or limited area via the CDS download webform or a CDS API request that users can build from the webform. The data download via the time-series entry is as described below with additional aspects:
Note Please be aware when you select a "Location" on the form, the latitude and longitude values are rounded to the closest neighborhood point of the 0.25 degrees grid. Similarly, selecting an “Area” returns all points within the region defined by the nearest neighborhood corner points to the user-specified S, W, N, and E latitude/longitude values (maximum 5° x 5°).
- The download form allows users to select a choice of netCDF or CSV. The conversion is done directly with xarray with no additional processing from the Zarr description above.
- Given the computational cost of writing to csv, users are limited to smaller downloads with this option.
- The surface and single level parameters (Table 1) and the wave parameters (Table 2) are in different Zarr stores, therefore they will be served in different output files.
| Note |
|---|
The entry may be temporarily disabled or completely deprecated at any point and it does not come with the same level of operational support as the parent entry. Additionally, the formats and structure of the data files are subject to change. |
Spatial grid
The pressure levels parameters have a grid of 0.25 degrees.
| Note |
|---|
Please be aware when you select a "Location" on the form, the latitude and longitude values are rounded to the closest neighborhood point of the degrees grid. Similarly, selecting an “Area” returns all points within the region defined by the nearest neighborhood corner points to the user-specified S, W, N, and E latitude/longitude values. |
Temporal frequency
Temporal frequency of the data is 6-hourly at 00:00 , 06:00, 12:00, 18:00 UTC.
Data
...
The format options available on the CDS are netCDF format or CSV format.
...
update frequency
ERA5 is updated on a daily basis. New daily data in ERA5 becomes available in ERA5 Time Series in a few hours.
| Note |
|---|
Variations in delivery times may occur due to the non-operational nature of this CDS service, as issues may arise which cause delays. |
Level list
The levels available in the files are: 50, 100, 150, 200, 250, 300, 400, 500, 600, 700, 850, 925, 1000 hPa.
Parameters listings
Table 1 below lists the pressure levels parameters.
Table 1: pressure levels parameters
| Name | Units | Variable name | Notes | |
|---|---|---|---|---|
| 1 | Geopotential | m2 s-2 | geopotential | |
| 2 | Specific humidity | kg kg-1 | specific_humidity | |
| 3 | Temperature | K | temperature | |
| 4 | U component of wind | m s-1 | u_component_of_wind | |
| 5 | V component of wind | m s-1 | v_component_of_wind | |
| 6 | Vertical velocity | Pa s-1 | vertical_velocity |
Known issues
Please refer to the ERA5 documentation.
References
Further ERA5 references are available from the ECMWF website.
| Info | ||
|---|---|---|
| ||
This document has been produced in the context of the Copernicus Climate Change Service (C3S). The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view. |
Related articles
| Content by Label | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|