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Created by
Michela Giusti, last updated on Mar 24, 2026
3 minute read
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
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 in time with a latency of 5 days behind real time.
The time-series dataset presented here contains a 6-hourly subset of a few selected variables from the full CDS ERA5 pressure levels hourly dataset and is stored in Analysis Ready Cloud Optimised (ARCO) format, which has been implemented for retrieving long time-series for a single point in a efficient way.
Methodology
The process to generate this dataset involves:
- Fetching ERA5 Pressure Levels data in GRIB format.
- Applying homogenization conventions, as applicable:
- Ensure latitude, longitude ranges are between [-90, +90], [-180, +180].
- Rename vertical dimension to pressureLevels, to homogenize all parameters.
- Leave only essential coordinates latitude, longitude, time and pressureLevels.
- Writing to an ARCO Zarr archive (which is similar in structure to netCDF).
- The CDS requests the data from the Zarr archive using xarray and writes the data to netCDF or CSV (as requested).
Data organization and access
The ARCO data is stored as Zarr datacubes.
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
Spatial grid
The pressure levels parameters have a grid of 0.25 degrees.
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 format
The format options available on the CDS are netCDF format or CSV format.
Data update frequency
ERA5 is updated on a daily basis. New daily data in ERA5 becomes available in ERA5 Time Series in a few hours.
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.
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