Downloading ERA5 Forecasts

Important

From September 26, 2024, the legacy CDS and legacy ADS were decommissioned and are no longer accessible. CDS-Beta and ADS-Beta have officially become the new CDS and the new ADS. The new CDS and ADS also use an updated GRIB to netCDF conversion, which changes both the formatting and the variable/dimension names of the downloaded files.

As of EarthSHAB v2.0, this new post-September-2024 CDS NetCDF *is* the canonical format (see Canonical NetCDF Forecast Schema v2). Raw downloads from the current CDS load directly with no conversion step. Only pre-September-2024 ERA5 archives (and any older “processed” intermediates) need a one-time conversion with python -m EarthSHAB.forecast_processing.migrate_v1 — see the migration guide. The ERA5-Utils toolkit remains useful for downloading complete ERA5 reanalysis (more pressure levels) via API.

Overview

ERA5 is ECMWF’s fifth-generation global atmospheric reanalysis dataset, providing hourly estimates of atmospheric variables from 1979 to present.

Reanalysis combines numerical weather prediction models with observational data to produce a physically consistent estimate of the atmosphere over time. ERA5 is the standard benchmark for historical analysis and trajectory simulations.

ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) is accessed via the Copernicus Climate Data Server.

Required Variables

EarthSHAB requires the following variables across all pressure levels:

  • Geopotential (z)

  • U-component of wind (u)

  • V-component of wind (v)

  • Temperature (t)

Note

ERA5 data is available at hourly resolution, which provides finer temporal fidelity than GFS (typically 3-hour intervals).

Let’s say you want data over the Hawaiian Islands for January 1-2, 2021, then a typical selection would look like:

../_images/era5_data_selection.png ../_images/era5_data_selection2.png

Be sure to select NetCDF as the download format to use with EarthSHAB. (On the current CDS this is the standard NetCDF option; the post-September-2024 layout it produces is the v2 canonical format EarthSHAB reads directly.)

The data download request is then added to a queue and can be downloaded a later time (typically only takes a few minutes). Save the netcdf reanalysis file to the forecast directory and feel free to rename the file to something more useful.

Note

ECMWF reanalysis data is available every hour unlike GFS which is avilable in 3 hour increments.

The download option will look like the following:

../_images/era5_download.png