CopernicusClimateDataStore.jl

🌍 Julia interface to the Copernicus Climate Data Store for downloading ERA5 reanalysis data

CopernicusClimateDataStore.jl wraps the era5cli command-line tool, providing a convenient Julia interface for downloading ERA5 hourly and monthly data to NetCDF or GRIB.

Installation

using Pkg
Pkg.add("CopernicusClimateDataStore")

Before you start

You need a Copernicus Climate Data Store account:

1. Create an account at https://cds.climate.copernicus.eu/
2. Accept the ERA5 Terms of Use at https://cds.climate.copernicus.eu/datasets/reanalysis-era5-single-levels
3. Configure your API key:

   era5cli config --key YOUR_PERSONAL_ACCESS_TOKEN

Your personal access token is on your CDS profile page.

Quick start

Download and visualize 2-metre temperature over Europe:

using CopernicusClimateDataStore
using NCDatasets
using CairoMakie

files = hourly(variables = "2m_temperature",
               startyear = 2020,
               months = 6,
               days = 21,
               hours = 12,
               area = (lat = (35, 70), lon = (-15, 40)),
               outputprefix = "europe")

# Load the data
ds = NCDataset(first(files))
λ = ds["longitude"][:]         # degrees East
φ = ds["latitude"][:]          # degrees North
T = ds["t2m"][:, :, 1] .- 273.15  # K → °C
close(ds)

# Plot
fig, ax, hm = heatmap(λ, φ, T; colormap = :thermal)
Colorbar(fig[1, 2], hm; label = "Temperature (°C)")
ax.xlabel = "λ (°E)"
ax.ylabel = "φ (°N)"
save("temperature.png", fig)

This will produce

Key arguments

Argument	Description
variables	Variable name, e.g. "2m_temperature", "total_precipitation"
startyear	Year to download (required)
months	Month or months (1–12)
days	Day or days (1–31)
hours	Hour or hours (0–23)
area	Bounding box: (lat = (south, north), lon = (west, east))
format	"netcdf" (default) or "grib"
outputprefix	Prefix for output filename
merge	Merge all data into a single file (default: false)

By default, one file is created per month. Use merge = true for a single file.

Common variables

Request name	NetCDF name	Description
2m_temperature	t2m	2-metre temperature (K)
10m_u_component_of_wind	u10	10-metre zonal wind (m/s)
10m_v_component_of_wind	v10	10-metre meridional wind (m/s)
total_precipitation	tp	Total precipitation (m)
mean_sea_level_pressure	msl	Mean sea level pressure (Pa)

See the CDS ERA5 documentation for a complete list.