GREBClimate.jl

A Julia translation of the Globally Resolved Energy Balance (GREB) climate model, originally developed by Dietmar Dommenget and colleagues at Monash University.

The model simulates the global energy balance on a 3.75° × 3.75° grid (96 longitudes × 48 latitudes), stepping every 12 hours with 30-minute sub-steps for atmospheric circulation (730 time steps per year).

Features

Global grid resolution: 96×48 (longitude × latitude)
12-hour main time steps with 30-minute sub-steps for circulation
Support for multiple climate datasets (NCEP, ERA-Interim)
Future climate scenarios (RCP 2.6, 4.5, 6.0, 8.5)
Orbital forcing and paleoclimate experiments
SIMD-vectorized physics kernels (LoopVectorization.@turbo)

Installation

Requires Julia 1.10 (the current LTS) or later, matching the julia = "1.10" compat bound in Project.toml.

using Pkg
Pkg.develop(url = "https://github.com/EnvDroneSense/GREBClimate.jl")

Or, working from a clone:

julia --project=.
using Pkg; Pkg.instantiate()

Input data

The model reads a JLD2 dataset - climatology, flux corrections, solar forcing and scenario tables - laid out under a single directory. At ~439 MB it is not shipped with the package; greb_data_dir fetches and caches it on first use via DataDeps.jl:

dir    = greb_data_dir()
fields = load_greb_jld2!(dir; dataset = :ncep)

Resolution order - only the last step touches the network:

an explicit path, greb_data_dir("/path/to/greb_input_data")
ENV["GREB_DATA"]
greb_input_data/ beside the package
the GREB-input-data DataDep (~353 MB download, SHA256-verified)

load_greb_jld2! returns the loaded state; it does not populate globals. The returned value must be handed to greb_model! as fields = ..., which refuses to run on an unloaded ClimateFields rather than silently producing a meaningless ≈233 K world. The Tutorial walks through this.

Non-interactive sessions

Set DATADEPS_ALWAYS_ACCEPT=true to skip the download consent prompt. In CI or any session without a terminal this is required - otherwise the process blocks waiting on stdin. DATADEPS_DISABLE_DOWNLOAD=true makes a would-be download throw instead.

Regenerating the dataset from the original GREB .bin files is a maintainer task, not a prerequisite for using the package; see DATA_README.md and tools/ in the repository.

See the Tutorial for a runnable end-to-end example, or the API Reference for every exported function and type.

An interactive alternative

The repository also ships an interactive Pluto.jl notebook (notebooks/GREB_explorer.jl) with widget-driven experiment configuration - useful for exploration. It is a front-end onto the same package; this documentation covers the plain-Julia API it calls.