ClimaCore.jl

The dynamical core (dycore) of the CliMA Earth System Model: composable, GPU-capable tools for discretizing and solving partial differential equations on the sphere and in Cartesian domains.

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ClimaCore.jl provides the spatial discretization building blocks for the Climate Modeling Alliance (CliMA) Earth System Model, which is written entirely in Julia. It pairs a high-level API for composing differential operators and defining flexible discretizations with low-level APIs for data layouts, specialized implementations, and threading — targeting both CPU and GPU architectures from a single codebase.

Features

• Spectral-element horizontal discretizations: continuous (CG) and discontinuous (DG) Galerkin spectral elements.
• Flexible vertical discretization: staggered finite differences on center/face grids.
• Multiple geometries: Cartesian and spherical domains, with governing equations expressed in covariant vectors for curvilinear systems and Cartesian vectors for Euclidean spaces.
• Field abstraction: scalar-, vector-, or struct-valued fields carrying values, geometry, and mesh information, with flexible memory layouts (AoS, SoA, AoSoA) and useful overloads (sum, norm, ...).
• Composable operators via broadcasting: differential operators (grad, div, interpolate, ...) act like functions when broadcast over a Field, fusing operators and function calls into a single pass.
• GPU acceleration: broadcast expressions compile to custom CUDA kernels, with specialization on polynomial degree for kernel performance.
• Time-stepper compatible: works with SciML/OrdinaryDiffEq time steppers.

Quick Example

import ClimaComms
ClimaComms.@import_required_backends
import ClimaCore: Domains, Meshes, Spaces, Fields, Geometry, Operators

FT = Float64

# Build a 1D column: interval domain -> mesh -> finite-difference space
domain = Domains.IntervalDomain(
    Geometry.ZPoint{FT}(0),
    Geometry.ZPoint{FT}(2π),
    boundary_names = (:bottom, :top),
)
mesh = Meshes.IntervalMesh(domain; nelems = 128)
space = Spaces.CenterFiniteDifferenceSpace(ClimaComms.device(), mesh)

# Define a field over the space and differentiate it with a composed operator
z = Fields.coordinate_field(space).z
θ = sin.(z)
grad = Operators.GradientC2F(
    bottom = Operators.SetValue(FT(0)),
    top = Operators.SetValue(FT(0)),
)
∂θ = @. Geometry.WVector(grad(θ))   # face-valued vertical gradient (≈ cos(z))

More runnable examples (column, plane, and sphere configurations) are in the examples/ directory.

Documentation

• Stable docs — installation, introduction, mathematical framework, and API reference
• Dev docs — latest development version
• examples/ — runnable examples across geometries

Integration with CliMA models

ClimaCore.jl is the dynamical core used throughout the CliMA ecosystem, including:

• ClimaAtmos.jl — atmosphere model
• ClimaLand.jl — land model

Contributing

Contributors should follow the shared CliMA engineering standards in docs/dev-guides/, which cover architecture, performance, code quality, documentation, and workflows. These are vendored from CliMA/DeveloperGuides. The repo's AGENTS.md is a starting point for AI agents with repo-specific guidance.