pratmo

pratmo rewrites the original Fortran 77 model in Rust and exposes it through a command-line runner and a typed Python/NumPy interface. The project aims to preserve the original model structure while making the code easier to test, inspect, and embed. It also adds an experimental inorganic iodine mechanism that is not present in PRATMO v6.0.

Implementation tests and selected numerical comparisons with the compiled Fortran program are included, but these are software consistency checks—not scientific validation of the Rust rewrite, its inputs, or its predictions.

Features

• Rust model core with structured CTM steady-state and full DIURN-cycle APIs.
• Python package named pratmo, with typed configuration objects and NumPy arrays for profiles, grids, coordinates, time series, and diagnostics.
• 40 implicit gas-phase species and 19 long-lived species or chemical families.
• Experimental inorganic iodine chemistry, including ten iodine species, iodine photolysis, higher iodine oxides, and heterogeneous recycling.
• Standard atmospheres, custom atmospheric profiles, configurable aerosol and sea-salt surface areas, and observation-constrained NO2 workflows.
• Compatibility paths for the original fixed-format inputs and legacy CLI outputs, plus opt-in tooling for numerical comparisons with Fortran.
• Runnable CTM, DIURN, iodine, custom-atmosphere, and OMPS batch examples.

The iodine mechanism's assumptions and known omissions are documented in Iodine chemistry.

Python quickstart

The published distribution and import name are both pratmo. To install a released wheel:

python -m pip install "pratmo[plot]"

For development, build the extension into the project environment:

uv sync --dev
uv run maturin develop --release

Run a CTM altitude profile with runnable, validated defaults:

from pratmo import Model
from pratmo.plotting import plot_profile

model = Model()
output = model.ctm(latitude=60.0, day="2026-03-16")

print(output.altitude_km)
print(output.species_profile("o3"))       # cm^-3
print(output.long_lived_profile("noy"))  # dimensionless mixing ratio
plot_profile(output, ["o3", "no2", "oh"]).show()

Atmosphere accepts pressure, temperature, altitude, ozone, and aerosol profiles with explicit units. Helpers such as ppmv(5), ppbv(300), pressure(values, "Pa"), and number_density(values, "m-3") keep conversions visible. Suspicious values emit PratmoWarning; inconsistent profiles raise ValueError before integration.

The lower-level PratmoModel, CtmConfig, and DiurnConfig API remains available. The package also exposes IMPLICIT_SPECIES_NAMES, LONG_LIVED_NAMES, and JVALUE_NAMES for discovery. See the rendered Python guide and examples for CTM, DIURN, custom-atmosphere, and observation-constrained workflows.

Rust and CLI

cargo build --workspace
cargo run -p pratmo-cli -- --input-dir fortran

pratmo-core provides the structured Rust API. pratmo-cli preserves the original file-based workflow and writes Fortran-compatible output files into the selected input directory.

Development verification

These checks test software behavior and selected Fortran agreement. Passing them does not mean that the model is scientifically validated.

Run the normal development checks with:

cargo fmt --all -- --check
cargo clippy --workspace --all-targets --all-features -- -D warnings
cargo test --workspace
cargo test --workspace --all-features
uv run pytest
uv run sphinx-build -W --keep-going -b html docs docs/_build/html

GitHub Actions runs these Rust checks, the Python tests, a strict documentation build, and the complete cross-platform wheel build on every push and pull request. Built distributions are retained as workflow artifacts. The publish job runs only for release tags matching v* and uses PyPI Trusted Publishing. The extension uses PyO3's Python 3.9 stable ABI, so each platform build produces one cp39-abi3 wheel compatible with Python 3.9 and newer.

The clean-room compiled-Fortran differential is available separately:

scripts/fortran_differential.sh

The detailed numerical comparisons, parity policy, and unsupported legacy modes are tracked in STATUS.md and FORTRAN_PARITY.md. Release procedures and archived implementation notes are separated under developer documentation.

Current boundaries

• DERIVS sensitivity mode and PZSTD conversion are rejected explicitly.
• The original multi-case Fortran driver loop is not implemented.
• Full CTM climatology-grid coverage remains broader than the comparison fixture.
• The iodine extension has mechanism-level tests but no Fortran reference and has not been scientifically validated.

License

pratmo is available under the MIT License.