Scene Builder

The Scene class is the central configuration object in pyRadtran. It uses an immutable, chainable API — each set_*() method returns a new Scene via copy.deepcopy() to avoid mutability traps.

Core Concepts

Immutable Builder Pattern

Every set_*() call creates a new scene. This makes it safe to reuse base configurations:

from pyradtran import Scene

base = (
    Scene()
    .set_atmosphere(profile="us")
    .set_source_solar(sza=30.0)
    .set_wavelength(250.0, 1200.0)
)

# Each of these is independent
scene_a = base.set_solver(method="disort", streams=16)
scene_b = base.set_solver(method="twostream")

Explicit Cloning

Use clone() for an explicit deep copy:

scene_copy = scene.clone()

Configuration Categories

The scene builder supports all major uvspec configuration categories:

Atmosphere

scene = Scene().set_atmosphere(profile="us", altitude=2.663)

Available profiles: "us", "ms", "mw", "tp", "ss", "sw".

Molecular Modifications

scene = scene.set_mol_modify("H2O", 10.0, "MM")  # mm precipitable water
scene = scene.set_mol_modify("O3", 300.0, "DU")  # Dobson units

Source

Solar source:

scene = Scene().set_source_solar(sza=30.0)

Thermal source:

scene = Scene().set_source_thermal()

Wavelength

scene = Scene().set_wavelength(250.0, 1200.0)

Solver

scene = Scene().set_solver(method="disort", streams=16)

Available solvers: "disort", "twostream", "rodents", "mystic", etc.

Output

scene = Scene().set_output(
    quantities=["lambda", "edir", "edn"],
    quantity="transmittance",
    format="netcdf",
)

Surface

scene = Scene().set_surface(albedo=0.2)

Aerosol

See Aerosol Models for detailed aerosol configuration.

Cloud

scene = Scene().set_cloud(
    water_file="wc.dat",
    ice_file="ic.dat",
)

Advanced Options

For options not yet covered by the Python API, use raw keywords:

scene = scene.add_raw_keyword("sza", "30.0")

Building Input

Generate the uvspec input text directly:

input_text = scene.build_input(data_files_path="/path/to/data")
print(input_text)

This is useful for debugging or when you need to run uvspec manually.