# =============================================================================
# atmorad simulation configuration file
# =============================================================================

[metadata]
experiment_name = "demo001"
description     = "a demo simulation of radiative transfer over a heterogeneous surface."

[engine]
random_seed                   = 42
num_photons                   = 400_000
batch_size                    = 100_000  # photons per simulation chunk
roulette_weight_threshold     = 1e-4
roulette_survival_probability = 0.1      # 10% chance to survive with 10x multiplied weight
num_threads                   = 4
resume_from_checkpoint        = false

[source]
zenith_angle_deg  = 30
azimuth_angle_deg = 0
wavelength_nm     = 530  # only for reference, wavelength-dependent parameters not implemented yet

[domain]
size_x_km          = 100
size_y_km          = 100
boundary_condition = "periodic"

# -----------------------------------------------------------------------------
# active detectors (comment out a block to deactivate)
# -----------------------------------------------------------------------------

[detectors.energy_budget]

[detectors.trajectories]
max_tracked_paths = 200

[detectors.flux_profile]
vertical_resolution_km = 0.1

[detectors.absorption_profile]
vertical_resolution_km = 0.2

[detectors.flux_maps]
horizontal_resolution_km = 2.1
z_levels_km              = [0.0, 4.0, 10.0]

[detectors.surface_absorption_map]
horizontal_resolution_km = 2.1

[output]
save_plots = true
overwrite  = true
base_dir   = "results"
fig_dir    = "plots"

# -----------------------------------------------------------------------------
# material types and properties
# -----------------------------------------------------------------------------

[surface_materials.snow]
albedo = 0.85
brdf   = { type = "lambertian" }

[surface_materials.ocean]
albedo = 0.01
brdf   = { type = "specular", roughness = 0.0 }

[atmosphere_materials.air]
extinction_coeff_per_km = 0.01  # optical density
ssa                     = 0.999
phase_function          = { type = "rayleigh" }

[atmosphere_materials.light_clouds]
extinction_coeff_per_km = 1.0
ssa                     = 0.999999  # negligible absorption
phase_function          = { type = "hg", g = 0.85 }  # g > 0 means forward scattering

[atmosphere_materials.dark_clouds]
extinction_coeff_per_km = 5.0
ssa                     = 0.999999
phase_function          = { type = "hg", g = 0.85 }

# -----------------------------------------------------------------------------
# atmospheric layers (bottom to top)
# -----------------------------------------------------------------------------

[[layer]]
thickness_km = 2.0
components   = { air = 1.0 }

[[layer]]
thickness_km = 4.0
components   = { air = 1.0, dark_clouds = 0.9 }  # { material: extinction coefficient multiplier }

[[layer]]
thickness_km = 4.0
components   = { air = 1.0 }

# -----------------------------------------------------------------------------
# surface map configuration (choose one by uncommenting)
# -----------------------------------------------------------------------------

# [surface]
# type     = "uniform"
# material = "snow"

[surface]
type         = "circle"
radius_km    = 20.0
material_in  = "snow"
material_out = "ocean"

# [surface]
# type           = "split_half_x"
# material_left  = "snow"
# material_right = "ocean"

# [surface]
# type         = "checkerboard"
# tile_size_km = 10.0
# material_a   = "snow"
# material_b   = "ocean"

# -----------------------------------------------------------------------------
# scenarios and sweeps (batch experiments)
# -----------------------------------------------------------------------------

# scenario overrides: each block runs a separate simulation
# [[scenario]]
# name    = "checkerboard-surface"
# surface = { type = "checkerboard", tile_size_km = 10.0, material_a = "snow", material_b = "ocean" }

# [[scenario]]
# name               = "less-photons"
# engine.num_photons = 50_000
# engine.batch_size  = 12_500

# multiple sweep blocks are combined using a cartesian product
# [[sweep]]
# parameter = "source.zenith_angle_deg"
# values    = [0, 15, 30, 45, 60]

# [[sweep]]
# parameter = "source.azimuth_angle_deg"
# values    = [0, 45, 90, 135, 180]

import xarray as xr

# open NetCDF file
ds = xr.open_dataset("results/demo001/atmorad_demo001_baseline.nc", engine="h5netcdf")

# access arrays
map_2d = ds["surface_absorption_map"].values
flux_profile = ds["flux_down_profile"].values

# access scalars
total_reflected_energy = ds["energy_toa_outgoing"].item()
total_absorbed_surf = ds["energy_surface_absorbed"].item()

# access attributes
num_photons = ds.attrs["num_photons"]
sim_time = ds.attrs["simulation_time_s"]
active_detectors = ds.attrs["active_detectors"]

Or via atmorad:

from atmorad import load
ds = load("results/demo001/atmorad_demo001_baseline.nc")

Extracting configuration file from results

Each data .nc file contains configuration data used to run the simulation. You can extract it by running:

atmorad --extract-config <path-to-data.nc>

This creates an <exp_name>_<scen_name>_config.toml file in the current working directory.