Top-Level API

These are the functions and types most users call directly after using vSmartMOM. They load a scene, construct an RT model, run the solver, and select the compute architecture.

Scene Loading

vSmartMOM.IO.read_parameters Function

read_parameters(x)

Multi-dispatch convenience wrapper:

• String (file path) → parameters_from_file

• IOSource → parameters_from_source

• Dict → parameters_from_dict

• vSmartMOM_Parameters → pass-through

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vSmartMOM.IO.parameters_from_file Function

parameters_from_file(path::AbstractString) -> vSmartMOM_Parameters

Load a registered configuration file and return a fully populated vSmartMOM_Parameters object.

The file format is selected by extension through the Formats.load_config registry. Built-in extensions are .yaml, .yml, and .toml. The loaded document must contain the same parameter schema accepted by parameters_from_dict.

Arguments

• path::AbstractString: Path to a registered configuration file.

Returns

• params::vSmartMOM_Parameters{FT}: Parsed parameter struct ready for model_from_parameters.

Example

using vSmartMOM
params = parameters_from_file("config/my_scene.toml")
params.architecture = vSmartMOM.Architectures.CPU()
model = model_from_parameters(params)

See also

• parameters_from_source for typed sources such as GEOS-Chem NetCDF.

• parameters_from_dict for loading from an in-memory Dict.

• parameters_from_yaml for the legacy YAML-specific wrapper.

• model_from_parameters to build the RT model.

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vSmartMOM.IO.parameters_from_source Function

parameters_from_source(src::Formats.IOSource) -> vSmartMOM_Parameters

Load parameters from a typed IO source.

This is the extension point for non-file or domain-specific inputs: implement Formats.load_config(src::MySource) to return a configuration Dict, then parameters_from_source(src) will reuse the shared parameter parser.

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vSmartMOM.IO.parameters_from_dict Function

parameters_from_dict(params_dict::Dict) -> vSmartMOM_Parameters

Convert a configuration Dict (e.g., loaded from YAML) into vSmartMOM_Parameters. Validates schema and parses radiative_transfer, geometry, atmospheric_profile, and optional absorption/scattering sections.

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vSmartMOM.IO.parameters_from_yaml Function

parameters_from_yaml(path::AbstractString) -> vSmartMOM_Parameters

Compatibility wrapper for YAML parameter files.

New code should prefer parameters_from_file, which also supports TOML and any future registered file formats.

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vSmartMOM.CoreRT.default_parameters Function

Generate default set of parameters for Radiative Transfer calculations (from ModelParameters/)

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Model Construction and Solver Entry Points

vSmartMOM.CoreRT.model_from_parameters Function

model_from_parameters(params::vSmartMOM_Parameters) -> RTModel

Construct an RTModel from user-supplied vSmartMOM_Parameters.

Computes all derived quantities needed by the RT solver:

• Observation geometry and quadrature points

• Rayleigh scattering coefficients (Greek/Cabannes)

• Aerosol optics via Mie theory with δ-M truncation

• Gas absorption cross-sections and optical depth profiles

• Per-band Fourier truncation limits

Arguments

• params::vSmartMOM_Parameters: Configuration struct (typically from parameters_from_yaml).

Returns

• model::RTModel{ARCH, FT}: Hierarchical model ready for rt_run(model).

See also

• model_from_parameters(LinMode(), params) for the linearized (Jacobian) variant.

• parameters_from_yaml(path) to load parameters from a YAML file.

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Take the parameters specified in the vSmartMOM_Parameters struct, and calculate derived attributes into an RTModel

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model_from_parameters(::LinMode, params::vSmartMOM_Parameters)

Construct both the forward RTModel and the linearized RTModelLin objects from the input parameters, for use in linearized (Jacobian) RT computations.

This is the linearized counterpart of model_from_parameters(params). It computes:

1. Forward optical properties (same as the forward-only model):

• Rayleigh optical depth per layer and spectral point.

• Aerosol optical properties (via Mie theory) with δ-M truncation.

• Trace gas absorption cross-sections and optical depths.

2. Linearized optical properties (derivatives of the above):

• τ̇_aer[iB][iaer, 7, nSpec, nLayers]: Derivatives of aerosol τ w.r.t. 7 sub-parameters [τ_ref, nᵣ, nᵢ, rₘ, σᵣ, p₀, σp] per aerosol type.

• τ̇_abs[iB][NGas, nSpec, nLayers]: Derivatives of gas absorption τ w.r.t. VMR.

• lin_aerosol_optics[iB][iaer]: Derivatives of Mie properties (ω̃, fᵗ, greek coefficients) w.r.t. Mie parameters [nᵣ, nᵢ, rₘ, σᵣ].

Returns

• model::RTModel: Forward model (optical properties, geometry, quadrature).

• lin_model::RTModelLin: Linearized model (all derivative arrays).

Notes

• The atmospheric profile may be truncated to the observer altitude for tower/airborne sensors.

• Aerosol Mie calculations use ForwardDiff.Dual numbers to simultaneously obtain derivatives of the extinction cross-section, single-scattering albedo, truncation factor, and greek coefficients with respect to [nᵣ, nᵢ, rₘ, σᵣ].

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vSmartMOM.CoreRT.rt_run Function

rt_run(model::RTModel; i_band=1) -> (R, T, ...)

Run the forward radiative transfer solver for one or more spectral bands.

Performs polarized adding-doubling RT through the atmosphere defined in model, computing top-of-atmosphere (TOA) reflectance and bottom-of-atmosphere (BOA) transmittance. The solver iterates over azimuthal Fourier moments m = 0, …, max_m-1, building layer R/T/J matrices via elemental → doubling → interaction steps, then applies surface coupling and postprocessing.

Equivalent to rt_run(noRS(), model, i_band) (no Raman scattering).

Arguments

• model::RTModel: Pre-built model from model_from_parameters.

• i_band::Integer=1: Spectral band index (or vector of indices) to compute.

Returns

A tuple (R_SFI, T_SFI, ieR_SFI, ieT_SFI, hdr, bhr_uw, bhr_dw) when using source-function integration (default), where:

• R_SFI::Array{FT,3}: TOA reflectance [nVZA × nStokes × nSpec]

• T_SFI::Array{FT,3}: BOA transmittance [nVZA × nStokes × nSpec]

For most use cases, only the first two elements are needed:

R, T = rt_run(model)

Example

params = parameters_from_yaml("config/my_scene.yaml")
model = model_from_parameters(params)
R, T = rt_run(model)
R[1, 1, :]  # Stokes-I reflectance at first VZA across the spectrum

See also

• rt_run(model, lin_model, NAer, NGas, NSurf) for linearized RT with Jacobians.

• model_from_parameters to build the model from parameters.

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rt_run(RS_type, model::RTModel, iBand; sources=nothing)

Perform Radiative Transfer calculations with explicit Raman type.

Accepts an optional sources::AbstractSource argument (v0.6 source-term refactor, Phase 2). When nothing, the legacy F₀ default is preserved bit-for-bit. When a SourceSet (or a single AbstractSource) is supplied, the F₀ carried by the first SolarBeam is routed into RS_type.F₀ ahead of the existing SFI kernel call. Phase 5 will remove the RS_type.F₀ indirection.

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Architectures

vSmartMOM.Architectures.CPU Type

CPU <: AbstractArchitecture

Run on a single-core of a CPU.

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vSmartMOM.Architectures.GPU Type

GPU <: AbstractArchitecture

Run on a single NVIDIA CUDA GPU.

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vSmartMOM.Architectures.MetalGPU Type

MetalGPU <: AbstractArchitecture

Run on an Apple Silicon GPU through Metal.jl. Metal support is loaded through the optional vSmartMOMMetalExt package extension and requires Float32 arrays. The current Metal batched inverse path uses a conservative 32 KiB threadgroup memory guard, so large stream/Stokes matrices should use CPU or CUDA until a global-memory fallback lands.

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vSmartMOM.Architectures.default_architecture Function

default_architecture()

Return GPU() if CUDA is available, MetalGPU() if Metal is available, and otherwise CPU().

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vSmartMOM.Architectures.array_type Function

array_type(arch::AbstractArchitecture)

Return the array constructor for the given architecture (Array for CPU, CuArray for CUDA GPU, and MtlArray for MetalGPU when the matching optional backend extension is loaded).

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Return the array constructor for the model's architecture

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