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RADIANT: An Efficient Radiative Transfer Model for Multiple Scattering Calculations

RADIANT is a groundbreaking plane-parallel, multi-stream radiative transfer model designed to efficiently compute radiances for user-defined viewing angles while incorporating absorption, emission, and multiple scattering effects. It addresses limitations of existing methods like eigenmatrix and doubling-adding by transforming the solution of the radiative transfer equation into an initial value problem. It allows for specification of various surface types and phase functions, optimizing calculations even for optically thick layers, enhancing numerical efficiency, and providing a more accurate representation of atmospheric radiative processes.

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RADIANT: An Efficient Radiative Transfer Model for Multiple Scattering Calculations

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  1. Radiative Transfer Model Vijay Natraj

  2. Why RADIANT? • Standard methods for multiple scattering RT calculations are: • Eigenmatrix (e.g. DISORT) • Doubling-adding • Doubling methods are inefficient for optically thick layers • Eigenmatrix methods re-compute entire atmosphere even if properties change only in one layer (e.g., computing PDs) • Goal: Remove above weaknesses

  3. RADIANT: Overview • Plane-parallel, multi-stream RT model • Allows for computation of radiances for user-defined viewing angles • Includes effects of absorption, emission, and multiple scattering • Can operate in a solar only, thermal only, or combined fashion • Allows stipulation of multiple phase functions due to multiple constituents in individual layers • Allows stipulation of the surface reflectivity and surface type (lambertian or non-lambertian)

  4. RADIANT: Solution Methodology • Convert solution of the RTE (a boundary value problem) into a initial value problem • Using the interaction principle • Applying the lower boundary condition for the scene at hand • Build individual layers (i.e. determine their global scattering properties) via an eigenmatrix approach • Combine layers of medium using adding to build one “super layer” describing entire medium • Apply the radiative input to the current scene to obtain the RT solution for that scene The Interaction Principle I+(H) = T(0,H)I+(0) + R(H,0)I-(H) + S(0,H) Lower Boundary Condition: I+(0) = RgI-(0) + agfoe-/o

  5. Operational Modes: Normal

  6. Operational Modes: Layer Saving

  7. Numerical Efficiency: Eigenmatrix vs. Doubling Send to first page

  8. Numerical Efficiency: RADIANT vs. DISORT2 Show new figure

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