Radiative Transfer Model Vijay Natraj

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

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

Welcome-4 RADIANT: Solution Methodology Convert solution of the RTE (a boundary value problem) into a initial value problem Convert solution of the RTE (a boundary value problem) into a initial value problem Using the interaction principle Using the interaction principle Applying the lower boundary condition for the scene at hand Applying the lower boundary condition for the scene at hand Build individual layers (i.e. determine their global scattering properties) via an eigenmatrix approach 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 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 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) = R g I - (0) + a g f o e -  /  o

Welcome-5 Operational Modes: Normal

Welcome-6 Operational Modes: Layer Saving

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

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