radiative transfer model vijay natraj
DESCRIPTION
Radiative Transfer Model Vijay Natraj. Why RADIANT?. The optical depth sensitivity of doubling The necessity of re-computing the entire RT solution if using a code such as DISORT if only a portion of the atmosphere changes - PowerPoint PPT PresentationTRANSCRIPT
Radiative Transfer Model
Vijay Natraj
Welcome-2
Why RADIANT?Why RADIANT?
The optical depth sensitivity of doublingThe optical depth sensitivity of doubling
The necessity of re-computing the entire RT The necessity of re-computing the entire RT solution if using a code such as DISORT if only solution if using a code such as DISORT if only a portion of the atmosphere changesa portion of the atmosphere changes
Goal: Employ the strengths of both while Goal: Employ the strengths of both while leaving the undesirable characteristics behindleaving the undesirable characteristics behind
Welcome-3
RADIANT: OverviewRADIANT: Overview
Plane-parallel, multi-stream RT modelPlane-parallel, multi-stream RT model
Allows for computation of radiances for user-defined Allows for computation of radiances for user-defined viewing anglesviewing angles
Includes effects of absorption, emission, and multiple Includes effects of absorption, emission, and multiple scatteringscattering
Can operate in a solar only, thermal only, or combined Can operate in a solar only, thermal only, or combined fashion for improved efficiencyfashion for improved efficiency
Allows stipulation of multiple phase functions due to Allows stipulation of multiple phase functions due to multiple constituents in individual layersmultiple constituents in individual layers
Allows stipulation of the surface reflectivity and surface Allows stipulation of the surface reflectivity and surface type (lambertian or non-lambertian)type (lambertian or non-lambertian)
Welcome-4
RADIANT: Solution MethodologyRADIANT: Solution Methodology
Convert solution of the RTE (a Convert solution of the RTE (a boundary value problem) into boundary value problem) into a initial value problem a initial value problem
Using the interaction principleUsing the interaction principle Applying the lower boundary Applying the lower boundary
condition for the scene at condition for the scene at handhand
Build individual layers (i.e. Build individual layers (i.e. determine their global determine their global scattering properties) via an scattering properties) via an eigenmatrix approacheigenmatrix approach
Combine layers of medium Combine layers of medium using adding to build one using adding to build one “super layer” describing “super layer” describing entire mediumentire medium
Apply the radiative input to Apply the radiative input to the current scene to obtain the current scene to obtain the RT solution for that scenethe 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
Welcome-5
Operational Modes: NormalOperational Modes: Normal
Welcome-6
Operational Modes: Layer SavingOperational Modes: Layer Saving
Welcome-7
Obtaining Radiances at TOAObtaining Radiances at TOA
I+(z*) = {T(0,z*)Rg[E-R(0,z*) Rg] -1T(z*,0)
+ R(z*,0) } I-(z*)
+ {T(0,z*)Rg[E-R(0,z*) Rg] –1R(0,z*)
+ T(0,z*)}agfoe-/o
+ T(0,z*)Rg[E-R(0,z*) Rg] –1S(z*,0)
+ S(0,z*)
RT Solution:
Welcome-8
Numerical Efficiency: Numerical Efficiency: Eigenmatrix vs. DoublingEigenmatrix vs. Doubling
Welcome-9
Numerical Efficiency: RADIANT vs. Numerical Efficiency: RADIANT vs. DISORTDISORT