Title: Radiative Transfer Model
1Radiative Transfer Model Vijay Natraj
2Why 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 - Goal Employ the strengths of both while leaving
the undesirable characteristics behind
3RADIANT 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 for improved efficiency - 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)
4RADIANT 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
5Operational Modes Normal
6Operational Modes Layer Saving
7Obtaining Radiances at TOA
RT Solution
I(z) T(0,z)RgE-R(0,z) Rg -1T(z,0)
R(z,0) I-(z)
T(0,z)RgE-R(0,z) Rg 1R(0,z)
T(0,z)agfoe-?/?o
T(0,z)RgE-R(0,z) Rg 1S(z,0)
S(0,z)
8Numerical Efficiency Eigenmatrix vs. Doubling
9Numerical Efficiency RADIANT vs. DISORT