ccrtm: ccrtm: Coupled Chain Radiative Transfer Models.

In MarcoDVisser/ccrtm: Coupled Chain Radiative Transfer Models

ccrtm: Coupled Chain Radiative Transfer Models.

Description

A collection of radiative transfer models that can form a coupled chain to model radiative transfer across multiple spatial scales from leaf to canopy to stand.

Details

Currently implemented models that can be coupled:

• 1 = PROSPECT 5, 5B and D

• 2 = FOURSAIL, and FOURSAIL2

• 3 = FLIM

Currently being tested / or to be implemented models

• 1 = LIBERTY, PROCOSINE

• 2 = INFORM*

*available as lower-level library (see ccrtm github page).

Generating predictions

To generate model prediction the typical approach is to use the fRTM function and apply a formula that specifies the both the expected output (left hand) and the different models you would like to couple to generate the output (right hand).

At current the following radiative transfer models, and corresponding formula, are given in the next table

Example of a formula	Model
rho ~ prospect5	prospect5
rho ~ prospectd	prospectd
rho ~ prospect5 + foursail	PROSAIL
rho ~ prospect5 + foursail	PROSAIL
rho ~ prospectd + foursail2	PROSAIL
rho ~ prospectd + prospect5 + foursail2	PROSAIL2
rho ~ prospectd + foursail2b	PROSAIL2b
rho ~ prospectd + foursail + flim + sky	INFORM*
rho ~ prospectd + foursail + flim	INFORM*

*INFORM is currently restricted to a lower-level function only. See the cctrm github readme page on how to use it.

In the above examples, prospectd can be replaced with prospect5

• or vice versa - if so desired.

Also, note that the formula "rho ~ prospectd + foursail2" is the same as "rho ~ prospectd + prospectd + foursail2" and both expect a names list of 3 parameter vectors.

See the help files for details on each right hand component. For instance, ?foursail provides more elaboration on the 4SAIL model and gives an example for lower-level implementations of each component model. See also ?flim, ?foursail2, ?foursail2b, ?prospect5, and ?prospectd.

Tranmission can also be returned if specified in the left-hand component of the formula:

Formula	Model
rho + tau ~ prospect5	prospect5
rho + tau ~ prospectd + foursail	4SAIL

The examples above indicate that the users wishes to predict transmission next to reflectance. More specifically, The first returns leaf reflectance and transmission while the second returns 4 components of canopy reflectance and canopy transmission in the solar and viewing direction.

PROSAIL and diffuse and direct light

In contrast to some FORTRAN and MATLAB implementation, the sky light model is not implemented by default in ccrtm. This is because it is not a standard component of 4SAIL. In addition, this would affect limit the application of other more realistic atmospheric models. You can apply it by using ?skyl on model output obtained from fRTM (see example in ?skyl). The sky light model is implemented for the INFORM model as per March 2022.

Parameters

Parameters are given as input to fRTM as a named list. See ?getDefaults for examples on how to structure parameters. Individual models can consulted on each parameter (e.g. see ?foursail2b or ?prospect5).

Leaf inclination models.

Canopy models such as foursail use leaf inclination models. In cctrm four inclination models are implemented. see ?lidf for more details.

Author(s)

Marco D. Visser

MarcoDVisser/ccrtm documentation built on Feb. 19, 2025, 1:15 p.m.