ALG allows coupling the OPAC v3.1 aerosol database with MODTRAN5. This coupling allows higher versatility on defining additional aerosol types by introducing as MODTRAN inputs the aerosol optical properties (i.e., extinction coefficient, single scattering albedo and asymmetry parameter) of OPAC aerosols. This process is automatic and transparent to the user.
When selecting aerosol models as Key Input Variables in the LUT, the user will have available the RTM default aerosol models (IHAZE for MODTRAN) and the OPAC aerosol models (AERTYPE). Among them, the User-defined (OPAC) option allows users to introduce a larger number of discrete aerosol types.
After introducing the User-defined (OPAC) as one of the aerosol model values, a window will pop-up allowing users to configure the user-defined aerosols in terms of their basic components (PARTYPE).
Here, the user can select one or more OPAC basic aerosol components (up to 5) from the menu at the left. For each of selected component, their default minimum and maximum
number-density values (in cm-3) will then be visible and editable (first and second column on the table at the right). After introducing the number of aerosol mixtures (N)
on the corresponding text block and clicking on the mix particles button (or press ↵), ALG will randomly generate N new aerosol
mixtures with the selected components and particle densities uniformly distributed between the min/max values.
This process can be repeated as many times as desired with various aerosol components and particle density values.
The user can manually modify the values in each cell of the table and, eventually, delete an aerosol mixture (one at a time) by clicking on any cell of the desired aerosol and pressing the Delete aerosol button.
The user can remove one or more of these parameters from the table by selecting them () and pressing the Remove button.
Also, the introduced variable values can be editted on the corresponding Values cell on the table. Notice here that the values must be comma-separated.
After pressing the Accept button, the new aerosol mixtures will be added on the Key Input Variables table. These user-defined OPAC aerosols will have a numeric value ≤ -11.
Further information about user-defined OPAC aerosol parameters and refractive indices can be found in (Hess et al., 1998) and (Koepke et al., 2015).
Hess, M., Koepke, P., & Schult, I. (1998), "Optical properties of aerosols and clous: the software package OPAC." Bulletin of the Americal Meteorologic Soctiety. Vol. 79, No. 5, pp. 831‒ 844.
Koepke, P., Gasteiger, J., & Hess (2015), "Technical Note: Optical properties of desert aerosol with non-spherical mineral particles data incorporated to OPAC." Atmos. Chem. Phys.. Vol. 15, No. 5, pp. 5947‒ 5946.