Scale the aerosol optical depth using the Ångström formula:

\tau=\beta\lambda^{{-\alpha}} (1)

where \lambda is in units of micrometer Angstrom1929. Specify the Ångström alpha and beta coefficients by  

aerosol_angstrom alpha beta

 
The optical thickness defined here is the integral from the user-defined altitude to TOA (top of atmosphere).