ASTMX

Angstrom exponent

Attributes

float | continuous | dynamic | unit-less | medium

Description

The variable ASTMX defines the spectral dependence of the aerosol extinction coefficient through the Ångström approximation (Ångström, 1908):

$$ε_k(λ)=ε_k(λ_0){(λ_0/λ)^α}$$

where εk is the extinction coefficient, λ0 if a reference wavelength (typically 550 nm) and α is the Ångström exponent.

Thus, this variable has an impact on the absorption and scattering effects caused by aerosols.

For typical aerosols, $α$ values range from 1 to 2 (Holben et al., 1998, Hess et al., 1998, Dubovik et al., 2002). If ASTMX=0 (default value) , MODTRAN will use the spectral dependency of the aerosol extinction coefficient from the aerosol model selected in IHAZE.

References