Direct beam irradiance on Mars surface normal to solar rays

Calculates the direct beam solar irradiance on the Martian surface normal to the solar rays (i.e., perpendicular to the sun's direction). Uses Beer's law to account for atmospheric attenuation. Implements Equation 14 from Appelbaum & Flood (1990).

Usage

G_b(Ls, phi = NULL, Ts = NULL, z = Z(Ls = Ls, phi = phi, Ts = Ts), tau)

Arguments

Ls

Areocentric longitude [deg]

phi

Planetary latitude [deg]. Can be NULL if z is provided

Ts

Solar time [h]. Can be NULL if z is provided

z

Sun zenith angle [deg]. If not provided, calculated from Ls, phi, and Ts

tau

Atmospheric optical depth (dimensionless)

Value

Direct beam irradiance normal to sun [W/m²]