Visibility calculation

[Will H]

Has anyone ever come up with a way to calculate visibility?

I have a python calculation I stumbled upon but I'm not sure if it is valid:

    # Extract necessary variables with their respective units
    q_rain = wrf.getvar(wrf_file, "QRAIN")[0,:,:]  # Mixing ratio for rain (kg/kg)
    q_snow = wrf.getvar(wrf_file, "QSNOW")[0,:,:]  # Mixing ratio for snow (kg/kg)
    q_graupel = wrf.getvar(wrf_file, "QGRAUP")[0,:,:]  # Mixing ratio for graupel (kg/kg)
    pressure = wrf.getvar(wrf_file, "PSFC")  # Surface pressure (Pa)
    temperature = wrf.getvar(wrf_file, "T2")  # 2-meter temperature (K)
    R = 287.05  # Specific gas constant for dry air, J/(kg·K)

    # Calculate air density (kg/m³)
    rho = pressure / (R * temperature)

    # Constants for extinction coefficients calculation
    visfactor = 3.912  # Extinction coefficient to visibility conversion factor (dimensionless)
   
    # Calculate mass concentration from mixing ratios and density (convert to g/m³)
    br = 1.1 * (1000 * rho * (q_rain + q_graupel))**0.75  # Rain and graupel extinction coefficient (m⁻¹)
    bs = 10.36 * (1000 * rho * q_snow)**0.78  # Snow extinction coefficient (m⁻¹)

    # Calculate extinction coefficient (m⁻¹) and visibility (m)
    hydro_ext_coeff = (br + bs) / 1000  # Total hydrometeor extinction coefficient (m⁻¹)
    vis_hydro = np.where(hydro_ext_coeff > 0, visfactor / hydro_ext_coeff, 999999.0)  # Visibility in meters
    vis_hydro_miles = vis_hydro * 0.000621371  # Convert visibility to miles