def refractivity_dry_nondispersive(ν, θ, pd, e):
    """Complex refractivity due to dry airnondispersive term.

    ν       GHz     frequency at which refractivity is evaluated
    θ       -       reciprocal temperature
    pd      hPa     pressure of dry air
    e       hPa     pressure of water vapor

    Liebe et al. (1993).
    """
    return 0.2598e-6 * pd * θ