Total surface spectral irradiance (T, red line), ratios of direct and diffuse irradiances to T, B/T (blue line) and D/T (green line), and ratio of T to the irradiance at the TOA, T/E (black line), between 200 and 1100 nm for clear (left) and dusty (right) conditions. Simulations run for ϕ = 0°, L _s  = 270°, τ _ca,12.1  = 0.02,  μm-atm, at local noon.