Does dust change the clear sky top of atmosphere shortwave flux over high surface reflectance regions?

Abstract

Using four stream radiative transfer calculations, satellite‐derived aerosol optical thickness at 558 nm and top of atmosphere (TOA) broadband radiative fluxes we examine the effect of mineral dust aerosols on the clear sky TOA shortwave (0.3–5 μm) fluxes over the Saharan desert [30E‐10W, 15N‐30N]. Over very bright surfaces (surface albedo > 35%), the TOA shortwave flux, from both satellite measurements and model calculations, is nearly insensitive to the increase in dust optical thickness. Below this surface albedo value, known as the critical albedo, mineral dust aerosols show scattering effects and above this they show absorbing effects. Therefore, over desert regions with a large range of surface albedo values, scattering and absorbing effects compensate each other thereby making the TOA shortwave aerosol radiative effect rather small.