Study of the sensitivity of optical properties of mineral dust to the direct aerosol radiative perturbation using a global aerosol transport model

The sensitivity of optical properties of mineral dust aerosol to its direct radiative effect was investigated using four dust optical datasets (ADEC-1, ADEC-2, OPAC-MD and Dust-Like) with a global aerosol transport model. The annual and global mean direct aerosol radiative perturbation (DARP) by dust at the top of the atmosphere (TOA) can be positive or negative (-0.52 to +0.11 Wm^-2) depending on the absorptive property of dust aerosol dataset. The annual and global mean DARP at the surface is negative for all the dust optical datasets (-1.25 to -0.27 Wm^-2). If dust is strongly absorptive, DARP at the TOA over oceans at high latitude (> 40°) is positive due to the vertical configuration of dust and clouds. The longwave heating at the surface is strong and can exceed the shortwave cooling over desert regions if the absorption of dust is weak. Over a surface with high dust loading, the annual mean shortwave (longwave) DARP can reach -28 Wm^-2 (+16 Wm^-2). The global mean DARP values both at the TOA and surface are almost proportional to the imaginary part of the refractive index of dust. Seasonal variations of global mean DARP at the TOA significantly depend on the optical properties of dust.