Analysis of the Composition and Direct Radiative Effects of Polluted Dust Using Satellite Observations and Reanalysis Data

Abstract. Mineral dust particles influence the global energy budget through interactions with both solar and terrestrial radiation. During long-range transport, dust can be not only externally but also internally mixed with local pollutant aerosols such as sulfate, nitrate, organic carbon, and black carbon. These physical and chemical interactions alter the optical properties of the resulting polluted dust particles, which remain a major source of uncertainty in computing the dust direct radiative effect (DRE). This study aims to quantify how pollution influences the shortwave and longwave optical properties and the direct radiative effects of dust aerosols using observational and reanalysis data. Following previous studies, a concentric spherical core-shell model is adopted to simulate the mixing state of dust-sulfate mixtures. In the urban environment, the pollutants such as sulfate and nitrate mainly originate from industrial activities. In the shortwave region, internal mixing of dust and pollution reduces the atmospheric reflectance, increases radiative absorption, resulting in a weaker enhancement of optical depth than that of external mixing. In the longwave region, internal mixing absorbs more radiation than external mixing, resulting in a stronger positive DRE. The study highlights the need for improved representation of dust–pollution mixing in climate models.