Aerosol optical characteristics in the urban area of Rome, Italy, and their impact on the UV index

Abstract. The impact of the aerosol optical properties on ultraviolet index (UVI) in urban area Rome is investigated this study. In particular, influence depth (AOD) and single scattering albedo (SSA), estimated at wavelength 340 nm, Ångström exponent, calculated range 340–500 over a period 11 years (2010–2020) months from March to September are analyzed. UVI monitored by Brewer spectrophotometer, whereas measurements direct Sun diffuse sky irradiances performed co-located PREDE-POM sun–sky radiometer ESR/SKYNET network; obtained Skyrad MRIv2 retrieval. A novel method, based physical principles easily adaptable other contexts, developed extrapolate UV during periods when only visible near-infrared available. retrievals consistent with chemical characterization PM10 (particulate matter 10 mm or less diameter) samples collected an intensive field campaign held summer 2011 same site (URBan Sustainability Related Observed Monitored Aerosol – URBS ROMA). PM macro components identified grouped order evaluate contribution main sources (soil, sea, secondary inorganic, organics, traffic) whose relative role indeed expected strongly affect absorption capability. surface forcing efficiency, as change for unit AOD variation, shows that primary parameter affecting irradiance under clear-sky conditions Rome. SSA exponent also influencing factors, i.e., efficiency found be greater smaller zenith angles larger more absorbent particles (such as, e.g., mineral dust).