Relative humidity dependence of light absorption by mineral dust after long‐range atmospheric transport from the Sahara

The relative humidity (RH) dependence of light absorption for a Saharan dust‐dominated air mass transported to the Gulf of Mexico was measured during the 2006 TexAQS/GoMACCS study using a photo‐acoustic absorption spectrometer (PAS). Aerosol absorption was measured at low (25%) and high (73%) RH indicating a 1.5(±0.3) absorption enhancement [f(RHAbs)] under high RH conditions. f(RHAbs) estimates, based on air‐mass physical and optical properties and Mie theory modeling, were between 1.2–1.4. Reasons for differences between the measured and modeled f(RHAbs) are discussed. The mass absorption coefficient of the long‐range transported dust was calculated to be 0.04(±0.02) m2g−1.