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) m(2)g(-1). Citation: Lack, D. A., et al. (2009), Relative humidity dependence of light absorption by mineral dust after long-range atmospheric transport from the Sahara, Geophys. Res. Lett., 36, L24805, doi:10.1029/2009GL041002.