Optical properties of aerosols: southern Mexico City

measurements of aerosol absorption (σa) and scattering (σs) at wavelengths of 550 nm and 530 nm, respectively, and particle (0.01 to 3 μm) concentration were obtained in south of méxico city (19° 21' 00'' n, 99° 09' 42'' w and 2276 masl) during dry (february-may) and rainy (june-august) seasons of 2005. the averages over the sampling days of each month for σa presented small variations on each season, ranging from 20 to 29.4 mm-1 and from 12 to 14.7 mm-1 in dry and rainy seasons, respectively. however, σs values varied notoriously, from 78.1 to 93.3 mm-1 in dry season, compared with 20.6 to 35.5 mm-1 during rainy season. the single scattering albedo (ssa) average was 0.82 during dry season while in the rainy season it was slightly lower, that is 0.68. these data are useful in atmospheric photochemistry studies where aerosol effects are considered.