Atmospheric Turbidity in the Polar Regions

Abstract

Analysis is presented of 800 measurements of atmospheric monochromatic aerosol optical depth made poleward of ?65° latitude. The atmosphere of the southern polar region appears to be uncontaminated but is charged with a background aerosol having a mean size of 0.1 ?m radius, an almost constant mixing ratio throughout the troposphere, a sea level optical depth (? = 500 nm) of ?0.025 and an inferred columnar mass loading of 4-15 ? 10?7 g cm?2. At around the time of spring equinox the northern polar region (all longitudes) is invaded with Arctic Haze, an aerosol showing a strong anthropogenic chemical fingerprint. The optical depth anomaly introduced by this man-caused haze is τ0 ≈ 0.110 and the associated columnar mass loading is ?1.5 ? 10?6 g cm?2. Turbidity measured seven decades ago at the solar observatory at Uppsala (60°N), suggests that Arctic optical depth has been rising at a rate of dτ/dt ≈ 0.01 ± 0.005 per decade.