Aerosols affect atmospheric circulation

CANBERRA, Australia, Jan. 15 (UPI) -- Australian researchers have confirmed the theory that human-generated aerosols are affecting atmospheric circulation trends in the Southern Hemisphere.

Although most human-generated aerosols are located in the Northern Hemisphere, the new study led by Wenju Cai and Tim Cowan of Australia's Commonwealth Scientific and Industrial Research Organization showed in response to rising aerosol concentrations, the Southern Hemisphere's ocean circulation intensifies and shifts poleward.

The researchers analyzed data from two sets of 20th century simulations in a coupled ocean-atmosphere global climate model and discovered that, as a result of the poleward shift in oceanic circulation, maximum sea surface temperatures, mid-latitude storms, and the westerly jet shift southward.

They found the shift in air circulation intensifies the trend of the Southern Annular Mode -- a low-frequency pattern of atmospheric variability near Antarctica -- causing a poleward shift and intensification in zonal wind and vertical velocities generated from the atmosphere-ocean interface to the middle of the troposphere.

Those atmospheric circulation responses, in turn, reinforce the ocean circulation changes, the researchers said, suggesting a contribution by human-generated aerosols to the observed trend of the Southern Annular Mode.

The study is detailed in the journal Geophysical Research Letters.