Ocean warming likely to alter regional rainfall

April 14th, 2010  |  by  |  Published in Research News

climage change map

Patterns of sea surface temperature warming and precipitation change in 2050 as compared with 2000. Annual mean precipitation change is shown in green/gray shade and white contours in mm/month. Precipitation tends to increase over regions with ocean warming above the tropical mean (contours of warm colors), and to decrease where ocean warming is below the tropical mean (contours of cool colors).

Climate models project an increase of more than 1 degree centigrade in global average surface temperatures by the middle of the century. However, actual change in ocean surface temperatures will vary by region, according to a team of scientists headed by meteorologist Shang-Ping Xie at the University of Hawaiʻi at Mānoa’s International Pacific Research Center.

That could cause significant changes in rainfall patterns in the tropics and subtropics, the scientists write in the February Journal of Climate.

They analyzed warming projections in models used by the Intergovernmental Panel on Climate Change, and two patterns stood out.

  • In the Pacific, a temperature maximum emerges as a broad band across the equator. By changing atmospheric heating along the equator, this warming pattern sustains a rainband similar to that during El Niño, influencing climate around the world through large-scale, long-term atmospheric teleconnections.
  • In the Indian Ocean, a pattern emerges during part of the year that is like the Indian Ocean Dipole, which occurs every decade or so today. The resulting dramatic shift in rainfall would bring droughts to Indonesia and Australia and increased rainfall in India and regions of Africa bordering the Arabian Sea.

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