Droughts part of longer trend toward more anticyclones

Droughts part of longer trend toward increasing number of anticyclones

March 6, 2013

Extensive droughts across parts of New Zealand are part of long term trend towards increased frequency of anticyclones over New Zealand, a University of Canterbury (UC) weather expert said today.

Drought has been declared in the Auckland region, Northland, Waikato, Bay of Plenty, Hawke’s Bay, Coromandel and Taupo.

UC meteorologist Professor Andrew Sturman said anticyclones are generally associated with weaker winds, clearer skies and very little rainfall.

"This increase in their occurrence fits in with observed shifts in the major atmospheric circulation zones of the southern hemisphere, which is reflected in an observed southward shift in atmospheric circulation zones.

"Because of the associated clear skies, the increase in occurrence of anticyclones is responsible not only for drier conditions in many areas, particularly in summer, but also more frosts in some parts of the country at other times of the year.

"This all illustrates how complex climate change can be globally. People are predicting a general warming trend often associated with increased storminess and rainfall in some areas. But regionally and locally the patterns can be made more complicated by New Zealand’s location relative to these major atmospheric circulation systems and the effects of our complex terrain that cause regional variations."

ENDS

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