29 Jul 2013

Widespread drought may become more common - NIWA

6:27 am on 29 July 2013

NIWA says the widespread summer drought that hit the entire North Island and western South Island may become more common.

A comparative study on this year's drought has confirmed it was one of the most extreme on record for New Zealand and the worst since 1945 - 1946.

It was also one of the most widespread New Zealand has experienced, with only the 1972 - 1973 drought that affected Wairarapa, Tasman, Otago and Southland coming close to its geographical spread.

The study was done by NIWA for the Primary Industries Ministry.

NIWA said what made the latest drought different from previous severe dry spells, was that it was related to persistent high pressure centres over New Zealand during summer, rather than El Nino or La Nina type weather patterns.

Principal scientist Brett Mullan said long term records indicate that trend may be increasing.

The report says a high pressure index has been developed of high pressures across New Zealand from Tasmania out to the Chatham Islands.

Dr Mullan said that was tracked through time and there is good pressure data for the past 100 years.

"And there's been a very significant increase in high pressures in the summer time over the past 100 years, like all climate features it jumps around, up and down, but there's a strong trend towards increasing high pressures in the summer."

Dr Mullan said the climate models are also predicting this will happen in the future.

He said widespread droughts of that nature restrict the ability of farmers to shift stock to other parts of the country or find stock feed.