Sunday, July 3, 2022

Worst drought in 70 years

A comparative study on the 2013 drought released today by the Ministry for Primary Industries (MPI) confirms it was one of the most extreme on record for New Zealand and the worst since 1945-46. The 2013 drought was also one of the most widespread New Zealand has experienced with only the drought of 1972-73 that affected Wairarapa, Tasman, Otago and Southland coming close to its geographical spread. The Ministry for Primary Industries (MPI) confirms the 2013 drought was one of the most extreme on record for New Zealand and the worst since 1945-46. The report states that the cause of the drought was not El Niño but in fact slow-moving or ‘blocking’ high pressure systems over the Tasman Sea and New Zealand over summer. Commissioned by MPI and undertaken by NIWA, the study looked at two sets of data records – NIWA’s gridded Virtual Climate Station Network that goes back to 1972, and longer-term station records that go back to the early 1940s. Calculations of a drought index known as potential evapotranspiration deficit (PED) which measures estimates of soil water content showed that 2013 was the worst drought since 1972, and particularly serious for the North Island. The longer-record station calculations indicate that in some regions it was the most severe drought since 1945-46. The areas most affected by the 2012-13 drought were southern Northland, Auckland, Waikato, Bay of Plenty, Central North Island, Gisborne, Hawke’s Bay, Wairarapa, and parts of the north and west of the South Island. NIWA principal scientist Brett Mullan says the July 2012-May 2013 PED accumulation was the worst since 1972 over one-third of the North Island. “Previous severe droughts occurred in 1972-73 and 1997-98, both El Niño years. This latest drought was different, being related to persistent high pressure centres over New Zealand during summer – a trend that is increasing according to century-long pressure
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