New Zealand national climate summary 2010: Settled and warm.
Annual mean sea level pressures were above average over the New Zealand region in 2010. The increased prevalence of anticyclones (‘highs’) near New Zealand produced a relatively settled climate for the year overall, with average or above average annual temperatures in all regions, normal or above normal sunshine hours in most districts, and drought at either end of the year.
The large-scale climate setting changed from a moderate El Niño at the start of the year, to a La Niña by July. The La Niña climate pattern intensified to moderate-to-strong by September, and prevailed through the end of 2010. The Southern Annular Mode (SAM), a climate pattern affecting the westerly wind strength and location over and to the south of the country, was strongly positive overall in 2010. This contributed to the prevalence of anticyclones experienced near New Zealand.
Mean annual temperatures were above average (between 0.5°C and 1.2°C above the long-term average) in the northeast of the North Island, and in Nelson, Marlborough, parts of Canterbury, Fiordland and parts of Westland, the southern Lakes District and central Otago. Mean annual temperatures were near average elsewhere (within 0.5°C of the long-term average). The national average temperature for 2010 based on a 7-station series was 13.1 °C, 0.5 °C above the 1971–2000 annual average. 2010 was the 5th warmest year since 1900, based on this 7-station series. The four warmer years were 1971 (+0.6 °C), 1998 (+0.9 °C), 1999 (+0.8 °C), and 2005 (+0.6 °C).
In broad terms, six months of the year were wetter than normal and six were drier than normal (with clear geographical exceptions). The net result was that annual rainfall totals for 2010 as a whole were in the near normal range (80 to 119 percent of normal) across most of the country. The exceptions were eastern parts of the North Island (specifically Coromandel, parts of the Bay of Plenty, Gisborne, Hawke’s Bay, and Wairarapa), Blenheim, parts of North Canterbury and southwest Fiordland, which experienced above normal annual rainfall (with totals more than 120 percent of normal). In contrast, areas of Northland, Auckland and Waikato, Otago, the Lakes District and parts of the West Coast and Buller recorded below normal annual rainfall totals (between 50 and 85 percent of normal).
It was a sunny year in the west, both in the North Island, and in the west and south of the South Island. It was the sunniest year on record for Te Kuiti, since records began there in 1962. Whakatane was the sunniest location in 2010, recording 2561 hours, followed by Nelson (2474 hours) and Blenheim (2415 hours).
Notable climate features of 2010 (in various parts of the country) included two droughts, several heat waves, and three significant rainfall events. Drought was declared in January in Northland, and in Auckland, Waikato, Bay of Plenty, South Taranaki, South Canterbury and Otago in April. The drought broke in May, only to be declared again in December in Northland, Waikato and Ruapehu. Heat waves affected the West Coast at the end of January, Central Otago on 8–9 March, and numerous locations on 28–30 November and 12–15 December. Exceptionally heavy rain occurred on 31 January in the northeast North Island; widespread heavy rain and flooding occurred in the southwest South Island from 25–27 April, resulting in flood-threshold levels of Lake Wakatipu; and a sustained period of heavy rain during 24–30 May in the eastern South Island caused numerous floods, slips, road and property damage. On December 28, heavy rain, flooding and high winds caused havoc for many areas of the country.
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Dr James Renwick, NIWA Principal Scientist, Climate Variability & Change Tel 04 386 0343 mobile 021 178 5550
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