Figure 3.1: Observed New Zealand national-average temperature (top; in °C) and Southerly Index (bottom; in hPa)
Return to the point in the document where this figure is located.
Text description of figure
The upper panel in this figure displays the year-to-year variability of the New Zealand national-average temperature for the period from 1908 to 2006. Data are shown as departures from the 1980-1999 climatological period.
Superimposed on these departures is a smoothed line to indicate the long-term trend. There is a steady increase in the New Zealand temperature series since 1908 of nearly one tenth of a degree Celsius per decade. However year-to-year changes in temperatures can be substantially larger than the 1908-2006 trend, with fluctuations up to plus or minus one degree Celsius about the long-term average.
The lower panel in this figure displays the Annual Southerly Index (or Trenberth M1 Index). Periods when the figure indicates more northerly winds than climatology generally match with relatively warm years in the upper panel. Superimposed on the index values is a smoothed curve showing decadal M1 variations and highlighting the trend towards more southerly airflow since the mid-1950s.
