Regionally dissected temperature and rainfall models for the South Island of New Zealand

Abstract

In this study we examine the long term temperature and rainfall trends of the South Island of New Zealand, on a regionally dissected basis. The results are reported on examination of temperature and rainfall data from the South Island of New Zealand, segmented into nine regions, broadly based on NIWA’s South Island climate zones (West Coast, Nelson, Marlborough, Canterbury and Southland). The Canterbury climate zone was split into Coastal, Foothills and Mountain regions for both North and South Canterbury. The Southland climate zone was divided into a Northern (Otago) and Southern zone for analysis. ARIMA and regression models have been developed to allow an estimation of longer term temperature and rainfall variability on a regional basis. The study identified regional differences in current and ARIMA simulated rainfall and temperature trends. Broadly, the data indicates decreasing rainfall in the Eastern coastal regions and Southland, especially in the last 35 years of observed data, with a small increase in temperature. Against this a trend of increasing rainfall was identified in the West Coast, Marlborough, Canterbury Foothills and Otago regional data. Temperature trends in these regions showed a very small increase in the West Coast temperature data, but significant increases in the remaining non-coastal regional data. The ARIMA models developed in this study were able to simulate likely temperature and rainfall variability over the next 100 years. There has been much speculation how climate change may affect the New Zealand climate: especially potential effects on agricultural production. The results of this study may be of help in putting the outputs of potential climate change scenarios in context for the New Zealand environment.