A study of atmospheric circulation over the South Island of New Zealand (1961-1980)
A subjective synoptic classification scheme is used to examine atmospheric circulation over the South Island. Daily surface isobaric charts have been categorised for twenty years (1961-1980) and monthly circulation indices derived. Both data sets are used to describe general characteristics of atmospheric circulation over the South Island, particularly the annual regime and circulation variability over the twenty years. Anticyclonic circulation and gradient winds from one of the westerly directions clearly dominate, with anticyclonic southwesterly being the most frequent type in all seasons. Evidence of biennial, annual and semi-annual variations is given by the derived circulation indices. Distinct fluctuations of atmospheric circulation are identified over the twenty years, complementing results of previous research.