RELATIONSHIPS BETWEEN NEW-ZEALAND RAINFALL AND SOUTH-WEST PACIFIC PRESSURE PATTERNS

The relationships between New Zealand regional rainfall and south-west Pacific pressure patterns are investigated. Principal components of m onthly sea-level pressure are computed from 14 Australasian climate st ations and interpreted as physical features of the circulation near Ne w Zealand. Monthly rainfall data at eight New Zealand locations are re gressed against these components revealing significant relationships, although the percentage of explanation seldom exceeds 50%. At almost a ll New Zealand locations the dominant pressure-rainfall relationship i s that with the first principal component. The physical interpretation of this component varies slightly from month to month, however, in ge neral it represents the strength of prevailing westerlies or south-wes terlies over New Zealand, as described by the location and intensity o f regions of high pressure. Other principal components relate to the d irection of airflow over New Zealand, to which rainfall at some statio ns is very sensitive. The relationships described in this paper furthe r advance the understanding of the large-scale processes that contribu te to the weather and climate of New Zealand. (C) 1998 Royal Meteorolo gical Society.