Some aspects of the distribution of frost over New Zealand
Aspects of the spatial distribution of air frost in New Zealand are discussed, using frost-frequency and chronology data. A natural frost season is defined by the data, and shown to cross the calendar division of the year for some stations in the South Island. This is attributed to both synoptic and local factors. As well as observing the better known broad-scale variations, provisional identifications are made of a number of interesting local patterns. Differences between frequency and chronology data are used to suggest differing sources of variation, on the regional scale. Within the Canterbury region the wide range of climate variability may be enhanced by the presence of the larger river systems, for which evidence is adduced via simple probability arguments concerning mean annual frequency, and variability of occurrence in time of the last air frost.