A new map of the rainfall patterns below 1600 mm for the Canterbury high country
During the summer of 1982-83 the Forest Research Institute surveyed the growth of exotic trees throughout the Canterbury high country. Edaphic, physiographic and climatic site factors were also recorded so that relationships between tree growth and site characteristics could be examined. Because of the presence of a strong rainfall gradient in the area, we anticipated that rainfall would be the key variable influencing tree growth. Consequently, any inaccuracies in rainfall estimates could obscure the more subtle influences of other site factors. When we started the field work, the Meteorological Service Isohyetal map (N.Z. Meteorological Service 1978) based on 1941-1970 rain station normal was the only means for estimating rainfall for most plots. After finding inaccuracies in the isohyet map we decided to make further investigations in an attempt to improve the accuracy of rainfall estimates.