Mapping Frost Occurrence Using Satellite Data

Abstract

Detailed maps of the date of the first and last frost, the length of the frost-free period, and the number of days of frost during spring have been produced for the Otago region of New Zealand. These frost occurrence variables are estimated using a combination of channel-5 (11.5?12.5 ?m) infrared brightness temperature data and the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR) satellite instrument. It is shown that a generalized linear model with quasi-likelihood estimation is best suited to the estimation of these frost occurrence variables. The maps show that frosts occur earlier in the autumn and later in the spring with increasing distance away from the coast and from major rivers and lakes. Frost is most prevalent on the top of high mountain ranges where the air temperature is coldest and is shown to be more common near the bottom of inland basins as compared with the sides of the surrounding hills because of cold-air drainage and ponding.