Abstract
We chronologically summarized Hokkaido's winter meteorological conditions and examined warming trends and climatic disturbance trends, based on meteorological records. It was found that temperatures in Hokkaido in recent years have been higher than the average of past years (1961-1970), and the increase in miriimum temperature has been greater than the increase in maximum temperature. Summary and categorization of meteorological charts on heavy rain and snowfall events in winter also confirmed a decrease in the number of such weather events that were caused by winter pressure patterns and an increase in such weather events caused by low pressure. Furthermore, a trial calculation of the degree of effect of increased temperature on runoff in this cold, snowy region indicated that runoff in seasons of snow cover (snow accumulation season and snow melting season) is more strongly influenced by increased temperature than is the runoff in summer.
