Most Japanese high school students learn about climatology and its classifications by studying geography. Of the numerous forms of climate classification, the Koeppen classification (Koeppen, 1936) is the most widely used. This classification method illustrates the differences in global climate according to vegetation associated with five main climate types including A, tropical; B, arid; C, temperate; D, continental; and E, polar. These climate types are defined by monthly temperature and precipitation and are further divided into various subtypes according to seasonal temperature and precipitation changes. Only two of these types, C and D, and certain subtypes apply to Japan. The main transition band between these types is distributed through Hokkaido and Tohoku. Miyamoto (2009) analyzed the Automated Meteorological Data Acquisition System (AMeDAS) data reported by the Japan Meteorological Agency in local areas and divided Hokkaido into the following four climate provinces: Cfa, humid subtropical characterized by mild climate with hot summer and no dry season; Cfb, marine west coast characterized by mild climate with warm summer and no dry season; Dfa, humid continental characterized by humid climate with severe winter, hot summer, and no dry season; and Dfb, characterized by humid climate with severe winter, warm summer, and no dry season. Moreover, numerical land data in Japan is prepared by the national government and is based on 1-km mesh climate data including temperature, precipitation, and solar radiation. This information is calculated by AMeDAS observation data, which considers topographical and urban effects on climate. The present study area is Hokkaido, Japan, excluding the four northern territories occupied by Russia after World War II. The local climate distribution was analyzed by applying the 1-km mesh climate data for two periods: 1971-2000 and 1981-2010. Climate change during these periods was clarified by comparing the two distribution maps. As a result, the climate in Hokkaido was classified into the following regions: temperate in the southern coastal area

A strong local wind has been observed in Rumoi, northwestern Hokkaido, Japan. In order to investigate the wind around Rumoi, an analysis was performed using 30-year AMeDAS wind observations and numerical experiments with the Weather Research and Forecasting (WRF) model. Observation results show that there is a frequent strong wind in Rumoi in comparison with other areas around Rumoi. In relation to seasonal changes in wind direction, more than 50% of the wind in summer blows from ESE, but westerly winds are frequent in winter. To clarify the mechanisms involved in producing a strong local wind in winter, we compared two events using observations and numerical experiments. One case involves a strong local wind with a speed of approximately 12 m/s in Rumoi and a weak wind of less than 5 m/s in the surrounding areas; the prevailing wind direction is ESE (03:00 on January 28, 2003). The other case is that of a strong wind over 10 m/s blowing over the entire study area (on the afternoon of March 8, 2005), with a westerly prevailing wind. The experimental results show a relatively good correspondence with those of the observation. A cross-section view demonstrates the existence of a mountain wave when the strong local wind is observed in Rumoi. The wind then passes through the valleyshaped topography, and wind speeds are accelerated in the vicinity of Rumoi, which suggests the existence of a gap wind. Additionally, a sensitivity experiment is performed by changing the land surface model without considering snow, and the wind speed over land is seen to be reduced by 2 m/s, with very little change in the wind direction.