Climatological Characteristics of Local Wind in the Tokachi District, Hokkaido, JAPAN

河合　隆繁 ＊ ・中條　麻衣 ＊＊ ・加藤　央之 ＊＊＊ ・山川　修治 ＊ Climatological characteristics of local strong wind in the Tokachi district are analyzed. Strong wind appeared most frequently in April, while not in Januar y and August. Approximately 70% of strong wind blew in the wind direction of WNW . The strong winds are classified into 4 types judging from air temperature and water vapour pressure. These are 1) Type Fw accompanies Foehn with rain on the windward mountain side. 2) Type Fd, Foehn without rain on the windward mountain side. 3) Type B, Bora. 4) Type N, no substantial change of air temperature and water vapour pressure. The strong wind is also classified into 3 types depending on the wind flow patterns in Tokachi district. Type 1 is divergence pattern both in south and north side of Tokachi district. Type 2 is divergence pattern in south side. Type 3 is divergence pattern in the northern part. Type 1 occurred under the stable layer in the lower troposphere and accompanies foehn phenomenon. Type 2 occurred under the strong stable layer in the lower troposphere with a north wind. Type 3 appeared in the unstable layer in the lower troposphere. From these results, the various strong wind flow patterns in the Tokachi district are mainly controlled by the stability in the lower atmosphere and 850hPa wind direction.