十勝平野における北西強風の発生機構に関する考察  [in Japanese] On the Generation of the Strong Northwesterly Winds in the Tokachi Plain  [in Japanese]

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Abstract

アメダスデータと高層気象観測データ(期間:1992~2001年)を解析して,北海道十勝平野の局地的強風である十勝風の特性と発生機構を考察した.十勝風の発生頻度は初冬の11・12月と初春の3・4月に最も高く,最大瞬間風速が15m/sを超える日は月に5~7日である.総観場の気象条件を調べると,十勝風は北海道東方に低気圧があり札幌上空に強い北西風が吹き込むときに発生している.また札幌では09時段階で大気下層に混合層が発達している.平均的な十勝風には正午過ぎに最も強く夜間に収まるという日変化が見られる.風は北西方向にある狩勝峠方面から吹き,08時頃から急激に十勝平野全域で強まる.また,風速は風下に向かって次第に増加している.一方,帯広では風が強い日ほど日照時間が長く,下層大気が不安定になっている.これらのことから,十勝平野では日中日射による対流が発生し,熱対流が上空の強風を下層に運ぶために地表で強い北西風が吹くと推測される.

Characteristics of strong northwesterly winds in the Tokachi Plain, Tokachi winds, are investigated by analyzing hourly meteorological observations at AMeDAS stations and upper air observations at Sapporo for the years 1992-2001. It is shown that the Tokachi winds are most frequently observed during the early winter (November-December) and the early spring (March and April) when strong northwesterly winds blow above Sapporo under synoptic meteorological conditions of a strong low pressure to the east of Hokkaido. At the same time, strong upper air winds blow over Sapporo being associated with a convective surface layer even in the early morning. The Tokachi winds are found to show a clear diurnal variation with strong wind speeds in the early afternoon and weak speeds in the mid-night. In general, the northwesterly winds begin to blow from the Karikachi Pass to the Pacific in the early morning, and then the wind speed increases with time as they spread over the Tokachi Plain. On the other hand, higher wind speeds in the Tokachi Plain are accompanied with longer sunshine durations, implying that the air is unstable to cause vertical convection. Consequently, we may conclude that the Tokachi winds are caused by the transport of strong upper winds to the surface layer through the thermal convection over the Tokachi Plain during the daytime.

Journal

  • 天気

    天気 53(10), 773-784, 2006-10-31

    日本気象学会

References:  27

Cited by:  2

Codes

  • NII Article ID (NAID)
    110004857922
  • NII NACSIS-CAT ID (NCID)
    AN00151568
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    05460921
  • NDL Article ID
    8562878
  • NDL Source Classification
    ZM43(科学技術--地球科学--気象)
  • NDL Call No.
    Z15-35
  • Data Source
    CJP  CJPref  NDL  NII-ELS  NDL-Digital 
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