地表面粗度による観測風の補正手法を用いた関東平野における夏季晴天日の局地風循環の把握 Analysis of Local Wind Circulation in Summer over the Kanto Plain Using the Adjustment Technique of Observed Wind with Roughness Parameter

この論文にアクセスする

この論文をさがす

著者

抄録

一般には,地上風の収束域では上昇流,発散域では下降流の存在が大気下層で期待される.本研究では,関東平野の夏季日中における局地風構造の把握を目的として,海風日の地上観測風から発散量分布を求め,顕著に認められた収束域と発散域との出現位置や時間的関係について検討した.その際に,風速の観測高度が観測点ごとに異なるため,周囲の土地利用状況をもとに各観測点における地表面粗度を推定し,対数則に基づいて統一高度における風速を求めた.<br>午前中には,水平規模が10~30km程度の典型的な局地循環として,東京湾付近に海風循環,関東北部には谷風循環がそれぞれ独立して存在することが示された.午後になると,谷風循環に伴う群馬・埼玉県境付近の発散域は弱まって,関東北部の谷風循環は不明瞭となり,広域海風の発達に対応した循環構造の変化を観測風の解析からもとらえることができた.

This study clarifies the vertical structure of diurnal variation in local wind systems, including sea breezes over the Kanto region, by focusing on temporal changes in the wind system structure caused by large-scale sea-breeze development. Because direct observation of the atmosphere's vertical motion is difficult, we developed an alternative index in which the quantity of divergence is calculated using observed surface wind data. However, observed surface wind data are inappropriate for calculating divergence fields because of differences in the observation heights of wind at different stations. Therefore, a roughness parameter corresponding to the wind direction at each observation point is estimated from land utilization data around the observation points based on the empirical formula proposed by Kuwagata and Kondo (1990). The adjustment of wind velocity is based on the logarithmic law of wind velocity. After adjustment, the wind velocity in the area near Tokyo Bay and absolute values of the quantity of divergence increased.<br>Typical sea-breeze days were selected, and temporal changes in the characteristics of the average wind and divergence fields were examined. Next, correlation coefficients of the quantity of divergence were calculated between marked divergence areas and each grid point in the study area. This analysis was performed to understand the relationship between the divergence and convergence areas and to identify areas where the diurnal variation in the divergence value is equal to that of marked divergence areas. At 09:00, a divergence area formed in Tokyo Bay (area TB), and sea-breeze circulation was observed between area TB and the convergence area in the neighborhood of Tokyo. At 11:00, with sea-breeze development, the influence of the Sagami Bay sea breeze in area TB weakened the correlation with the convergence area of Tokyo. Conversely, a valley wind developed in North Kanto, and valley wind circulation was observed between the divergence area around the prefectural border between Gunma and Saitama (area GS) and the convergence area of a neighboring mountainous district. It appears that typical valley wind circulation developed on a comparatively small scale; moreover, at that time, the valley wind circulation of North Kanto appeared to be independent of the seabreeze circulation of South Kanto. After midday, the original correlation level with area TB was observed in the area between Kanagawa and Sagami Bay, which suggested a switch from the typical sea-breeze circulation to a large-scale sea breeze. With this large-scale sea-breeze development, the valley wind circulation in North Kanto became indistinct. Simultaneously, area TB developed a negative correlation with area GS. When the large-scale sea-breeze development was marked, the divergence in area GS corresponding to valley wind circulation weakened.

収録刊行物

  • 地理学評論 = Geographical review of Japan

    地理学評論 = Geographical review of Japan 84(6), 529-552, 2011-11-01

    公益社団法人 日本地理学会

参考文献:  24件中 1-24件 を表示

各種コード

  • NII論文ID(NAID)
    10030364347
  • NII書誌ID(NCID)
    AA11591990
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    18834388
  • NDL 記事登録ID
    023428861
  • NDL 請求記号
    Z8-571
  • データ提供元
    CJP書誌  NDL  J-STAGE 
ページトップへ