都市と森林の遮断蒸発特性に違いをもたらすメカニズム  [in Japanese] Differences of characteristics between urban and forest's rainfall interception  [in Japanese]

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Abstract

都市の遮断蒸発の動態解明に向け,屋外準実都市模型(以下COSMO)上にて遮断蒸発実験を行った.遮断蒸発量は平均して降雨の6%程度であり,森林域での報告例(10-50%)より小さく,その熱源は晴天時,都市キャノピーに貯えられた熱量であった.また,森林域で報告されているような降雨継続時間・総降雨量の関係は見られなかった一方,降雨初期飽差と強い相関があることが分かった.都市と森林域でのこれらの違いは両者のキャノピー構造の違いに起因することが考察された.つまり,キャノピー構造によって規定される,有効表積率,キャノピー構成要素のサイズ,熱容量の違いが都市と森林の遮断蒸発の絶対量,熱源・支配パラメータに違いをもたらしていると考えられた.

Rainfall interception (RI) over an outdoor urban scale model was investigated. On average, RI was 6% of the total rainfall and smaller than typical values in forests (10-50%). No correlation was found between RI and gross rainfall or rainfall duration unlike the correlations found in forests. RI was dependent on the saturation deficit at the beginning of the rainfall event. The latent heat for RI was approximately balanced by heat conduction from the concrete surfaces. Differences in the canopy structure are considered as possible reasons for the different behaviors of RI between the present site and forests. These differences in canopy structure include the area of the effective wet surface, the size of the roughness elements, and canopy heat capacity.

Journal

  • Proceeding of Annual Conference

    Proceeding of Annual Conference 21(0), 34-34, 2008

    THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

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