低緯度河川における水温の決定要因  [in Japanese] DETERMINANTS OF WATER TEMPERATURE IN THE RIVERS OVER LOW-LATITUDE REGIONS  [in Japanese]

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Abstract

河川水温は物質循環や人間活動に影響を及ぼす要因の1つである.しかし低緯度地域の河川では,既往研究の指摘する気温-水温関係が成立たないことが本研究によって発見されたため,河川水温の決定要因の解明を試みた.本研究では,移流や氾濫といった水動態が水温形成に与える影響を全球河川水温モデルHEAT-LINKによって検証した.その結果,現実的な水動態の考慮は水温の再現性を向上させ,また氾濫が水温に与える影響は流域によって異なることが分かった.すなわちアマゾン川とメコン川では,氾濫原は短波放射の吸収率増加によって水体を温める効果を有する一方で,低温期のラプラタ川では水面面積の拡大に伴う蒸発量の増加によって水体を冷やす効果が見られた.また水温鉛直成層に関する実験から,アマゾン川での水温の季節変動には成層の発達が影響している可能性が示唆された.

 River water temperature is one of the factors closely related with material circulation and human activities, and its numerical representation in global modeling has received increasing attention in recent years. In particular, we discovered that the relationship between water and adjacent air temperature which was pointed out in previous researches is not observed in the large rivers over low-latitude regions. In this study, we investigated the influence of the various determinants including fluvial dynamics (e.g., advection, water depth change, flood inundation) and vegetation canopy in the global river water temperature model, HEAT-LINK. It was found that considering additional factors improves the reproducibility of river water temperature variability in general, but the impact of the flooding varies for different basins. Simple experiments on vertical stratification of water temperature suggested a potential development of thermal stratification in the Amazon river.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(4), I_583-I_588, 2018

    Japan Society of Civil Engineers

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