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Topographic effects on the thermal structure of Himalayan glacial lakes : Observations and numerical simulation of wind

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Title: Topographic effects on the thermal structure of Himalayan glacial lakes : Observations and numerical simulation of wind
Authors: Chikita, Kazuhisa A. Browse this author →KAKEN DB
Keywords: Glacial lakes
Nepal Himalayas
Thermal structure
Wind-driven currents
Calving
Issue Date: 20-Apr-2007
Publisher: Elsevier Ltd.
Journal Title: Journal of Asian Earth Sciences
Volume: 30
Issue: 2
Start Page: 344
End Page: 352
Publisher DOI: 10.1016/j.jseaes.2006.10.005
Abstract: The thermal structure of two Himalayan glacial lakes, Tsho Rolpa and Imja in the eastern Nepal, was examined by observations in the pre-monsoon seasons of 1996 and 1997. Tsho Rolpa had an isothermal mixed layer at water depths of 0–20 m, whereas Imja did not possess such an isothermal layer. This difference in the thermal structure is explained by the condition that diurnal valley winds, producing wind-driven currents, blow strongly near the water surface of Tsho Rolpa, but very weakly near that of Imja. The wind observations above or near the end moraine indicated that a daily wind system of strong, diurnal valley winds and weak, nocturnal mountain winds is common to the lakes. It was suggested that with respect to the valley winds, the weak winds near the surface of Imja result from topographic screening effects of the upwind dead-ice zone and end moraine 20–25 m higher than the water surface. In order to ascertain the topographic effects, three-dimensional numerical simulation of airflow was carried out by making topographic models of actual size in the calculation domain, corresponding to Tsho Rolpa and Imja and their surrounding topography. The simulation revealed that, when winds blow at constant velocities of 1–5 m s−1 at 2 m above the points corresponding to the weather stations, the wind velocity at 2 m above the water surface for Imja is 33–42% smaller than for Tsho Rolpa. With increasing heights of the end moraine and dead-ice zone, the wind velocity near the lake surface efficiently decreased by decreasing the lake length from 3.1 or 2.2 km to 1.2 km.
Relation: http://www.sciencedirect.com/science/journal/13679120
Type: article (author version)
URI: http://hdl.handle.net/2115/28230
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 知北 和久

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