An observational study of the wind structure, momentum and sensible heat fluxes over a grass-covered slope of Mt. Kuju [Oita, Japan]
2001
Komoda, H. (Nagasaki Univ. (Japan)) | Kobayashi, T. | Teshima, J. | Ueno, Y.
The wind and temperature structure over a grass-covered slope of Mt. Kuju were examined by making meteorological observations for two months at the Kuju Agricultural Research Center of Kyushu University, located on the south-southeast-facing slope. The following characteristics were revealed from the observations. 1) The rate of increase of surface wind speed with increasing altitude on the slope was smaller when the wind blew down-slope or up-slope than cross-slope. 2) The friction velocities of down-slope or up-slope winds under rather high wind conditions were on the average larger than those of cross-slope winds at the same wind speed. 3) For WSW winds, when the wind speed exceeded a critical value the surface wind speed over the upper part of the slope, which is immediately downwind of a ridge that projects southward and ends suddenly halfway down the hill, increased less than over the lower part as a result of the formation of a wake. 4) On clear nights, the downward sensible heat flux in the 1.5-2.8 m air layer over the slope was almost the same, or about twice as large as the net radiation, which suggests that the cold-air-drainage layer (CADL) produced by radiation cooling near the surface was often warmed by entraining ambient air.
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