Nocturnal Cooling Near the Ground : (1) Observation of the Effects of Topography on the Nocturnal Cooling

夜間の接地気層の冷却について : (1)観測で得られた夜間の冷却に及ぼす地形の影響

Nocturnal Cooling Near the Ground : (1) Observation of the Effects of Topography on the Nocturnal Cooling

Creators Hayakawa Seiji

Creators Tani Hiroshi

Creators Gu Wei

Creators Suzuki Yoshinori

Creators Motoda Yushiro

To make clear the effects of topographic features of flatland on nocturnal cooling process, micro-meteorological observations were carried out in the fields near Koga town in the northern part of Fukuoka Prefecture, Japan. The observation area was in a place crossed by the large bank of the Kyushu Express-way and divided into two parts :the upward side and downward side of air flow from the mountainside. Horizontal and vertical distribution of minimum air temperature, wind speed and net radiation at several points in the field were measured during the winter of 1978-1979. Increases in negative net radiation aceelerated cooling of the air layer, and decreases in wind speed made air temperature lower. When the wind speed was weak, the lowest value of minimum air temperature appeared on the upward part of the bank of the Express-way facing to the mountainside, because of the accumulation of cold air from the mountain. While the wind speed became rather strong, the lowest value appeared on the reverse side-downward of the bank. This phenomenon was caused by the lowering of wind speed in the leeward of the bank, where convection of sensible heat from the upper warm air layer to the ground surface was much interfered. The surface temperature of plants becomes cool when the air layer becomes cool in consequence of advection of cold air, that is, the plants is affected by cold air.

[ISSN]0513-1715

[NCID]AN00244250