Yamatanikaze - Yamatanikaze

The wind that blows from the plains into the valley during the day is called valley wind, and the wind that blows from the valley to the plains at night is called mountain wind; these are considered a pair of winds that change over a period of one day, and are called mountain/valley winds. The volume of the air in the mountain valleys is smaller than that above the plains, so it warms and cools easily, creating a circulating air current with a daily cycle. The actual wind that blows in the mountain valleys is a combination of mountain/valley winds and slope winds that rise and fall along the mountain slopes, and so it blows as a complex wind system. In general, the regular daily circulation of mountain/valley winds is seen as a sign of continued good weather, and when the weather is deteriorating the circulation of mountain/valley winds is disrupted.

[Nemoto Junkichi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

日中に平地から谷間に吹き込む風を谷風、夜間に谷間から平地に吹き出してくる風を山風といい、これを1日を周期として変わる一対の風と考えて山谷風という。山あいの部分の空気は容積が平地上空より小さいので暖まりやすく、また冷えやすいために、このような1日を周期とした循環気流を生ずる。山あいを吹く実際の風は山谷風に、さらに山地の斜面に沿って上昇下降する斜面風が加わったものであり、複雑な風系として吹く。一般に山谷風の循環が毎日規則的に現れるのは、好天が続く一つの現れとみられ、天気が下り坂のときは山谷風の循環は乱れる。

［根本順吉］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例