Potential vorticity - vortex

Japanese: 渦位 - うずい

When considering a vertical air column or water column, the product of its absolute vorticity and horizontal cross-sectional area is called potential vorticity or potential vorticity. It is the same whether it is defined as the product of absolute vorticity and hydrostatic stability, or as the value obtained by dividing absolute vorticity by the pressure difference between the top and bottom of the air column. In the ocean, potential vorticity is often considered to be the absolute vorticity divided by the height (depth) of the water column. In a barotropic fluid, where friction is ignored, the fluid moves in a way that preserves the potential vorticity. (Nagata)

Source: Japan Hydrographic Association, Ocean Information Research Center, Encyclopedia of the Sea

Japanese:

鉛直気柱あるいは鉛直水柱を考えたとき、その絶対渦度と水平断面積の積を渦位あるいはポテンシャル渦度という。絶対渦度と静力学的安定度の積として定義しても、気柱の上端と下端の気圧差で絶対渦度を割った値としても同じ。海洋では絶対渦度を水柱の高さ（水深）で割ったものを渦位と考えることが多い。摩擦が無視される順圧流体では、渦位を保存するように流体の運動が起こる。（永田）

出典　(財)日本水路協会海洋情報研究センター海の事典について　情報

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