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Earth and Space Sciences · 术语表

什么是 Rossby wave; upper-level trough and ridge？

又称： Rossby wave · upper-level trough · upper-level ridge

Definition 22.5 University Earth and Space Sciences — Year 2 · 第 22 章 — Weather Systems

A Rossby wave is a wave of the westerly flow of the upper troposphere, a series of troughs and ridges thousands of kilometres long with a large north–south amplitude. An upper-level trough is an elongated region of relatively low pressure in such a wave, where the flow bends towards the equator; an upper-level ridge is an elongated region of relatively high pressure, where it bends towards the pole.

Rossby waves in the jet stream seen from above the North Pole (schematic): five waves round the hemisphere, troughs reaching towards the equator and ridges towards the pole. The jet flows eastward, anticlockwise seen from above the pole (arrows). Latitude circles drawn as on a polar stereographic map.

示例

Example 22.6 (Three waves at 45° N)

With $\Omega = 7.292 \times 10^{-5}\,\mathrm{s}^{-1}$ (a sidereal day of $23.9345\,\mathrm{h}$ ) and $a = 6371\,\mathrm{km}$ , $\beta = 1.62 \times 10^{-11}\,\mathrm{m}^{-1}\,\mathrm{s}^{-1}$ at $45{}^{\circ}$ N. In a westerly of $15\,\mathrm{m}/\mathrm{s}$ , a wave of $4000\,\mathrm{km}$ has $\beta/k^2 = 6.6\,\mathrm{m}/\mathrm{s}$ and moves east at $8.4\,\mathrm{m}/\mathrm{s}$ ; one of $6000\,\mathrm{km}$ has $\beta/k^2 = 14.8\,\mathrm{m}/\mathrm{s}$ and barely moves, at $0.2\,\mathrm{m}/\mathrm{s}$ ; one of $8000\,\mathrm{km}$ moves west at $11.2\,\mathrm{m}/\mathrm{s}$ .

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