TERMIUM Plus^®

Fiche 1,  Justifications,  Anglais

Record number: 1, Textual support number: 1 CONT

The above photo shows a halo phenomenon known as the upper tangent arc. When cirrus clouds contain columnar ice crystals aligned so that their axes are all in a horizontal direction, this type of arc may be produced. A characteristic of this arc-shaped patch of light is that it's directly above the Sun (it bends upward away from the Sun), and it's approximately 22 degrees away from the Sun itself - about 2 fists held at arms length.  1, fiche 1, Anglais, - upper%20tangent%20arc

Record number: 1, Textual support number: 2 CONT

The 22° halo is most common, but other halo forms are sometimes seen. The tangent arcs to the 22° halo can appear if the sun's declination is less than 32°. One is called the lower tangent arc to the 22° halo, and the other is the upper tangent arc to the 22° halo. The shape of these tangent haloes depends upon the sun's declination. If the sun is close to the horizon, the two upper arcs angle sharply away from the 22° halo. As the sun rises higher in the sky, the tangent arcs move toward the 22° halo. When the sun's declination reaches 32°above the horizon, the lower and upper tangent arcs make contact, and the resulting ring is called the circumscribed halo. It touches the 22° halo above and beneath the sun. When the sun is just above 32°the circumscribed halo resembles a double oval. As the sun rises higher it becomes increasingly circular and draws nearer to the 22° halo. When the sun's declination exceeds 70°, the circumscribed arc nearly coincides with the 22° halo.  2, fiche 1, Anglais, - upper%20tangent%20arc

Fiche 1,  Justifications,  Français

Record number: 1, Textual support number: 1 CONT

Un peu au-dessus ou au-dessous de l'astre lumineux [soleil], à la distance de 22 degrés, on peut fréquemment voir des arcs supérieurs et inférieurs tangents au petit anneau. En fait, on observe plus souvent les arcs supérieurs; ils ont souvent de belles couleurs. [...] Sur l'image suivante, on voit un arc tangent supérieur.  2, fiche 1, Français, - arc%20tangent%20sup%C3%A9rieur

Fiche 1,  Justifications,  Espagnol