haloilmiöitä

Haloilmiöitä, also known as halos, are optical phenomena in the atmosphere that typically appear as rings, arcs, or spots of light surrounding a light source, most commonly the Sun or Moon. These visual effects are caused by the refraction and reflection of light by ice crystals suspended in the atmosphere, particularly in cirrus or cirrostratus clouds. The shape and appearance of the halo depend on the size, shape, and orientation of the ice crystals, as well as the angle of the light source.

The most common halo is a 22-degree halo, which forms a circle around the Sun or Moon with a radius of approximately 22 degrees. This is due to light being refracted by hexagonal ice crystals at a minimum deviation angle of 22 degrees. Other halo types include the circumzenithal arc, which appears as a brightly colored arc high in the sky, and the parhelic circle, a horizontal band of light that runs through the Sun. The colors seen in halos are similar to those of a rainbow, with red appearing on the inside of the ring and blue on the outside, although they are often fainter and less distinct.

Haloilmiöitä are a natural and widespread atmospheric phenomenon. They are observed globally and are not indicative of any particular weather event, though they often appear in fair weather conditions when high-altitude ice clouds are present. Different cultures have historically attributed various meanings to halos, sometimes viewing them as omens or celestial signs, but scientifically they are purely physical optical effects. The study of halos contributes to our understanding of atmospheric optics and the properties of ice crystals in clouds.