A local wind that blows up a slope heated by sunshine.
One of the 10 characteristic cloud types (or cloud genera) recognised by the International Cloud Atlas. Its name comes from altum (height) and stratus (spread out). It appears as a greyish or bluish sheet of cloud, partly or totally covering the sky, but with parts sufficiently thin to at least vaguely reveal the sun.
One of the 10 characteristic cloud types (or cloud genera) recognised by the International Cloud Atlas. Its name comes from altum (height) and cumulus (heap). It is usually white or grey, and tends to appear as sheets or patches of wavy, rounded masses or rolls.
An instrument used to measure the altitude of an object above a fixed level.
A beautiful illumination effect seen in mountainous regions around sunset, beginning when the sun is around 2º above the horizon. At its most spectacular, snow-covered mountains in the east assume vivid tones of yellow, pink and purple.
Centred near the Aleutian Islands in the North Pacific, this semi-permanent depression is one of the main centres of activity in the atmospheric circulation of the Northern Hemisphere in the winter.
The measure of how reflective a surface is. Everything from a desert to a forest will have an albedo value, which impacts directly upon the temperature of the air around it.
A term used for a flash of lightening that doesn’t reach the ground.
The mixture of gasses that make up the Earth’s atmosphere. Excluding water vapour and dust, the main components of air are nitrogen, oxygen, argon, carbon dioxide, neon, helium, krypton, hydrogen, xenon and ozone.
The process of growth of snow or ice crystals through collision with each other. Without aggregation, the snowman would be extinct.