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→Thermals
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=== Thermals === | === Thermals === | ||
Convective clouds form when the sun heats up a thin layer of air in contact with the ground. As warm air is lighter than cold air, eventually the situation becomes unstable and pockets of air start rising, creating a column of lifting air, a thermal. If this column reaches above the condensation level, a Cumulus cap cloud forms, marking its position. | Convective clouds form when the sun heats up a thin layer of air in contact with the ground. As warm air is lighter than cold air, eventually the situation becomes unstable and pockets of air start rising, creating a column of lifting air, a thermal. If this column reaches above the condensation level, a Cumulus cap cloud forms, marking its position. | ||
The likelihood for development of thermals depend on the moisture of the ground, its type and also the angle of the sunshine. For example, lakes or rivers are not so good, but rock and concrete is. A mountain slope has a higher chance for developing a thermal if it is hit directly from the Sun, and not so if it’s on the shady side. | |||
Glider pilots can enter the thermals and circle in them to gain altitude. A good thermal might have a radius of about 1000 m and provide 1 - 3 m/s of lift. However, where there is lift, there is also sink: thermals are usually surrounded by a region of sinking airmass, and the convective upward motion of air also creates turbulence. | Glider pilots can enter the thermals and circle in them to gain altitude. A good thermal might have a radius of about 1000 m and provide 1 - 3 m/s of lift. However, where there is lift, there is also sink: thermals are usually surrounded by a region of sinking airmass, and the convective upward motion of air also creates turbulence. | ||