Gliders climb and maintain height by making use of currents of rising air.

Rising air occurs as a result of a number of phenomena. Thermals are columns of rising air similar in shape to an ice cream cone. These are caused by temperature differences between adjacent areas on the ground. Air heated by the warmer ground rises, and there is frequently enough energy in the rising air to take a glider up with it.

Thermals often give rise to cumulus clouds, and these can be good markers for thermal activity. A cauliflour shaped cloud with a flat bottom is a likely source of lift.

Ridge lift can occur when prominent ground features such a hills or ridges deflect the wind upwards. If the wind is in the right direction, good lift may be encountered.

Wave is a phenomenon which can occur when the wind blows over the top of a large hill or mountain. The motion of the wind is deflected by the hill, and it behaves rather like a wave on the ocean. Areas of strong lift and strong sink alternate. The trick is to fly in the lift and avoid the sink. This type of lift is sometimes marked by a particular cloud formation. Lenticular clouds lying across the wind and remaining stationary are indicators of wave conditions.

A glider turning in tight circles is most likely climbing in a thermal, rather like flying up a corkscrew. A glider flying backwards and forwards along a ridge will be making use of ridge lift. A glider flying high in the gaps between strips of cloud will be soaring in wave.

How much of these effects can be used is closely related to the pilot’s skill.

Wave Clouds as seen from a Glider.