Lenticular clouds over South Georgia

Lenticular clouds over the mountainous island of South Georgia in the southern ocean. These clouds are formed as a result of perturbations in temperature due to gravity waves, which are generated as the strong winds of the southern ocean collide with the island's high mountains. This picture was taken during a fieldwork campaign on the island in January 2015, using radiosondes to measure these waves in the troposphere and lower stratosphere.