Peter Cairns / Reflections over Masvatn lake in winter, Iceland, September 2013.

Peter Cairns / Stormy seas with Olafsvik, Snaefellsnes, Iceland, September 2013.

Peter Cairns / View north from Meall nan Sleac over Glenfeshie, Cairngorms National Park, Scotland, August 2013.

Peter Cairns / View north from Meall nan Sleac over Glenfeshie, Cairngorms National Park, Scotland, August 2013.

Peter Cairns / Overcast day over River Feshie, Glenfeshie, Cairngorms National Park, Scotland, August 2013.

Peter Cairns / Procession of migrating Elk (Cervus elaphus) and Bison (Bison bison) through the National Elk Refuge, Wyoming, USA, February.

Peter Cairns / Snow Geese (Chen caerulescens) on roost pond at dawn. Bosque del Apache, New Mexico, USA, December.

Peter Cairns / Teton range at sunset in winter, seen from Jackson Hole Valley, Grand Teton National Park, Wyoming, USA, February 2013.

Bryan and Cherry Alexander / Stratocumulus cloud formation hanging over the Ellsworth Mountains while a higher stratus formation is backlit over the Polar Plateau, Antarctica, January 2006.

Yva Momatiuk & John Eastcott / Stratocumulus clouds above ocean, Kaikoura, South Island, New Zealand

Yva Momatiuk & John Eastcott / Stratocumulus clouds, Kaikoura, South Island, New Zealand

Philippe Clement / Stratocumulus undulatus clouds in blue sky, Arizona, USA

Philippe Clement / Stratocumulus undulatus clouds.

Philippe Clement / Stratocumulus cloud formation over land, France

Dong Lei / A flock of Bar-headed geese (Anser indicus) flying through a rainbow lenticular stratocumulus cloud, a rare cloud that lasted a week in Yunnan province late in 2020