Australian Weather Calendar: January 2019

January Photograph by Aaron Stanley, APS Photography

A moment frozen in time

When it comes to photographing the weather, the sights and experiences in Antarctica are poles apart from mainland Australia. And no one knows this better than photographer and engineer Aaron Stanley, who worked for the Bureau of Meteorology as a Technical Officer at Davis Research Station in 2016. Aaron was responsible for maintaining the automatic weather station network, taking 3-hourly weather observations, and releasing weather balloons while stationed at Davis. He says the whole experience was very surreal but also very challenging. 'During the winter it would take us about 15 minutes to get dressed because of all the layers you needed for the freezing conditions!' Aaron says it was the auroras that helped him make it through the bitterly cold and dark winters in Antarctica, with a dazzling display of the Southern Lights almost every night. 'I would usually set my camera up on a time lapse and leave it out overnight, then change the batteries every 3–4 hours. Aaron says another highlight was capturing this halo and light pillar created by 'diamond dust'—ground-level cloud composed of tiny ice crystals which is generally only observed in Antarctica and the Artic. It's these moments photographing rare weather phenomena in extreme locations that keeps the sparkle in his eyes.

The science

When the air is very cold, such as in Antarctica, ice crystals can form in the air close to the ground. This ground-level cloud is called 'diamond dust'. Interaction between light and the ice crystals can cause different optical phenomena, depending on the shape and orientation of the crystals. Light pillars, like the one at the centre of this photo, form when light reflects off ice crystals. A 22° halo, parts of which are seen here to either side of the pillar, forms when the sun or moon shines through ice crystals: as light passes through the crystals its path is refracted (bent) by 22–50°. No light is refracted at less than 22°, so an observer sees a halo around the light source.