Usually invisible gravity waves have been captured while moving through clouds over the Indian Ocean from Western Australia, as images taken by the Japanese weather satellite Himawari-8 on 21 October revealed.
A gusty south easterly surge over NW WA - perhaps enhanced by outflow from last night's thunderstorms over the Northern Interior - carries a plume of dust out over the Indian Ocean. pic.twitter.com/TqySYPa3NL— Andrew Miskelly (@andrewmiskelly) October 21, 2019
A longer animation highlighting the atmospheric gravity waves. Waves cause the air to rise and sink, cooling and warming its water vapour and making upper water vapour temperature an effective means of visualisation. In some cases, cloud forms on the crests. pic.twitter.com/af6kfO2U9Q— Andrew Miskelly (@andrewmiskelly) October 22, 2019
Also known as buoyancy waves, gravity waves represent a physical phenomenon where waves are generated in any fluid medium, including our atmosphere, usually created by obstructions to airflow such as mountain ranges or by clashes between air masses with different temperatures.
“Essentially gravity waves are disturbances in any sort of fluid, so we see them often in water, but the atmosphere is a fluid as well — so any sort of disturbances in there can generate waves”, senior meteorologist from the Australian Bureau of Meteorology (BOM) Adam Morgan explained to ABC.
“When you think of waves in the ocean, they're a type of gravity wave”, he added.
The captured gravity waves are believed to have been triggered by temperature differences from thunderstorms in Australia's Pilbara and Kimberley regions, spreading to the Indian Ocean. While this phenomenon is usually invisible to the naked eye, this time gravity waves were particularly visible due to a large plume of dust originating from the storms.
"When we do see them it's usually when there's enough moisture in the air to form a bit of cloud along the leading edge of the gravity wave", Morgan said.
“The cold outflow that falls out of that thunderstorm is quite gusty and those gusts have picked up a lot of dust and pushed it offshore", meteorologist added. “So when you look at the satellite image, it actually looked quite impressive”.
Gravity waves are not believed to pose any danger to humans.