Decoding where the cleanest air on the planet is

The Southern Ocean has clean air with very little aerosols - microscopic particles of matter that form naturally or as a result of human activity .

The Southern Ocean is located far from where there is much human activity, but this is not the only reason why the air here is the freshest in the world , Science Alert reported on April 14. In new research published in the journal Nature , a team of experts from Monash University and the University of Melbourne discovered new information about cloud structure that shows that the Southern Ocean and unique honeycomb-like clouds play a large role as how to regulate climate . They also discovered the key role clouds and rain play in cleaning the air.

Open (circled above) and closed (circled below) honeycomb clouds in the Southern Ocean. (Photo: Tahereh Alinejadtabrizi/npj Climate and Atmospheric Science)

These honeycomb clouds can have a closed cell structure - a bright, white cloud that reflects sunlight back into space, cooling the Earth - or an open cell structure, allowing in more sunlight. shine more down on Earth. "These complexities are a source of error in modeling Earth's climate because they are not included appropriately. It is important to strike the right balance between open and closed cells , otherwise the results may be wrong ," the research team wrote.

The team of experts believes they have found the right balance and better understand the role of precipitation in cleaning the air. Using satellite images, they compared the honeycomb cloud with aerosol measurements from the Kennook/Cape Grim observatory and precipitation from nearby gauges and found that the cleanest air samples were associated with the presence of of open honeycomb rattan.

Open honeycomb clouds have more moisture, about 6 times more than closed cotton white clouds. They make it look cloudy when viewed from satellites, but actually provide the most effective showers that help wash away aerosols. Meanwhile, closed rattan looks thick but is less effective.

Open honeycomb clouds are most common in winter, resulting in the cleanest air at that time. In addition to the Southern Ocean, this type of cloud also appears in the North Atlantic and North Pacific regions during winter.

Although aerosol density in the air above the Southern Ocean is influenced by many factors, precipitation still plays a key role. "Rainfall is key , especially rain from these open honeycomb clouds. Rain cleans aerosols from the sky in the same way a washing machine cleans clothes ," the team wrote.