ENVIRONMENT
TINY LIVING RAINMAKERS
Scientists have tracked down the culprits behind some of our rain, and they could become a force for good
WORDS IAN EVENDEN
How clouds form is one of the natural processes we thought we’d cracked. It seems so simple. First, water vapour sticks to tiny particles such as salt and dust, known as aerosols, high up in the atmosphere. Then bigger droplets form, and when these stick together, clouds are produced. The trouble is, recent research is showing that tiny organisms floating in the atmosphere – bacteria, to be exact – can act as what meteorologists refer to as ‘cloud condensation nuclei’.
These are the particles around which water droplets and ice crystals, another component of clouds, form. These bacteria can therefore have a profound effect on our weather.
Did you know?
British chemist Luke Howard classified clouds in 1802
DID YOU KNOW? Clouds on Jupiter are made of ammonia gas, rather tha
“Recent research is showing that tiny organisms in the atmosphere can act as cloud condensation nuclei”
A SPOTTER’S GUIDE TO CLOUDS
Learn your stratus from your nimbostratus
1 STRATUS From the Latin for ‘flattened’, stratus are common, low-level grey clouds that can even appear at ground level as mist or fog. They’re uniform in colour and are what you see when the weather’s drizzly.
2 CUMULUS Latin for ‘heap’, cumulus are the classic white, fluffy clouds that usually occur in fair weather. Due to their white colouration, cumulus clouds can cool the ground below them by reflecting solar radiation away.
3 NIMBOSTRATUS ‘Nimbus’ is Latin for ‘rain’. Nimbostratus clouds can cover most of the sky and block out the Sun. As the name suggests, they can bring rain.
4 ALTOSTRATUS These are thin, grey or bluish clouds that the Sun can shine through. These are mid-level clouds – ‘altum’ is Latin for ‘height’ – and can cover areas up to thousands of square miles.
5 CIRRUS Wispy and almost hair-like, cirrus are largely made up of ice crystals and can take on the colours of a sunset for a spectacular display. Their name comes from the Latin for a tuft of hair.
6 CONTRAILS Condensation from aircraft engines produces lines across the sky that resemble cirrus clouds. They slowly expand after the plane has passed and eventually vanish.