Next time you’re outside, look up. Is there a cloud in the sky? You might know that these clouds are made of drops of water or ice, but that’s not all. Scientists in the US have now directly measured the biological material and mineral dust in the ice crystals found in clouds.
When the temperature is just right, clouds form around aerosols such as dust, smoke, salt, bacteria, plant matter and even the spores of fungi. Water and ice in the atmosphere grow around these aerosols and eventually this leads to rain or snow.
The scientists sampled clouds while flying at high speeds in an aircraft to find out more about these aerosols. They had a scientific instrument onboard called a mass spectrometer. This allowed them to measure the chemicals that make up ice particles in the clouds.
“By determining the chemical composition of the very cores of individual ice particles, they discovered that both mineral dust and, surprisingly, biological particles play a major role in the formation of clouds,” says Anne-Marie Schmoltner of the National Science Foundation’s Division of Atmospheric Sciences. Previously this could only be predicted from laboratory experiments and measurements on the ground.
The team of scientists found that biological matter made up 33 per cent of the particles in ice crystals and mineral dust made up 50 per cent.
It was impossible for the scientists to determine whether the plant matter, fungal spores and bacteria they found were alive. This is because the mass spectrometer they used ionised the samples, smashing the samples to bits, in order to work out what chemicals were in the ice crystals.
Working out the exact composition of clouds will help scientists produce more accurate predictions about climate change. It may also lead to new ways of producing rain clouds to lessen drought.
Article and photo source: CSIRO Science by Email