Have you ever wondered what happens when lightning hits ice? This is a very pertinent question since according to NASA, lightning is caused when tiny ice crystals constantly bump against larger ice pellets many miles above the earth, in cumulonimbus clouds.
In laymen’s terms, it’s like when socks rub against the carpet, causing the cloud to crackle with electrical potential – and it’s not long before a bolt of lightning explodes towards the ground. It’s difficult to imagine that a bolt of lightning that heats the air three times hotter than the sun’s surface can spring from bits of ice.
The theory sounded so unbelievable that scientists at the National Space Science and Technology Centre in Alabama decided to check it out for themselves, using a tropical rainfall measurement mission satellite with the capability to check inside more than a million clouds.
The tropical rainfall measuring mission was a joint initiative between the Japan Aerospace Exploration Agency and NASA to study rainfall for climate and weather research. Launched in 1997, it produced valuable scientific data for 17 years, enabling research that improved scientists’ knowledge of lightning-storm relationships, weather forecasting and flood and drought monitoring. The data that it collected was returned in 3D images, enabling scientists to see and better understand the internal structure of storms.
Using the satellite’s onboard radar and optical detector (lightning imaging sensor), the study took three years to complete. By counting the lightning flashes, the study found that lightning and ice do in deed go together in a number of environments, including coastal areas and over land and sea. It revealed around 10 million kilograms of ice produced one lightning flash every minute.
In a thundercloud, millions of chunks of ice pushed by updrafts with speeds ranging from 10mph to 100mph, continually bump together, causing small ice crystals. These become positively electrically charged and float to the top of the cloud. The larger, bulkier pieces of ice known as graupel are negatively charged – these fall to the bottom of the cloud, causing mega-volts of electrical tension and hence lightning.
The findings of the study are useful, as the computer programs used to predict the weather need to know the amount of ice in clouds but this is hard to track. Due to the strong link between lightning and ice, scientists can get a good idea of the amount of ice by counting lightning flashes. The sensors are sited in the earth’s orbit and on the ground, making the whole process easier.
This more accurate method of tracking the ice can improve the computer programs that help to predict the weather. Thanks to the cutting-edge technology of the instruments onboard the tropical rainfall measurement mission satellite, it reached orbit at exactly the right time to benefit from the rapid advances in data sharing and computer capabilities.
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