CLOUD FACTS

DRUM - - In The Classroom -

Most clouds form in the low­est part of Earth’s at­mos­phere, called the tro­po­sphere ­(it has an av­er­age height of 10km above the planet’s sur­face), but some­times they can reach as high as the strato­sphere (50km) and even the meso­sphere (85km).

Sci­en­tists have cal­cu­lated that the av­er­age cu­mu­lus cloud con­tains about 500 tons of wa­ter, which is the weight of about 100 ele­phants (weigh­ing an av­er­age of five tons each).

In 1802 English me­te­o­rol­o­gist Luke Howard clas­si­fied the types of clouds and gave them Latin names.

Other plan­ets that have their own at­mos­phere – such as Venus, Jupiter (right) and Saturn – also have clouds. The word cu­mu­lus means “heap” or “pile”. The word stra­tus means “layer” or “sheet”. The word cir­rus refers to a “curl of hair”. Cir­rus clouds can move as fast as 160km/h. Some peo­ple mis­tak­enly be­lieve that con­trails (below) – the line-shaped clouds that trail be­hind planes – are chem­i­cals ex­pelled by the plane but they are man-made clouds. Con­trails form when the vapour in the hot air from the plane’s ex­haust mixes with the cold air in the at­mos­phere and con­denses to form ice crys­tals.

On Jupiter the Great Red Spot – a swirling storm of clouds twice as wide as Earth – has been ob­served on the gi­ant planet for more than 300 years.

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