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Snowballs
 

Snowballs

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    Snowballs Snowballs Presentation Transcript

    • There is no meteorological term for this natural phenomenon which happens when large amounts of snow fall around large lakes or oceans. With the movement of the waves, the snow becomes ice and is transformed into “ice-balls”
    • Hundreds and thousands of ice-balls with a centre of snow, the size of a football gather along the beaches to give this wonderful spectacle. This happens when the water temperature is at 0 . Its a phenomenon known as "Lolly " by the fishermen of the Cap Breton island of Nova Scotia.
    • According to the Swedish meteorological agancy, SMHI, this rare phenomenon when the soft snow accumulates and is rolled over and over by the wind on the beaches. Its the same processus as when the erosion of stoned transforms them into pebbles.
    • Ice-balls on Lake Michigan, USA.
    • Snow rolls
    • This other meteorological phenomenon which forms rolls of snow, also called ’snowrollers’, is also quite rare.
    • This happens when the wind winds layers of snow, one on top of the other. Due to the combined temperature, humidity, speed of the wind and the slope of the ground, rolls are formed
    • A surface of ice or ground covered in snow enables the rolls to form. If the surface is made of ice, this ice must also be covered by a layer of “loose snow” of about 2cm and a temperature very near the ice’s melting point.
    • -Air temperature must be constant between 0 and 1 - The wind must be strong enough to mobe the rolls of snow, but not too strong, so that it breaks them up so it must blow at approximately 40 Km/h.
    • -A gust of wind lifts some snow, like a spoon would with some iced cream. Repetition of these gusts of wind enables the « roll » to move forward and to collect more snow each time.
    • The size of the rolls can be of several centimeters. Some have even been seen up to 70cm.
    • When the « roll » is too heavy to be moved by the wind or if it comes upon an obstacle, it stops, leaving behind it the imprint of its journey.
    • There is often a hole, in the very centre, because the layers are thinner than those on the outside and so they melt easily leaving a shape like a « Doughnut ».
    • These snow balls can also be formed by the action of gravity itself; like when snow falls from a tree or a cliff and lands on a slope, it can start rolling and form a ball. In this way « rolls » can form in hilly areas.
    • Translated by Karen Burns