The glaze is a deposit of Glace compact and smooth, generally transparent, coming from a rain or a drizzle of superfused Eau , in a state of superfusion (water remains in the liquid state in spite of the negative temperature) which freezes while coming into contact with a solid surface whose temperature is generally lower or slightly higher than 0°C. Water can be presented in form superfused in a going interval of temperature of 0 °C at -39 °C.

Attention, the glaze comes from the rain or of drizzle verglaçante but is not an interchangeable term with those. Thus, one cannot say that it “falls from the glaze” but rather than it “falls from the rain verglaçante which forms glaze on the objects”.


Mechanism of formation

A typical situation of rain verglaçante occurs when mass of a soft and wet air, in which precipitation is formed, is raised by a thin blade of cold air on the surface at the time of a situation of Blocage of cold air. The snow which is formed in altitude falls through a layer above the bottom and freezing point. The surfacing keeping the room temperature under zero °C, the rain freezes in contact with any object. If the cold layer is too thick, the rain recongèle before reaching the ground and gives Grésil.

The glaze can also come from Bruine. In this case, the mass of air is slightly unstable on low level and stable just above with temperatures under zero in all the layer. The vertical movement is then limited in a thin layer of the atmosphere giving of the Stratus and Stratocumulus. The precipitation which comes from this kind of clouds is made of very small drops which cannot freeze before -10°C and can even remain in this state until -39°C. These superfused droplets freeze instantaneously with the contact.

Finally, one can speak about glaze, by analogy, when superfused droplets of fog settle on surfaces under zero but in general one calls that of the freezing fog.

Dangers

The glaze contains very few imprisoned bubbles of air. However, without these bubbles of air, the Lumière is reflected very little by the glaze and this last thus takes the color of the surface on which it rests. It is thus particularly dangerous when it is present on the roads because the motorists almost do not see it and that he is very slipping.

The glaze is also very dangerous for the Avion S and Hélicoptère S in flight by forming a layer of ice on all surfaces what changes the aerodynamic characteristics of the apparatus. If the layer becomes too important, the aircraft can lose its Portance completely and be crushed.

The glaze affects the distribution of electricity and can cause power cuts because the ice which accumulates on the cables can make them break. In great quantity, it can even make collapse the structures on which they are tended (posts and electric pylon S). This leads to electric breakdowns which can spread as it already occurred some at many places. A case of most important is that of the massive Verglas of 1998 which has affected more than four million people along a band between Ottawa and the Nova Scotia with the Canada and certain sectors of the New England. More than three million those found themselves in the great area of Montreal where certain sectors were private of current lasting more than one month and where it was necessary to rebuild part of the electric delivery system.

See too

Related articles

Other comparable phenomena:

Historical storms:

External bonds

  • Photographs of glaze by AlerteMeteto.com

  • Storm of glaze January 1998 (By Frederic Dussault - Photographer)

  • Large glaze of 1998

Nds-nl: Iesel (weer)

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