Page 105 - ภาษาอังกฤษสำหรับสายวิทยาการอุตุนิยมวิทยา

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(1) The aircraft must be flying through visible water such as rain or the small drops of
water that form clouds.

(2) The temperature of the water or of the plane must be O'.

3. Clear Ice

a. Clear ice is a transparent ice that has a glassy surface. It is ldentical to the
transparent ice that forms on trees and other objects during a freezing rain. It is formed by
the relatively slow freezing of large supercooled water drops. The 1ce is smooth and
transparent when it is formed from raindrops or large supercooled cloud drops with- out
solid precipitation. Ice tends to take the shape of the surface on which it freezes, but it
accumulates more at the part of the surface that first meets the flow of air. The icing tends to
be thicker and on the front edge of a surface such as a wing, and be thinner as it extends
back over the surface.

b. Clear ice is the most serious of the various forms of ice be of its rapid accumulation.
It adheres strongly to the surfaces it forms on and is difficult to remove.

c. The conditions most favorable for the formation of clear ice are: large amounts of
water present in the air, large size rain drops or large cloud-forming drops, temperatures only
slightly below freezing, high speed of the aircraft through the air, and thin aircraft structures
such as wings. Clear ice is encountered most frequently in cumulus-type clouds and freezing
rain or drizzle