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Freezing Levels

Asked by: 1671 views Instrument Rating

Here's a questions I've often pondered about... I understand that the standard atmospheric lapse temperature rate is 2*c per 1,000ft. Now, If the freezing levels are forecasted to be at an altitude where clouds are at, I understand that acft structural icing can/will/possibly occur... Now, my question is, at which temperature will a cloud at a certain temperature not cause alarm for icing...?? If It's -2*f at 8,000ft and clouds are at present... will icing mostly likley occur? Hope this is clear enough

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2 Answers



  1. Tijmen de Boer on Oct 29, 2013

    Depends on several things, but most importend are: Layered or convective cloud and how much water the clouds contain and T range.
    Simplified:
    Thick Layered clouds: mod/sev icing up to -15 degr C, colder light ice
    Thin layered cloud: light/moderate icing up to -10 degr C. Colder only light.
    Convective cloud (CB): mod/sev icing up to -23 degr C, Up to -40 only light ice.

    Tijmen
    Senior forecaster NL

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  2. Lion on Oct 30, 2013

    If there is a VISIBLE moisture and the temperature at or below 32F, there will always be a chance of icing (depending on the amount of moisture and the OAT).

    Tijmen provided nice and simplified way as how to determine the severity of the icing using the amount of moisture (as he represented by the the thickness of the clouds) and the OAT at your altitude.

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