How to obtain ice cloud fraction?

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jane997
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How to obtain ice cloud fraction?

by jane997 » Sun Dec 24, 2023 11:43 pm America/New_York

The CERES SYN1deg products provide Cloud Particle Phase and Cloud Area Fraction. The Data Quality Summaries state, "The Cloud Particle Phase is the ratio of liquid and ice cloud fraction." In my opinion,if Cloud Particle Phase = 1, it should mean half ice cloud and half liquid cloud fractions.
Cloud Particle Phase = liquid cloud fraction / ice cloud fraction (1)
Cloud Area Fraction = liquid cloud fraction + ice cloud fraction (2)
Combining formulas (1) and (2), we can separately obtain the liquid/ice cloud fraction

However, the Data Quality Summaries state, "A phase of 1 indicates all cloud pixels are liquid while a phase of 2 means ice. A phase of 1.5 is a cloud region where half of the MODIS pixels are ice and the other half are liquid." I'm confused.

Thanks for your help!

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ASDC - David W.
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Re: How to obtain ice cloud fraction?

by ASDC - David W. » Tue Dec 26, 2023 1:57 pm America/New_York

hi jane997,

A subject matter expert has been contacted about your question relating to ice cloud fraction.

Thank you,

David W.
NASA Langley ASDC DAAC Lifecycle

wfmiller
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Re: How to obtain ice cloud fraction?

by wfmiller » Tue Dec 26, 2023 3:35 pm America/New_York

The second statement is correct, "A phase of 1 indicates all cloud pixels are liquid while a phase of 2 means ice. A phase of 1.5 is a cloud region where half of the MODIS pixels are ice and the other half are liquid."

The cloud phase is calculated as below in CERES processing:
Cloud Particle Phase = (1.0 * liquid cloud fraction + 2.0 * ice cloud fraction) / Cloud Area Fraction

To obtain the contributions for liquid and ice.
liquid cloud fraction = (2.0 - Cloud Particle Phase) * Cloud Area Fraction
ice cloud fraction = (Cloud Particle Phase - 1.0) * Cloud Area Fraction

The use of ratio in the DQS is not meant in the strict Mathematical sense, but that the value is proportional to how much water and ice are determined in the cloud based on the definition for the two phases.

jane997
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Re: How to obtain ice cloud fraction?

by jane997 » Sat Dec 30, 2023 8:39 pm America/New_York

Thanks for your reply! It helps me a lot.

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