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!
How to obtain ice cloud fraction?
-
- User Services
- Posts: 64
- Joined: Tue Jun 08, 2021 11:29 pm America/New_York
Re: How to obtain ice cloud fraction?
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
A subject matter expert has been contacted about your question relating to ice cloud fraction.
Thank you,
David W.
NASA Langley ASDC DAAC Lifecycle
-
- Subject Matter Expert
- Posts: 21
- Joined: Tue Nov 26, 2019 3:58 pm America/New_York
- Location: Langley Research Center
- Been thanked: 2 times
- Contact:
Re: How to obtain ice cloud fraction?
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.
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.