Inquiry Regarding CERES_SSF_NOAA-20_Edition1B IWP Data

[spirityyf]

Dear Professor,

I hope this letter finds you well. My name is Yifan Yang, a graduiate student at the University of Chinese Academy of Sciences. Currently, I am conducting research utilizing the IWP (Ice Water Path) data from the CERES_SSF_NOAA-20_Edition1B product.

I have a specific question regarding the interpretation of the Lower and Upper values for IWP. In the attached document, I observed a column labeled Lower and another labeled Upper. Could you kindly clarify whether the values in the left column correspond to Lower and those on the right to Upper? Furthermore, if both Lower and Upper values are present simultaneously, does the IWP value represent the sum of the two?

I appreciate your time and expertise in addressing these inquiries. Your guidance will greatly contribute to the progress of my research. I eagerly await your response.

Thank you very much for your assistance.

Sincerely,

Yifan Yang

[ASDC - cheyenne.e.land]

Hello,

Thank you for your interest in CERES data.

According to the SSF Collection Guide on page 117 The lowest cloud layer parameter value is always recorded before the upper layer value. Therefore the values on the left correspond to the lower cloud layer and the values on the right correspond to the upper cloud layer.

Also, if you have Panoply and open a file from this product, it will tell you that the first index that for this dimension is for the lower layer values and the second index from this dimension is for the upper layer values.



Hope this helps.

Regards,
ASDC

[spirityyf]

Thanks for your reply, If I want to calculate the iwp for the whole air column and the iwp values for the upper cloud layer as well as the lower cloud layer are present, can I add them together as the iwp for the whole air column?

[spirityyf]

ASDC - cheyenne.e.land wrote:
> Hello,
>
> Thank you for your interest in CERES data.
>
> According to the
> [url=https://ceres.larc.nasa.gov/documents/collect_guide/pdf/SSF_CG_R2V1.pdf]SSF
> Collection Guide[/url] on page 117 [i]The lowest cloud layer parameter
> value is always recorded before the upper layer value. [/i] Therefore the
> values on the left correspond to the lower cloud layer and the values on
> the right correspond to the upper cloud layer.
>
> Also, if you have
> [url=https://www.giss.nasa.gov/tools/panoply/]Panoply[/url] and open a file
> from this product, it will tell you that the first index that for this
> dimension is for the lower layer values and the second index from this
> dimension is for the upper layer values.
>
>
> [img=https://i.postimg.cc/KvGn7bf5/Screenshot-2023-12-12-at-10-39-33-AM.png][/img]
>
> Hope this helps.
>
> Regards,
> ASDC
Thanks for your reply, If I want to calculate the iwp for the whole air column and the iwp values for the upper cloud layer as well as the lower cloud layer are present, can I add them together as the iwp for the whole air column?

[ASDC - cheyenne.e.land]

Hello,

A member of the CERES Science team has suggested that to get a total IWP, you should weight each layer’s IWP by the corresponding layer 1 or layer 2 fraction before adding and then dividing by the sum of the two layer fractions. You could use either percentage or fraction as long as you don’t mix them. These are in the layers_coverages variable, layers_coverages:long_name = "Clear/layer1/layer2/overlap of layers 1 and 2, percent coverages.

Regards,
ASDC