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This question was submitted on behalf of a user.


I am trying to derive extinction coefficient profile using CALIPSO data (product name:CAL_LID_L2_05kmApro-Standard-V4-10).

I have two questions regarding product:

1. CAD_Score is a 3 dimensional array(2x399x3728). How to read CAD_Score to know aerosol existence from such data set?

2. How to find out the vertical resolution information ?

I greatly appreciate to get your help.

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  1. As you may be aware the ASDC is currently experiencing unplanned downtime on certain websites that reside in the legacy web cluster. CALIPSO's data is currently being affected.  Our subject expert was able to provide the following information. Unfortunately, with the CALIPSO website is down, appropriate hyperlinks could not be provided. Once the website is back online we will update this post.

    Extinction in the level 2 profile products is reported at 60 meters vertical resolution. The extinction array size is 399 altitudes x N profiles. However, below 8.2 km the CAD score and feature type information are derived at 30 m vertical resolution. Therefore the CAD score array has a size of 2 x 399 x N so that the 30 m resolution CAD scores can be reported for each 60 m resolution altitude bin in the profile product. The first dimension reports the CAD score of the higher altitude 30 m resolution bin in index 1 and the CAD score for the lower altitude 30 m bin in index 2.

    In order to establish aerosol existence, use the Atmospheric Volume Description, also reported in the level 2 profile products. It reports feature type information. By querying bits 1-3, feature type can be established. This data set has the same dimensions as the CAD score in the level 2 profile product. Aerosol existence can also be established by identifying negative CAD scores (excluding the -127 fill value) since aerosols are assigned CAD scores between 0 and -100. Note that some layers having the “cloud” feature type can also have CAD = 0. The best method to establish aerosol existence is with the feature type information in the atmospheric volume description as previously described. The documentation for the Atmospheric Volume Description can be found on the data product descriptions pages of the CALIPSO Data User’s Guide website. This website is currently down for maintenance so please check back for site accessibility.

    The vertical resolution of the level 2 profile product is 60 m below 20.2 km and 180 m from 20.2 to 30 km. More information about resolution of the data products can be found in the data products description section of the Data User’s Guide once the website is back online.