Units and scale for AOT and WV bands?


I can’t find in any of the specs what the units and scale are for the L2 AOT and WV bands. More precisely, http://step.esa.int/thirdparties/sen2cor/2.5.5/docs/S2-PDGS-MPC-L2A-PDD-V2.5.5.pdf says that both AOT and WVP is unitless. AOT probably is, but its scale is not specified - looks like its values are <= 100, so the scale is 0.01? But should not water vapor pressure have units?


in the L2A metadata you can find the following regarding the units and the quantification values:

The quantification value is the number needed to convert the pixel value to AOT or WVP, but if you are opening the full L2A product in SNAP, it is done automatically. If you are opening the AOT or the WVP images individually, then you have to divide the values by these quantification values.

Thanks! Why are pressure units cm? Is it cm Hg?

From http://www.remss.com/measurements/atmospheric-water-vapor/

“Total column water vapor is a measure of the total gaseous water contained in a vertical column of atmosphere. It is quite different from the more familiar relative humidity, which is the amount of water vapor in air relative to the amount of water vapor the air is capable of holding. Atmospheric water vapor is the absolute amount of water dissolved in air. When measured in linear units (millimeters, mm), it is the height (or depth) the water would occupy if the vapor were condensed into liquid and spread evenly across the column. Using the density of water, we can also report water vapor in kg/m2 = 1 mm or g/cm2 = 10 mm.”

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Thank you, it’s now clear.