Masking cloud shadow in l2gen (for Sentinel-2)

dogun · by **dogun** » Fri Sep 21, 2018 12:49 pm America/New_York

Hi All,

What command do I need to mask cloud shadow for S2 images during atmospheric correction - I assume cloud shadow isn't masked by default?

I tried to produce a mask for cloud shadow (l2_flags.LOWLW) but looks like cloud shadow isn't masked at all.

Thanks!

OB.DAACx - SeanBailey · by **OB.DAACx - SeanBailey** » Sat Sep 22, 2018 3:39 pm America/New_York

There is no way to mask data flagged as LOWLW in the atmospheric correction process. I is only used as a mask during the L3 binning process.
The LOWLW flag is a simple threshold on the retrieved water-leaving radiance in the green band closest to 555nm. The value of that threshold
is 0.15 uWatts/cm2/nm/sr - or one half the nominal open ocean clear sky value. While it is used to flag data as likely within a cloud shadow, it's
not perfect and it has not been evaluated for it's effectiveness with the MSI instrument.

Sean