Earthdata Forum

While I was referencing the state layer for removing clouds and their shadows from MODIS images, I noticed there are two indicators related to cloud layers: "cloud state" and "Internal Cloud Algorithm Flag." I am not sure which indicator I should follow for cloud removal and would like to seek your advice on this matter. Additionally, when removing cloud shadows, using "cloud shadow" is correct, isn't it?

hi @zhooukee Could you please mention which specific MODIS product you are working with? (For example: MOD09A1) that will help us direct your question to the right team. Thank you - Danielle

Apologies for the previous oversight. The product being used is MOD09GA.Thanks for your helping
Zhou

Hi Zhou,
It is recommended to use the Cloud State, as that is more definitive. Also, It contains, cloud mask from MOD35 and cloud/snow/aerosol/fire/shadow etc as determined by the reflectance algorithm. Hence users are encouraged to use the state flag from the MOD09GA.
Thanks,
Brett

OK, thank you. I have one more question. If I want to perform vegetation physical and chemical parameter inversion, is it necessary to remove pixels with high aerosol levels?

Ideally, that would be the case, if you are asking me is it more necessary for that purpose then it is with others, I am not sure. But undoubtedly the more accurate Surface Reflectance value is with the lower Aerosol level. One of the inherent issues with daily data is to find the balance between several factors including the solar and sensor angles and minimal clouds. So you really will need to decide how to balance the thresholds between those factors.
Thanks

ok,thanks