Sen2Cor Atmospheric Correction Verification



I am working in a comparison of different images of Sentinel 2 from different dates in the same place.

In this temporal sequence there are images with Level 2A and 1C.

In order to compare the two Levels, I am using the atmospheric Correction of Sen2Cor to the images 1C.

Because I want to verify that I am using the correct values in Sen2Cor I compare its outputs with the original image 2A of the same day. Because Sen2Cor is the tool used to create 2A images.

When I use Sen2Cor and I compare the output with the original image 2A from the same day, I see big differences in the values of the bands. In some bands, like B8 (842 nm), the difference is around 3% but in other bands, like B2(490 nm), the difference is bigger than 200%.

I have tried with many conbinations, but I can not find the good one.

Does anyone know how we can know which are the correct values to create 2A images? Should I change it in different dates?

My study area is in Madrid, Spain.

Thank you very much, I have spent too much time in this verification and any help will be welcome.