When I checked the outputs of sen2cor, I found some files starting with S2A_USER_AOT…, S2A_USER_WVP…, and S2A_USER_VIS. What do these files for?
You should find some useful informations in the user manual: http://step.esa.int/thirdparties/sen2cor/2.2.1/S2PAD-VEGA-SUM-0001-2.2.pdf