I dont have knowledege about it

I cannot imagine a method a satellite could spectroscopically "see" the halogen radicals in the troposphere through the stratosphere's higher amount of the same molecules.

ClO and BrO are produced by radical processes of organic and inorganic molecules in the entire atmosphere. Only CFCs and a few other molecules requires "hard" UV photolysis to initiate the degradation and thus only break down in the stratosphere there ozone doesn't shield the UV part of the sunlight.

In the troposphere the halogen radical's lifetime are short due to the higher concentration of gas molecules and especially water that forms non-radical species like HCl that precipitate. This fate also applies to the radicals that are formed in the stratosphere as they eventually return to the troposphere.

Apparently Kenneth found an unrelated article about aquatic radical chemistry. In water ClO· and BrO· are never formed because the radical reactions always begin with Cl· and Br· which prefers to react with the sea of hydrogen available (H2O).

I do not agree as I understand ground level to be the atmosphere close to earth, troposphere - not under water.

Thank you all for this interesting discussion.

I would like to add an article in this context.

Article Global observations of tropospheric BrO columns using GOME-2...

I agree that "Arindam Roy said nothing about under water" and indeed it is silly to look for halogen oxide radicals in water.

Kenneth has contributed with a reference from PNAS with the title "Halogen radicals contribute to photooxidation in coastal and estuarine waters" and Arindam Roy with "Global observations of tropospheric BrO columns using GOME-2 satellite data".