The lower sun angles in the mid-afternoon are the key. The lower sun angles interact more powerfully with the oxygen and nitrogen atoms, heating them more efficiently. In contrast, the noon (highest) sun angles appear transparent to oxygen and nitrogen. Oxygen and nitrogen are the key here, because they make up over 90% of the lower atmosphere.
The lower sun angles in the mid-afternoon are the key. The lower sun angles interact more powerfully with the oxygen and nitrogen atoms, heating them more efficiently. In contrast, the noon (highest) sun angles appear transparent to oxygen and nitrogen. Oxygen and nitrogen are the key here, because they make up over 90% of the lower atmosphere.