The claim that atmospheric humidity has a maximum limit determined by temperature and saturation vapor pressure is a fundamental thermodynamic definition (described by laws like the Clausius-Clapeyron relation); therefore, it is common knowledge and requires no citation.
The claim states a basic physical principle governing saturation vapor pressure and temperature, which is standard meteorological and thermodynamic knowledge. None of the retrieved papers specifically test or evaluate this definitional limit as their primary thesis, so no indices are placed. The verdict is COMMON_KNOWLEDGE.