Solar insolation peaking at local noon in a diurnal cycle is a matter of elementary geometry and direct everyday observation, requiring no formal citation.
The claim states a fundamental astronomical and physical fact: solar insolation reaches its daily maximum when the sun is at its highest point in the sky at local noon. This is a basic matter of everyday observation and geometrical definition. Following STEP 0 of the instructions, trivially true statements of direct observation are classified as COMMON_KNOWLEDGE without attaching empirical papers.