What quality of the midday sun begins to subtly improve as days lengthen after the solstice, signaling an atmospheric shift?

Answer

A slightly warmer quality of illumination.

As the angle of the midday sun begins to climb slightly after the solstice, the light can pierce the gloom with a warmer quality of illumination, signaling an atmospheric change.

What quality of the midday sun begins to subtly improve as days lengthen after the solstice, signaling an atmospheric shift?
lightseasonYeardaySolstice