Atmospheric refraction causes the Sun to be seen while it is still below the horizon.
Light from the lower edge of the Sun’s disk is refracted more than light from the upper edge. This reduces the apparent height of the Sun when it appears just above the horizon. The width is not affected, so the Sun appears wider than it is high.
The Sun appears larger at sunrise than it does while higher in the sky, in a manner similar to the moon illusion.
The Sun appears to rise above the horizon and circle the Earth, but it is actually the Earth that is rotating, with the Sun remaining fixed. This effect results from the fact that an observer on Earth is in a rotating reference frame.
Occasionally a false sunrise occurs, demonstrating a very particular kind of Parhelion belonging to the optical phenomenon family of halos.
Sometimes just before sunrise or after sunset a green flash can be seen. This is an optical phenomenon in which a green spot is visible above the sun, usually for no more than a second or two. Wikiperdia