Some settings that affect the parent strand can make their length shorter than what the keypoints seem to indicate, so at times they can seem to “float” above the emitter. Without seeing all your hair system settings it’s not possible to be specific about why this happens, but it can be fixed fairly easily. In Particle Mode enable the display mode that shows all the hair strand keypoints. Then select all the keypoints of the strands to be moved. If the root keypoints are not embedded in the scalp emitter, disable the “Roots” option in Particle mode so the root keypoints can also be moved. Then simply grab (G-KEY) and move the strands down to scalp level.