Next time you lift to the hover take a look at the VSI, it will indicate that you are DESCENDING. Why?
The increase in collective pitch as you raise the collective results in an increase in the total mass flow through the rotor disc, this air flow creates a a divergent duct (between rotor disc and the ground) which results in an increase in pressure. The same phenomena occurs when you come to the hover post transition from forward flight; how marked this is will depend on approach profile, wind strength, all up mass, etc.
Hope that helps.........
