A dipole antenna will emit a vertically polarized wave if it is:

The polarization of an electromagnetic wave is determined by the orientation of the electric field, which perfectly aligns with the physical orientation of the radiating antenna elements. A dipole antenna typically consists of a straight wire or metal tubing. If you want it to emit a vertically polarized wave, you simply need to mount the physical elements vertically relative to the ground. Mounting it horizontally will result in horizontally polarized waves. Factors like the antenna's height above the ground or its proximity to the earth affect the radiation pattern and impedance, but they do not change the fundamental polarization of the wave as it leaves the antenna.