Compared with a horizontal antenna, a vertical antenna will receive a vertically polarized radio wave:

In radio communications, maximum signal transfer occurs when the transmitting and receiving antennas share the same polarization. This principle is known as polarization matching. A vertically polarized radio wave is optimally captured by an antenna whose elements are also aligned vertically. Therefore, a vertical antenna will receive this wave at a significantly higher strength than a horizontal antenna. If a horizontal antenna attempts to receive a vertically polarized wave, it suffers from cross-polarization loss. This mismatch can reduce the received signal strength by as much as 20 to 30 decibels (dB), making the vertical antenna the far superior choice in this scenario.