TABLE OF CONTENTS The polarization of the electromagnetic wave of the radar has a complex and not well understood effect on reflectivity. In a perhaps oversimplified description, the reflecting parts of the wave structure react differently to horizontally and vertically polarized signals. For low to moderate grazing angles and lower sea states, the echo from vertically polarized radars is heavily dependent on the gravity wave, while the echoes from horizontally polarized radars are more dependent on the smaller (<1.7 cm) capillary waves. The signals on each polarization are to a certain extent independent. It will be shown in later sections that the Doppler shift is higher for horizontal polarization. In addition, if the pulse length in distance units is less than or comparable to the distance between ocean waves (especially when looking upwind or downwind) the amplitude and spatial distributions depend on polarization. It has been shown that there is a degree of clustering of the echoes on the polarization sphere (see Chap. 5). With a dual polarized radar this may lead to better discrimination of specific targets, but it is not clear that it is operationally significant in general target-detection radars.
For typical moderate- to long-pulse radars Tables 7.2 through 7.8 show that the mean reflectivity is somewhat higher on vertical than on horizontal polarizations. This is even more clear when looking at results of specific experimenters such as Daley [157, 158, 159] and Long [444] plus many papers in the remote-sensing world. Note...
