4-10] 



SEA RETURN 



215 



The variation of o-*^ with depression angle is a function of wind speed. 

 Fig. 4-37 shows measurements on vertical and horizontal polarization at 

 24 cm as reported by MacDonald,^^ while Figs. 4-38 and 4-39 show measure- 



-20 



-30 



-60 



0.1° 



1.0° 10' 



DEPRESSION ANGLE 



100^ 



Fig. 4-37 Sea Clutter, 1250 Mc: Solid Line = Transmitted and Received Vertical 

 Polarization. Dotted Line = Transmitted and Received Horizontal Polarization. 



20 



10 







S-lO 

 b 

 -20 



-30 

 -40 



15-20 

 Knots 



Fig. 4-38 

 Velocity; 



20° 40° 60° 80' 

 ANGLE OF DEPRESSION 



cj"" as a Function of Wind 

 X = 8.6 mm. 



20° 40° 60° 8 

 ANGLE OF DEPRESSION 



Fig. 4-39 

 Velocity, X 



as a Function of Wind 

 1.25 cm. 



ments on vertical polarization at X = 8.6 mm and 1.25 cm by Grant and 

 Yaplee."* At small depression angles, a^ increases with wind speed, but near 

 vertical incidence this trend is reversed and a^ decreases with increasing wind 



2^F. C. MacDonald, "Correlation of Radar Sea Clutter on Vertical and Horizontal Polar- 

 ization with Wave Height and Slope," IRE Convention Record \ (1), 29-32 (1956). 



2*C. R. Grant and B. S. Yaplee, "Back-Scattering from Water and Land at Centimeter and 

 Millimeter Wavelengths, Proc. IRE 45, 976-982 (1957). 



