An Empirical Study of Breaking Wave Contribution to Radar Backscatter from the Ocean Surface at Low Grazing Angle

The anomaly of radar sea spikes, defined here as the non-Bragg scattering events with backscattering cross section of horizontal polarization exceeding that of vertical polarization, has been associated with steep wave features possibly going through wave breaking process. This property is employed for remote detection of breaking waves. The results are used to quantify the effect of wave breaking on radar returns. Large increase due to breaking is found in the Doppler velocities of both polarizations (about 50% faster with breaking). The effect of breaking on the backscattering cross section is much stronger for the horizontal polarization (with 15 to 20 dB enhancement) and relatively small in the vertical polarization (on the order of 0.5 dB fluctuations). The presence of swell reduces the impact of breaking waves on radar return in comparison to the scattering from wind seas.

[1]  Robert E. McIntosh,et al.  Space-time properties of radar sea spikes and their relation to , 1998 .

[2]  J. P. Hansen,et al.  High Range Resolution Radar Measurements of the Speed Distribution of Breaking Events in Wind-Generated Ocean Waves: Surface Impulse and Wave Energy Dissipation Rates , 2001 .

[3]  D. Trizna.  Statistics of low grazing angle radar sea scatter for moderate and fully developed ocean waves , 1991 .

[4]  O. M. Phillips,et al.  Wave breaking in the presence of wind drift and swell , 1974, Journal of Fluid Mechanics.

[5]  Robert E. McIntosh,et al.  Measurement and classification of low-grazing-angle radar sea spikes , 1998 .

[6]  Jakov V. Toporkov,et al.  Breaking wave contribution to low grazing angle radar backscatter from the ocean surface , 2008 .

[7]  V. Pidgeon.  Doppler dependence of radar sea return , 1968 .

[8]  O. M. Phillips,et al.  On the incipient breaking of small scale waves , 1974, Journal of Fluid Mechanics.

[9]  Jakov V. Toporkov,et al.  Analysis of radar sea return for breaking wave investigation , 2008 .

[10]  Paul A. Hwang,et al.  An empirical investigation of source term balance of small scale surface waves , 2004 .

[11]  I. D. Olin,et al.  Experimental study and theoretical model of high‐resolution radar backscatter from the sea , 1980 .

[12]  Dennis B. Trizna,et al.  Studies of dual polarized low grazing angle radar sea scatter in nearshore regions , 1996, IEEE Trans. Geosci. Remote. Sens..

[13]  William J. Plant,et al.  Observation of Breaking Ocean Waves with Coherent Microwave Radar , 1986 .