破碎波与重力波相耦合海面的微波多普勒雷达散射特性仿真分析

Simulation Analysis of Microwave Doppler Radar Scattering Characteristics onSea Surface Coupled with Breaking Waves and Gravity Waves

海洋中不仅存在满足频散关系的自由短波,还存在由中尺度波发生破碎后生成的短波。微波电磁波和上述两种短波均能发生布拉格散射。为验证破碎短波的回波多普勒特性,通过构建自由波、破碎短波及重力波相耦合海面的X波段多普勒雷达复合海面散射模型,研究了该模型下不同入射角、不同风速和不同方向的回波多普勒谱。结果表明:破碎短波的存在可以有效地解释雷达在中等入射角和掠射角,以及顺风和逆风照射海面后回波多普勒谱的不对称性;此外,通过不同条件下的回波分析,进一步揭示海面波动对雷达散射特性的影响机制。研究结果可为相干微波雷达复合海面散射机理提供重要的理论支撑。

In the ocean,there exist not only free short waves that satisfy the dispersion relation,but also short waves that are generated by the breaking of the mesoscale waves.Microwave electromagnetic waves undergo Bragg scattering with both the aforementioned two types of short waves.To verify the echo Doppler characteristics of these broken short waves,a composite sea surface scattering model for X-band Doppler radar was constructed,which considers the mutual coupling of free waves,broken short waves,and gravity waves on the sea surface.Under this model,the echo Doppler spectra were studied under different incident angles,wind speeds,and directions.It is shown that the existence of broken short waves effectively explains the asymmetry of the echo Doppler spectra observed by radar at moderate incident angles and grazing angles,as well as under upwind and downwind conditions.The influence mechanism of sea surface fluctuations on radar scattering characteristics is further revealed through the analysis of echoes under different conditions.Important theoretical support for the scattering mechanism of coherent microwave radar on composite sea surfaces is provided by the research findings.