一次伴随雷达异常地物回波的超视距探测成因分析与数值模拟研究

Cause analysis and numerical simulation research of over-the-horizon detection accompanied with radar anomalous terrain echo

大气波导对电磁波的陷获作用可以通过雷达超视距探测和异常地物回波等现象被直观感知和捕获.文中基于欧洲中期数值预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)ERA5再分析资料、葵花卫星云图和WRF4.2模式,对福建中南部及粤东沿海天气雷达探测到的一次伴随异常地物回波的超视距探测现象开展成因分析和数值模拟研究.研究结果表明:此次大范围异常地物回波的出现与台湾海峡持续存在的显著大气波导过程有关.台湾海峡受高空槽后下沉运动与低空暖脊共同影响,存在逆温层结与强烈的湿度随高度锐减层,有利于大气波导形成;模拟时段中后期,台湾海峡几乎被顶高200-600 m的表面波导全覆盖,且波导强度持续增强,最终整体强度达到40 M单位以上.进一步利用WRF模式模拟预报的气象雷达传播路径上非均匀大气波导廓线,输入电磁波传播模型,结果与雷达实测回波的主体结构吻合,证实了利用中尺度模式开展大气波导预报与传播应用的良好前景.

The trapping effect of atmospheric duct on electromagnetic wave can be intuitively discovered through the phenomenon of radar over-the-horizon detection and anomalous terrain echo.Based on European Centre for Medium-Range Weather Forecasts(ECMWF)ERA5 reanalysis data,Himawari-8 satellite images and WRF4.2 model,this paper conducts research on over-the-horizon detection phenomenon accompanied with radar anomalous terrain echo detected by the weather radar in south-central Fujian and East coast of Guangdong.The results show following points.The appearance of this large-scale anomalous terrain echo is related to the continued existence of significant atmospheric duct process in the Taiwan Strait.The Taiwan Strait is jointly affected by the post high-altitude trough sinking movement and the low-altitude warm ridge.The existence of temperature inversion stratification and strong humidity decrease layer with height is conducive to the formation of atmospheric duct.During the mid-to-late simulation period,the Taiwan Strait is almost completely covered by surface duct with height of 200-600 m.Moreover,duct strength continues to increase,and overall strength reaches more than 40 M-units finally.Furthermore,by using WRF model to simulate and forecast the non-uniform atmospheric duct structure on the electromagnetic wave propagation path of the meteorological radar,inputting the electromagnetic wave propagation model,the obtained electromagnetic wave propagation characteristics are consistent with the main structure of the radar measured echo.