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

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.