A Radar Electromagnetic Beam Non-Standard Blockage Compensated Technology Based on SRTM Terrain Data

In order to solve the problem of precipitation observation spatial discontinuity caused by artificial buildings, forests and other non-topography factors, one non-standard beam blockage compensated algorithm is proposed based on high resolution STRM DEM data. First, SRTM DEM data and radar volume coverage pattern (VCP) are used to calculate the radar beam blockage at each tilt, and then generate the lowest hybrid scan tilt; secondly, the precipitation spatial discontinuity caused by non-standard beam blockage is identified through long-term radar quantitative precipitation estimation (QPE) accumulation with one fixed Z-R relationship. And, then based on the identified non-standard beam blockage, the lowest hybrid scan tilt is updated; Finally, the updated hybrid scan tilt is used to generate hybrid scan reflectivity, and the azimuth cross interpolation and linear weighted mean will be applied on the hybrid reflectivity field to remove the discontinuity caused by non-standard beam blockage. In this paper, the precipitation events from 2017 to 2019 in flood season are selected, and the non-standard beam blockage compensated algorithm is used to generate the seamless hybrid reflectivity. Then, the radar QPE is calculated with a fixed Z-R relationship. Through the qualitative analysis, it is found that the seamless radar QPE can better describe the spatial distribution of surface precipitation. The results show that the root mean square error (RMSE) and mean absolute error (MAE) are significantly reduced, and the correlation coefficient (CC) is significantly improved. This nonstandard beam blockage compensated algorithm can effectively remove the spatial discontinuity of precipitation, and provide the real precipitation spatial distribution accurately.