基于SRTM地形数据的天气雷达电磁波非常规遮挡回波补偿技术研究

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

  • 摘要: 为解决多普勒天气雷达电磁波因人造建筑物、森林等非地形因素造成的降水观测空间不连续问题,基于精细的地形数据信息,提出一种雷达电磁波非常规遮挡回波补偿技术。首先利用SRTM地形数据信息和雷达体扫信息,计算雷达扫描最低有效混合仰角信息;其次通过长时间雷达定量降水估计(QPE)累积,识别非地形遮挡导致的降水空间不连续区域,采用交叉方位角插值、更高一层仰角数据填补和线性加权滑动平均等方法,形成最优无缝非常规电磁波遮挡回波补偿技术。选取2017—2019年陕西汛期降水过程,采用最优无缝非常规电磁波遮挡回波补偿技术,计算雷达无缝混合仰角反射率,再通过固定的Z-R关系计算雷达QPE。最后通过定性评估分析发现,经过雷达电磁波非常规遮挡回波补偿技术订正后的雷达QPE能够更好地描述地面降水空间分布,并且通过与地面雨量计定量比较分析,结果表明均方根误差(RMSE)和平均绝对误差(MAE)都明显减小,相关系数(CC)得到了明显提高。该雷达电磁波非常规遮挡回波补偿技术能够有效填补由雷达电磁波遮挡导致的降水空间不连续,并较为准确地还原真实降水空间分布。

     

    Abstract: 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.

     

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