Research on the development of data correction algorithm for expanding the observation area by the spaceborne precipitation radar

星载降水雷达能够定量观测降雨率，是从空间观测降雨的主要传感器。不幸的是，当天线试图覆盖更宽的波段时，由于来自天线旁瓣方向的地杂波的增加，来自天线主瓣方向的雨回波急剧恶化。本研究针对未来星载降水雷达，从天线旁瓣方向研究对受地杂波影响的雨雷达数据进行校正的算法的可行性。研究期间，利用35.5 GHz极化散射仪建立了不同条件下土壤、植被和水面散射系数σ^0数据库。在不同的入射角和不同的发射-接收极化条件下，通过改变土壤含水量和表面粗糙度、植被叶面积指数值、地表风速等参数来采集数据。基于13.8 GHz波段的TRMM降水雷达数据，建立了大降雨模型，模拟了雷达的空间降雨观测。通过与该模型的雨率进行比较，我们考察了海面杂波对观测雨率的影响程度，这种影响随天线扫描角度的增加而增加。在仿真中，我们采用了实际TRMM降水雷达的理想高斯型天线方向图和平面相控阵天线方向图。结果表明，当我们采用后一种天线方向图时，即使天线波束扫描角增加30度，观测到的雨率与模式雨率的相关系数仍高达0.74，远远大于TRMM实际扫描角17度。本文还对雨水部分波束填充的影响进行了评价，研究结果表明，增大天线扫描角度是有可能的，并且对地面杂波对雨水回波恶化的校正算法也有很好的发展前景。少

Spaceborne precipitation radar can observe rain rate quantitatively, and is the main sensor to observe rain from space.Unfortunately when the antenna tries to cover a wider swath, the rain echo from the antenna mainlobe direction is sharply deteriorated due to the increase of the ground clutter from the antenna sidelobe direction.This study, for the future spaceborne precipitation radars, aims at examining the feasibility of developing the algorithm that corrects the rain radar data when it is affected by the ground clutter from the antenna sidelobe direction.During this research period, we compiled the database of scattering coefficients σ^0 of soil, vegetation and water surface in various conditions using the 35.5 GHz polarimetric scatterometer. We collected the data at different incidence angles and with different transmit-receive polarizations, while changing the moisture contents and surface roughness of the soil, the leaf area index values of vegetation and the wind speeds over t … More he water surface.Based on the TRMM precipitation radar data at 13.8 GHz, we established a large rain model to simulate rain observation from space by the radar. By comparing with the rain rates of this model, we examined how much the observed rain rate is deteriorated by the effects of the sea surface clutter, which happens with the increase of the antenna scan angle. In the simulation, we used the ideal Gaussian type antenna pattern and the planar phased array antenna pattern of the actual TRMM precipitation radar. As a result, when we applied the latter antenna pattern, the correlation coefficients between the observed rain rates and the model rain rates were as high as 0.74 even though the antenna beam scan angle increases as large as 30 degrees, which is far larger than the actual TRMM scan angle of 17 degrees. We also worked on the evaluation of the effects of partial beam filling of rainThe results we obtained from our research has shown us a good possibility of larger antenna scan angles and also a good prospect in developing the algorithms to correct the deterioration of rain echo by the ground clutters. Less