【作者】 李艳芳；

【导师】 黄兴友；

【作者基本信息】 南京信息工程大学 ， 大气遥感科学与技术， 2011， 硕士

【摘要】 天气雷达以较高的时空分辨率实时探测大气中的降水过程,在中小尺度降水监测中具有无可替代的优势。相比雨量计,用雷达估测降水具有明显的优势,但雷达资料的质量影响着降水估测的准确度。因此,应当进行雷达资料质量控制,以便获得准确的降水估测。为了减小非降水回波及零度层亮带对雷达降水估测的影响,本文首先利用雷达反射率因子的水平结构和垂直梯度特征对基数据进行质量控制,识别出降水回波和非降水回波,消除低仰角非降水回波的影响。在此基础上对降水回波进行均匀型和对流型识别。利用区域分层平均法建立层状云降水回波反射率因子的垂直廓线VPR,采用自动识别技术识别零度层亮带平均高度及厚度,并对其进行抑制。经过亮带订正后的VPR在融化层高度的显著弯曲特征消失,PPI及VCS上高值区被抑制。雷达反射率因子数据经过订正之后,利用扩展的交叉相关追踪技术计算得到环境风矢量场,作为回波运动外推的依据。利用Z-I关系,得到基于雷达估测的小时降雨量。地面实际雨量和预测雨量的对比分析表明：0-10mm雨量预测值与实际值吻合度相对较高,雷达估测雨量大于实际雨量；10-20mm和20mm雨量大值区,估测值明显偏低于实际值,相关性不好。以地面雨量计测值为标准评估外推降雨量的结果表明,混合云降水的评估指标优于对流云和层状云的评估指标,外推小时降水量与实况有较好的相关性,相关系数达0.6737。雨量小的区域预报精度较高；随着雨量的增大,外推预报的可靠性下降。因为雷达测量降雨量的基础是Z-I关系,所以,利用质量控制后的回波强度作外推参量,进行降水临近预报有一定的指示意义。更多还原

【Abstract】 The weather radar has important significance in disastrous precipitation measurement of meso-microscale with high space-time resolution.Compared to raingauges, radar rainfall estimation had obvious advantages, but the quality of radar data have impact on the accuracy of rainfall estimation. Therefore, the quality control of radar data should be taken in order to obtain more accurate rainfall estimattion.For the purpose of decreasing the effect of non-precipitation echoes and bright band on surface rainfall estimation, Radar reflectivity three-dimensional structure characteristic was presented to distinguish precipitation and non-precipitaion echoes removed afterwards,and then the stratiform and convective clouds were distinguished respectively from precipitation echoes. The VPR of stratiform clouds were constructed by averaging the layered reflectivies at near range to identify the height and depth of bright band. Both the curvature feature of VPR and the high area of echoes on PPI and VCS disappeared after the bright band reflectivities were corrected.On the base of quality control of radar reflectivity factor, TREC vector field was calculated by using extend corrected (Tracking Radar Echo by Correlations) TREC technique to extrapolate radar reflectivity factors and obtain extrapolative hourly rainfall with the corresponding Z-I relationship. The comparative analysis between predicted values and actual values show that the predicted values overestimated and were still closest to the actual value in 0-10mm,,and the ruslts were opposite when predicted values were above 10mm. Then the raingauge data were used to evaluate the accuracy of hourly rainfall. Result show that precision evaluation index of mixed clouds were better than that of stratiform and convective clouds, the extrapolative hourly rainfall were closer to raingauge data and the correlation coefficient reaches 0.6737. The forecast accuracy of relatively small thershlods were much better than that of larger values. Because the radar rainfall estimation was based on the relationship between Z and I, using radar echo after quality control as the extrapolation parameter has certain indication to precipitation nowcasting.更多还原