雄安新区X波段相控阵阵列天气雷达估测降水技术研究

Research on Precipitation Estimation Technology of X-band Phased Array Weather Radar in Xiong’an New Area

暴雨与强对流天气是汛期影响雄安新区最主要的灾害性天气,常常给社会经济和人民生命财产造成很大损失。当前X波段天气雷达因更高的时空分辨率受到越来越多的关注和应用,但对其定量估测降水研究还较少。为此,利用2021年7—10月雄安新区X波段相控阵阵列天气雷达的组合反射率资料和33个自动雨量站实况资料,分不同系数、不同高度、不同降水类型对雷达定量估测降水结果进行检验。结果表明,Z=200I^(1.6)公式的整体估测效果最好。其中,Z=200I^(1.6)公式采用3.0 km以下高度的组合反射率平均值的估测方案对1 h估测降水效果最好,尤其对对流云降水的小时雨量估测效果最好,选取1.5 km以下高度组合反射率最大值的估测方案总体上对层状云降水估测效果最好。利用最优化法得到雄安新区两种本地化优化Z-I关系方案:Z=93I^(1.4)时选取3.0 km以下高度组合反射率平均值方案和Z=100I^(1.5)时选取1.5 km以下高度组合反射率最大值方案,将其与当前业务运行的估测方案(Z=275I^(1.55))、优化前效果最佳估测方案(Z=200I^(1.6))进行对比检验分析发现,优化方案(Z=93I^(1.4))对于1 h降水估测效果略差于优化前效果最佳的估测方案(Z=200I^(1.6)),优于另一种优化方案(Z=100I^(1.5))和业务运行估测方案(Z=275I^(1.55)),但优化公式Z=100I^(1.5)选取3.0 km以下高度的组合反射率平均值估测方案的降水估测平均相对误差却比优化前最佳估测方案的降低2%,优化表现最佳,说明还需要累积更多天气个例样本进行参数的进一步优化。

Rainstorm and severe convection weather are the major disastrous weather affecting the Xiong’an New Area in flood season,often causing heavy losses to social economy and people’s lives and property.At present,the X-band weather radar has received more and more attention and application due to its higher spatial and temporal resolution,but there is still less research on its capability of quantitatively estimating precipitation.In this paper,using the composite reflectivity data of X-band phased array weather radar in Xiong’an New Area from July to October 2021 and the observations of 33 automatic rainfall stations,we test the results of radar quantitative estimation of precipitation by different coefficients,different heights and different precipitation types.The results denote that the overall estimation effect of Z=200I^(1.6)formula is the best.Among them,the estimation scheme of Z=200I^(1.6)formula using the average value of composite reflectivity below 3.0 km has the best performance for 1 h precipitation estimation,especially for hourly rainfall amount estimation of convective cloud precipitation.The estimation scheme of selecting the maximum value of composite reflectivity below the 1.5 km height has the best effect for the stratiform cloud precipitation estimation in general.By the optimization method,we obtain two localized optimization Z-I relationship schemes for the Xiong’an New Area:when Z=93I^(1.4),we select the average value scheme of composite reflectivity at height below 3.0 km;and when Z=100I^(1.5),we select the maximum value scheme of composite reflectivity at height below 1.5 km.The two schemes are compared with the current operation estimation scheme(Z=275I^(1.55))and the best estimation scheme before optimization(Z=200I^(1.6)).The comparative analysis results show that the estimation effect of the optimization formula Z=93I^(1.4)scheme for 1 h precipitation is slightly worse than that of the best estimation scheme before optimization(Z=200I^(1.6)),which is superior to the other two schemes.However,the average relative error of precipitation estimation of the optimization formula Z=100I^(1.5)with the composite reflectivity average estimation scheme selected below the 3.0 km height is reduced by 2%compared to the optimal estimation scheme before optimization.This is the best optimization performance,and it indicates that more weather case samples need to be collected for further optimization of parameters.