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首页> 外文期刊>Journal of hydrometeorology >Polarimetric Estimates of a 1-Month Accumulation of Light Rain with a 3-cm Wavelength Radar
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Polarimetric Estimates of a 1-Month Accumulation of Light Rain with a 3-cm Wavelength Radar

机译：用3厘米波长雷达对小雨进行1个月累积的极化估计

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The authors evaluate rainfall estimates from the new polarimetric X-band radar at Bonn, Germany, for a period between mid-November and the end of December 2009 by comparison with rain gauges. The emphasis is on slightly more than 1-month accumulations over areas minimally affected by beam blockage. The rain regime was characterized by reflectivities mainly below 45 dBZ, maximum observed rain rates of 47 mm h~(-1), a mean rain rate of 0.1 mm h~(-1), and brightband altitudes between 0.6 and 2.4 km above the ground. Both the reflectivity factor and the specific differential phase are used to obtain the rain rates. The accuracy of rain total estimates is evaluated from the statistics of the differences between radar and rain gauge measurements. Polarimetry provides improvement in the statistics of reflectivity-based measurements by reducing the bias and RMS errors from 225% to 7% and from 33% to 17%, respectively. Essential to this improvement is separation of the data into those attributed to pure rain, those from the bright band, and those due to nonmeteorological scatterers. A type-specific (rain or wet snow) relation is applied to obtain the rain rate by matching on the average the contribution by wet snow to the radar-measured rainfall below the bright band. The measurement of rain using specific differential phase is the most robust and can be applied to the very low rain rates and still produce credible accumulation estimates characterized with a standard deviation of 11% but a bias of 225%. A composite estimator is also tested and discussed.
机译：通过与雨量计进行比较，作者评估了德国波恩新型极化X波段雷达在2009年11月中旬至2009年12月下旬期间的降雨估计。重点是在受光束阻塞影响最小的区域上略超过1个月的累积量。降雨状态的特点是反射率主要低于45 dBZ，观测到的最大降雨速率为47 mm h〜（-1），平均降雨速率为0.1 mm h〜（-1），亮带高度在海拔之上0.6至2.4 km之间。地面。反射系数和特定的微分相位都用于获得降雨率。根据雷达和雨量计测量值之间的差异统计数据来评估降雨总量估算的准确性。极化分析可通过将偏差和RMS误差分别从225％降低到7％和从33％降低到17％来改善基于反射率的测量的统计数据。改进的关键是将数据分为归因于纯雨的数据，来自明亮带的数据和归因于非气象散射的数据。通过平均匹配湿雪对明亮带以下雷达测得的降雨的贡献，可以应用特定类型的（雨雪或湿雪）关系来获得降雨率。使用特定的微分相位进行降雨测量是最可靠的方法，可以应用于极低的降雨率，并且仍可以得出可靠的累积估算值，其标准偏差为11％，而偏差为225％。还对综合估计量进行了测试和讨论。

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