Relating the Radar Bright Band and Its Strength to Surface Rainfall Rate Using an Automated Approach
Relating the Radar Bright Band and Its Strength to Surface Rainfall Rate Using an Automated Approach
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DOI：
10.1175/jhm-d-19-0085.1
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发表时间：
2020-02
影响因子：
3.8
通讯作者：
Dongqi Lin;B. Pickering;Ryan Reynolds Neely
中科院分区：
文献类型：
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作者：
Dongqi Lin;B. Pickering;Ryan Reynolds Neely
在对水凝物的雷达观测中，大气中的0°C等温线（即，冻结水平）通常表现为反射率增强的区域。这个区域被称为亮带（BB）。在这项研究中，超过12个月的观察，从垂直指向35 GHz雷达和并置disdrometer在自然环境研究理事会（NERC）设施的大气和无线电研究（NFARR）被用来识别和比较微物理BB和非亮带（NBB）期间之间的差异。结果表明，BB期雷达反射率Z与降雨强度R的关系为Z = 772 R ~（0.57），NBB期为Z = 108 R ~（0.99）。此外，明带强度（BBS）的计算使用一种新的方法来自迈克尔逊对比度方程，试图解释所观察到的BB降水的变化。计算了BBS的一系列Z-R关系。系数随着BBS从227增加到926而增加，而指数随着BBS从0.85增加到0.38而减小。结果还表明，在其他研究中，在0°C等温线存在的情况下识别的NBB周期可能会被错误分类，因为它们无法识别弱亮带周期。因此，假设NBB周期仅仅是由于暖雨过程。
In radar observations of hydrometeors, the 0°C isotherm in the atmosphere (i.e., the freezing level) usually appears as a region of enhanced reflectivity. This region is known as the bright band (BB). In this study, observations over 12 months from a vertically pointing 35-GHz radar and a collocated disdrometer at the Natural Environment Research Council (NERC) Facility for Atmospheric and Radio Research (NFARR) are used to identify and compare microphysical differences between BB and non-brightband (NBB) periods. From these observations, the relationship between radar reflectivity Z and rainfall intensity R is found to be Z = 772R0.57 for BB periods and Z = 108R0.99 for NBB periods. Additionally, the brightband strength (BBS) was calculated using a novel method derived from the Michelson contrast equation in an attempt to explain the observed variability in BB precipitation. A series of Z–R relationships are computed with respect to BBS. The coefficients increase with increasing BBS from 227 to 926, while the exponents decrease with increasing BBS from 0.85 to 0.38. The results also indicate that NBB periods identified in the presence of a 0°C isotherm in other studies may be misclassified due to their inability to identify weak brightband periods. As such, it is hypothesized that NBB periods are solely due to warm rain processes.