The Dual Wavelength Ratio Knee: A Signature of Multiple Scattering in Airborne Ku-Ka Observations
The Dual Wavelength Ratio Knee: A Signature of Multiple Scattering in Airborne Ku-Ka Observations
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双波长比拐点：机载 Ku-Ka 观测中多重散射的特征
DOI：
10.1175/jamc-d-13-0341.1
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发表时间：
2014
影响因子：
3
通讯作者：
Battaglia A
中科院分区：
文献类型：
--
作者：
Battaglia A
2011年俄克拉荷马州中纬度大陆对流云实验(MC3E)现场活动期间，高空成像风雨剖面仪(HIWRAP)雷达观测到的深对流系统首次提供了在Ku和Ka波段同时存在多重散射效应的证据。有一个特征是新的和值得注意的：通常，对应于具有强对流的竖井，当从云顶向下移动时，双波长比(DWR)首先在Ku-Ka波段观测中像往常一样增加，然后达到最大值，然后一直稳定地减小到地表，形成下文中所称的Aknee。在几乎任何可能的云微物理廓线下，单次散射理论都不能再现这个DWR膝部。另一方面，对于水平范围较大的冰雹对流核的数值模拟，利用多重散射理论进行了直观的解释。对流层下部DWR的减小(即DWR随高度增加)被解释为高度扩散的冰雹层引起的多次散射脉冲展宽的结果，Ka多次散射通常超过Ku通道的多次散射。由于多次散射的影响随着足迹大小的增加而增加，如果在飞机测量中存在多次散射效应，那么在2014年2月发射的NASA-日本宇宙航空研究开发机构(日本宇宙航空研究开发机构)全球降水测量任务设想的星载双频Ku-Ka雷达观测中，这种影响可能更加明显。这项理论研究支持GPM雷达在飞越大型对流系统中嵌入的高密度冰穴时会观测到DWR膝部的观点，并建议不能通过微分衰减或微分Mie效应来寻求解释，而应该通过多次散射效应来寻求解释。
Deep convective systems observed by the High Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) radar during the 2011 Midlatitude Continental Convective Clouds Experiment (MC3E) field campaign in Oklahoma provide the first evidence of multiple-scattering effects simultaneously at Ku and Ka band. One feature is novel and noteworthy: often, in correspondence to shafts with strong convection and when moving from the top of the cloud downward, the dual wavelength ratio (DWR) first increases as usual in Ku–Ka-band observations, but then it reaches a maximum and after that point it steadily decreases all the way to the surface, forming what will be hereinafter referred to as aknee. This DWR knee cannot be reproduced by single-scattering theory under almost any plausible cloud microphysical profile. On the other hand, it is explained straightforwardly with the help of multiple-scattering theory when simulations involving hail-bearing convective cores with large horizontal extents are performed. The DWR reduction in the lower troposphere (i.e., DWR increasing with altitude) is interpreted as the result of multiple-scattering pulse stretching caused by the highly diffusive hail layer positioned high up in the atmosphere, with Ka multiple scattering typically exceeding that occurring in the Ku channel. Since the effects of multiple scattering increase with increasing footprint size, if multiple-scattering effects are present in the aircraft measurements, they are likely to be more pronounced in the spaceborne dual-frequency Ku–Ka radar observations, envisaged for the NASA–Japan Aerospace Exploration Agency (JAXA) Global Precipitation Measurement (GPM) Mission, launched in February 2014. This notional study supports the idea that DWR knees will be observed by the GPM radar when overflying high-density ice shafts embedded in large convective systems and suggests that their explanation must not be sought in differential attenuation or differential Mie effects but via multiple-scattering effects.
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影响因子：
3.1
作者：
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通讯作者：
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影响因子：
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作者：
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DOI：
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发表时间：
2013
期刊：
影响因子：
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作者：
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通讯作者：
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