Polarization signatures and brightness temperatures caused by horizontally oriented snow particles at microwave bands: Effects of atmospheric absorption
Polarization signatures and brightness temperatures caused by horizontally oriented snow particles at microwave bands: Effects of atmospheric absorption
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微波波段水平定向雪颗粒引起的偏振特征和亮度温度：大气吸收的影响
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. Miao
中科院分区：
文献类型：
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作者：
Xinxin Xie;S. Crewell;U. Löhnert;C. Simmer;J. Miao
本文分析了大气吸收和发射对水平方向雪粒子产生的偏振差和亮温的影响。一个三层平面平行大气模型与一个简化的辐射传输（RT）方案结合使用，以说明二向色性和非二向色性介质对地面和星载传感器观测到的微波特征的综合影响。基于理想化的情况下，其中包括一个二色性雪层和相邻的nondichroic层组成的过冷液态水（SCLW）的水滴和水蒸气，我们证明了大气吸收/发射的存在下，从地面观察时，增强TB和阻尼PD。然而，从航天器的角度来看，TB可以通过雪层上方的吸收/发射层来减少或增强，而二向色雪层下方的强吸收/发射层甚至可以增强PD。由于SCLW的温度依赖性吸收，依赖于雪微物理假设的诱导PD和TB可以分别变化高达2 K和10 K。基于欧洲中期天气预报中心数据集的223个降雪剖面的RT计算表明，SCLW的存在对降雪期间三个窗口频率（150 GHz，243 GHz和664 GHz）的PD和TB有明显的影响。我们的研究结果意味着，虽然在三个窗口通道的极化通道有可能的降雪特性，准确的信息，液态水需要正确解释极化观测。
This study analyzes the effects of atmospheric absorption and emission on the polarization difference (PD) and brightness temperature (TB) generated by horizontally oriented snow particles. A three‐layer plane‐parallel atmosphere model is used in conjunction with a simplified radiative transfer (RT) scheme to illustrate the combined effects of dichroic and nondichroic media on microwave signatures observed by ground‐based and spaceborne sensors. Based on idealized scenarios which encompass a dichroic snow layer and adjacent nondichroic layers composed of supercooled liquid water (SCLW) droplets and water vapor, we demonstrate that the presence of atmospheric absorption/emission enhances TB and damps PD when observed from the ground. From a spaceborne perspective, however, TB can be reduced or enhanced by an absorbing/emitting layer above the snow layer, while a strong absorbing/emitting layer below the dichroic snow layer may even enhance PD. The induced PD and TB, which rely on snow microphysical assumptions, can vary up to 2 K and 10 K, respectively, due to the temperature‐dependent absorption of SCLW. RT calculations based on 223 snowfall profiles selected from European Centre for Medium‐Range Weather Forecasts data sets indicate that the existence of SCLW has a noticeable impact on PD and TB at three window frequencies (150 GHz, 243 GHz, and 664 GHz) during snowfall. Our results imply that while polarimetric channels at the three window channels have the potential for snowfall characterization, accurate information on liquid water is required to correctly interpret the polarimetric observations.
更好地理解降雪微物理的多传感器方法托斯卡项目
影响因子：
8
作者：
Löhnert;S. Kneifel;A. Battaglia;M. Hagen;L. Hirsch;S. Crewell
通讯作者：
S. Crewell