CloudSat spaceborne 94 GHz radar bright bands in the melting layer: An attenuation‐driven upside‐down lidar analog
CloudSat spaceborne 94 GHz radar bright bands in the melting layer: An attenuation‐driven upside‐down lidar analog
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CloudSat 星载 94 GHz 雷达熔化层中的明亮波段：衰减驱动的倒置激光雷达模拟
DOI：
10.1029/2007gl030291
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发表时间：
2007
影响因子：
5.2
通讯作者：
J. Campbell
中科院分区：
文献类型：
--
作者：
K. Sassen;S. Matrosov;J. Campbell
CloudSat卫星支持W波段（94 GHz）云廓线雷达。在这个3.2毫米波长下，与融化的雪花相关的降雨的地面测量没有显示出雷达反射率峰值，这是在较长波长（瑞利散射主导）的亮带测量的特征。尽管如此，对降水中向下看的CloudSat返回的检查通常表明在融化区域有一个明显的信号峰值。通过融化层微物理和散射模型模拟，我们证明了这种向下观察的雷达特征类似于从地面观察到的激光雷达亮带，因为它的存在是由于强烈的衰减。在上视激光雷达的情况下，强烈的衰减来自大的低密度雪花。在向下看的94 GHz雷达情况下，这是由于与冰相比水粒子的折射率更大的影响：它与倒置的激光雷达亮带相当。一个W波段雷达暗带，这有助于明带的能见度，被证明是由于降雪的衰减。为了进行比较，还对向上观察激光雷达的亮带和暗带进行了建模：后者通过降低含冰雨滴的光后向散射效率来模拟。
The CloudSat satellite supports a W‐band (94 GHz) cloud profiling radar. At this 3.2 mm wavelength, ground‐based measurements of rainfall associated with melting snowflakes do not show the radar reflectivity peak that is characteristic of bright band measurements at longer (Rayleigh scattering‐dominated) wavelengths. Nonetheless, examination of downward‐looking CloudSat returns in precipitation often indicate an obvious signal peak in the melting region. Through melting layer microphysical and scattering model simulations, we demonstrate that this downward‐viewing radar feature is analogous to the lidar bright band observed from the ground in that it owes its existence to strong attenuation. In the upward‐looking lidar case, the strong attenuation comes from large low‐density snowflakes. In the downward‐looking 94 GHz radar case, it is due to the effects of the greater refractive index of water particles compared to ice: it is comparable to an upside‐down lidar bright band. A W‐band radar dark band, which contributes to the visibility of the bright band, is shown to be due to attenuation in the snowfall. For comparison, the bright and dark bands for an upward viewing lidar are also modeled: the latter is simulated by a reduction in light backscattering efficiency of ice‐containing raindrops.