Modeling of the Melting Layer. Part III: The Density Effect
Modeling of the Melting Layer. Part III: The Density Effect
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DOI：
10.1175/jas3563.1
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发表时间：
2005-10
影响因子：
3.1
通讯作者：
I. Zawadzki;W. Szyrmer;C. Bell;F. Fabry
中科院分区：
文献类型：
--
作者：
I. Zawadzki;W. Szyrmer;C. Bell;F. Fabry
本文提出了积雪融化及其雷达反射率的模型。对先前关于融化层的描述的主要补充是明确地引入雪密度作为一个变量。用雷达观测资料对模型进行了验证。在可比降水率下，亮带强度的差异与过冷云水（SCW）与融雪水平以上的雪的共存有关，这导致了雪密度的变化。根据融化层以上反射率通量垂直剖面和低密度雪垂直多普勒速度快于预期值的特点，选择了怀疑有冰凌的情况。对于有融化层的层状降水，雪雨速度比高表明雪密度高，因此峰雨反射率差较小。这种关系由模型计算得出，并由垂直指向雷达观测证实。尽管熔融层中存在着复杂的物理过程，但该模型似乎捕捉到了基本要素。
A model of the melting snow and its radar reflectivity is presented here. The main addition to previous description of the melting layer is the explicit introduction of snow density as a variable. The model is validated with radar observations. Differences in brightband intensity for comparable precipitation rates are related here to the coexistence of supercooled cloud water (SCW) with snow above the melting level leading to riming and change in snow density. Cases where riming was suspected were selected according to the characteristics of the vertical profile of reflectivity flux above the melting layer and vertical Doppler velocities faster than expected from low-density snow. For stratiform precipitation with a melting layer, high snow-to-rain velocity ratio indicates high-density snow and consequently a small peak-to-rain reflectivity difference is expected. This relationship was computed from the model and confirmed with vertically pointing radar observations. In spite of the complexity of the physical processes present in the melting layer the model appears to capture the essential elements.