摘要
摘要:通过飞机直接进入降雪云进行探测，并配合MICPAS（气象信息综合分析处理系统）、雷达和卫星等资料，对2011年11月29日山西一次降雪云宏、微观结构特征进行分析。研究发现：本次降雪过程的雷达回波以10～20 dBZ大片层状云回波为主，镶嵌了超过30 dBZ的块状强回波，雷达径向速度零线呈较强的“S”型弯曲，出现“牛眼”结构，从低层到高层有较强的风垂直切变。液态水含量主要位于3.2 km以下，最大值为0.0697 g m^?3，N₅₀（粒子直径大于50 μm的冰雪晶数浓度）、N₂₀₀（粒子直径大于200 μm的冰雪晶数浓度）和冰水含量主要产生于层积混合降雪云的上部，极大值出现在?9.3°C附近，分别为188.4 L^?1、33.5 L^?1和0.121 g m^?3。?14.4°C～?19.7°C冰晶图像以针状、柱状和不规则状为主，以冰晶的凝华增长为主。?9.3°C附近冰雪晶图像以辐枝状、不规则状为主，辐枝状冰晶的聚并碰撞和折裂繁生可能是造成此处冰雪晶高浓度的主要原因。利用指数形式能较好地拟合冰雪晶谱分布，谱拟合参数可以用幂函数N_os=1.021λ^1.684表示（其中，N_os、λ分别表示截距和斜率，N_os越大表示小粒子数浓度越大，λ越大表示小粒子数浓度占总粒子数浓度比例越高），相关系数R²为0.86。3.2 km以下存在三次逆温，逆温层的出现使云微物理特征量和拟合参数N_os减小，抑制了云内凇附增长和凝华增长，导致本次观测谱拟合参数N_os、λ随温度的变化规律与以往的观测不一致，逆温强度越大抑制作用越大。
关键词:降雪云/
冰雪晶图像/
形成机制/
飞机探测
Abstract:Based on observations from an aircraft that directly entered the snowfall cloud and MICPAS (Meteorological Information Comprehensive Analysis and Processing System), radar and satellite data, the macro and micro structure characteristics of a snowfall cloud in Shanxi Province on 29 November 2011, were analyzed. Notably, the radar echo of this snowfall process was mainly between 10 dBZ and 20 dBZ large stratiform cloud echo, inlaid with more than 30 dBZ massive and strong echo. The zero line of the radar radial velocity had a strong “S” curve with a bull’s eye structure. Strong vertical wind shear was observed from the lower level to the upper level. The liquid water content was mainly below 3.2 km, and the maximum value was 0.0697 g m^?3. The ice and snow crystal number concentrations N₅₀ (Number concentration of ice and snow crystals with particle diameter greater than 50 μm) and N₂₀₀ (Number concentration of ice and snow crystals with particle diameter greater than 200 μm) and the ice water content were mainly produced in the upper part of the stratiform mixed-phase snowfall cloud, and the maximum values, which were 188.4 L^?1, 33.5 L^?1, and 0.121 g m^?3, were obtained at approximately ?9.3°C. From ?14.4°C to ?19.7°C, the images of ice crystals were mainly needle, columnar, and irregular, and the ice particles grew mainly by deposition. The images of ice and snow crystals at approximately ?9.3°C were mainly dendritic and irregular. The aggregation, collision, and fracture of radial dendritic ice crystals may be the main reason for the high concentration of ice and snow crystals. The distribution of the ice and snow crystal spectra can be well fitted by the exponential form. The spectrum fitting parameters can be expressed by the power function N_os=1.021λ^1.684 (N_os and λ represent intercept and slope, respectively. The larger N_os was, the higher the concentration of small particles was. The larger λ was, the higher the proportion of small particle number concentration to total particle number concentration was.), and the correlation coefficient R² was 0.86. Three inversion times below 3.2 km were detected. The appearance of the inversion layer influenced the cloud microphysical characteristics, decreased the fitting parameter N_os, and inhibited the growth of rimming and deposition. As a result, the variation of the fitting parameters N_os and λ with temperature in this study was inconsistent with that in previous studies. The greater the inversion intensity was, the greater the inhibition effect.
Key words:Snowfall cloud/
Ice and snow image/
Formation mechanism/
Aircraft observation



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