西北干旱半干旱区一次层状云系微物理特征分析

利用西北干旱半干旱区一次飞机探测资料、卫星资料，分析了层状云微物理结构以及作业前后云微物理变化，结果表明：（1） 此次层状云系垂直结构配置为冷暖两层，云层发展厚实。云的垂直和水平分布极不均匀。相对层积云，高层云小云粒子浓度低，大云粒子浓度高，液态含水量高。小云粒子浓度尤其是峰值区域与平均直径呈明显反相关。大于60个·cm^-3和35个·L^-1的小云、大云粒子浓度分别主要由3.5~10 μm、50~200 μm粒径段决定。（2） 不同高度云粒子谱为单峰或双峰分布，总体呈单调递减趋势，但云形成和增长条件存在差异。强可播、不可播和可播性冷云粒子谱基本符合负幂指数的单调递减规律，云粒子浓度差异较大，自然冰晶浓度不可播云较高，可播云次之，强可播云较低。（3） 作业后小云粒子浓度明显降低，在6.5~20 μm粒径段降低了2个量级左右，大云粒子浓度明显增加，谱宽增大，尤其在大于150 μm粒径段。

Cloud microphysical characteristics on a stratiform nephsystem in the arid and semi-arid regions of northwest China

In order to qualitatively evaluate the effect of the aircraft artificial rain enhancement in the arid and semi-arid regions of northwest China, the stratiform cloud microphysical structure and its changes before and after the seeding were analyzed by using observation data of an airborne detection, and satellite data. The results are summarized as follows: (1) The stratiform cloud contains a cold layer and a warm layer from the vertical structure perspective and the clouds were thick. The vertical and horizontal distribution of the cloud in the detection area are very uneven. Compared to stratocumulus cloud, the concentration of the small cloud particles in altostratus cloud is low, while the concentration of the large cloud particles is high and the liquid state water content is high. The concentration of the small cloud particles was negatively correlated with its average diameter, particularly in the peak regions. The concentration of small cloud particles greater than 60 individual·cm^-3 and large cloud particles greater than 35 individual·L^-1 depended mainly on the particles whose diameters ranged from 3.5 to 10 μm and from 50 to 200 μm, respectively. (2) The cloud particle spectrum with different heights follows unimodal or bimodal distributions, but shows a declining trend in general. There is difference in the cloud forming and developing. The particle spectrum of the strong seedable, not-seedable and seedable cold cloud basically accords with the monotone decreasing law of negative power exponent, but there are great difference in cloud particles concentration,with the not-seedable ice crystal cloud having the highest concentration,followed by those with seedable cloud,and the strong seedable cloud the lowest. (3) The concentration of the small cloud particles was significantly decreased after seeding,by about two orders of magnitude in the diameter range from 6.5 to 20 μm.The concentration of the large cloud particles was significantly increased after seeding,and the spectral width was expanded,especially in the diameter range larger than 150 μm.