2004年8～9月利用机载粒子测量系统 (Particle Measuring System, 简称PMS) 对我国北京及周边地区的三次锋面云系进行了探测, 本文分析了三次降水性层积云中各种粒子的垂直、水平和谱分布。结果表明, 三次降水云系基本是冷锋或者暖锋系统下形成的层积混合云系。云内以直径5～9 μm、200 μm和400～1000 μm的云和降水粒子为主。9月14日暖锋层积云系的粒子浓度最大, FSSP-100 (前向散射粒子谱探头)、 GA2(二维灰度云粒子图像探头)、 GB2(二维灰度降水粒子探头)分别探测的最大粒子浓度为318.97 cm-3、0.03 cm-3、0.0065 cm-3。8月12日和8月15日的冷锋层积云系有多个干层。GA2探测的平均浓度谱基本为单峰分布, 并找出了合适的拟合函数。冷锋层积云系的负温云层中存在着相同浓度量级的过冷云水和雨水、霰粒、柱状和针状冰晶, 过冷水含量可达到0.26 g/m3, 暖锋云系中则以霰粒、结淞粒子和冰雪晶聚合体为主, 也存在少量柱状、针状冰晶和过冷水滴。与我国北方地区13架次飞行探测结果比较, 北京及周边地区2003年8月15日、2004年8月12日和9月14日层积云0 ℃层以上的冰雪晶粒子直径最大, 浓度居中, 过冷水含量因云系结构不同而变化较大。
By using probes of FSSP-100, GA2 and GB2 of an airborne PMS (Particle Measuring System), the stratocumulus clouds during August to September in 2004 over Beijing and its surrounding areas were probed. The results showed that the diameter of particles was primarily distributed around 5－9 μm, 200 μm and 400－1000 μm. On 14 September 2004, the warm frontal stratocumulus presents the maximum number concentration of 318.97 cm-3, 0.03 cm-3, and 0.0065 cm-3measured by FSSP-100, GA2, and GB2, respectively. On 12 August and 15 August, 2004, controlled by the cold frontal system, several dry layers were observed. The size distributions of particles derived from probe GA2 in the three flights mainly followed unimodal distribution and the better fitting function was found. Based on the analyses of two-dimensional images of probe GA2, the unimodal distribution was primary for different particles of natural condition. The supercooled cloud and rain water, graupel, columnar and needle crystal have the same order of number concentration above 0 ℃ layer in the cold frontal clouds. The peak content of supercooled water was 0.26 g/m3. In the warm frontal clouds, graupel, riming particles, and large aggregates were the main ice particles, and the supercooled water, columnar and needle crystals were measured. Compared with the GA2 data above the layer of 0 ℃ for 13 flights over northern China, stratocumulus clouds over Beijing and its surrounding areas present the maximum diameter of ice and snow crystal, the middle number concentration, and different content of supercooled water depending on different stratocumulus structures.