Microphysical responses as seen in a stratocumulus aircraft seeding experiment in autumn over the Sanjiangyun National Nature Reserve

Making use of the Globe Positioning System (GPS) and the Particle Measuring System (PMS) observation data from a saw-shape artificial seeding and backward-forward probe experiment above stratocumulus over the Sanjiangyuan National Nature Reserve, microphysica1 responses are studied through analysis of the variation of total number concentration of liquid cloud particles and ice crystal, cloud particle spectrum and f1 (fraction of liquid water), which is based on distinguishing of cloud particle's phase state when the effective area for comparing has been defined between before and after the operation. The results show that the size of cloud particles in liquid phase are mostly in the median diameter range of 3.5-18.5 μm, with ice crystal in the range 21.5-45.5 μm and the particles greater than 50 μm being in ice phase in the experiment area. At the leeward of routine within the scope of 36 km about 2-23 min later, the variation of number concentration and diameter detected by FSSP and 2DC in the test region, is not out of the range of normal fluctuation. However, in the high supercooled water area (HSWA) with the supercooled liquid water content (SLWC) larger than 0.01 g/m3, the number concentration of cloud particles for liquid phase decreases obviously, and the density of ice crystal particles increases in the FSSP's range, which is the same as the variation tendency of the Ice Water Content (IWC), with the mean value of f1 reduced to (34.2±12.4)% from (68.3±23.1)%. The effects of seeding are remarkable in the high supercooled water area, but not obviously in the low supercooled water area and the routine cross points just influenced by the original seeding.