Forecast on Convective Cloud Condition and Analysis on Seeding Plan of an Artificial Mitigation Case

In order to do well artificial rainfall mitigation on specific target period and area, cloud seeding condition such as cloud properties and structure, moving speed and direction, cloud evolution, precipitation mechanism and so on was forecast by using Cloud Precipitation Explicit Forecast System (CPEFS). The results showed that on Aug. 8, 2017 in Hohhot there would appear scattering convective clouds, with cold-warm mixed vertical structure and strong updrafts. Horizontal scale of single convective cloud was about tens of kilometers, lifetime was about 1.5-3 hours. Cloud top (bottom) height of 10 (3) km, 0℃ height of 4.3 km. Cloud microphysics aspects were with high content of snow and graupel, low cloud water content in warm regions, maximum content of supercooled water of 0.7 g·kg^-1, less ice crystals in areas with rich supercooled water, mainly with cold precipitation mechanism. Convective clouds were first appeared in the northwest direction of the core zone in Hohhot, rapidly developed and moved eastward and southward gradually to the core zone with speed about 30-40 km·h^-1. Satellite and radar observation also showed there were convective clouds. The generation time of convective clouds of forecast was 1-2 hours later than the observation, and moving direction was consistent with observation. Moving speed was 10-20 km·h^-1 slower. The maximum liquid water content was 0.6 g·m^{– 3} at 5400 m height (-8℃) by airborne cloud physical detection. Cloud water content of forecast was consistent with detection. The reserve seeding plan was made based on cloud condition forecast. 50-30 km northwest of the core zone was chosen as key defense zone. AgI over-seeding would suitable to be implemented during 5.1-7.0 km height. In the morning of Aug. 8, the aircraft would carry out detection in weak echo areas of the first defense line. Ground operations would focus on the implementation of over-seeding in the initial stage of convective clouds in the third defense line to achieve the goal of rainfall mitigation. Based on the reserve plan, additional five sets of ground mobile seeding equipment had been added to reinforce the capability of rainfall mitigation ahead of 24 hours of target time. Rainfall mitigation was carried out with the 5 sets equipment. In summary, cloud seeding condition forecast was proper, reserve seeding plan services was reasonable, which provided strong support for field rainfall mitigation action.