Seeding Modeling Study of Two Precipitation Processes over Northern China in the Spring of 2014

The CAMS (Chinese Academy of Meteorological Sciences) cloud microphysics scheme, developed by the Weather Modification Center of the China Meteorological Administration, was coupled to the WRF model, and two kinds of cloud seeding schemes-seeding artificial ice crystal (S1) and seeding AgI aerosol particles (S2)-were constructed in the CAMS scheme. Using the WRF model with the new cloud microphysics scheme and cloud seeding scheme, numerical simulations of cloud seeding during two precipitation processes in 2014 (CASE1: 9-10 May; CASE2: 10-11 May) over northern China were conducted. Cloud seeding effects on rainfall and cloud microphysics structure resulting from the S1 and S2 schemes were analyzed separately. The results show that a seeding catalyst in an appropriate part of a precipitating cloud can lead to a change in precipitation, and precipitation enhancement effects were attained using both S1 and S2. Seeding resulted in evident variation in all kinds of hydrometeors in the seeding area, where it also stirred up change in temperature and updraft. In CASE1, the affected area of S2 was wider than that of S1, and the seeding effect of S2 was also more intense than that of S1 downstream of the seeding area. However, the difference in the seeding effect between S1 and S2 was not obvious in CASE2. The differences in seeding mechanism, cloud dynamics and water vapor were important factors causing different behavior in the seeding effects of both S1 and S2. A similar seeding effect could be attained through employing a proper seeding amount and setting the other seeding conditions the same in S1 and S2. Crucially, the difference in seeding mechanism of the two seeding schemes may result in the change in seeding effects in some clouds. The S2 scheme is more suitable for research on artificial precipitation operations in which AgI seeding agent is employed.