AgI Dispersion and Seeding Impacts on a Wintertime Orographic Cloud Simulated by WRF LES

Large eddy simulations (LES) with 100-m grid spacing by the AgI cloud seeding microphysics scheme embedded in the Weather Research and Forecasting (WRF) model have been performed to investigate the dispersion of AgI particles and their seeding effect from ground-based generators on a wintertime orographic cloud case on Feb. 18, 2009 in the southern Wyoming. This case has been well observed by a suite of in-situ airborne microphysical instruments and remote sensing platforms (Wyoming Cloud Radar and Lidar) on board of the Wyoming King Air aircraft (Geerts et al., 2010). Detail comparisons showed nice agreements between LES results and observations in terms of the dynamical, the thermodynamical and the microphysical structures of the cloud (Chu et al., 2014).

In this study, we focus on how the presence of cloud impacts the AgI dispersion over the mountainous region and what impacts AgI seeding impose to the cloud microphysics and the precipitation pattern on the ground. The turbulent kinetic energy properties, the AgI dispersion features and signals of seeding effect are analyzed. The results show that the presence of cloud makes the AgI vertical dispersion more efficient compared to the clear condition, the AgI impacts on the cloud are limited below 1 km AGL, and the seeding enhanced precipitation is mostly confined within the AgI plumes.