Effect of mutual cloud-aerosol interaction on boundary layer cumulus clouds and a mesoscale convective system

 We consider effects of two-way cloud-aerosol interactions on  cumulus clouds (Cu) in the maritime boundary layer and on  properties of mesoscale convective system (MCS) accompanying by a squall line formation. The simulations are performed using spectral bin microphysics (SBM). The fields of Cu clouds are simulated using the model SAM in LES with an 10 m grid resolution. The mixed phase MCS was simulated using  the WRF model with 1.5 km resolution and calculating aerosol, drop, snow, graupel and hail size distributions. The  SAM/SBM includes an aerosol budget that tracks aerosols as they are activated into cloud droplets, evolve within growing droplets through diffusional growth and drop collisions. The WRF simulate mixed phase clouds. Acordingly, the budget of aerosols in ice is taken into account. In the WRF/SBM aerosols are transported into ice hydrometeors via immersion freezing. Aerosol mass (size) increases in drops due to drop-drop collisions and in ice particles during drop-ice (riming) and ice-ice collisions. Finally, aerosols are either released back into the surrounding environment through droplet evaporation and ice sublimation or fall to the surface within precipitating particles. The results show that Cu as well as deep convective clouds effectively transport aerosols to the upper atmosphere. It was found that convective clouds and cloud systems  are effective generators of giant CCN even in pulluted cases. The released aerosols significantly raise background aerosol concentrations, altering the mean size distribution over a large area surrounding cumulus clouds and the MCS, respectively. Some of the released aerosols re-enter the cloud through the  lateral boundaries, leading to changes in cloud microphysics.   These changes  lead to increased liquid water content, as well the mass contents of graupel and hail.  Strengthening cloud dynamics intensify convection and precipitation.

.