Joint Impact of Aerosol Radiation Interaction and Aerosol-Cloud-Interactions on the Development of Convective Clouds and Severe Storms

Development of a convective cloud system is influenced by numerous factors, most of which are linked with aerosol properties in one way or another. Its initiation is dictated by surface flux and atmospheric stability that is strongly influenced by aerosol radiative properties due to aerosol-cloud-interaction (ARI). Once a cloud is formed, aerosol-cloud-interaction (ACI) starts to play an increasing role. Throughout the lifetime of a convective system, there exist the mixed influences of ARI and ACI whose relative strengths and joint effects both depend on and alter, atmospheric dynamic setting, leaving very complex outcomes ranging from suppression to enhancement, modifying both the magnitude and phase of a severe thunderstorms, etc. We have conducted a comprehensive studies on both individual effects and their joint influences during various stages of convective cloud systems by observation analyses and model simulations as summarized in a comprehensive review article (Li et al. 2017) and in some recent research papers (e.g. Guo et al., 2016; Lee et al. 2017; Liu et al. 2018) on the following sequential impacts.

1. Impact of the ARI on the initiation of convection

Analyzing comprehensive aerosol and meteorological measurements in the boundary layer and WRF-Chem modeling, we found that the ARI affects both the initiation of convection and aerosol dissipation, leading to a delay in the onset of convective clouds.

2. Impact of aerosol composition on the aerosol first indirect effects

Once a convective cloud is formed, its microphysical properties are affected by aerosol hygroscopcity and composition. Yet, estimation of this effect may differ systematically as inferred from satellite and ground-based measurements due to different regions to which the measurements are sensitive to.

3. Joint impact of aerosol radiative effects and microphysical effects

Further development of a convective cloud is dictated by the joint effects of ARI and ACI. In the beginning stage of cloud development, aerosol radiative effects are dominant over aerosol microphysical effects, hence, aerosol perturbations suppress updrafts and precipitation. However, aerosol microphysical effects become dominant over aerosol radiative effects during the late stage of cloud development.

I will try to put these diverse, but inherently related, effects from a perspective of the lifetime of convective cloud system.