Impact of Aerosol-Cloud-Interactions (ACI) by Various Aerosol and Meteorological Factors
Authors
Zhanqing Li — University of Maryland
Seoung-Soo Lee — NOAA - Earth System Research Laboratory
Jianjun Liu — University of Maryland
Yuwei Zhang — Pacific Northwest National Laboratory
Youtong Zheng — Geophysical Fluid Dynamics Laboratory/Princeton University
Category
Convective clouds, including aerosol interactions
Description
ACI has been widely recognized, but understanding and estimation of the ACI has been fraught with very large uncertainties due to various interconnected factors. We are conducting a systematic pursuit to tackle the ACI:
1. Impact of aerosol composition on the aerosol first indirect effects
Based on surface measurements of aerosol and cloud properties made from multiple ARM Mobile Facility sites around the world, we investigated the impact of aerosol hygroscopcity and composition on the ACI and found the significant impact of aerosol composition on the first aerosol indirect effect on warm clouds.
2. Impact of aerosol radiative effects and microphysical effects
Through simulations of mesoscale convective systems, we found that around the beginning stage of cloud development, aerosol radiative effects dominate over aerosol microphysical effects; hence, aerosol perturbations suppress updrafts and precipitation. However, eventually, aerosol microphysical effects become dominant over aerosol radiative effects.
3. Impact of aerosol and PBL interactions
Using WRF-Chem, the direct effect of aerosol on PBL is inferred by comparing two simulations with and without aerosol direct effect. The results show that the PBL height is decreased on days with high aerosol loading. With the contribution of absorbing aerosols, PBL height may be even lower since that the boundary layer may be more stable due to the heating of the lower atmosphere.
4. Impact of model resolutions on the simulation of ACI
By model tests, we found that the treatment of ACI strongly depends on model resolution. CAPI is sensitive to aerosol perturbations that are controlled by parameterization of saturation processes. Many GCM and NWP models underestimate aerosol effects on clouds and precipitation.
Besides these studies, we are also developing novel remote-sensing methods to infer updraft and cloud condensation nuclei at cloud base, which would help a great deal in unraveling the influences of meteorology and aerosol properties.
