Multi-constraint analysis reveals distinct aerosol effects on high cloud properties at SACOL and SGP sites

Abstract

Aerosols significantly influence high cloud microphysical properties, playing a crucial role in Earth's radiation budget. This study introduces an innovative analytical framework that integrates multi-meteorological constraints through Principal Component Analysis (PCA) with derivative expansion to disentangle aerosol and ice water content (IWP) effects on high cloud properties. Analyzing satellite and reanalysis datasets (2014–2020), we investigate aerosol-cloud interactions at two mid-latitude continental sites with distinct aerosol compositions: the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and the US Southern Great Plains (SGP) atmospheric observatory. By combining multiple meteorological factors into a single indicator, our approach enables an effective quantification of aerosol impacts. We find that aerosols enhance IWP at both sites, with SGP showing markedly higher susceptibility (1.22) than SACOL (0.89). Initial unconstrained analysis of ice particle radius (IPR) revealed opposing trends: decreasing with aerosols at SACOL but increasing at SGP. Through partial correlation analysis, we identified IWP as a key modulator of the IPR-aerosol relationship. After constraining both meteorological and IWP conditions, the increased aerosol concentrations consistently reduce IPR at both sites, resolving the apparent contradiction. Further investigation revealed distinct nucleation mechanisms: sulfate aerosols may dominate homogeneous nucleation, producing numerous smaller ice particles, while dust aerosols facilitate heterogeneous nucleation, forming fewer but larger ice particles when sufficient water vapor is present. These findings advance our understanding of regional variations in aerosol-cloud interactions and provide essential insights for improving cloud microphysics parameterization in climate models.