A review of aerosol-cloud interactions: Mechanisms, climate effects, and observation methods

Aerosols and clouds significantly influence the climate system. This paper systematically reviews the microphysical processes of aerosol-cloud interactions (ACI), recent advances in precipitation studies, associated radiative effects, and the development of observational techniques. The primary mechanisms of the ACI process depend on the cloud type and evolutionary stage, with distinct interactions identified for liquid, ice, and mixed-phase clouds. Understanding the effects of aerosols on ice and mixed-phase clouds poses greater challenges than on liquid clouds. In terms of climate effects, we summarize recent advancements regarding how aerosols influence precipitation by affecting the characteristics and development of clouds, including their impacts on precipitation amount, distribution area, onset timing, and vertical structure. Statistical analyses reveal a weakening negative trend in global ACI-induced radiative forcing and effective radiative forcing, linked to declining aerosol concentrations in many regions, which accelerates climate change. Regarding observational techniques, the joint observation strategy, by integrating the advantages of different techniques, provides a multi-angle view and improves the temporal and spatial resolution and accuracy of the data. Finally, challenges to ACI research are discussed. By reporting the latest research results and methods, this review will help to provide the current state of knowledge on ACI and their impact on climate, providing valuable insights for those working on this research.