Observational evidence and mechanisms of aerosol effects on precipitation.

Aerosols greatly influence precipitation characteristics, thereby impacting the regional climate and human life. As an indispensable factor for cloud formation and a critical radiation budget regulator, aerosols can affect precipitation intensity, frequency, geographical distribution, area, and time. However, discrepancies exist among current studies due to aerosol properties, precipitation types, the vertical location of aerosols and meteorological conditions. The development of technology has driven advances in current research, but understanding the aerosol effects on precipitation remain complex and challenging. This paper revolves around the following topics from the two perspectives of Aerosol-Radiation Interaction (ARI) and Aerosol-Cloud Interaction (ACI): (1) the influence of different vertical locations of absorbing/scattering aerosols on the atmospheric thermal structure; (2) the fundamental theories of ARI reducing surface wind speed, redistributing water vapour and energy, and then modulating precipitation intensity; (3) different aerosol types (absorbing versus scattering) and aerosol concentrations causing different precipitation diurnal and weekly variations; (4) microphysical processes (cloud water competition, invigoration effect, and evaporation cooling) and observational evidence of different effects of aerosols on precipitation intensity, including enhancing, inhibiting, and transitional effects from enhancement to suppression; and (5) how meteorology, water vapor and dynamics influencing the effect of ACI and ARI on precipitation. In addition, this review lists the existing issues and future research directions for attaining a more comprehensive understanding of aerosol effects on precipitation. Overall, this review advances our understanding of aerosol effects on precipitation and could guide the improvement of weather and climate models to predict complex aerosol-precipitation interactions more accurately.
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