Year: 2025
Type: article
Abstract: . Recent studies by Tsalikis et al. (2023, 2024) predicted that the mean free path of air (λair) could be significantly smaller than widely used values by a factor of ~2. Given the fundamental importance of λair, it has been a question that whether an overestimation of λair would have profound influences on a number of aerosol processes. Here we assume that the newly proposed value of λair is accurate and examine its influences on our understanding of atmospheric aerosols. We show that for collisions-induced aerosol dynamics such as the condensation growth of atmospheric particles, the collision rate and hence the growth rate are determined by an effective mean free path for vapor and particle collision rather than λair. Similar to the cause of a smaller λair, the overlooked force field in hard-sphere models may enhance vapor-particle collisions; however, this enhancement has been accounted for in previous studies. As a result, we find that the smaller λair does not directly influence particle collisions, i.e., it does not challenge the previous understandings on particle growth in the lowertroposhpere. Other potential influences on growth involving a high excess latent heat and the uncertainties in the sub-5 nm size range are also addressed.
Source: Aerosol Research
Authors: Runlong Cai, Markku Kulmala
Institutions: Fudan University, University of Helsinki
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: diamond
Awards: G1329624222, G170715881, G2242925455, G2923830210, G3007842293, Managing Forests for Climate Change Mitigation (ForClimate), G5476029912, G5723969971, G5746445563, G6651099172, G692496274, G7280918080, G7901181058, G8009214406, Atmosphere and Climate Competence Center (ACCC), Multi-benefit solutions to climate-smart agriculture (MULTA), Atmosphere and Climate Competence Center (ACCC), Arctic Community Resilience to Boreal Environmental change: Assessing Risks from fire and disease (ACRoBEAR)
OpenAlex ID: W4410080004