Parameterization of particle formation rates in distinct atmospheric environments

Abstract

Atmospheric particle formation rate (J) is one of the key characteristics of new particle formation (NPF) processes worldwide. It is related to the development of ultrafine particle growth to cloud condensation nuclei (CCN) and, hence, Earth radiative forcing in global models, which helps us to better understand the impact of NPF on cloud properties and climate change. In this work, we parameterized four semi-empirical J models for 5 nm atmospheric particles using field measurements obtained from distinct environments that varied from clean to heavily polluted regions and from tropical to polar regions. The models rely primarily on sulfuric acid as a condensing vapor, a condensation sink to account for the vapor loss, and relative humidity for the meteorological contribution to J. However, the dependencies between J, condensation sink, and relative humidity are affected by their interlinked relations to sources and sinks of condensable vapors other than sulfuric acid and that of the potential traffic emissions to the observed size range. The parameterization results showed that our models were able to produce plausible predictions for boreal forest environments, heavily polluted environments, and biogenic environments with high relative humidity. We further tested the models in the global simulation module Tracer Model 5 (TM5, massively parallel version) to simulate the particle number size distribution across 14 global atmospheric measurement sites. The simulated results showed satisfactory predictions of particle number concentrations for all of the tested environments, with significant improvement in the nucleation mode and better prediction accuracy for the Aitken and accumulation modes compared to the binary sulfuric acid-organic vapor model in Riccobono et al. (2014). Our study has successfully provided powerful tools for predicting J5 on a global scale across various environment types using the most essential and more accessible variables involved in the NPF processes. Essentially, this work reinforces the necessity for global research into the investigation of environment-oriented meteorology-involved NPF processes.