The Effect of Using a New Parameterization of Nucleation in the WRF-Chem Model on New Particle Formation in a Passive Volcanic Plume

Abstract

We investigated the role of the passive volcanic plume of Mount Etna (Italy) in the formation of new particles in the size range of 2.5–10 nm through the gas-to-particle nucleation of sulfuric acid (H2SO4) precursors, formed from the oxidation of SO2, and their evolution to particles with diameters larger than 100 nm. Two simulations were performed using the Weather Research and Forecasting Model coupled with chemistry (WRF-Chem) under the same configuration, except for the nucleation parameterization implemented in the model: the activation nucleation parameterization (JS1 = 2.0 × 10−6 × (H2SO4)) in the first simulation (S1) and a new parameterization for nucleation (NPN) (JS2 = 1.844 × 10−8 × (H2SO4)1.12) in the second simulation (S2). The comparison of the numerical results with the observations shows that, on average, NPN improves the performance of the model in the prediction of the H2SO4 concentrations, newly-formed particles (~2.5–10 nm), and their growth into larger particles (10–100 nm) by decreasing the rates of H2SO4 consumption and nucleation relative to S1. In addition, particles formed in the plume do not grow into cloud condensation nuclei (CCN) sizes (100–215 nm) within a few hours of the vent (tens of km). However, tracking the size evolution of simulated particles along the passive plume indicates the downwind formation of particles larger than 100 nm more than 100 km far from the vent with relatively high concentrations relative to the background (more than 1500 cm−3) in S2. These particles, originating in the volcanic source, could affect the chemical and microphysical properties of clouds and exert regional climatic effects over time.

Substantially positive contributions of new particle formation to Cloud Condensation Nuclei under low supersaturation in China based on numerical model improvements

“…For instance, in the study of NPF in East Asia in the spring of 2009, even after lowering the nucleation rate in a regional model of WRF-Chem applied in their study, the reduced number concentration of particles at 10-130 nm remained to be overestimated (Matsui et al, 2013). Using the same regional model and a similar method to reduce the nucleation rate, Arghavani et al (2022) found particle number concentration at 10-100 nm was still overestimated by nearly one order of magnitude, despite the effectiveness to reduce the overestimates for the smaller particles such as 2.5-10 nm. In addition to the rate of NPF, the growth process of particles also has a crucial effect on particle number concentration and size distribution.…”

“…The overestimate of condensation nuclei (CN) in numerical models are commonly seen, despite the attempt to correctify the bias (Matsui et al, 2013;Arghavani et al, 2022). It is a common way to reduce the nucleation rate which may reduce the particle number concentration in proportion (Matsui et al, 2013).…”

Modelling Paroxysmal and Mild-Strombolian Eruptive Plumes at Stromboli and Mt. Etna on 28 August 2019

“…Etna and ordinary explosive activity at Stromboli. More recently, Arghavani et al 2022 [29] implemented a novel parameterisation of nucleation in the WRF-Chem model regarding new particle formation of a passive degassing of the Mt. Etna plume observed on 15 June 2016 [29].…”