| 04 Sep 2025
Enhancing Volcanic Eruption Simulations with the WRF-Chem v4.8
Abstract. Volcanic eruptions are one of the major natural hazards, exerting profound effects on the environment and climate. The emissions associated with such eruptions pose substantial risks to terrestrial systems and public health, particularly through the induction of acid rain and air pollution. Volcanic ash influences populations at distances reaching several thousand kilometers from the erupted volcano. Also, accurate forecasting of volcanic clouds is crucial for air traffic control. This study introduces enhancements in the simulation of volcanic eruptions and the transport of volcanic material using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) v4.8 model. Improvements include the addition of wet and dry deposition of ash and sulfate, improved SO2 chemical transformation mechanisms, and corrections of the gravitational deposition of ash. Ash, sulfate, and SO2 mass budget analyses were conducted. Furthermore, we included the direct radiative effect of ash and sulfate aerosols. Additionally, we developed an open-source Python-written emission preprocessor called PrepEmisSources to facilitate and streamline the preparation of volcanic emissions. Accordingly, the model code was extended to simulate complex volcanic emission scenarios using the emissions file prepared using the PrepEmisSources tool. The results suggest that the enhanced WRF-Chem v4.8 code provides an accurate representation of volcanic ash, SO2, and sulfate dispersion, deposition, and chemical transformation. These improvements will aid in volcanic debris forecasting and will allow for the use of the model for assessments of volcanic aerosols on climate and for geoengineering problems, including modeling of stratospheric aerosol injection.
General comments:
This paper introduces several key enhancements to the WRF-Chem v4.8 model aimed at improving the simulation of volcanic eruptions, including the implementation of wet and dry deposition for ash and sulfate, SO2 oxidation mechanisms, gravitational settling corrections, and the direct radiative effects of volcanic aerosols. The authors also developed the calculation of ash and aeresol radiation, which has the feedback effects to the meteorology. Using the 1991 Mt. Pinatubo eruption as a case study, the authors evaluate the model’s performance through both short-term and long-term experiments, demonstrating clear improvements in mass conservation and a better agreement with satellite observations, particularly when radiative feedback is activated.Â
Overall, the paper presents a thorough and valuable contribution to the field of volcanic plume modeling. The enhancements address important shorts in WRF-Chem’s capabilities. Here recommend minor revisions before publication.
Main comments:
1. Fig. 4 and 5 show significant improvements in aerosol and SO₂ transport when radiative feedback is included. To further strengthen the model–satellite comparison, the authors should consider applying satellite-specific Averaging Kernels  to the model output. This would account for the vertical sensitivity of the satellite retrievals and enable a more rigorous and physically consistent validation.
2. Figure 5 illustrates how radiative feedback alters the spatial pattern and magnitude of the SOâ‚‚ plume. The manuscript would benefit from a more detailed explanation of the underlying physical mechanism. Specifically, how does the absorption of solar radiation by ash influencing SOâ‚‚ transport and dispersion? A brief discussion linking the radiative heating (e.g., as shown in Fig. 10) to the dynamical response (e.g., enhanced lofting or altered wind patterns) would strengthen the scientific insight of the paper.
3. Some abbreviations are not explicitly defined upon first use, such as LW/SW/PRTB/CTRL.Â
4. In conclusion section, it is claimed that  an open-source preprocessor called PrepEmisSources is developed. However, there is no detail introduction to this tool. Please expand it for more details.
Technical corrections/suggestions:
L. 85: "fixed and error" -> "fixed an error"
L. 119: "The updated SO2 concentration(mol mol−1) is calculated":The rate coefficient k is given in units of cm^3 molecule^-1 s^-1. Please verify and ensure unit consistency throughout the calculation