Development of a Fast-Response Volcanic SO2 Prediction System: A Study for the 2018 Mt. Kilauea Eruption using a Chemical Transport Model and Satellite Data

During the sustained eruption of Mt. Kilauea through May and June 2018, significant SO₂ and PM2.5 enhancements were observed. We study this case using the National Air Quality Forecasting Capability (NAQFC) over Hawaii. Based on the SO₂ column data provided by the Ozone Mapping and Profiling Suite (OMPS) Nadir-Mapper (NM) sensor and the CMAQ chemical transport model with certain assumptions, we estimated the SO₂ and ash daily emissions during this period, and found the peak SO₂ emission peaked at up to 15000 moles/s near the Kilauea's east rift zone and summit area. The vertical distribution of the volcanic emission, which depends on the source-area heat flux, is a primary factor affecting the formation and transport of volcanic smog (VOG). We estimated the lava heat flux according to the lava outflow volume, which is assumed to be proportional to the SO₂ emission. Based on this estimation, we conducted a model simulation of this eruption event and compared the results with satellite aerosol retrievals for SO₂ and aerosol optical depth, as well as with in-situ SO₂ and PM_2.5 concentration measurements. The comparison showed good agreement between modeling and independent measurements but discrepancies with some short-duration SO₂ concentration peaks. Our sensitive study also showed that the simulated volcanic SO₂ plume and thus the VOG plume remained in low altitudes as a consequence of low exit velocity of the volcanic emission. This study demonstrates a rapid-response capability of assessing the impact of volcanic emissions on the air quality through the forecasting of surface SO₂ and PM2.5 concentrations using a chemical-transport model constrained by satellite measurements.