Updating sea spray aerosol emissions in the Community Multiscale Air Quality (CMAQ) model version 5.0.2

• Published in: Geoscientific Model Development 2015-11, Vol.8 (11), p.3733-3746
• Main Authors: Gantt, B, Kelly, J. T, Bash, J. O
• Format: Article
• Language: English
• Subjects: Aerosol effects; Aerosols; Air; Air pollution; Air pollution control; Air quality; Air quality models; Analysis; Atmospheric chemistry; Chemical partition; Chemistry; Chloride; Climate change; Coastal environments; Coastal zones; Coasts; Communities; Computer simulation; Condensation; Data processing; Ecosystems; Emissions; Environmental aspects; Global temperature changes; Laboratories; Marine pollution; Mathematical models; Multiscale analysis; Nitrates; Nitric acid; Nitric acids; Nitrogen deposition; Outdoor air quality; Parameterization; Particle mass; Particle size distribution; Partitioning; Predictions; Regional analysis; Salt; Sea spray; Sea spray aerosols; Sea surface; Sea surface temperature; Seawater; Size distribution; Sodium; Spray; Surface temperature; Temperature; Temperature dependence; Urban areas; Viscosity
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-8-3733-2015

Sea spray aerosols (SSAs) impact the particle mass concentration and gas-particle partitioning in coastal environments, with implications for human and ecosystem health. Model evaluations of SSA emissions have mainly focused on the global scale, but regional-scale evaluations are also important due to the localized impact of SSAs on atmospheric chemistry near the coast. In this study, SSA emissions in the Community Multiscale Air Quality (CMAQ) model were updated to enhance the fine-mode size distribution, include sea surface temperature (SST) dependency, and reduce surf-enhanced emissions. Predictions from the updated CMAQ model and those of the previous release version, CMAQv5.0.2, were evaluated using several coastal and national observational data sets in the continental US. The updated emissions generally reduced model underestimates of sodium, chloride, and nitrate surface concentrations for coastal sites in the Bay Regional Atmospheric Chemistry Experiment (BRACE) near Tampa, Florida. Including SST dependency to the SSA emission parameterization led to increased sodium concentrations in the southeastern US and decreased concentrations along parts of the Pacific coast and northeastern US. The influence of sodium on the gas-particle partitioning of nitrate resulted in higher nitrate particle concentrations in many coastal urban areas due to increased condensation of nitric acid in the updated simulations, potentially affecting the predicted nitrogen deposition in sensitive ecosystems. Application of the updated SSA emissions to the California Research at the Nexus of Air Quality and Climate Change (CalNex) study period resulted in a modest improvement in the predicted surface concentration of sodium and nitrate at several central and southern California coastal sites. This update of SSA emissions enabled a more realistic simulation of the atmospheric chemistry in coastal environments where marine air mixes with urban pollution.