A New Aerosol Dry Deposition Model for Air Quality and Climate Modeling

Area of Science:

• Atmospheric Science
• Environmental Chemistry
• Air Quality Modeling

Background:

• Dry deposition of atmospheric aerosols is crucial for climate and air quality but is poorly understood and modeled.
• Existing aerosol dry deposition models show poor agreement with field measurements across various particle sizes and landscapes.

Purpose of the Study:

• To develop and test a novel aerosol dry deposition model that improves upon current models.
• To enhance the accuracy of atmospheric aerosol deposition simulations.

Main Methods:

• Modified the Community Multiscale Air Quality (CMAQ) model's dry deposition component.
• Incorporated a second inertial impaction term to account for microscale surface features.
• Validated the new model against published field measurement studies.

Main Results:

• The new model demonstrates significantly improved agreement with measured dry deposition velocities for a wide range of particle sizes.
• The model substantially increases the modeled dry deposition of accumulation mode aerosols, especially in forested areas.
• Simulations show reductions in peak PM2.5 concentrations by up to 40% in some forested regions.

Conclusions:

• The enhanced aerosol dry deposition model provides more accurate predictions of atmospheric particle deposition.
• The improved modeling reduces bias and error in PM2.5 concentration estimates, particularly in complex terrain and vegetated areas.
• This advancement offers better insights into atmospheric processes impacting air quality and climate.