A single-point modeling approach for the intercomparison and evaluation of ozone dry deposition across chemical transport models (Activity 2 of AQMEII4)

Abstract

Abstract. A primary sink of air pollutants and their precursors is dry deposition. Dry deposition estimates differ across chemical transport models, yet an understanding of the model spread is incomplete. Here, we introduce Activity 2 of the Air Quality Model Evaluation International Initiative Phase 4 (AQMEII4). We examine 18 dry deposition schemes from regional and global chemical transport models as well as standalone models used for impact assessments or process understanding. We configure the schemes as single-point models at eight Northern Hemisphere locations with observed ozone fluxes. Single-point models are driven by a common set of site-specific meteorological and environmental conditions. Five of eight sites have at least 3 years and up to 12 years of ozone fluxes. The interquartile range across models in multiyear mean ozone deposition velocities ranges from a factor of 1.2 to 1.9 annually across sites and tends to be highest during winter compared with summer. No model is within 50 % of observed multiyear averages across all sites and seasons, but some models perform well for some sites and seasons. For the first time, we demonstrate how contributions from depositional pathways vary across models. Models can disagree with respect to relative contributions from the pathways, even when they predict similar deposition velocities, or agree with respect to the relative contributions but predict different deposition velocities. Both stomatal and nonstomatal uptake contribute to the large model spread across sites. Our findings are the beginning of results from AQMEII4 Activity 2, which brings scientists who model air quality and dry deposition together with scientists who measure ozone fluxes to evaluate and improve dry deposition schemes in the chemical transport models used for research, planning, and regulatory purposes.

Modeling the Oxygen Isotope Anomaly (Δ17O) of Reactive Nitrogen in the Community Multiscale Air Quality Model: Insights into Nitrogen Oxide Chemistry in the Northeastern United States

“…The conducted model simulations were based on replicated runs from the US EPA’s Air QUAlity TimE Series Project (EQUATES). , Briefly, model simulations were conducted using CMAQv5.4 utilizing Carbon Bond 6, revision 3 with aerosol 7 (cb6r3-ae07) chemical mechanism including the addition of chlorine chemistry as implemented in CMAQ. − The model simulations included bidirectional ammonia (NH 3 ) exchange, , the Surface Tiled Aerosol Gaseous Exchange (STAGE) dry deposition, ,− Weather Research and Forecasting (WRF) model version 4.1.1 meteorology, and emission inputs based on the EQUATES methods, which are largely based on the 2017 national emissions inventory (NEI) with updates by sector and appropriately scaled for the simulation year. ,,, Model simulations were conducted for the northeastern US domain with a resolution of 12 × 12 km within the northern hemisphere boundary conditions for 2015. Boundary and initial conditions for the northeast US domain were obtained from CMAQ simulations performed as part of EQUATES, which is a continuous set of CMAQ simulations over both the northern hemisphere (108 km horizontal resolution) and contiguous U.S. (12 km horizontal resolution) starting December 2001 and continuing through 2019.…”

Role of chemical production and depositional losses on formaldehyde in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

“…Biogenic emissions are computed inline in CMAQ using the BEIS module (Bash et al, 2016). The Surface Tiled Aerosol and Gaseous Exchange (STAGE) dry deposition model is used (Appel et al, 2021;Clifton et al, 2023). Annual simulations for 2019 were conducted using the base CRACMM1 mechanism and the updated CRACMM2 mechanism with one month spin up in December 2018 to reduce the influence of initial conditions.…”

Spatial Distribution of Ammonia Concentrations and Modeled Dry Deposition in an Intensive Dairy Production Region

“…A newly developed bidirectional air-surface exchange scheme used in the Community Multi-scale Air Quality Model (CMAQ) version 5.3 [17], the Surface Tiled Aerosol and Gaseous Exchange (STAGE) model, is used in this study to estimate the NH 3 fluxes. Previously, STAGE was evaluated for ozone as a participating model in the Air Quality Model Evaluation International Initiative 4 [25], and for reactive nitrogen deposition against measurements from a deciduous forest in the Appalachian Mountains [26].…”