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1. Examining the Summertime Ozone Formation Regime in Southeast Michigan Using MOOSE Ground-Based HCHO/NO2 Measurements and F0AM Box Model

   Huang, Y; Xiong, Y; Chai, JC; Mao, H; Mariscal, N; Yacovitch, TI; Lerner, BM; Majluf, F; Canagaratna, MR; Olaguer, EP (December 2023, American Geophysical Union)

   The summertime surface ozone (O3) concentrations over Southeast Michigan (SEMI) often exceed 70 ppbv. However, the associated O3 formation regime is still not well known. In this study, we examined the chemical drivers of O3 exceedances in SEMI, based on the Michigan-Ontario Ozone Source Experiment (MOOSE) field campaign during the period of May 20 – June 30, 2021. We employed a zero-dimensional (0-D) box model, which was constrained by measurements of meteorology and trace gas concentrations during MOOSE. Our model simulations demonstrated that the formaldehyde to nitrogen dioxide ratio (HCHO/NO2) for the transition between the VOC- and NOx-limited O3 production regimes was 3.0 ± 0.3 (mean ± 1σ) in SEMI. The midday (12:00-16:00) averaged HCHO/NO2 ratio during MOOSE was 1.62 ± 1.03, suggesting that O3 production in SEMI was likely limited by VOC emissions. Our study has significant implications for air quality policy and the design of effective O3 pollution control strategies through ground-based HCHO/NO2 measurements and model simulations. 

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2. Evaluation of ozone and its precursors using the Multi-Scale Infrastructure for Chemistry and Aerosols Version 0 (MUSICAv0) during the Michigan–Ontario Ozone Source Experiment (MOOSE)

   https://doi.org/10.5194/gmd-18-6737-2025  

   Mariscal, Noribeth; Emmons, Louisa K; Jo, Duseong S; Xiong, Ying; Judd, Laura M; Janz, Scott J; Chai, Jiajue; Huang, Yaoxian (January 2025, Geoscientific Model Development)

   Abstract. Surface ozone (O3) in Southeast Michigan (SEMI) often exceeds US National Ambient Air Quality Standards, posing risks to human health and agroecosystems. SEMI, a relatively small region in the state of Michigan, contains most of the state's anthropogenic emission sources and more than half of the state's population and is also prone to long-range and transboundary pollutant transport. Here, we explore the distribution of O3 and its precursors, such as nitrogen oxides (NOx) and volatile organic compounds, over SEMI during the summer of 2021 using the chemistry–climate model MUSICAv0 (Multi-Scale Infrastructure for Chemistry and Aerosols Version 0). Using the regional refinement capabilities of MUSICAv0, we create a custom grid over the state of Michigan of 1/16° (∼ 7 km) to better understand the local-scale impacts of chemical and dynamic complexity in SEMI and compare it with a grid with 1/8° (∼ 14 km) resolution over the contiguous United States. Model simulations are evaluated using a comprehensive suite of observations from Phase I of the Michigan–Ontario Ozone Source Experiment (MOOSE) field campaign. MUSICAv0, with its higher horizontal grid resolution, showed excellent skill in capturing peak O3 concentrations but showed larger variation in the simulation of O3 precursors (e.g., NOx, HCHO, isoprene). In addition, we implement a diurnal cycle for anthropogenic nitric oxide (NO) emissions, which is generally not included in global models. As a result, modeled nighttime O3 is improved because of lower NOx concentrations during the night. This work shows that when conceptualizing models in urban regions, it is important to consider a combination of high horizontal resolution and the diurnal cycle of emissions, as they can have important implications for the simulation of secondary air pollutants. 

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3. The Michigan–Ontario Ozone Source Experiment (MOOSE): An Overview

   https://doi.org/10.3390/atmos14111630  

   Olaguer, Eduardo P; Su, Yushan; Stroud, Craig A; Healy, Robert M; Batterman, Stuart A; Yacovitch, Tara I; Chai, Jiajue; Huang, Yaoxian; Parsons, Matthew T (November 2023, Atmosphere)

   The Michigan–Ontario Ozone Source Experiment (MOOSE) is an international air quality field study that took place at the US–Canada Border region in the ozone seasons of 2021 and 2022. MOOSE addressed binational air quality issues stemming from lake breeze phenomena and transboundary transport, as well as local emissions in southeast Michigan and southern Ontario. State-of-the-art scientific techniques applied during MOOSE included the use of multiple advanced mobile laboratories equipped with real-time instrumentation; high-resolution meteorological and air quality models at regional, urban, and neighborhood scales; daily real-time meteorological and air quality forecasts; ground-based and airborne remote sensing; instrumented Unmanned Aerial Vehicles (UAVs); isotopic measurements of reactive nitrogen species; chemical fingerprinting; and fine-scale inverse modeling of emission sources. Major results include characterization of southeast Michigan as VOC-limited for local ozone formation; discovery of significant and unaccounted formaldehyde emissions from industrial sources; quantification of methane emissions from landfills and leaking natural gas pipelines; evaluation of solvent emission impacts on local and regional ozone; characterization of the sources of reactive nitrogen and PM2.5; and improvements to modeling practices for meteorological, receptor, and chemical transport models. 

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4. Isotopic characterization of reactive nitrogen in summertime Detroit Metropolitan Area during MOOSE campaign

   Mariscal, N; Huang, YH; Emmons, LK; Jo, DS; Xiong, XY; Chai, JC (December 2023, American Geophysical Union)

   Surface ozone (O3) levels in Southeast Michigan (SEMI) exceeds U.S. National Ambient Air Quality Standards (NAAQS), posing risks to human health and agroecosystems. SEMI, a relatively small region in the state of Michigan, contains a majority of anthropogenic emission sources and more than half of the state’s population, and is also prone to long-range and transboundary pollutant transport. Understanding the physical and chemical drivers of elevated O3 through detailed and innovative modeling studies are crucial to address the issue. In this study, we explore the distribution of O3 and its precursors (e.g., NOx & VOCs) over SEMI for the summer of 2021 using the 3-D chemistry-climate model, MUSICAv0 (Multi-Scale Infrastructure for Chemistry and Aerosols, Version 0). Model simulations are evaluated with Michigan-Ontario Ozone Source Experiment (MOOSE) field campaign measurements. A finer horizontal resolution of ~7 km x 7km in MUSICAv0 was developed over Michigan to better understand the local-scale impacts of chemical and dynamic complexity existing in SEMI. MUSICAv0 with the refined model grid shows excellent skill in capturing diurnal variations of temperature and O3, but shows larger variations for nitrogen dioxide (NO2). The MUSICAv0 results for NOx and its oxidation products (e.g., HNO3) were improved by applying a diurnal cycle to anthropogenic nitric oxide (NO) emissions, as global models generally do not include diurnal variation of emissions. The source attribution of O3 in SEMI is also quantified using a carbon monoxide (CO) tagging method. Optimization of a regionally-refined, coupled model such as MUSICAv0, through resolution and emission modeling studies, have significant implications for air quality projects at the local-scale and the design of effective surface O3 mitigation strategies. 

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5. Sensitivity of Ozone Production to NOx and VOC along the Lake Michigan Coastline

   Vermeuel, Michael P; Novak, Gordon A; Alwe, Hariprasad D; Hughes, Dagen D; Kaleel, Rob; Dickens, Angela F; Kenski, Donna; Czarnetzki, Alan; Stone, Elizabeth A; Stanier, Charles O; et al (September 2019, Journal of geophysical research. Atmospheres)

   We report on the sensitivity of enhanced ozone (O3) production, observed during lake breeze circulation along the coastline of Lake Michigan, to the concentrations of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). We assess the sensitivity of O3 production to NOx and VOC on a high O3 day during the Lake Michigan Ozone Study 2017 (LMOS 2017) using an observationally-constrained chemical box model that implements the Master Chemical Mechanism (MCM v3.3.1) and recent emission inventories for NOx and VOCs. The MCM model is coupled to a backward air mass trajectory analysis from a ground supersite in Zion, IL where an extensive series of measurements of O3 precursors and their oxidation products, including hydrogen peroxide (H2O2), nitric acid (HNO3), and particulate nitrates (NO3-) serve as model constraints. We evaluate the chemical evolution of the Chicago-Gary urban plume as it advects over Lake Michigan and demonstrate how modeled indicators of VOC- vs. NOx- sensitive regimes can be constrained by measurements at the trajectory endpoint. Using the modeled ratio of the instantaneous H2O2 and HNO3 production rates (PH2O2 / PHNO3), we suggest that O3 production over the urban source region is strongly VOC-sensitive and progresses towards a more NOx-sensitive regime as the plume advects north along the Lake Michigan coastline on this day. We also demonstrate that ground-based measurements of the mean concentration ratio of H2O2 to HNO3 describe the sensitivity of O3 production to VOC and NOx as the integral of chemical production along the plume path. 

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