A5030488043- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric aerosols and clouds
- Vehicle emissions and performance
- Mercury impact and mitigation studies
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Marine and coastal ecosystems
- Pulsars and Gravitational Waves Research
- Toxic Organic Pollutants Impact
- Water Quality Monitoring and Analysis
- Ocean Acidification Effects and Responses
- Climate variability and models
- Ionosphere and magnetosphere dynamics
- Plant responses to elevated CO2
- Advanced Chemical Sensor Technologies
- Geophysics and Gravity Measurements
- Complex Network Analysis Techniques
- Cold Atom Physics and Bose-Einstein Condensates
- COVID-19 impact on air quality
- Spectroscopy and Laser Applications
- Geophysics and Sensor Technology
University of York
2015-2024
National Centre for Atmospheric Science
2015-2024
Franciscan University of Steubenville
2022-2024
University of Leeds
2006-2024
Massachusetts Institute of Technology
2000-2023
Western Carolina University
2023
IIT@MIT
2022
L-3 Communications (United States)
2022
Moscow Institute of Thermal Technology
2021
University of Nottingham
2019-2021
We use tropospheric NO 2 columns from the Global Ozone Monitoring Experiment (GOME) satellite instrument to derive top‐down constraints on emissions of nitrogen oxides (NO x ≡ + ), and combine these with a priori information bottom‐up emission inventory (with error weighting) achieve an optimized posteriori estimate global distribution surface emissions. Our GOME retrieval improves previous work by accounting for scattering absorption radiation aerosols; effect air mass factor (AMF) ranges...
Abstract. The budget of atmospheric secondary organic aerosol (SOA) is very uncertain, with recent estimates suggesting a global source between 12 and 1820 Tg a−1. We used dataset mass spectrometer (AMS) observations from 34 different surface locations to evaluate the GLOMAP chemical transport model. standard model simulation (which included SOA monoterpenes only) underpredicted (OA) observed by AMS had little skill reproducing variability in dataset. simulated formation biogenic...
We investigate the impact of new laboratory studies N 2 O 5 hydrolysis in aerosols on global model simulations tropospheric chemistry. use data from these to parameterize reaction probability (γ N2O5 ) GEOS‐CHEM as a function local aerosol composition, temperature, and relative humidity. find much lower mean γ (0.02) than commonly assumed models (0.1). Relative simulation assuming uniform = 0.1, we increases mass‐averaged NO x , 3 OH concentrations 7%, 4%, 8% respectively. The bring better...
Abstract. We present a simulation of the global present-day composition troposphere which includes chemistry halogens (Cl, Br, I). Building on previous work within GEOS-Chem model we include emissions inorganic iodine from oceans, anthropogenic and biogenic sources halogenated gases, gas phase chemistry, parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) do not sea-salt debromination. Observations radicals (BrO, IO) are sparse but has some skill...
Abstract. We present a comprehensive simulation of tropospheric chlorine within the GEOS-Chem global 3-D model oxidant–aerosol–halogen atmospheric chemistry. The includes explicit accounting chloride mobilization from sea salt aerosol by acid displacement HCl and other heterogeneous processes. Additional small sources (combustion, organochlorines, transport stratosphere) are also included. Reactive gas-phase Cl*, including Cl, ClO, Cl2, BrCl, ICl, HOCl, ClNO3, ClNO2, minor species, is...
Abstract. We present a new model for the global tropospheric chemistry of inorganic bromine (Bry) coupled to oxidant-aerosol in GEOS-Chem chemical transport (CTM). Sources Bry include debromination sea-salt aerosol, photolysis and oxidation short-lived bromocarbons, from stratosphere. Comparison GOME-2 satellite climatology BrO columns shows that can reproduce observed increase with latitude, northern mid-latitudes maximum winter, Arctic spring. This successful simulation is contingent on...
Abstract. We use observations from the April 2008 NASA ARCTAS aircraft campaign to North American Arctic, interpreted with a global 3-D chemical transport model (GEOS-Chem), better understand sources and cycling of hydrogen oxide radicals (HOx≡H+OH+peroxy radicals) their reservoirs (HOy≡HOx+peroxides) in springtime Arctic atmosphere. find that standard gas-phase mechanism overestimates observed HO2 H2O2 concentrations. Computation HOx HOy budgets on basis also indicates large missing sink...
Abstract. The lifetime of methane is controlled to a very large extent by the abundance OH radical. tropics are key region for removal, with oxidation in lower tropical troposphere dominating global removal budget (Bloss et al., 2005). In forested environments where biogenic VOC emissions high and NOx concentrations low, assumed be low due rapid reactions sink species such as isoprene. New, simultaneous measurements reactivity, k'OH, Borneo rainforest reported show much higher than...
Low cost pollution sensors have been widely publicized, in principle offering increased information on the distribution of air and a democratization quality measurements to amateur users. We report laboratory study commonly-used electrochemical quantify number cross-interferences with other atmospheric chemicals, some which become significant at typical suburban concentrations. highlight that artefact signals from co-sampled pollutants such as CO2 can be greater than sensor signal generated...
Abstract. The oxidation of dimethyl sulfide (DMS) in the troposphere and subsequent chemical conversion into sulfur dioxide (SO2) methane sulfonic acid (MSA) are key processes for formation growth sulfur-containing aerosol cloud condensation nuclei (CCN), but highly simplified large-scale models atmosphere. In this study, we implement a series gas-phase multiphase mechanisms Goddard Earth Observing System-Chemistry (GEOS-Chem) global transport model – including two important intermediates,...
Abstract Aircraft and satellite observations indicate the presence of ppt (ppt ≡ pmol/mol) levels BrO in free troposphere with important implications for tropospheric budgets ozone, OH, mercury. We can reproduce these GEOS‐Chem global chemistry model by including a broader consideration multiphase halogen (Br‐Cl) than has been done past. Important reactions regenerating from its nonradical reservoirs include HOBr + Br − /Cl both aerosols clouds, oxidation ClNO 3 ozone. Most is troposphere,...
Abstract. The formation of inorganic nitrate is the main sink for nitrogen oxides (NOx = NO + NO2). Due to importance NOx tropospheric oxidants such as hydroxyl radical (OH) and ozone, understanding mechanisms rates paramount our ability predict atmospheric lifetimes most reduced trace gases in atmosphere. oxygen isotopic composition (Δ17O(nitrate)) determined by relative sinks thus can provide an observational constraint chemistry. Until recently, utilize Δ17O(nitrate) observations this...
Abstract. Social distancing to combat the COVID-19 pandemic has led widespread reductions in air pollutant emissions. Quantifying these changes requires a business-as-usual counterfactual that accounts for synoptic and seasonal variability of pollutants. We use machine learning algorithm driven by information from NASA GEOS-CF model assess nitrogen dioxide (NO2) ozone (O3) at 5756 observation sites 46 countries January through June 2020. Reductions NO2 coincide with timing intensity...
Abstract. We present an updated mechanism for tropospheric halogen (Cl + Br I) chemistry in the GEOS-Chem global atmospheric chemical transport model and apply it to investigate radical cycling implications oxidants. Improved representation of HOBr heterogeneous its pH dependence our simulation leads less efficient recycling mobilization bromine radicals enables include mechanistic sea salt aerosol debromination without generating excessive BrO. The resulting mean BrO mixing ratio is 0.19...
Abstract Atmospheric ozone (O 3 ) is a pollutant produced through chemical chain reactions where volatile organic compounds (VOCs), carbon monoxide and methane are oxidized in the presence of oxides nitrogen (NO x ). For decades, controlling termination step has been used to separate regions into either ‘NO limited’ (peroxyl-radical self-reactions dominate) or ‘VOC (hydroxyl radical (OH) + dioxide 2 reaction dominates). The regime would then guide policies for reducing emissions so O...
Abstract. Satellite-based retrievals of tropospheric NO2 columns are widely used to infer NOx (≡ NO + NO2) emissions. These rely on model information for the vertical distribution NO2. The free background above 2 km is particularly important because sensitivity increases with altitude. Free also has a strong effect OH and ozone concentrations. Here we use observations from three aircraft campaigns (SEAC4RS, DC3, ATom) four atmospheric chemistry models (GEOS-Chem, GMI, TM5, CAMS) evaluate...
Airborne measurements of a large number oxygenated volatile organic chemicals (OVOC) were carried out in the Pacific troposphere (0.1–12 km) winter/spring 2001 (24 February to 10 April). Specifically, these included acetone (CH 3 COCH ), methylethyl ketone COC 2 H 5 , MEK), methanol OH), ethanol (C acetaldehyde CHO), propionaldehyde peroxyacylnitrates (PANs) n +1 COO NO and nitrates ONO ). Complementary formaldehyde (HCHO), methyl hydroperoxide OOH), selected tracers also available. OVOC...
Measurements of several short‐lived photochemical species (e.g., OH, HO 2 , and CH O) were obtained from the DC‐8 P3‐B aircraft during NASA Transport Chemical Evolution over Pacific (TRACE‐P) campaign. To assess fast theory east Asian coast western Pacific, these measurements are compared to predictions using a time‐dependent box model constrained by coincident long‐lived tracers physical parameters. Both OH generally overpredicted throughout troposphere, which is different result previous...
We examine the ozone production efficiency in transpacific Asian pollution plumes, and implications for air quality California, by using aircraft surface observations April–May 2002 from Intercontinental Transport Chemical Transformation (ITCT 2K2) campaign off California coast Pacific Exploration of Continental Emission–B (PEACE‐B) over northwest Pacific. The are interpreted with a global three‐dimensional chemical transport model (GEOS‐CHEM). reproduces mean features observed CO, reactive...
Reducing surface ozone (O 3 ) to concentrations in compliance with the national air quality standard has proven be challenging, despite tighter controls on O precursor emissions over past few decades. New evidence indicates that isoprene changed considerably from mid‐1980s mid‐1990s owing land‐use changes eastern United States (Purves et al., 2004). Over this period, U.S. anthropogenic VOC (AVOC) decreased substantially. Here we apply two chemical transport models (GEOS‐CHEM and MOZART‐2)...
We examine the major outflow pathways for North American pollution to Atlantic in summer by conducting a 4‐year simulation with GEOS‐CHEM global chemical transport model, including coupled ozone‐aerosol 1° × horizontal resolution 2000. The is driven principally cyclones tracking eastward across America at 45–55°N, every 5 days on average. Anthropogenic and fire effluents from western are mostly transported north east, eventually merging eastern U.S. Atlantic. A semipermanent upper‐level...
Abstract. Methane and ozone are two important climate gases with significant tropospheric chemistry. Within chemistry-climate transport models this chemistry is simplified for computational expediency. We compare the state of art Master Chemical Mechanism (MCM) six schemes (CRI-reduced, GEOS-CHEM a adduct, MOZART-2, TOMCAT CBM-IV) that could be used within composition models. test box model framework under conditions derived from field observations regional scale pollution event. find...