A5071706154- Atmospheric chemistry and aerosols
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Air Quality and Health Impacts
- Mercury impact and mitigation studies
- Atmospheric aerosols and clouds
- Fire effects on ecosystems
- Toxic Organic Pollutants Impact
- Vehicle emissions and performance
- Plant responses to elevated CO2
- Air Quality Monitoring and Forecasting
- Methane Hydrates and Related Phenomena
- Marine and coastal ecosystems
- Fire dynamics and safety research
- Arctic and Antarctic ice dynamics
- Geophysics and Gravity Measurements
- Hydrocarbon exploration and reservoir analysis
- Climate variability and models
- Water Quality Monitoring and Analysis
- Fire Detection and Safety Systems
- Maritime Transport Emissions and Efficiency
- Marine animal studies overview
- Plant Water Relations and Carbon Dynamics
- Advanced Materials Characterization Techniques
- Remote Sensing in Agriculture
Florida State University
2016-2025
UC Irvine Health
2022
Research Institute for Sustainability at GFZ
2021
University of California, Irvine
2011-2014
Irvine University
2011-2014
Harvard University Press
2012
University of Nevada, Reno
2012
Louisiana Department of Natural Resources
2012
Planetary Science Institute
2006-2011
Harvard University
2006-2011
Knowledge of the atmospheric chemistry reactive greenhouse gases is needed to accurately quantify relationship between human activities and climate, incorporate uncertainty in our projections gas abundances. We present a method for estimating fraction attributable activities, both currently future scenarios. Key variables used calculate budgets major non‐CO 2 are codified along with their uncertainties, then project abundances under new climate‐change This approach uses knowledge changing...
Abstract. Global models of atmospheric mercury generally assume that gas-phase OH and ozone are the main oxidants converting Hg0 to HgII thus driving deposition ecosystems. However, thermodynamic considerations argue against importance these reactions. We demonstrate here viability atomic bromine (Br) as an alternative oxidant. conduct a global 3-D simulation with GEOS-Chem model assuming Br be sole oxidant (Hg + model) compare previous version OH/O3 model). specify concentration fields...
Abstract. Atmospheric deposition of Hg(II) represents a major input mercury to surface environments. The phase (gas or particle) has important implications for deposition. We use long-term observations reactive gaseous (RGM, the component Hg(II)), particle-bound (PBM, particulate fine matter (PM2.5), and temperature (T) at five sites in North America derive an empirical gas-particle partitioning relationship log10(K−1) = (10±1)–(2500±300)/T where K (PBM/PM2.5)/RGM with PBM RGM common mixing...
Geostationary satellites have provided routine, high temporal resolution Earth observations since the 1970s. Despite long period of record, use these data in climate studies has been limited for numerous reasons, among them that no central archive geostationary all international exists, full and spatial are voluminous, diverse calibration navigation formats encumber uniform processing needed multisatellite studies. The International Satellite Cloud Climatology Project (ISCCP) set stage...
We develop an improved treatment of the surface ocean in GEOS-Chem global 3-D biogeochemical model for mercury (Hg). replace globally uniform subsurface Hg concentrations used original with basin-specific values based on measurements. Updated chemical mechanisms Hg0/HgII redox reactions include both photochemical and biological processes, we parametrization particle-associated scavenging. Modeled aqueous are consistent limited water observations. Results more accurately reproduce...
Abstract. Accurate prediction of future methane abundances following a climate scenario requires understanding the lifetime changes driven by anthropogenic emissions, meteorological factors, and chemistry-climate feedbacks. Uncertainty in any these influences or underlying processes implies uncertainty abundance radiative forcing. We simulate three chemical transport models (CTMs) – UCI CTM, GEOS-Chem, Oslo CTM3 over period 1997–2009 compare models' year-to-year variability against...
Abstract. The direct radiative effect (DRE) of aerosols, which is the instantaneous impact all atmospheric particles on Earth's energy balance, sometimes confused with forcing (DRF), change in DRE from pre-industrial to present-day (not including climate feedbacks). In this study we couple a global chemical transport model (GEOS-Chem) transfer (RRTMG) contrast these concepts. We estimate mean all-sky aerosol DRF −0.36 Wm−2 and −1.83 for 2010. Therefore, natural sources (here fire) affect...
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. 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...
Wildfires are a substantial but poorly quantified source of tropospheric ozone (O3). Here, to investigate the highly variable O3 chemistry in wildfire plumes, we exploit situ chemical characterization western wildfires during FIREX-AQ flight campaign and show that production can be predicted as function experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, fate peroxy radicals. The exhibits rapid transition regimes. Within few daylight hours, formation...
Abstract The NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was a multi‐agency, inter‐disciplinary research effort to: (a) obtain detailed measurements of trace gas aerosol emissions from wildfires prescribed fires using aircraft, satellites ground‐based instruments, (b) make extensive suborbital remote sensing fire dynamics, (c) assess local, regional, global modeling fires, (d) strengthen connections observables the ground such as fuels...
Abstract We analyze the effects of diurnal cycle fire emissions (DCFE) and plume rise on U.S. air quality using MUSICAv0 (Multi‐Scale Infrastructure for Chemistry Aerosols Version 0) model during FIREX‐AQ (Fire Influence Regional to Global Environments Air Quality) WE‐CAN (Western wildfire Experiment Cloud chemistry, Aerosol absorption Nitrogen) field campaigns. To include DCFE in model, we employ two approaches: a climatology derived from satellite radiative power product. also implemented...
We calculate the global mean atmospheric lifetime of elemental mercury (Hg 0 ) against oxidation by atomic bromine (Br) in troposphere combining recent kinetic data for Hg‐Br system with modeled concentrations tropospheric Br. obtain a 0.5–1.7 years based on range data, implying that Hg Br is major, and possibly dominant, sink . Most takes place middle upper troposphere, where are high cold temperatures suppress thermal decomposition HgBr intermediate. This mechanism consistent observations,...
Abstract. We use aircraft observations of carbon monoxide (CO) from the NASA ARCTAS and NOAA ARCPAC campaigns in April 2008 together with multiyear (2003–2008) CO satellite data AIRS instrument a global chemical transport model (GEOS-Chem) to better understand sources, transport, interannual variability pollution Arctic spring. Model simulation gives best estimates emissions 26 Tg month−1 for Asian anthropogenic, 9.4 European 4.1 North American 15 Russian biomass burning (anomalously large...
Global policies regulating anthropogenic mercury require an understanding of the relationship between emitted and deposited on intercontinental scales. Here, we examine source–receptor relationships for present-day conditions four 2050 IPCC scenarios encompassing a range economic development environmental regulation projections. We use GEOS-Chem global model to track from its point emission through rapid cycling in surface ocean land reservoirs accumulation longer lived soil pools. Deposited...
Abstract We present a new method for simulating heterogeneous (surface and multiphase) cloud chemistry in atmospheric models that do not spatially resolve clouds. The accounts entrainment within the chemical rate expression, making it more accurate stable than other approaches. Using this “entrainment‐limited uptake,” we evaluate role of clouds tropospheric NO x cycle. Past literature suggests on large scales, losses N 2 O 5 3 are much less important aerosols. find, however, reactions...
Abstract. National parks in the United States are protected areas wherein natural habitat is to be conserved for future generations. Deposition of anthropogenic nitrogen (N) transported from human activity (fuel combustion, agriculture) may affect these habitats if it exceeds an ecosystem-dependent critical load (CL). We quantify and interpret deposition Class I US national present-day (2050) conditions using GEOS-Chem global chemical transport model with 1/2° × 2/3° horizontal resolution...
Abstract. We have developed a new nested-grid mercury (Hg) simulation over North America with 1/2° latitude by 2/3° longitude horizontal resolution employing the GEOS-Chem global chemical transport model. Emissions, chemistry, deposition, and meteorology are self-consistent between nested domains. Compared to model (4° 5° longitude), shows improved skill at capturing high spatial temporal variability of Hg wet deposition observed Mercury Deposition Network (MDN) in 2008–2009. The resolves...
Abstract The atmospheric methane (CH 4 ) chemical feedback is a key process for understanding the behavior of CH and its environmental impact. This work reviews how defined used, then examines meteorological, chemical, emission factors that control strength. Geographical temporal variations in are described explained by HO x (HO = OH + 2 production partitioning. Different boundary conditions used models, however, make no meaningful difference to calculation. strength depends on composition,...
Oceans emit large quantities of dimethyl sulfide (DMS) to the marine atmosphere. The oxidation DMS leads formation and growth cloud condensation nuclei (CCN) with consequent effects on Earth's radiation balance climate. quantitative assessment impact emissions CCN concentrations necessitates a detailed description in presence existing aerosol particles clouds. In unpolluted atmosphere, is efficiently oxidized hydroperoxymethyl thioformate (HPMTF), stable intermediate chemical trajectory...
Abstract. Wildfires are increasing in size across the western US, leading to increases human smoke exposure and associated negative health impacts. The impact of biomass burning (BB) smoke, including wildfires, on regional air quality depends emissions, transport, chemistry, oxidation emitted BB volatile organic compounds (BBVOCs) by hydroxyl radical (OH), nitrate (NO3), ozone (O3). During daytime, when light penetrates plumes, BBVOCs oxidized mainly O3 OH. In contrast, at night or optically...
Abstract Studies of wintertime air quality in the North China Plain (NCP) show that particulate‐nitrate pollution persists despite rapid reduction NO x emissions. This intriguing ‐nitrate relationship may originate from non‐linear nitrate‐formation chemistry, but it is unclear which feedback mechanisms dominate NCP. In this study, we re‐interpret observations 17 O excess nitrate (∆ O(NO 3 − )) Beijing using GEOS‐Chem (GC) chemical transport model to estimate importance various...
Understanding the efficiency and variability of photochemical ozone (O3) production from western wildfire plumes is important to accurately estimate their influence on North American air quality. A set measurements were made NOAA Twin Otter research aircraft as a part Fire Influence Regional Global Environments Air Quality (FIREX-AQ) experiment. We use zero-dimensional (0-D) box model investigate chemistry driving O3 in modeled plumes. Modeled afternoon reached maximum mixing ratio 140 ± 50...
Carbonaceous emissions from wildfires are a dynamic mixture of gases and particles that have important impacts on air quality climate. Emissions feed atmospheric models estimated using burned area fire radiative power (FRP) methods rely satellite products. These approaches show wide variability large uncertainties, their accuracy is challenging to evaluate due limited aircraft ground measurements. Here, we present novel method estimate plume-integrated total carbon speciated emission rates...