A5028330542- 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
- Spectroscopy and Laser Applications
- Advanced Chemical Physics Studies
- Plant responses to elevated CO2
- Molecular Spectroscopy and Structure
- Spectroscopy and Quantum Chemical Studies
- Odor and Emission Control Technologies
- Water Quality Monitoring and Analysis
- Fire effects on ecosystems
- Particle accelerators and beam dynamics
- Marine and coastal ecosystems
- Nuclear Physics and Applications
- Quantum, superfluid, helium dynamics
- Molecular spectroscopy and chirality
- Advanced Chemical Sensor Technologies
- Groundwater and Isotope Geochemistry
- Particle Accelerators and Free-Electron Lasers
- Analytical Chemistry and Sensors
- Ionosphere and magnetosphere dynamics
Planetary Science Institute
2016-2025
University of California, Berkeley
2016-2025
University of California System
2015-2020
Berkeley College
2015-2020
University of Washington
2020
Lawrence Berkeley National Laboratory
2002-2018
Environmental Technologies (United States)
2010-2011
SRI International
2010
Menlo School
2010
California Air Resources Board
2010
A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup a microjet. Analysis data over range 251 to 288 kelvin (-22 degrees +15 C) yields value 1.5 +/- 0.5 kilocalories per mole average thermal energy required effect an observable rearrangement between fully coordinated ("ice-like") distorted ("broken-donor") local hydrogen-bonding configurations responsible pre-edge...
Abstract. Soils have been identified as a major source (~15%) of global nitrogen oxide (NOx) emissions. Parameterizations soil NOx emissions (SNOx) commonly used in the current generation chemical transport models were designed to capture mean seasonal behaviour. These parameterizations do not, however, respond quantitatively meteorological triggers that are observed result pulsed SNOx. Here we present new parameterization SNOx implemented within model (GEOS-Chem). The represents available...
Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one important interactions between anthropogenic emissions related to combustion and natural from biosphere. This interaction has been recognized for more than 3 decades, during which time a large body research emerged laboratory, field, modeling studies. NO3-BVOC reactions influence air quality, climate visibility through regional global budgets reactive nitrogen (particularly nitrates), ozone,...
Abstract. Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates surface ozone concentrations tend to be biased high region this is concern for designing effective emission control strategies meet air quality standards. We use detailed chemical observations from SEAC4RS aircraft campaign August September 2013, interpreted with GEOS-Chem transport model at 0.25° ×...
Variations in the isotopic content ( 18 O/ 16 O and D/H ratios) of water natural environment provide a valuable tracer present‐day global hydrologic cycle record climate over at least 400,000 years that is preserved glacial ice. The interpretation observed ratios vapor, rain, snow, ice depends on our understanding processes (mainly phase changes) produce fractionation. Whereas equilibrium fractionation well understood, kinetic effects, or diffusion‐controlled fractionation, has limited...
The unique chemical and physical properties of liquid water are a direct result its highly directional hydrogen-bond (HB) network structure associated dynamics. However, despite intense experimental theoretical scrutiny spanning more than four decades, coherent description this HB remains elusive. essential question whether continuum or multicomponent (“intact,” “broken bond,” etc.) models best describe the interactions in has engendered particularly discussion. Most notably, temperature...
Simultaneous in situ measurements of the concentrations OH, HO(2), ClO, BrO, NO, and NO(2) demonstrate predominance odd-hydrogen halogen free-radical catalysis determining rate removal ozone lower stratosphere during May 1993. A single catalytic cycle, which rate-limiting step is reaction HO(2) with ozone, accounted for nearly one-half total O(3) this region atmosphere. Halogen-radical chemistry was responsible approximately one-third photochemical O(3); reactions involving BrO account loss....
Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part the Southern Oxidant Aerosol Study. A large fraction pONs is highly functionalized, possessing between six eight oxygen atoms within each carbon number group, not common first generation alkyl previously reported. Using calibrations for isoprene hydroxynitrates measured molecular compositions, we estimate that account 3% 8% total...
Abstract. The measurement of OH reactivity, the inverse lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne reactivity instrument was designed and deployed for first time on NASA DC-8 aircraft during second phase Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign, which focused Asian pollution outflow over Pacific Ocean based in Hawaii Alaska. measured by adding OH, generated photolyzing water vapor with 185 nm UV light moveable wand,...
Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO(x)) affect atmospheric organic aerosol (OA) production. However, these effects not been directly observed in ambient OA. We report measurements particulate nitrates Bakersfield, California, the nighttime formation increases with NO(x) and is suppressed high concentrations molecules that rapidly react nitrate radical (NO(3))--evidence multigenerational chemistry responsible for This class represents...
Abstract We implement a new isoprene oxidation mechanism in global 3‐D chemical transport model (GEOS‐Chem). Model results are evaluated with observations for ozone, products, and related species from the International Consortium Atmospheric Research on Transport Transformation aircraft campaign over eastern United States summer 2004. The achieves an unbiased simulation of ozone boundary layer free troposphere, reflecting canceling effects recent updates chemistry, bromine HO 2 loss to...
We use observations from two aircraft during the ICARTT campaign over eastern United States and North Atlantic summer 2004, interpreted with a global 3‐D model of tropospheric chemistry (GEOS‐Chem) to test current understanding regional sources, chemical evolution, export NO x . The boundary layer data provide top‐down verification 50% decrease in power plant industry emissions between 1999 2004. Observed concentrations at 8–12 km altitude were 0.55 ± 0.36 ppbv, much larger than previous...
Abstract. The yields of organic nitrates and secondary aerosol (SOA) particle formation were measured for the reaction NO3+β-pinene under dry humid conditions in atmosphere simulation chamber SAPHIR at Research Center Jülich. These experiments conducted low concentrations NO3 (NO3+N2O5<10 ppb) β-pinene (peak~15 ppb), with no seed aerosol. SOA was observed to be prompt substantial (~50% mass yield both 60% RH), highly correlated nitrate formation. gas/aerosol partitioning can simulated...
Abstract. Observations of tropospheric NO2 vertical column densities over the United States (US) for 2005–2011 are evaluated using OMI Berkeley High Resolution (BEHR) retrieval algorithm. We assess changes in on day-of-week and interannual timescales to impact emissions from mobile non-mobile sources observed trends. observe consistent decreases cities across US, with an average total reduction 32 ± 7% 7 yr. Changes large power plants have been more variable (−26 12%) due regionally-specific...
Abstract. We determine enhancement ratios for NOx, PAN, and other NOy species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign examine impact of these emissions on tropospheric ozone in Arctic. find an initial emission factor NOx 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations plumes, also one third value recommended extratropical fires. Our analysis provides first observational confirmation rapid PAN formation a smoke...
Abstract Brown carbon aerosol consists of light‐absorbing organic particulate matter with wavelength‐dependent absorption. Aerosol optical extinction, absorption, size distributions, and chemical composition were measured in rural Alabama during summer 2013. The field site was well located to examine sources brown aerosol, influence by high biogenic concentrations, pollution from two nearby cities, biomass burning aerosol. We report the closure between dry extinction at 365 nm calculated...
Abstract. We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms transpacific ozone pollution its implications North American air quality. The are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO2 satellite constrain Asian anthropogenic NOx emissions indicate factor 2 increase from 2000 in China. Satellite CO AIRS TES two major events during INTEX-B....
Abstract. The understanding of oxidation in forest atmospheres is being challenged by measurements unexpectedly large amounts hydroxyl (OH). A significant number these OH were made laser-induced fluorescence low-pressure detection chambers (called Fluorescence Assay with Gas Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure parallel traditional FAGE California forest. gives on average only...
Abstract The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout in May, June, July 2010. organized to address issues simultaneously relevant atmospheric pollution climate change, including (1) emission inventory assessment, (2) transport dispersion, (3) chemical processing, (4) cloud‐aerosol interactions aerosol radiative effects. Measurements from networks ground sites, a research ship, tall towers, balloon‐borne ozonesondes,...
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. Formation of organic nitrates (RONO2) during oxidation biogenic volatile compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry RONO2 formation and degradation remains uncertain. Here we implement new BVOC mechanism (including updated isoprene chemistry, monoterpene particle uptake RONO2) in GEOS-Chem global chemical transport model with ∼ 25 × km2 resolution over North America. We evaluate using...
The secondary organic aerosol (SOA) mass yields from NO3 oxidation of a series biogenic volatile compounds (BVOCs), consisting five monoterpenes and one sesquiterpene (α-pinene, β-pinene, Δ-3-carene, limonene, sabinene, β-caryophyllene), were investigated in continuous flow experiments 10 m3 indoor Teflon chamber. By making situ measurements the nitrate radical employing kinetics box model, we generate time-dependent yield curves as function reacted BVOC. SOA varied dramatically among...