A5103267276- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric aerosols and clouds
- Atmospheric and Environmental Gas Dynamics
- Air Quality and Health Impacts
- Vehicle emissions and performance
- Photonic and Optical Devices
- Fire effects on ecosystems
- Ultrasonics and Acoustic Wave Propagation
- Ionosphere and magnetosphere dynamics
- Gyrotron and Vacuum Electronics Research
- Rocket and propulsion systems research
- Microwave Engineering and Waveguides
- Air Quality Monitoring and Forecasting
- Gas Dynamics and Kinetic Theory
- Aeolian processes and effects
- Cyclone Separators and Fluid Dynamics
- Spectroscopy and Laser Applications
- Spacecraft and Cryogenic Technologies
- Photoacoustic and Ultrasonic Imaging
- Electrical and Bioimpedance Tomography
- Wireless Power Transfer Systems
- Catalytic Processes in Materials Science
- Field-Flow Fractionation Techniques
- Molecular Spectroscopy and Structure
Earth Observing Laboratory
2018-2023
NSF National Center for Atmospheric Research
2013-2022
University of Denver
2002-2011
Portsmouth College
1974-2005
Hanscom Air Force Base
2003
Goddard Space Flight Center
2003
National Aeronautics and Space Administration
2003
State University of New York
1994-2002
University of Michigan
1997
Iowa State University
1997
A single‐particle soot photometer (SP2) was flown on a NASA WB‐57F high‐altitude research aircraft in November 2004 from Houston, Texas. The SP2 uses laser‐induced incandescence to detect individual black carbon (BC) particles an air sample the mass range of ∼3–300 fg (∼0.15–0.7 μm volume equivalent diameter). Scattered light is used size remaining non‐BC aerosols ∼0.17–0.7 diameter. We present profiles both aerosol types boundary layer lower stratosphere two midlatitude flights. Results for...
Unexpectedly high concentrations of ultrafine particles were observed over a wide range latitudes in the upper troposphere and lower stratosphere. Particle number size distributions simulated by numerical model ion-induced nucleation, constrained measured thermodynamic data atmospheric key species, consistent with observations. These findings indicate that, at typical stratosphere conditions, are formed this nucleation process grow to measurable sizes sufficient sun exposure low preexisting...
Black carbon (BC) is the dominant aerosol absorber of solar radiation in atmosphere and an important component anthropogenic climate forcing. BC's role strongly dependent on its physical state, which can influence way that BC particles may act as ice cloud nuclei, well they interact with radiation. In situ measurements made a single‐particle soot photometer flown NASA high‐altitude research aircraft show mass size individual tropics, their propensity to be found mixed additional materials....
Abstract Nocturnal dinitrogen pentoxide (N 2 O 5 ) heterogeneous chemistry impacts regional air quality and the distribution lifetime of tropospheric oxidants. Formed from oxidation nitrogen oxides, N is heterogeneously lost to aerosol with a highly variable reaction probability, γ ), dependent on composition ambient conditions. Reaction products include soluble nitrate (HNO 3 or NO − nitryl chloride (ClNO ). We report first‐ever derivations wintertime aircraft measurements in critically...
Abstract Most intensive field studies investigating aerosols have been conducted in summer, and thus, wintertime aerosol sources chemistry are comparatively poorly understood. An mass spectrometer was flown on the National Science Foundation/National Center for Atmospheric Research C‐130 during Wintertime INvestigation of Transport, Emissions, Reactivity (WINTER) 2015 campaign northeast United States. The fraction boundary layer submicron that organic (OA) about a factor 2 smaller than 2011...
Abstract. Long-range transport of biogenic emissions from the coast Antarctica, precipitation scavenging, and cloud processing are main processes that influence observed variability in Southern Ocean (SO) marine boundary layer (MBL) condensation nuclei (CN) (CCN) concentrations during austral summer. Airborne particle measurements on HIAPER GV north–south transects between Hobart, Tasmania, 62∘ S Clouds, Radiation Aerosol Transport Experimental Study (SOCRATES) were separated into four...
Particle size distributions and gas‐phase particle precursors tracer species were measured aboard an aircraft in the plumes downwind from industrial urban sources vicinity of Houston, TX during daytime late August early September 2000. Plumes originating Parish gas‐fired coal‐fired power plant, petrochemical industries along Houston ship channel, facilities near Gulf coast, center studied. Most mass flux advected came electrical utilities at periphery city rather than core. In SO 2 ‐rich...
Abstract. New particle formation (NPF), which generates nucleation mode aerosol, was observed in the tropical Upper Troposphere (UT) and Tropical Tropopause Layer (TTL) by situ airborne measurements over South America (January–March 2005), Australia (November–December West Africa (August 2006) Central (2004–2007). Particularly intense NPF found at bottom of TTL. Measurements with a set condensation counters (CPCs) different dp50 (50% lower size detection efficiency diameter or "cut-off...
Abstract Nitryl chloride (ClNO 2 ) plays an important role in the budget and distribution of tropospheric oxidants, halogens, reactive nitrogen species. ClNO is formed from heterogeneous uptake reaction dinitrogen pentoxide (N O 5 on chloride‐containing aerosol, with a production yield, ϕ ), defined as moles produced relative to N lost. The has been increasingly incorporated into 3‐D chemical models where it parameterized based laboratory‐derived kinetics currently accepted aqueous‐phase...
Abstract. Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in magnitude spatiotemporal distribution nucleation (less than 10 nm diameter) Aitken (10–60 mode particles. Acquiring size-distribution measurements over large regions free troposphere most easily accomplished with research aircraft. We...
Submicron particle‐size distributions were measured with 10‐s resolution aboard the National Oceanic and Atmospheric Administration WP‐3D Orion research aircraft in plumes downwind of coal‐fired power generation plants eastern United States urban areas Nashville, Tennessee, Atlanta, Georgia. Recently formed particles present at edges some plant within 2 hours emission, coinciding OH maxima predicted by a numerical plume photochemistry model. Clearly detectable increases particle volume...
Abstract. We report measurements of bromine monoxide (BrO) and use an observationally constrained chemical box model to infer total gas-phase inorganic (Bry) over the tropical western Pacific Ocean (tWPO) during CONTRAST field campaign (January–February 2014). The observed BrO inferred Bry profiles peak in marine boundary layer (MBL), suggesting need for a source from sea-salt aerosol (SSA), addition organic (CBry). Both are found be C-shaped with local maxima upper free troposphere (FT)....
Abstract Secondary organic aerosol (SOA) from pollution sources is thought to be a minor component of (OA) and fine particulate matter beyond the urban scale. Here we present airborne observations OA in northeastern United States, showing that 58% over region during winter secondary originates sources. We observed doubling mass SOA formation aged emissions, with unexpected similarity growth polluted areas summer. A regional model simple parameterization based on summer measurements...
Abstract Small cumulus clouds over the western United States were measured via airborne instruments during wildfire season in summer of 2018. Statistics sampled are presented and compared to smoke aerosol properties. Cloud droplet concentrations enhanced regions impacted by biomass burning smoke, at times exceeding 3,000 cm −3 . Images elemental composition individual particles cloud residuals show that most dominantly organic, internally mixed with some inorganic elements. Despite their...
Wildfires are a source of primary aerosols and precursors for secondary to the atmosphere. In this work, we discover that evolution these depends strongly on coupled effects dilution, photooxidation, partitioning.
Aerosol particles from the upper troposphere (UT) and lower stratosphere (LS) were collected during Cirrus Regional Study of Tropical Anvils Layers‐Florida Area Experiment (CRYSTAL‐FACE) studied by transmission electron microscopy (TEM). Samples classified into three categories: (1) UT in‐cloud, (2) out‐of‐cloud, (3) LS. Sulfate particles, including former H 2 SO 4 droplets, are dominant in samples all categories. The morphology droplets indicates that they had been ammoniated to some extent...
Previous studies show that new particle formation takes place in the outflows of marine stratus and cumulus clouds. Here we measurements high concentrations ultrafine particles, diameters ( D p ) from 4 to 9 nm N 4–9 ), interstitial cloud aerosol. These particles indicate situ occurs interstitially cirrus Measurements were made at altitudes 7 16 km over Florida with instruments on WB‐57F aircraft during Cirrus Regional Study Tropical Anvils Layers‐Florida Area Experiments (CRYSTAL‐FACE) July...
Abstract We use observations from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) aircraft campaign to constrain proposed mechanism Cl 2 production ClNO reaction in acidic particles. To reproduce concentrations observed during WINTER with a chemical box model that includes reactive uptake form , required probability, γ (ClNO ), range 6 × 10 −6 7 −5 mean value 2.3 (±1.8 ). These field‐determined ) are more than an order magnitude lower those determined...
Abstract Southern Ocean (SO) low‐level mixed phase clouds have been a long‐standing challenge for Earth system models to accurately represent. While improvements the Community System Model version 2 (CESM2) resulted in increased supercooled liquid SO and improved model radiative biases, simulated CESM2 now contain too little ice. Previous observational studies indicated that marine particles are major contributor cloud heterogeneous ice nucleation, process initiates number of processes...
Abstract A chemical ionization mass spectrometer was used to measure BrO and HOBr + Br 2 over the Tropical West Pacific Ocean within altitude range of 1 15 km, during CONvective TRansport Active Species in Tropics (CONTRAST) campaign 2014. Isolated episodes elevated (up 6.6 pptv) and/or 7.3 were observed tropical free troposphere (TFT) associated with biomass burning. However, most time we did not observe significant or TFT tropopause layer (TTL) above our limits detection (LOD). The min...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCyclitols. VIII. Bromination of epi-Inositol. Synthesis Conduritol-C1a,2G. E. McCasland and John M. ReevesCite this: J. Am. Chem. Soc. 1955, 77, 7, 1812–1814Publication Date (Print):April 1, 1955Publication History Published online1 May 2002Published inissue 1 April 1955https://pubs.acs.org/doi/10.1021/ja01612a028https://doi.org/10.1021/ja01612a028research-articleACS PublicationsRequest reuse permissionsArticle Views76Altmetric-Citations17LEARN...
Iodine is an atmospheric trace element emitted from oceans that efficiently destroys ozone (O3). Low O3 in airborne dust layers frequently observed but poorly understood. We show a source of gas-phase iodine, indicated by aircraft observations iodine monoxide (IO) radicals inside lofted the Atacama and Sechura Deserts are up to factor 10 enhanced over background. Gas-phase photochemistry, commensurate with IO, needed explain low these (below 15 ppbv; 75% depleted). The added can decreases 8%...