A5064030912- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Atmospheric aerosols and clouds
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Fire effects on ecosystems
- Vehicle emissions and performance
- Meteorological Phenomena and Simulations
- Ionosphere and magnetosphere dynamics
- Aeolian processes and effects
- Rocket and propulsion systems research
- Astro and Planetary Science
- Gas Dynamics and Kinetic Theory
- Spectroscopy and Laser Applications
- Arctic and Antarctic ice dynamics
- Spacecraft and Cryogenic Technologies
- Climate variability and models
- Spacecraft Design and Technology
- Aerospace Engineering and Energy Systems
- Advanced Aircraft Design and Technologies
- Isotope Analysis in Ecology
- Oceanographic and Atmospheric Processes
- Space exploration and regulation
- Marine and coastal ecosystems
University of Colorado Boulder
2014-2025
University of Colorado System
2009-2024
NSF National Center for Atmospheric Research
2021
NOAA Oceanic and Atmospheric Research
2007-2014
National Oceanic and Atmospheric Administration
2005-2012
University of California, Irvine
1993-2005
Princeton University
2004
Irvine University
1994-1996
Harvard University
1987-1994
Jet Propulsion Laboratory
1994
Abstract. In March 2006 two instrumented aircraft made the first detailed field measurements of biomass burning (BB) emissions in Northern Hemisphere tropics as part MILAGRO project. The were National Center for Atmospheric Research C-130 and a University Montana/US Forest Service Twin Otter. initial up to 49 trace gas or particle species measured from 20 deforestation crop residue fires on Yucatan peninsula. This included gases useful indicators BB (HCN acetonitrile) several rarely, never...
How strong is the case linking global release of chlorofluorocarbons to episodic disappearance ozone from Antarctic stratosphere each austral spring? Three lines evidence defining a link are (i) observed containment in vortex ClO concentrations two orders magnitude greater than normal levels; (ii) situ observations obtained during ten high-altitude aircraft flights into as hole was forming that show decrease increased; and (iii) comparison between loss rates those predicted with use absolute...
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....
Abstract. Potential Aerosol Mass (PAM) can be defined as the maximum aerosol mass that oxidation of precursor gases produces. In measurement, all are rapidly oxidized with extreme amounts oxidants to low volatility compounds, resulting in formation. Oxidation occurs a small, simple, flow-through chamber has short residence time and is irradiated ultraviolet light. The amount ozone (O3), hydroxyl (OH), hydroperoxyl (HO2) were measured directly controlled by varying UV light relative humidity....
Organic aerosols (OA) in Pasadena are characterized using multiple measurements from the California Research at Nexus of Air Quality and Climate Change (CalNex) campaign. Five OA components identified positive matrix factorization including hydrocarbon‐like (HOA) two types oxygenated (OOA). The elemental composition when plotted as H : C versus O follows a line less steep than that observed for Riverside, CA. OOA both locations follow common line, however, indicating similar secondary...
Abstract Weather and climate models are challenged by uncertainties biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, processes, their interactions. Projects between 2016 2018 used situ probes, radar, lidar, other instruments make comprehensive measurements thermodynamics, surface radiation, cloud condensation nuclei (CCN), ice nucleating particles over the SO cold waters, ubiquitous liquid mixed-phase clouds common...
Abstract. The role of ice in the formation chemically active halogens environment requires a full understanding because its atmospheric chemistry, including controlling regional oxidizing capacity specific situations. In particular, and snow are important for facilitating multiphase oxidative chemistry as media upon which marine algae live. This paper reviews nature environmental substrates that participate halogen describes reactions occur on such substrates, presents field evidence...
Abstract. The emissions of NOx (defined as NO (nitric oxide) + NO2 (nitrogen dioxide)) and hydrogen cyanide (HCN), per unit amount fuel burned, from fires in the pine forests that dominate mountains surrounding Mexico City (MC) are about 2 times higher than normally observed for forest burning. ammonia (NH3) average upper limit mass ratio to volatile organic compounds (VOC) these MC-area mountain was ~0.38, which is similar NOx/VOC MC urban area inventory 0.34, but much larger tropical...
Simultaneous, in situ observations of ClO, BrO, O 3 , N 2 O, pressure, and temperature are used to examine the kinetics ozone destruction within Antarctic polar vortex. The high azimuthal symmetry vortex is simplify problem such that time rate change on isentropic surfaces between 450 360 K (18.3‐ 13.5‐km geometric altitude) can be calculated based proposed catalytic cycles involving HO O( P ). availability simultaneous, spatially resolved data reduce scatter observed ; this clarifies...
The fine‐scale structure in lower stratospheric tracer transport during the period of two Arctic Airborne Stratospheric Expeditions (January and February 1989; December 1991 to March 1992) is investigated using contour advection with surgery calculations. These calculations show that Rossby wave breaking an ongoing occurrence these periods air ejected from polar vortex form long filamentary structures. There good qualitative agreement between filaments measurements chemical tracers taken...
Abstract. We report airborne measurements of emission factors (EF) for trace gases and PM2.5 made in southern Mexico March 2006 on 6 crop residue fires, 3 tropical dry forest 8 savanna 1 garbage fire, 7 mountain pine-oak fires. The fire EF were measured early the local season when compared to late African they at least 1.7 times larger NOx, NH3, H2, most non-methane organic compounds. Our suggest that urban deposition high windspeed may also be associated with significantly elevated NOx EF....
[1] Water vapor in the subtropical troposphere plays an important role radiative balance, distribution of precipitation, and chemistry Earth's atmosphere. Measurements water mixing ratio paired with stable isotope ratios provide unique information on transport processes moisture sources that is not available data alone. D/H from Mauna Loa Observatory over 4 weeks October–November 2008 were used to identify components regional hydrological cycle. A model exploits fluxes time series data....
Abstract. The oxidation of secondary organic aerosol (SOA) is studied with mass spectra analysis SOA formed in a Potential Aerosol Mass (PAM) chamber, small flow-through photo-oxidation chamber extremely high OH and ozone levels. exposure from few minutes the PAM similar to that days weeks atmosphere. were measured Quadrupole Spectrometer (Q-AMS) for α-pinene, m-xylene, p-xylene, mixture three. fractions m/z 44 (CO2+) 43 (mainly C2H3O+), named f44 f43 respectively, are used as indicators...
Abstract Controls on pristine aerosol over the Southern Ocean (SO) are critical for constraining strength of global indirect forcing. Observations summertime SO clouds and aerosols in synoptically varied conditions during 2018 SOCRATES aircraft campaign reveal novel mechanisms influencing aerosol‐cloud interactions. The free troposphere (3–6 km) is characterized by widespread, frequent new particle formation events contributing to much larger concentrations (≥1,000 mg −1 ) condensation...
Abstract Stratocumulus clouds over the Southern Ocean have fewer droplets and are more likely to exist in predominately supercooled phase than at similar temperatures northern oceans. One reason is that this region has few continental anthropogenic sources of cloud‐nucleating particles can form ice. In work, we present an overview aerosol particle types Ocean, including new measurements made below, above region. These others indicate biogenic sulfur‐based >0.1 μm diameter contribute...
Abstract Wildfires in the western United States are large sources of particulate matter, and area burned by wildfires is predicted to increase future. Some particles released from can affect cloud formation serving as ice‐nucleating (INPs). INPs have numerous impacts on radiative properties precipitation development. potentially important INPs, indicated previous measurements, but their abundance free troposphere has not been quantified. The Western Wildfire Experiment for Cloud Chemistry,...
Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) the Arctic winter vortex showed large HCl losses, up to 1 part per billion by volume (ppbv), which were correlated with high ClO levels 1.4 ppbv. Air parcel trajectory analysis identified that this conversion inorganic occurred at air temperatures less than 196 ± 4 kelvin. High was always accompanied loss mixing ratios equal 1/2(ClO + 2Cl 2 O ). These data indicate heterogeneous reaction ClONO → Cl HNO 3...
During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar clouds (PSCs) lead to elevated abundances chlorine monoxide (ClO) that, in presence sunlight, destroy ozone. Here we show that PSCs were more widespread during 1999/2000 winter than for any other past two decades. We have used three fundamentally different approaches derive degree chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. losses derived these...
Large abundances of ClO were observed inside the arctic polar vortex during 14 flights NASA ER‐2 aircraft from Stavanger, Norway (59°N, 6°E) to 80°N latitude. Flights conducted at altitudes between and 20 km when solar zenith angle was 79° 101°. Data are reported for three flights, January 6, 16, Febmary 10, that represent main features mission. mixing ratios typically less than 50 parts per trillion by volume (pptv) outside exceeded 100 pptv all flights. more 500 four days in a row early...
The nature of the Arctic polar stratosphere is observed to be similar in many respects that Antarctic stratosphere, where an ozone hole has been identified. Most available chlorine (HCl and ClONO 2 ) was converted by reactions on stratospheric clouds reactive ClO Cl O throughout vortex before midwinter. Reactive nitrogen HNO 3 , some, with spatial inhomogeneity, fell out stratosphere. These chemical changes ensured characteristic losses 10 15% at altitudes inside had occurred. local can...
Abstract The subtropical convective boundary layer (CBL) plays a critical role in climate by regulating the vertical exchange of moisture, energy, trace gases, and pollutants between ocean surface free troposphere. Yet bulk features this are poorly constrained models. To improve our understanding moisture transport troposphere, paired measurements water vapor mixing ratio stable isotope 18 O/ 16 O used to evaluate moist entrainment processes near Big Island Hawaii. Profile data from island's...
Abstract. Some types of biological particles are known to nucleate ice at warmer temperatures than mineral dust, with the potential influence cloud microphysical properties and climate. However, prevalence these particle above atmospheric boundary layer is not well known. Many fluoresce when exposed ultraviolet light, Wideband Integrated Bioaerosol Sensor takes advantage this characteristic perform real-time measurements fluorescent aerosol (FBAPs). This instrument was flown on National...
Abstract The Southern Ocean plays a critical role in the global climate system by mediating atmosphere–ocean partitioning of heat and carbon dioxide. However, Earth models are demonstrably deficient Ocean, leading to large uncertainties future air–sea CO2 flux projections under warming incomplete interpretations natural variability on interannual geologic time scales. Here, we describe recent aircraft observational campaign, O2/N2 Ratio Airborne (ORCAS) study, which collected measurements...