A5090770685- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Air Quality and Health Impacts
- Ionosphere and magnetosphere dynamics
- Atmospheric aerosols and clouds
- Advanced Aircraft Design and Technologies
- Vehicle emissions and performance
- Innovative Teaching Methods
- Analytical chemistry methods development
- Various Chemistry Research Topics
- Experimental Learning in Engineering
- Air Traffic Management and Optimization
- Mass Spectrometry Techniques and Applications
- Toxic Organic Pollutants Impact
North Carolina State University
2022
Lake Forest College
2008-2010
Jet Propulsion Laboratory
2001
University of California, Berkeley
1999-2001
Middlebury College
2001
The Aerospace Corporation
1999
University of Colorado Boulder
1995-1999
Cooperative Institute for Research in Environmental Sciences
1995-1999
Harvard University
1998-1999
Environment and Climate Change Canada
1999
In situ measurements of the mass, mixing state, and optical size individual black‐carbon (BC) particles in fine mode (90–600 nm) have been made fresh emissions from urban biomass burning sources with an airborne single‐particle soot photometer. Contrasts between two are significant consistent. Urban BC tends to smaller sizes, fewer coated particles, thinner coatings, less absorption per unit mass than biomass‐burning BC. This suggests that may a longer lifetime atmosphere different impact on...
The concentrations of the hydrogen radicals OH and HO2 in middle upper troposphere were measured simultaneously with those NO, O3, CO, H2O, CH4, non-methane hydrocarbons, ultraviolet visible radiation field. data allow a direct examination processes that produce O3 this region atmosphere. Comparison calculations based on their production from water vapor, ozone, methane demonstrate these sources are insufficient to explain observed radical troposphere. photolysis carbonyl peroxide compounds...
Emission indices of reactive gases and particles were determined from measurements in the exhaust plume a Concorde aircraft cruising at supersonic speeds stratosphere. Values for NO x (sum 2 ) agree well with ground-based estimates. Measurements HO indicate limited role nitric acid plume. The large number submicrometer measured implies efficient conversion fuel sulfur to sulfuric engine or emission. A new fleet similar particle emissions would significantly increase stratospheric aerosol...
On May 8, 1997, vertical profiles of over 30 different gases were measured remotely in solar occultation by the Jet Propulsion Laboratory MkIV Interferometer during a balloon flight launched from Fairbanks, Alaska. These included H 2 O, N CH 4 , CO, NO x y HCl, ClNO 3 CCl F F, CHClF CClF SF 6 Cl, and C all which also situ instruments on board NASA ER‐2 aircraft, was making flights Fairbanks this same early time period as part Photochemistry Ozone Loss Arctic Region Summer (POLARIS)...
During the NOAA Southern Oxidant Study 1999 (SOS1999), Texas Air Quality 2000 (TexAQS2000), International Consortium for Atmospheric Research on Transport and Transformation (ICARTT2004), 2006 (TexAQS2006) campaigns, airborne measurements of isoprene monoterpenes were made in eastern United States Texas, results are used to evaluate biogenic emission inventories BEIS3.12, BEIS3.13, MEGAN2, WM2001. Two methods evaluation. First, emissions directly estimated from ambient monoterpene assuming a...
Extensive airborne measurements of the reactive nitrogen reservoir (NO y ) and its component nitric oxide (NO) have been made in lower stratosphere. Box model simulations that are constrained by observations radical long‐lived species which include heterogeneous chemistry systematically underpredict NO x (= + 2 to ratio. The agreement is substantially improved if newly measured rate coefficients for OH HNO 3 reactions used. When included 2‐D models, new significantly increase calculated...
Measurements of nitric oxide (NO), nitrogen dioxide (NO 2 ), and total reactive y = NO + 3 HNO ClONO 2N O 5 …) were made during austral fall, winter, spring 1994 as part the NASA Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing Effects Stratospheric Aircraft mission. Comparisons between measured values those calculated using a steady state (SS) approximation are presented flights at mid high latitudes. The SS results agree with measurements to within 8%, suggesting...
Airborne measurements of total reactive nitrogen (NO y ) and polar stratospheric cloud (PSC) aerosol particles were made in the Antarctic (68°S) as part NASA Southern Hemisphere Ozone Experiment/Measurements for Assessing Effects Stratospheric Aircraft (ASHOE/MAES A) campaign late July 1994. As found both regions during previous studies, substantial PSC volume containing NO was observed at temperatures above frost point, confirming presence other than water ice. The composition is evaluated...
Extensive in situ measurements of reactive nitrogen (NO y ) and ozone (O 3 were made the lower stratosphere over a broad latitude range (60°N–70°S) during two different seasons (March October) 1994. Both NO O mixing ratios show strong dependence, with values increasing toward poles. The /O ratio reveals high‐gradient region near tropics that is not well‐represented standard 2‐D photochemical transport models. Improving representation by changing horizontal eddy‐diffusion coefficients has...
The tracer species nitrous oxide, N 2 O, and the reactive nitrogen reservoir, NO y , were measured in situ using instrumentation carried aboard NASA ER‐2 high altitude aircraft as part of Airborne Southern Hemisphere Ozone Expedition/Measurements for Assessing Effects Stratospheric Aircraft (ASHOE/MAESA) Tracers Atmospheric Transport (STRAT) missions. Measurements made throughout latitude range 70°S to 60°N over time period March October 1994 1995 January 1996, which includes when Antarctic...
During the 1993 NASA Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE), anomalously low nitric oxide (NO) was found in a distinct sunlit layer located above mid‐latitude tropopause. The presence of significant amount reactive nitrogen (NO y ) implies systematic removal NO, which is without precedent stratospheric situ observations. Large increases measured chlorine monoxide (ClO) hydroperoxyl radical (HO 2 also were observed layer. Heterogeneous reaction rate constants...
The first in situ measurements of ClONO 2 the lower stratosphere, acquired using NASA ER‐2 aircraft during Polar Ozone Loss Arctic Region Summer (POLARIS) mission, are combined with simultaneous ClO, NO , temperature, pressure, and calculated photolysis rate coefficient (J ClONO2 ) to examine balance between production loss . observations demonstrate that photochemical steady state approximation, [ClONO ] PSS = k × [ClO] [NO / J is good agreement direct measurement, MEAS For bulk data (80%),...
Stratospheric measurements of NO, NO 2 , O 3 ClO, and HO were made during spring, early summer, late summer in the Arctic region 1997 as part Photochemistry Ozone Loss Region Summer (POLARIS) field campaign. In sunlit atmosphere, are steady state through photolysis reactions involving BrO, . By combining observations observed modeled values rate coefficient (J ), model estimates several comparisons between measured both J An apparent seasonal dependence discrepancies calculated was found;...
Measured particle volumes in a type I polar stratospheric cloud near the Antarctic vortex during ASHOE/MAESA show that onset of occurred 193 K, 3 degrees colder than nitric acid trihydrate (NAT) saturation. The temperature, smooth increase volume with decreasing inverse correlation and enhanced NO y (HNO particles) comparisons observations an equilibrium model ternary droplet growth all support notion much this PSC was solution droplets. This provides confirmation previous findings northern...
In situ observations Of NO 2 , NO, y ClONO OH, O 3 aerosol surface area, spectrally resolved solar radiation, pressure and temperature obtained from the ER‐2 aircraft during Photochemistry of Ozone Loss in Arctic Region Summer (POLARIS) experiments are used to examine factors controlling fast photochemistry connecting slower chemistry x HNO . Our analysis uses “chemical coordinates” gradients difference between a model precisely calibrated measurements provide quantitative assessment...
We compare measurements of six species taken aboard NASA DC‐8 and ER‐2 aircraft during two flight legs in the tropical middle troposphere near Hawaii. NO, NO y , O 3 CH 4 N 2 agree to within limits set by known systematic errors. For CO which can be measured with better relative precision than other five species, differences values from platforms are slightly larger expected if air masses sampled were indeed similar composition 0.08%.
During the 1997 Photochemistry of Ozone Loss in Arctic Region Summer (POLARIS) mission, simultaneous situ observations NOx and HOx radicals, their precursors, radiation field were obtained lower stratosphere. We use these to evaluate primary mechanisms that control NOx−HNO3 exchange understand over partitioning between NO2 HNO3 regions continuous sunlight. calculate production (PNOx) loss (LNOx) a manner directly constrained by measurements current rate constant recommendations, using...
The generation of sulfuric acid aerosols in aircraft exhaust has emerged as a critical issue determining the impact supersonic on stratospheric ozone. It long been held that first step mechanism aerosol formation is oxidation SO 2 emitted from engine by OH plume. We report situ measurements and HO plumes (Air France Concorde) subsonic (NASA ER‐2) lower stratosphere. These imply reactions with are responsible for oxidizing only small fraction (2%), thus cannot explain large number particles...
In situ measurements of radical and long‐lived species were made in the lower Arctic stratosphere (18 to 20 km) between spring early autumn 1997. The include O 3 , ClO, OH, HO 2 NO, NO N O, CO, overhead . A photochemical box model constrained by these other observations is used compute diurnally averaged destruction production rates this region. show a strong dependence on solar exposure ambient Total rates, which reach 19%/month summer, reveal predominant role x catalytic cycles throughout...
The mechanisms responsible for latitudinal and seasonal variations in the stratospheric NO y /N 2 O correlation, represented by effective yield from N loss, or F , are explored using Garcia‐Solomon two‐dimensional model. model is run with without Antarctic denitrification. Model results compared to situ measurements taken onboard NASA ER‐2 high‐altitude aircraft lower stratosphere during 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements Assessing Effects of Stratospheric...
Recent studies using NO, NO y , OH and HO 2 (HO x ) observations have postulated acetone convection of peroxides as significant sources in the upper troposphere (UT). This work focuses on effect these additional modeled partitioning comparisons /NO ratio to observations. The measured is usually much higher than predicted regardless presence model. exception occurs for air parcels having low O 3 values. For lower calculated unless included In all cases increases fraction that peroxy acetyl...
In situ measurements of NO, NO 2 , O 3 HO ClO, pressure, and temperature have been made at high solar zenith angles (SZA, 70°–93°) in the lower stratosphere. These are used to derive photolysis rate J using a time‐dependent method. The resultant values results multiple‐scattering actinic flux model show linear relationship throughout SZA range. difference two sets about 11% suggests that scattering calculation is very accurate conditions near sunrise sunset.
Due to the COVID-19 pandemic, in-person undergraduate chemistry laboratories at North Carolina State University were not available students during 2020–2021 academic year and replaced with online laboratories. With return in fall semester of 2021, there was widespread concern among faculty that majors might struggle application concepts techniques they learned lab environment. An event bring back campus for a day designed by charge teaching organic analytical extensive input from students....