Engineering topics

Huey, G.

Publications and source records attributed to Huey, G..

6 records

NASA NTRS2015

Quantifying Sources and Sinks of Reactive Gases in the Lower Atmosphere Using Airborne Flux Observations

Atmospheric composition is governed by the interplay of emissions, chemistry, deposition, and transport. Substantial questions surround each of these processes, especially in forested environments with strong biogenic emissions. Utilizing aircraft observations acquired over a forest in the southeast U.S., we calculate eddy covariance fluxes for a suite of reactive gases and apply the synergistic information derived from this analysis to quantify emission and deposition fluxes, oxidant concentrations, aerosol uptake coefficients, and other key parameters. Evaluation of results against state-of-the-science models and parameterizations provides insight into our current understanding of this system and frames future observational priorities. As a near-direct measurement of fundamental process rates, airborne fluxes offer a new tool to improve biogenic and anthropogenic emissions inventories, photochemical mechanisms, and deposition parameterizations.

emission↗

NASA NTRS2013

Source Attributions of Pollution to the Western Arctic During the NASA ARCTAS Field Campaign

We use the NASA GEOS-5 transport model with tagged tracers to investigate the contributions of different regional sources of CO and black carbon (BC) to their concentrations in the Western Arctic (i.e., 50-90 deg N and 190- 320 deg E) in spring and summer 2008. The model is evaluated by comparing the results with airborne measurements of CO and BC from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaigns to demonstrate the strengths and limitations of our simulations. We also examine the reliability of tagged CO tracers in characterizing air mass origins using the measured fossil fuel tracer of dichloromethane and the biomass burning tracer of acetonitrile. Our tagged CO simulations suggest that most of the enhanced CO concentrations (above background level from CH4 production) observed during April originate from Asian anthropogenic emissions. Boreal biomass burning emissions and Asian anthropogenic emissions are of similar importance in July domain wise, although the biomass burning CO fraction is much larger in the area of the ARCTAS field experiments. The fraction of CO from Asian anthropogenic emissions is larger in spring than in summer. European sources make up no more than 10% of CO levels in the campaign domain during either period. Comparisons of CO concentrations along the flight tracks with regional averages from GEOS-5 show that the alongtrack measurements are representative of the concentrations within the large domain of the Western Arctic in April but not in July.

Black Carbon↗

NASA NTRS2011

Emissions of Black Carbon, Organic, and Inorganic Aerosols From Biomass Burning in North America and Asia in 2008

Reliable assessment of the impact of aerosols emitted from boreal forest fires on the Arctic climate necessitates improved understanding of emissions and the microphysical properties of carbonaceous (black carbon (BC) and organic aerosols (OA)) and inorganic aerosols. The size distributions of BC were measured by an SP2 based on the laser-induced incandescence technique on board the DC-8 aircraft during the NASA ARCTAS campaign. Aircraft sampling was made in fresh plumes strongly impacted by wildfires in North America (Canada and California) in summer 2008 and in those transported from Asia (Siberia in Russia and Kazakhstan) in spring 2008. We extracted biomass burning plumes using particle and tracer (CO, CH3CN, and CH2Cl2) data. OA constituted the dominant fraction of aerosols mass in the submicron range. The large majority of the emitted particles did not contain BC. We related the combustion phase of the fire as represented by the modified combustion efficiency (MCE) to the emission ratios between BC and other species. In particular, we derived the average emission ratios of BC/CO = 2.3 +/- 2.2 and 8.5 +/- 5.4 ng/cu m/ppbv for BB in North America and Asia, respectively. The difference in the BC/CO emission ratios is likely due to the difference in MCE. The count median diameters and geometric standard deviations of the lognormal size distribution of BC in the BB plumes were 136-141 nm and 1.32-1.36, respectively, and depended little on MCE. These BC particles were thickly coated, with shell/core ratios of 1.3-1.6. These parameters can be used directly for improving model estimates of the impact of BB in the Arctic.

Kondo, Y.↗

NASA NTRS2008

Hybrid Gibbs Sampling and MCMC for CMB Analysis at Small Angular Scales

A) Gibbs Sampling has now been validated as an efficient, statistically exact, and practically useful method for "low-L" (as demonstrated on WMAP temperature polarization data). B) We are extending Gibbs sampling to directly propagate uncertainties in both foreground and instrument models to total uncertainty in cosmological parameters for the entire range of angular scales relevant for Planck. C) Made possible by inclusion of foreground model parameters in Gibbs sampling and hybrid MCMC and Gibbs sampling for the low signal to noise (high-L) regime. D) Future items to be included in the Bayesian framework include: 1) Integration with Hybrid Likelihood (or posterior) code for cosmological parameters; 2) Include other uncertainties in instrumental systematics? (I.e. beam uncertainties, noise estimation, calibration errors, other).

Gibbs sampling↗

NASA NTRS2007

Reactive Nitrogen Distribution and Partitioning in the North American Troposphere and Lowermost Stratosphere

A comprehensive group of reactive nitrogen species (NO, NOz, HN03, HOzN02, PANs, alkyl nitrates, and aerosol-NO3) were measured over North America during July/August 2004 from the NASA DC-8 platform (0.1 - 12 km). Nitrogen containing tracers of biomass combustion (HCN and CH3CN) were also measured along with a host of other gaseous (CO, VOC, OVOC, halocarbon) and aerosol tracers. Clean background air as well as air with influences from biogenic emissions, anthropogenic pollution, biomass combustion, convection, lightning, and the stratosphere was sampled over the continental United States, the Atlantic, and the Pacific. The North American upper troposphere (UT) was found to be greatly influenced by both lightning NO, and surface pollution lofted via convection and contained elevated concentrations of PAN, ozone, hydrocarbons, and NO,. Observational data suggest that lightning was a far greater contributor to NO, in the UT than previously believed. PAN provided a dominant reservoir of reactive nitrogen in the UT while nitric acid dominated in the lower troposphere (LT). Peroxynitric acid (H02N02) was present in sizable concentrations peaking at around 8 km. Aerosol nitrate appeared to be mostly contained in large soil based particles in the LT. Plumes from Alaskan fires contained large amounts of PAN and aerosol nitrate but little enhancement in ozone. A comparison of observed data with simulations from four 3-D models shows significant differences between observations and models as well as among models. We investigate the partitioning and interplay of the reactive nitrogen species within characteristic air masses and further examine their role in ozone formation.

Singh, H. B.↗

NASA NTRS2007

Reactive Nitrogen Distribution and Partitioning in the North American Troposphere and Lowermost Stratosphere

A comprehensive group of reactive nitrogen species (NO, NO2, HNO3, HO2NO2, PANs, alkyl nitrates, and aerosol-NO3) were measured in the troposphere and lowermost stratosphere over North America and the Atlantic during July/August 2004 (INTEX-A) from the NASA DC-8 platform (0.1-12 km). Less reactive nitrogen species (HCN and CH3CN), that are also unique tracers of biomass combustion, were also measured along with a host of other gaseous (CO, VOC, OVOC, halocarbon) and aerosol tracers. Clean background air as well as air with influences from biogenic emissions, anthropogenic pollution, biomass combustion, and stratosphere was sampled both over continental U. S., Atlantic and Pacific. The North American upper troposphere was found to be greatly influenced by both lightning NO(x) and surface pollution lofted via convection and contained elevated concentrations of PAN, ozone, hydrocarbons, and NO(x). Under polluted conditions PAN was a dominant carrier of reactive nitrogen in the upper troposphere while nitric acid dominated in the lower troposphere. Peroxynitric acid (HO2NO2) was present in sizable concentrations always peaking at around 8 km. Aerosol nitrate appeared to be mostly contained in large soil based particles in the lower troposphere. Plumes from Alaskan fires contained large amounts of PAN and very little enhancement in ozone. Observational data suggest that lightning was a far greater contributor to NO(x) in the upper troposphere than previously believed. NO(x) and NO(y) reservoir appeared to be in steady state only in the middle troposphere where NO(x)/NO(y) was independent of air mass age. A first comparison of observed data with simulations from four 3-D models shows significant differences between observations and models as well as among models. These uncertainties likely propagate themselves in satellites derived NOx data. Observed data are interpreted to suggest that soil sinks of HCN/CH3CN are at best very small. We investigate the partitioning and interplay of the reactive nitrogen species within characteristic air masses and further examine their role in ozone formation.

Singh, H. B.↗