Atmospheric effects of stratospheric aircraft - A status report from NASA's High-Speed Research Program

NASA Technical Reports Server (NTRS)

Wesoky, Howard L.; Prather, Michael J.

1991-01-01

Studies have indicated that, with sufficient technology development, future high-speed civil transport aircraft could be economically competitive with long-haul subsonic aircraft. However, uncertainty about atmospheric pollution, along with community noise and sonic boom, continues to be a major concern which is being addressed in the planned six-year High-Speed Research Program begun in 1990. Building on NASA's research in atmospheric science and emissions reduction, current analytical predictions indicate that an operating range may exist at altitudes below 20 km (i.e., corresponding to a cruise Mach number of approximately 2.4) where the goal level of 5 gm equivalent NO2 emissions/kg fuel will deplete less than one percent of column ozone. Because it will not be possible to directly measure the impact of an aircraft fleet on the atmosphere, the only means of assessment will be prediction. The process of establishing credibility for the predicted effects will likely be complex and involve continued model development and testing against climatological patterns. In particular, laboratory simulation of heterogeneous chemistry and other effects, and direct measurements of well understood tracers in the troposphere and stratosphere are being used to improve the current models.

Mapping Directly Imaged Giant Exoplanets

NASA Astrophysics Data System (ADS)

Kostov, Veselin; Apai, Dániel

2013-01-01

With the increasing number of directly imaged giant exoplanets, the current atmosphere models are often not capable of fully explaining the spectra and luminosity of the sources. A particularly challenging component of the atmosphere models is the formation and properties of condensate cloud layers, which fundamentally impact the energetics, opacity, and evolution of the planets. Here we present a suite of techniques that can be used to estimate the level of rotational modulations these planets may show. We propose that the time-resolved observations of such periodic photometric and spectroscopic variations of extrasolar planets due to their rotation can be used as a powerful tool to probe the heterogeneity of their optical surfaces. In this paper, we develop simulations to explore the capabilities of current and next-generation ground- and space-based instruments for this technique. We address and discuss the following questions: (1) what planet properties can be deduced from the light curve and/or spectra, and in particular can we determine rotation periods, spot coverage, spot colors, and spot spectra?; (2) what is the optimal configuration of instrument/wavelength/temporal sampling required for these measurements?; and (3) can principal component analysis be used to invert the light curve and deduce the surface map of the planet? Our simulations describe the expected spectral differences between homogeneous (clear or cloudy) and patchy atmospheres, outline the significance of the dominant absorption features of H2O, CH4, and CO, and provide a method to distinguish these two types of atmospheres. Assuming surfaces with and without clouds for most currently imaged planets the current models predict the largest variations in the J band. Simulated photometry from current and future instruments is used to estimate the level of detectable photometric variations. We conclude that future instruments will be able to recover not only the rotation periods, cloud cover, cloud colors, and spectra but even cloud evolution. We also show that a longitudinal map of the planet's atmosphere can be deduced from its disk-integrated light curves.

Sensitivity of solar-cell performance to atmospheric variables. 1: Single cell

NASA Technical Reports Server (NTRS)

Klucher, T. M.

1976-01-01

The short circuit current of a typical silicon solar cell under direct solar radiation was measured for a range of turbidity, water vapor content, and air mass to determine the relation of the solar cell calibration value (current-to-intensity ratio) to those atmospheric variables. A previously developed regression equation was modified to describe the relation between calibration value, turbidity, water vapor content, and air mass. Based on the value of the constants obtained by a least squares fit of the data to the equation, it was found that turbidity lowers the value, while increase in water vapor increases the calibration value. Cell calibration values exhibited a change of about 6% over the range of atmospheric conditions experienced.

Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry.

PubMed

Shelley, Jacob T; Wiley, Joshua S; Chan, George C Y; Schilling, Gregory D; Ray, Steven J; Hieftje, Gary M

2009-05-01

Two relatively new ambient ionization sources, direct analysis in real time (DART) and the flowing atmospheric-pressure afterglow (FAPA), use direct current, atmospheric-pressure discharges to produce reagent ions for the direct ionization of a sample. Although at a first glance these two sources appear similar, a fundamental study reveals otherwise. Specifically, DART was found to operate with a corona-to-glow transition (C-G) discharge whereas the FAPA was found to operate with a glow-to-arc transition (G-A) discharge. The characteristics of both discharges were evaluated on the basis of four factors: reagent-ion production, response to a model analyte (ferrocene), infrared (IR) thermography of the gas used for desorption and ionization, and spatial emission characteristics. The G-A discharge produced a greater abundance and a wider variety of reagent ions than the C-G discharge. In addition, the discharges yielded different adducts and signal strengths for ferrocene. It was also found that the gas exiting the discharge chamber reached a maximum of 235 degrees C and 55 degrees C for the G-A and C-G discharges, respectively. Finally, spatially resolved emission maps of both discharges showed clear differences for N(2)(+) and O(I). These findings demonstrate that the discharges used by FAPA and DART are fundamentally different and should have different optimal applications for ambient desorption/ionization mass spectrometry (ADI-MS).

Monthly Atmospheric 13C/12C Isotopic Ratios for 11 SIO Stations (1977-2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keeling, R. F.; Piper, S. C.; Bollenbacher, A. F.

Stable isotopic measurements for atmospheric 13C/12C and 18O/16O at global sampling sites were initiated by Dr. C.D. Keeling and co-workers at Scripps Institution of Oceanography (SIO) in 1977. These isotopic measurements complement the continuing global atmospheric and oceanic CO2 measurements initiated by Keeling in 1957. This work is currently being continued under the direction of R.F. Keeling, who also runs a parallel program at SIO to measure changes in atmospheric O2 and Ar abundances (Scripps O2 Program). A more complete set of 13CO2 data is found online at http://scrippsco2.ucsd.edu/data/atmospheric_co2.html

Unsteady density-current equations for highly curved terrain

NASA Technical Reports Server (NTRS)

Sivakumaran, N. S.; Dressler, R. F.

1989-01-01

New nonlinear partial differential equations containing terrain curvature and its rate of change are derived that describe the flow of an atmospheric density current. Unlike the classical hydraulic-type equations for density currents, the new equations are valid for two-dimensional, gradually varied flow over highly curved terrain, hence suitable for computing unsteady (or steady) flows over arbitrary mountain/valley profiles. The model assumes the atmosphere above the density current exerts a known arbitrary variable pressure upon the unknown interface. Later this is specialized to the varying hydrostatic pressure of the atmosphere above. The new equations yield the variable velocity distribution, the interface position, and the pressure distribution that contains a centrifugal component, often significantly larger than its hydrostatic component. These partial differential equations are hyperbolic, and the characteristic equations and characteristic directions are derived. Using these to form a characteristic mesh, a hypothetical unsteady curved-flow problem is calculated, not based upon observed data, merely as an example to illustrate the simplicity of their application to unsteady flows over mountains.

Prediction and measurement of direct-normal solar irradiance: A closure experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halthore, R.N.; Schwartz, S.E.; Michalsky, J.J.

1997-03-01

Direct-normal solar irradiance (DNSI), the total energy in the solar spectrum incident on a plane perpendicular to the Sun`s direction on a unit area at the earth`s surface in unit time, depends only on the atmospheric extinction of sunlight without regard to the details of extinction--whether absorption or scattering. Here the authors describe a set of closure experiments performed in north-central Oklahoma, wherein measured atmospheric composition is input to a radiative transfer model, MODTRAN-3, to predict DNSI, which is then compared to measured values. Thirty six independent comparisons are presented; the agreement between predicted and measured values falls within themore » combined uncertainties in the prediction (2%) and measurement (0.2%) albeit with a slight bias ({approximately} 1% overprediction) that is independent of the solar zenith angle. Thus these results establish the adequacy of current knowledge of the solar spectrum and atmospheric extinction as embodied in MODTRAN-3 for use in climate models. An important consequence is the overwhelming likelihood that the atmospheric clear-sky absorption is accurately described to within comparable uncertainties.« less

Prediction and measurement of direct-normal solar irradiance: A closure experiment

NASA Technical Reports Server (NTRS)

Halthore, R. N.; Schwartz, S. E.; Michalsky, J. J.; Anderson, G. P.; Ferrare, R. A.; Ten Brink, H. M.

1997-01-01

Direct-Normal Solar Irradiance (DNSI), the total energy in the solar spectrum incident on a plane perpendicular to the Sun's direction on a unit area at the earth's surface in unit time, depends only on the atmospheric extinction of sunlight without regard to the details of extinction-whether absorption or scattering. Here the authors describe a set of closure experiments performed in north-central Oklahoma, wherein measured atmospheric composition is input to a radiative transfer model, MODTRAN-3, to predict DNSI, which is then compared to measured values. Thirty six independent comparisons are presented; the agreement between predicted and measured values falls within the combined uncertainties in the prediction (2%) and measurement (0.2%) albeit with a slight bias ((approximately) 1% overprediction) that is independent of the solar zenith angle. Thus these results establish the adequacy of current knowledge of the solar spectrum and atmospheric extinction as embodied in MODTRAN-3 for use in climate models. An important consequence is the overwhelming likelihood that the atmospheric clear-sky absorption is accurately described to within comparable uncertainties.

High intensity ion beams from an atmospheric pressure inductively coupled plasma

NASA Astrophysics Data System (ADS)

Al Moussalami, S.; Chen, W.; Collings, B. A.; Douglas, D. J.

2002-02-01

This work is directed towards substantially improving the sensitivity of an inductively coupled plasma mass spectrometer (ICP-MS). Ions produced in the ICP at atmospheric pressure have been extracted with comparatively high current densities. The conventional approach to ion extraction, based on a skimmed molecular beam, has been abandoned, and a high extraction field arrangement has been adopted. Although the new approach is not optimized, current densities more than 180 times greater than that of a conventional interface have been extracted and analyte sensitivities ˜10-100× greater than those reported previously for quadrupole ICP-MS have been measured.

Self-similar magnetohydrodynamic model for direct current discharge fireball experiments

NASA Astrophysics Data System (ADS)

Tsui, K. H.; Navia, C. E.; Robba, M. B.; Carneiro, L. T.; Emelin, S. E.

2006-11-01

Ball lightning models and corresponding laboratory efforts in generating fireballs are briefly summarized to give an overview of the current status. In particular, emphasis is given to direct current discharge experiments at atmospheric pressure such as capillary discharge with a plasma plume in front of the anode opening [Emelin et al., Tech. Phys. Letters 23, 758 (1997)] and water resistor discharge with fluttering fireball overhead [Egorov and Stepanov, Tech. Phys. 47, 1584 (2002)]. These fireballs are interpreted as laboratory demonstrations of the self-similar magnetohydrodynamic (MHD) model of ball lightning [Tsui, Phys. Plasmas 13, 072102 (2006)].

Atomic Oxygen Cleaning Shown to Remove Organic Contaminants at Atmospheric Pressure

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.

1998-01-01

The NASA Lewis Research Center has developed and filed for a patent on a method to produce atomic oxygen at atmospheric pressure by using a direct current arc in a gas flow mixture of oxygen and helium. A prototype device has been tested for its ability to remove various soot residues from surfaces exposed to fire, and various varnishes such as acrylic and egg white.

Atmospheric-pressure cold plasma treatment of contaminated fresh fruit and vegetable slices: inactivation and physiochemical properties evaluation

NASA Astrophysics Data System (ADS)

Wang, R. X.; Nian, W. F.; Wu, H. Y.; Feng, H. Q.; Zhang, K.; Zhang, J.; Zhu, W. D.; Becker, K. H.; Fang, J.

2012-10-01

A direct-current, atmospheric-pressure air cold plasma microjet (PMJ) was applied to disinfect Salmonella directly deposited on fresh fruit and vegetable slices. Effective inactivation was achieved on sliced fruit and vegetables after 1 s plasma treatment. The physiochemical properties of the slices, such as water content, color parameters, and nutritional content were monitored before and after plasma treatment. It was found that the physiochemical properties changes caused by the plasma were within an acceptable range. Reactive oxygen species, which are believed to be the major bactericidal agents in the plasma, were detected by electron spin resonance spectroscopy and optical emission spectroscopy.

Direct current plasma jet at atmospheric pressure operating in nitrogen and air

NASA Astrophysics Data System (ADS)

Deng, X. L.; Nikiforov, A. Yu.; Vanraes, P.; Leys, Ch.

2013-01-01

An atmospheric pressure direct current (DC) plasma jet is investigated in N2 and dry air in terms of plasma properties and generation of active species in the active zone and the afterglow. The influence of working gases and the discharge current on plasma parameters and afterglow properties are studied. The electrical diagnostics show that discharge can be sustained in two different operating modes, depending on the current range: a self-pulsing regime at low current and a glow regime at high current. The gas temperature and the N2 vibrational temperature in the active zone of the jet and in the afterglow are determined by means of emission spectroscopy, based on fitting spectra of N2 second positive system (C3Π-B3Π) and the Boltzmann plot method, respectively. The spectra and temperature differences between the N2 and the air plasma jet are presented and analyzed. Space-resolved ozone and nitric oxide density measurements are carried out in the afterglow of the jet. The density of ozone, which is formed in the afterglow of nitrogen plasma jet, is quantitatively detected by an ozone monitor. The density of nitric oxide, which is generated only in the air plasma jet, is determined by means of mass-spectroscopy techniques.

Bird specimens track 135 years of atmospheric black carbon and environmental policy

NASA Astrophysics Data System (ADS)

DuBay, Shane G.; Fuldner, Carl C.

2017-10-01

Atmospheric black carbon has long been recognized as a public health and environmental concern. More recently, black carbon has been identified as a major, ongoing contributor to anthropogenic climate change, thus making historical emission inventories of black carbon an essential tool for assessing past climate sensitivity and modeling future climate scenarios. Current estimates of black carbon emissions for the early industrial era have high uncertainty, however, because direct environmental sampling is sparse before the mid-1950s. Using photometric reflectance data of >1,300 bird specimens drawn from natural history collections, we track relative ambient concentrations of atmospheric black carbon between 1880 and 2015 within the US Manufacturing Belt, a region historically reliant on coal and dense with industry. Our data show that black carbon levels within the region peaked during the first decade of the 20th century. Following this peak, black carbon levels were positively correlated with coal consumption through midcentury, after which they decoupled, with black carbon concentrations declining as consumption continued to rise. The precipitous drop in atmospheric black carbon at midcentury reflects policies promoting burning efficiency and fuel transitions rather than regulating emissions alone. Our findings suggest that current emission inventories based on predictive modeling underestimate levels of atmospheric black carbon for the early industrial era, suggesting that the contribution of black carbon to past climate forcing may also be underestimated. These findings build toward a spatially dynamic emission inventory of black carbon based on direct environmental sampling.

Bird specimens track 135 years of atmospheric black carbon and environmental policy

PubMed Central

DuBay, Shane G.; Fuldner, Carl C.

2017-01-01

Atmospheric black carbon has long been recognized as a public health and environmental concern. More recently, black carbon has been identified as a major, ongoing contributor to anthropogenic climate change, thus making historical emission inventories of black carbon an essential tool for assessing past climate sensitivity and modeling future climate scenarios. Current estimates of black carbon emissions for the early industrial era have high uncertainty, however, because direct environmental sampling is sparse before the mid-1950s. Using photometric reflectance data of >1,300 bird specimens drawn from natural history collections, we track relative ambient concentrations of atmospheric black carbon between 1880 and 2015 within the US Manufacturing Belt, a region historically reliant on coal and dense with industry. Our data show that black carbon levels within the region peaked during the first decade of the 20th century. Following this peak, black carbon levels were positively correlated with coal consumption through midcentury, after which they decoupled, with black carbon concentrations declining as consumption continued to rise. The precipitous drop in atmospheric black carbon at midcentury reflects policies promoting burning efficiency and fuel transitions rather than regulating emissions alone. Our findings suggest that current emission inventories based on predictive modeling underestimate levels of atmospheric black carbon for the early industrial era, suggesting that the contribution of black carbon to past climate forcing may also be underestimated. These findings build toward a spatially dynamic emission inventory of black carbon based on direct environmental sampling. PMID:29073051

Soil-atmosphere exchange of ammonia in a non-fertilized grassland: measured emission potentials and inferred fluxes

NASA Astrophysics Data System (ADS)

Wentworth, G. R.; Murphy, J. G.; Gregoire, P. K.; Cheyne, C. A. L.; Tevlin, A. G.; Hems, R.

2014-10-01

A 50-day field study was carried out in a semi-natural, non-fertilized grassland in south-western Ontario, Canada during the late summer and early autumn of 2012. The purpose was to explore surface-atmosphere exchange processes of ammonia (NH3) with a focus on bi-directional fluxes between the soil and atmosphere. Measurements of soil pH and ammonium concentration ([NH4+]) yielded the first direct quantification of soil emission potential (Γsoil = [NH4+]/[H+]) for this land type, with values ranging from 35 to 1850 (an average of 290). The soil compensation point, the atmospheric NH3 mixing ratio below which net emission from the soil will occur, exhibited both a seasonal trend and diurnal trend. Higher daytime and August compensation points were attributed to higher soil temperature. Soil-atmosphere fluxes were estimated using NH3 measurements from the Ambient Ion Monitor Ion Chromatograph (AIM-IC) and a simple resistance model. Vegetative effects were ignored due to the short canopy height and significant Γsoil. Inferred fluxes were, on average, 2.6 ± 4.5 ng m-2 s-1 in August (i.e. net emission) and -5.8 ± 3.0 ng m-2 s-1 in September (i.e. net deposition). These results are in good agreement with the only other bi-directional exchange study in a semi-natural, non-fertilized grassland. A Lagrangian dispersion model (Hybrid Single-Particle Lagrangian Integrated Trajectory - HYSPLIT) was used to calculate air parcel back-trajectories throughout the campaign and revealed that NH3 mixing ratios had no directional bias throughout the campaign, unlike the other atmospheric constituents measured. This implies that soil-atmosphere exchange over a non-fertilized grassland can significantly moderate near-surface NH3 concentrations. In addition, we provide indirect evidence that dew and fog evaporation can cause a morning increase of [NH3]g. Implications of our findings on current NH3 bi-directional exchange modelling efforts are also discussed.

NDE to Manage Atmospheric SCC in Canisters for Dry Storage of Spent Fuel: An Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyer, Ryan M.; Pardini, Allan F.; Cuta, Judith M.

2013-09-01

This report documents efforts to assess representative horizontal (Transuclear NUHOMS®) and vertical (Holtec HI-STORM) storage systems for the implementation of non-destructive examination (NDE) methods or techniques to manage atmospheric stress corrosion cracking (SCC) in canisters for dry storage of used nuclear fuel. The assessment is conducted by assessing accessibility and deployment, environmental compatibility, and applicability of NDE methods. A recommendation of this assessment is to focus on bulk ultrasonic and eddy current techniques for direct canister monitoring of atmospheric SCC. This assessment also highlights canister regions that may be most vulnerable to atmospheric SCC to guide the use of bulkmore » ultrasonic and eddy current examinations. An assessment of accessibility also identifies canister regions that are easiest and more difficult to access through the ventilation paths of the concrete shielding modules. A conceivable sampling strategy for canister inspections is to sample only the easiest to access portions of vulnerable regions. There are aspects to performing an NDE inspection of dry canister storage system (DCSS) canisters for atmospheric SCC that have not been addressed in previous performance studies. These aspects provide the basis for recommendations of future efforts to determine the capability and performance of eddy current and bulk ultrasonic examinations for atmospheric SCC in DCSS canisters. Finally, other important areas of investigation are identified including the development of instrumented surveillance specimens to identify when conditions are conducive for atmospheric SCC, characterization of atmospheric SCC morphology, and an assessment of air flow patterns over canister surfaces and their influence on chloride deposition.« less

Illusion and reality in the atmospheres of exoplanets

NASA Astrophysics Data System (ADS)

Deming, L. Drake; Seager, Sara

2017-01-01

The atmospheres of exoplanets reveal all their properties beyond mass, radius, and orbit. Based on bulk densities, we know that exoplanets larger than 1.5 Earth radii must have gaseous envelopes and, hence, atmospheres. We discuss contemporary techniques for characterization of exoplanetary atmospheres. The measurements are difficult, because—even in current favorable cases—the signals can be as small as 0.001% of the host star's flux. Consequently, some early results have been illusory and not confirmed by subsequent investigations. Prominent illusions to date include polarized scattered light, temperature inversions, and the existence of carbon planets. The field moves from the first tentative and often incorrect conclusions, converging to the reality of exoplanetary atmospheres. That reality is revealed using transits for close-in exoplanets and direct imaging for young or massive exoplanets in distant orbits. Several atomic and molecular constituents have now been robustly detected in exoplanets as small as Neptune. In our current observations, the effects of clouds and haze appear ubiquitous. Topics at the current frontier include the measurement of heavy element abundances in giant planets, detection of carbon-based molecules, measurement of atmospheric temperature profiles, definition of heat circulation efficiencies for tidally locked planets, and the push to detect and characterize the atmospheres of super-Earths. Future observatories for this quest include the James Webb Space Telescope and the new generation of extremely large telescopes on the ground. On a more distant horizon, NASA's study concepts for the Habitable Exoplanet Imaging Mission (HabEx) and the Large UV/Optical/Infrared Surveyor (LUVOIR) missions could extend the study of exoplanetary atmospheres to true twins of Earth.

Direct measurement of lower atmospheric vertical potential differences

NASA Technical Reports Server (NTRS)

Holzworth, R. H.; Dazey, M. H.; Schnauss, E. R.; Youngbluth, O.

1981-01-01

A high impedance system has been developed to make direct measurements of the atmospheric potential difference up to several thousand feet. A tethered balloon flown from Wallops Island, Virginia was used to loft a high voltage, insulated wire and a conducting collector in a test flight to 550 meters for two days of experiments in October 1980. The balloon was equipped with a payload to measure exact altitude, wind speed and direction, and other meteorological parameters. Electric potentials of 170,000 volts at 550 meters were measured. The collected currents which could be drawn through the wire by grounding the lower end were in the 10 microamp range indicating a system impedance of about 10 to the 10th ohms. This paper describes the apparatus and details of these measurements.

Geoengineering: Direct Mitigation of Climate Warming

EPA Science Inventory

For Frank Princiotta’s book, Global Climate Change—The Technology Challenge With the concentrations of atmospheric greenhouse gases (GHGs) rising to levels unprecedented in the current glacial epoch, the earth’s climate system appears to be rapidly shifting into a warmer regime....

Atmosphere-Forest Exchange: Important Questions Regarding the Atmosphere's Role in the Delivery of Nutrient Nitrogen and Impacts on Nitrogen and Carbon Cycling

NASA Astrophysics Data System (ADS)

Carroll, M.; Shepson, P. B.; Bertman, S. B.; Sparks, J. P.; Holland, E. A.

2002-12-01

Atmosphere-Forest Exchange: Important Questions Regarding the Atmosphere's Role in the Delivery of Nutrient Nitrogen and Impacts on Nitrogen and Carbon Cycling Atmospheric composition and chemistry directly affect ecosystem nitrogen cycling and indirectly affect ecosystem carbon cycling and storage. Current understanding of atmosphere-forest nitrogen exchange and subsequent impacts is based almost exclusively on nitrogen deposition data obtained from networks using buckets placed in open areas, studies involving inorganic nitrogen, frequently with enhanced N deposition inputs applied only to soils, and that ignore multiple stresses (e.g., the combined effects of aerosols, ozone exposure, elevated CO2, and drought). Current models of nitrogen cycling treat deposited nitrogen (e.g., HNO3 and NO3-) as a permanent sink whereas data appear to indicate that photolytic and heterogeneous chemical processes occurring on surfaces and in dew can result in the re-evolution of gaseous species such as NO and HONO. Similarly, the direct uptake of gaseous nitrogen compounds by foliage has been neglected, compromising conclusions drawn from deposition experiments and ignoring a mechanism that may significantly affect nitrogen cycling and carbon storage, one that may become more significant with future atmospheric and climate change. We hypothesize that the atmosphere plays a significant role in the delivery of nutrient nitrogen to the N-limited mixed hardwood forest at the PROPHET research site at the University of Michigan Biological Station. We assert that a complete understanding of atmosphere- biosphere interactions and feedbacks is required to develop a predictive capability regarding forest response to increasing atmospheric CO2, reactive nitrogen, oxidants, and aerosols, increasing nitrogen and acidic deposition, and anticipated climate change. We further assert that conclusions drawn from studies that are limited to inorganic nitrogen, fertilization of soils, and/or that neglect the role of the canopy (in N uptake and/or remobilization) may not produce a complete understanding of N and C cycling in terrestrial ecosystems, including atmosphere-biosphere interactions and feedbacks. Here, as part of a new PROPHET focus on Biosphere Exchange of Atmospheric Carbon and Odd Nitrogen (BEACON), we identify a number of issues associated with nitrogen limited forest ecosystems and nitrogen saturation and important science questions that require collaborative studies involving the atmospheric and biospheric science communities.

Energetic particle influences in Earth's atmosphere

NASA Astrophysics Data System (ADS)

Aplin, Karen; Harrison, R. Giles; Nicoll, Keri; Rycroft, Michael; Briggs, Aaron

2016-04-01

Energetic particles from outer space, known as galactic cosmic rays, constantly ionise the entire atmosphere. During strong solar storms, solar energetic particles can also reach the troposphere and enhance ionisation. Atmospheric ionisation generates cluster ions. These facilitate current flow in the global electric circuit, which arises from charge separation in thunderstorms driven by meteorological processes. Energetic particles, whether solar or galactic in origin, may influence the troposphere and stratosphere through a range of different mechanisms, each probably contributing a small amount. Some of the suggested processes potentially acting over a wide spatial area in the troposphere include enhanced scavenging of charged aerosol particles, modification of droplet or droplet-droplet behavior by charging, and the direct absorption of infra-red radiation by the bending and stretching of hydrogen bonds inside atmospheric cluster-ions. As well as reviewing the proposed mechanisms by which energetic particles modulate atmospheric properties, we will also discuss new instrumentation for measurement of energetic particles in the atmosphere.

Isothermal magnetostatic atmospheres. II - Similarity solutions with current proportional to the magnetic potential cubed

NASA Technical Reports Server (NTRS)

Webb, G. M.

1988-01-01

The paper presents a family of isothermal magnetostatic atmospheres with one ignorable coordinate corresponding to a uniform gravitational field in a plane geometry. The distributed current in the model J is directed along the x-axis, where x is the horizontal ignorable coordinate. The current J is taken to be proportional to the cube of the magnetostatic potential A and falls off exponentially with distance vertical to the base with an e-folding distance equal to the gravitational scale height. A range of similarity solution examples are displayed depending on the values of the similarity parameters. Each similarity parameter corresponds to a symmetry of the underlying nonlinear elliptic equation for A. The similarity parameters also determine the source currents for the potential field solution of the family. The solutions show the interplay between the gravitational force, the J & B force (B, magnetic field induction) and the gas pressure gradient.

The Association of High-Latitude Dayside Aurora With NBZ Field-Aligned Currents

NASA Astrophysics Data System (ADS)

Carter, J. A.; Milan, S. E.; Fogg, A. R.; Paxton, L. J.; Anderson, B. J.

2018-05-01

The relationship between auroral emissions in the polar ionosphere and the large-scale flow of current within the Earth's magnetosphere has yet to be comprehensively established. Under northward interplanetary magnetic field (IMF) conditions, magnetic reconnection occurs at the high-latitude magnetopause, exciting two reverse lobe convection cells in the dayside polar ionosphere and allowing ingress of solar wind plasma to form an auroral "cusp spot" by direct impact on the atmosphere. It has been hypothesized that a second class of NBZ auroras, High-latitude Dayside Aurora, are produced by upward field-aligned currents associated with lobe convection. Here we present data from the Special Sensor Ultraviolet Spectrographic Imager instrument and from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, from January 2010 to September 2013, in a large statistical study. We reveal a northward IMF auroral phenomenon that is located adjacent to the cusp spot and that is colocated with a region of upward electrical current in the clockwise-rotating lobe cell. The emission only occurs in the sunlit summer hemisphere, demonstrating the influence of the conductance of the ionosphere on current closure. In addition, fast solar wind speed is required for this emission to be bright. The results show that dayside auroral emission is produced by IMF-magnetosphere electrodynamic coupling, as well as by direct impact of the atmosphere by the solar wind, confirming the association of High-latitude Dayside Aurora with NBZ currents.

Probing Emissions of Military Cargo Aircraft: Description of a Joint Field Measurement Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Mengdawn; Corporan, E.; DeWitt, M.

2008-01-01

Direct emissions of NOx, volatile organic compounds, and particulate matter (PM) by aircraft contribute to the pollutant levels found in the atmosphere. Aircraft emissions can be injected at the ground level or directly at the high altitude in flight. Conversion of the precursor gases into secondary PM is one of the pathways for the increased atmospheric PM. Atmospheric PM interacts with solar radiation altering atmospheric radiation balance and potentially contributing to global and regional climate changes. Also, direct emissions of air toxics, ozone precursors and PM from aircraft in and around civilian airports and military air bases can worsen localmore » air quality in non-attainment and/or maintenance areas. These emissions need to be quantified. However, the current EPA methods for particle emission measurements from such sources, modified Method 5 and Conditional Test Method 039, are gravimetric-based, and it is anticipated that these methods will not be suitable for current and future generations of aircraft turbine engines, whose particle mass emissions are low. To evaluate measurement approaches for military aircraft emissions, two complementary projects were initiated in 2005. A joint field campaign between these two programs was executed during the first week of October 2005 at the Kentucky Air National Guard (KYANG) base in Louisville, KY. This campaign represented the first in a series of field studies for each program funded by the DoD Strategic Environmental Research and Development Program (SERDP) and provided the basis for cross-comparison of the sampling approaches and measurement techniques employed by the respective program teams. This paper describes the overall programmatic of the multi-year SERDP aircraft emissions research and presents a summary of the results from the joint field campaign.« less

Atmospheric propagation issues relevant to optical communications

NASA Technical Reports Server (NTRS)

Churnside, James H.; Shaik, Kamran

1989-01-01

Atmospheric propagation issues relevant to space-to-ground optical communications for near-earth applications are studied. Propagation effects, current optical communication activities, potential applications, and communication techniques are surveyed. It is concluded that a direct-detection space-to-ground link using redundant receiver sites and temporal encoding is likely to be employed to transmit earth-sensing satellite data to the ground some time in the future. Low-level, long-term studies of link availability, fading statistics, and turbulence climatology are recommended to support this type of application.

The Spectropolarimeter for Planetary Exploration: SPEX

NASA Astrophysics Data System (ADS)

Laan, Erik; Stam, Daphne; Snik, Frans; Karalidi, Theodora; Keller, Christoph; ter Horst, Rik; Navarro, Ramon; Oomen, Gijsbert; de Vries, Johan; Hoogeveen, Ruud

2017-11-01

SPEX (Spectropolarimeter for Planetary EXploration) is an innovative, compact remotesensing instrument for measuring and characterizing aerosols in the atmosphere. The shoebox size instrument is capable of accurate full linear spectropolarimetry without moving parts or liquid crystals. High precision polarimetry is performed through encoding the degree and angle of linear polarization of the incoming light in a sinusoidal modulation of the spectrum. Measuring this intensity spectrum thus provides the spectral dependence of the degree and angle of linear polarization. Polarimetry has proven to be an excellent tool to study microphysical properties of atmospheric particles. Such information is essential to better understand the weather and climate of a planet. Although SPEX can be used to study any planetary atmosphere, including the Earth's, the current design of SPEX is tailored to study Martian dust and clouds from an orbiting platform. SPEX' 9 entrance pupils can simultaneously measure intensity spectra from 0.4 to 0.8 microns, in different directions along the flight direction (including two limb viewing directions). This way, the scattering phase functions of dust and cloud particles within a ground pixel are sampled while flying over it. SPEX can provide synergy with instruments on rovers and landers, as it provides an overview of spatial and temporal variations of the Martian atmosphere.

The Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's OceanThe Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's Ocean

NASA Astrophysics Data System (ADS)

Centurioni, Luca

2017-04-01

The Global Drifter Program is the principal component of the Global Surface Drifting Buoy Array, a branch of NOAA's Global Ocean Observing System and a scientific project of the Data Buoy Cooperation Panel (DBCP). The DBCP is an international program coordinating the use of autonomous data buoys to observe atmospheric and oceanographic conditions over ocean areas where few other measurements are taken. The Global Drifter Program maintains an array of over 1,250 Lagrangian drifters, reporting in near real-time and designed measure 15 m depth Lagrangian currents, sea surface temperature (SST) and sea level atmospheric pressure (SLP), among others, to fulfill the needs to observe the air-sea interface at temporal and spatial scales adequate to support short to medium-range weather forecasting, ocean state estimates and climate science. This overview talk will discuss the main achievements of the program, the main impacts for satellite SST calibration and validation, for numerical weather prediction, and it will review the main scientific findings based on the use of Lagrangian currents. Finally, we will present new developments in Lagrangian drifter technology, which include special drifters designed to measure sea surface salinity, wind and directional wave spectra. New opportunities for expanding the scope of the Global Drifter Program will be discussed.

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, Andrew J.; Shelley, Jacob T.; Walton, Courtney L.

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here in this paper, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-likemore » spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma.« less

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge

DOE PAGES

Schwartz, Andrew J.; Shelley, Jacob T.; Walton, Courtney L.; ...

2016-06-27

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here in this paper, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-likemore » spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma.« less

High Arctic Forests During the Middle Eocene Supported by ~400 ppm Atmospheric CO2

NASA Astrophysics Data System (ADS)

Maxbauer, D. P.; Royer, D. L.; LePage, B. A.

2013-12-01

Fossils from Paleogene High Arctic deposits provide some of the clearest evidence for greenhouse climates and offer the potential to improve our understanding of Earth system dynamics in a largely ice-free world. One of the most well-known and exquisitely-preserved middle Eocene (47.9-37.8 Myrs ago) polar forest sites, Napartulik, crops out on eastern Axel Heiberg Island (80 °N), Nunavut, Canada. An abundance of data from Napartulik suggest mean annual temperatures of up to 30 °C warmer than today and atmospheric water loads 2× above current levels. Despite this wealth of paleontological and paleoclimatological data, there are currently no direct constraints on atmospheric CO2 levels for Napartulik or any other polar forest site. Here we apply a new plant gas-exchange model to Metasequoia (dawn redwood) leaves to reconstruct atmospheric CO2 from six fossil forests at Napartulik. Individual reconstructions vary between 405-489 ppm with a site mean of 437 ppm (337-564 ppm at 95% confidence). These estimates represent the first direct constraints on CO2 for polar fossil forests and suggest that the temperate conditions present at Napartulik during the middle Eocene were maintained under CO2 concentrations ~1.6× above pre-industrial levels. Our results strongly support the case that long-term climate sensitivity to CO2 in the past was sometimes high, even during largely ice-free periods, highlighting the need to better understand the climate forcing and feedback mechanisms responsible for this amplification.

A Global Electric Circuit on Mars

NASA Technical Reports Server (NTRS)

Delory, G. T.; Farrell, W. M.; Desch, M. D.

2001-01-01

We describe conditions on the surface of Mars conducive to the formation of a martian global electric circuit, in a direct analogy to the terrestrial case where atmospheric currents and electric fields are generated worldwide through the charging in thunderstorms. Additional information is contained in the original extended abstract.

Observation of current reversal in the scanning tunneling spectra of fullerene-like WS2 nanoparticles.

PubMed

Azulay, Doron; Kopnov, Frieda; Tenne, Reshef; Balberg, Isaac; Millo, Oded

2006-04-01

Current-voltage characteristics measured using STM on fullerene-like WS2 nanoparticles show zero-bias current and contain segments in which the tunneling current flows opposite to the applied bias voltage. In addition, negative differential conductance peaks emerge in these reversed current segments, and the characteristics are hysteretic with respect to the change in the voltage sweep direction. Such unusual features resemble those appearing in cyclic voltammograms, but are uniquely observed here in tunneling spectra measured in vacuum, as well as in ambient and dry atmosphere conditions. This behavior is attributed to tunneling-driven electrochemical processes.

Little or no solar wind enters Venus' atmosphere at solar minimum.

PubMed

Zhang, T L; Delva, M; Baumjohann, W; Auster, H-U; Carr, C; Russell, C T; Barabash, S; Balikhin, M; Kudela, K; Berghofer, G; Biernat, H K; Lammer, H; Lichtenegger, H; Magnes, W; Nakamura, R; Schwingenschuh, K; Volwerk, M; Vörös, Z; Zambelli, W; Fornacon, K-H; Glassmeier, K-H; Richter, I; Balogh, A; Schwarzl, H; Pope, S A; Shi, J K; Wang, C; Motschmann, U; Lebreton, J-P

2007-11-29

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.

Development of an autonomous unmanned aerial system for atmospheric data collection and research

NASA Astrophysics Data System (ADS)

Lee, Andrew; Hanlon, David; Sakai, Ricardo; Morris, Vernon; Demoz, Belay; Gadsden, S. Andrew

2016-05-01

This paper addresses the use of unmanned aerial systems (UAS) to carry out atmospheric data collection and studies. An important area of research is the study of the chemistry and physics of Earth's planetary boundary layer (PBL). The PBL, also known as the atmospheric boundary layer (ABL), is the lowest part of the atmosphere and its behavior is directly influenced by its contact with the planetary surface. Sampling of the PBL is performed in a timely and periodic manner. Currently, sensors and uncontrollable balloons are used to obtain relevant data and information. This method is cumbersome and can be ineffective in obtaining consistent environmental data. This paper proposes the use of autonomous UAS' to study the atmosphere in an effort to improve the efficiency and accuracy of the sampling process. The UAS setup and design is provided, and preliminary data collection information is shared.

Integrated circuit electrometer and sweep circuitry for an atmospheric probe

NASA Technical Reports Server (NTRS)

Zimmerman, L. E.

1971-01-01

The design of electrometer circuitry using an integrated circuit operational amplifier with a MOSFET input is described. Input protection against static voltages is provided by a dual ultra low leakage diode or a neon lamp. Factors affecting frequency response leakage resistance, and current stability are discussed, and methods are suggested for increasing response speed and for eliminating leakage resistance and current instabilities. Based on the above, two practical circuits, one having a linear response and the other a logarithmic response, were designed and evaluated experimentally. The design of a sweep circuit to implement mobility measurements using atmospheric probes is presented. A triangular voltage waveform is generated and shaped to contain a step in voltage from zero volts in both positive and negative directions.

Beyond Hammers and Nails: Mitigating and Verifying Greenhouse Gas Emissions

NASA Astrophysics Data System (ADS)

Gurney, Kevin Robert

2013-05-01

One of the biggest challenges to future international agreements on climate change is an independent, science-driven method of verifying reductions in greenhouse gas emissions (GHG) [Niederberger and Kimble, 2011]. The scientific community has thus far emphasized atmospheric measurements to assess changes in emissions. An alternative is direct measurement or estimation of fluxes at the source. Given the many challenges facing the approach that uses "top-down" atmospheric measurements and recent advances in "bottom-up" estimation methods, I challenge the current doctrine, which has the atmospheric measurement approach "validating" bottom-up, "good-faith" emissions estimation [Balter, 2012] or which holds that the use of bottom-up estimation is like "dieting without weighing oneself" [Nisbet and Weiss, 2010].

Atmospheric Effects of Aviation: First Report of the Subsonic Assessment Project

NASA Technical Reports Server (NTRS)

Thompson, Anne M. (Editor); Friedl, Randall R. (Editor); Wesoky, Howard L. (Editor)

1996-01-01

This document is the first report from the Office of Aeronautics Advanced Subsonic Technology (AST) Program's Subsonic Assessment (SASS) Project. This effort, initiated in late 1993, has as its objective the assessment of the atmospheric effects of the current and predicted future aviation fleet. The two areas of impact are ozone (stratospheric and tropospheric) and radiative forcing. These are driven, respectively, by possible perturbations from aircraft emissions of NOX and soot and/or sulfur-containing particles. The report presents the major questions to which project assessments will be directed (Introduction) and the status of six programmatic elements: Emissions Scenarios, Exhaust Characterization, Near-Field Interactions, Kinetics and Laboratory Studies, Global Modeling, and Atmospheric Observations (field studies).

Atmospheric Correction for Satellite Ocean Color Radiometry

NASA Technical Reports Server (NTRS)

Mobley, Curtis D.; Werdell, Jeremy; Franz, Bryan; Ahmad, Ziauddin; Bailey, Sean

2016-01-01

This tutorial is an introduction to atmospheric correction in general and also documentation of the atmospheric correction algorithms currently implemented by the NASA Ocean Biology Processing Group (OBPG) for processing ocean color data from satellite-borne sensors such as MODIS and VIIRS. The intended audience is graduate students or others who are encountering this topic for the first time. The tutorial is in two parts. Part I discusses the generic atmospheric correction problem. The magnitude and nature of the problem are first illustrated with numerical results generated by a coupled ocean-atmosphere radiative transfer model. That code allow the various contributions (Rayleigh and aerosol path radiance, surface reflectance, water-leaving radiance, etc.) to the topof- the-atmosphere (TOA) radiance to be separated out. Particular attention is then paid to the definition, calculation, and interpretation of the so-called "exact normalized water-leaving radiance" and its equivalent reflectance. Part I ends with chapters on the calculation of direct and diffuse atmospheric transmittances, and on how vicarious calibration is performed. Part II then describes one by one the particular algorithms currently used by the OBPG to effect the various steps of the atmospheric correction process, viz. the corrections for absorption and scattering by gases and aerosols, Sun and sky reflectance by the sea surface and whitecaps, and finally corrections for sensor out-of-band response and polarization effects. One goal of the tutorial-guided by teaching needs- is to distill the results of dozens of papers published over several decades of research in atmospheric correction for ocean color remote sensing.

The chemical composition of aerosols from Wildland fires: Current state of the science and possible new directions.

EPA Science Inventory

Wildland fire emits a substantial quantity of aerosol to the atmosphere. These aerosols typically comprise a complex mixture of organic matter and refractory elemental or black carbon with a relatively minor contribution of inorganic matter from soils and plant micronutrients. Id...

Penetrative convection

NASA Technical Reports Server (NTRS)

Moore, D. R.

1981-01-01

The current state of understanding of the most directly observable solar convection, the granulation and supergranulation is summarized. The body of work in which the complete time dependent Navier-Stokes equations and entropy transport equation are solved for a fully compressible atmosphere is considered. Relevant anelastic and incompressible calculations in two dimensions are also discussed.

Going the Second Mile. One Way of Looking at It

ERIC Educational Resources Information Center

Van Til, William

1974-01-01

Desegregation, still in process, constituted the first mile. Now desegregation is making few major gains. Through the approaches of "community study, democratic atmosphere, curriculum permeation, and group dynamics," joined by the current emphasis on the "direct experience" approach, perhaps the second mile can be traveled to achieve integration.…

Electron-bombarded CCD detectors for ultraviolet atmospheric remote sensing

NASA Technical Reports Server (NTRS)

Carruthers, G. R.; Opal, C. B.

1983-01-01

Electronic image sensors based on charge coupled devices operated in electron-bombarded mode, yielding real-time, remote-readout, photon-limited UV imaging capability are being developed. The sensors also incorporate fast-focal-ratio Schmidt optics and opaque photocathodes, giving nearly the ultimate possible diffuse-source sensitivity. They can be used for direct imagery of atmospheric emission phenomena, and for imaging spectrography with moderate spatial and spectral resolution. The current state of instrument development, laboratory results, planned future developments and proposed applications of the sensors in space flight instrumentation is described.

Advanced Acoustic Model Technical Reference and User Manual

DTIC Science & Technology

2009-05-01

the source directed from the source to the receiver. Aspread = Geometrical spherical spreading loss (point source). Aatm = ANSI/ ISO atmospheric...426.1 1,013.4 27000 722 422.5 1,009.2 28000 691 418.9 1,004.9 29000 660 415.4 1,000.6 30000 631 411.8 996.4 A d v a n c e d A c o u s t i c M...sound by molecular relaxation processes in the atmosphere is computed according to the current ANSI/ ISO standard.28 Examples of the weather effects

Equipment and techniques for low-altitude aerial sensing of water-vapor concentration and movement

USGS Publications Warehouse

Howell, R.L.

1969-01-01

Progress in the development of equipment and techniques for making rapid measurements of moisture movement through the atmosphere over a large area is described. Airborne sensing elements measure relative humidity, temperature, and air currents. These data are telemetered to a ground-based station and recorded. A radar unit tracks the aircraft and electronically plots its position on a base map of the area being studied. Thus the distribution of atmospheric conditions can be directly related to the underlying terrain and vegetation features. ?? 1969 American Elsevier Publishing Company, Inc.

Reflectance spectroscopy in planetary science: Review and strategy for the future

NASA Technical Reports Server (NTRS)

Mccord, Thomas B. (Editor)

1987-01-01

Reflectance spectroscopy is a remote sensing technique used to study the surfaces and atmospheres of solar system bodies. It provides first-order information on the presence and amounts of certain ions, molecules, and minerals on a surface or in an atmosphere. Reflectance spectroscopy has become one of the most important investigations conducted on most current and planned NASA Solar System Exploration Program space missions. This book reviews the field of reflectance spectroscopy, including information on the scientific technique, contributions, present conditions, and future directions and needs.

Atmospheric Electricity

NASA Astrophysics Data System (ADS)

Aplin, Karen; Fischer, Georg

2018-02-01

Electricity occurs in atmospheres across the Solar System planets and beyond, spanning spectacular lightning displays in clouds of water or dust, to more subtle effects of charge and electric fields. On Earth, lightning is likely to have existed for a long time, based on evidence from fossilized lightning strikes in ancient rocks, but observations of planetary lightning are necessarily much more recent. The generation and observations of lightning and other atmospheric electrical processes, both from within-atmosphere measurements, and spacecraft remote sensing, can be readily studied using a comparative planetology approach, with Earth as a model. All atmospheres contain charged molecules, electrons, and/or molecular clusters created by ionization from cosmic rays and other processes, which may affect an atmosphere's energy balance both through aerosol and cloud formation, and direct absorption of radiation. Several planets are anticipated to host a "global electric circuit" by analogy with the circuit occurring on Earth, where thunderstorms drive current of ions or electrons through weakly conductive parts of the atmosphere. This current flow may further modulate an atmosphere's radiative properties through cloud and aerosol effects. Lightning could potentially have implications for life through its effects on atmospheric chemistry and particle transport. It has been observed on many of the Solar System planets (Earth, Jupiter, Saturn, Uranus, and Neptune) and it may also be present on Venus and Mars. On Earth, Jupiter, and Saturn, lightning is thought to be generated in deep water and ice clouds, but discharges can be generated in dust, as for terrestrial volcanic lightning, and on Mars. Other, less well-understood mechanisms causing discharges in non-water clouds also seem likely. The discovery of thousands of exoplanets has recently led to a range of further exotic possibilities for atmospheric electricity, though lightning detection beyond our Solar System remains a technical challenge to be solved.

An evaluation of the current radiative forcing benefit of the Montreal Protocol at the high-Alpine site Jungfraujoch.

PubMed

Steinbacher, M; Vollmer, M K; Buchmann, B; Reimann, S

2008-03-01

A combination of reconstructed histories, long-term time series and recent quasi-continuous observations of non-CO2 greenhouse gases at the high-Alpine site Jungfraujoch is used to assess their current global radiative forcing budget and the influence of regulations due to the Montreal Protocol on Substances that Deplete the Ozone Layer in terms of climate change. Extrapolated atmospheric greenhouse gases trends from 1989 assuming a business-as-usual scenario, i.e. no Montreal Protocol restriction, are presented and compared to the observations. The largest differences between hypothetical business-as-usual mixing ratios and current atmospheric observations over the last 16 years were found for chlorinated species, in particular methyl chloroform (CH3CCl3) at 167 to 203 ppt and chlorofluorocarbon-12 (CFC-12) at 121 to 254 ppt. These prevented increases were used to estimate the effects of their restrictions on the radiative forcing budget. The net direct effect due to the Montreal Protocol regulations reduces global warming and offsets about 14 to 30% of the positive greenhouse effect related to the major greenhouse gases CO2, CH4, N2O and also SF6, and about 12 to 22% of the hypothetical current radiative forcing increase without Montreal Protocol restrictions. Thus, the Montreal Protocol succeeded not only in reducing the atmospheric chlorine content in the atmosphere but also dampened global warming. Nevertheless, the Montreal Protocol controlled species still add to global warming.

Middle atmosphere electrical energy coupling

NASA Technical Reports Server (NTRS)

Hale, L. C.

1989-01-01

The middle atmosphere (MA) has long been known as an absorber of radio waves, and as a region of nonlinear interactions among waves. The region of highest transverse conductivity near the top of the MA provides a common return for global thunderstorm, auroral Birkeland, and ionospheric dynamo currents, with possibilities for coupling among them. Their associated fields and other transverse fields map to lower altitudes depending on scale size. Evidence now exists for motion-driven aerosol generators, and for charge trapped at the base of magnetic field lines, both capable of producing large MA electric fields. Ionospheric Maxwell currents (curl H) parallel to the magnetic field appear to map to lower altitudes, with rapidly time-varying components appearing as displacement currents in the stratosphere. Lightning couples a (primarily ELF and ULF) current transient to the ionosphere and magnetosphere whose wave shape is largely dependent on the MA conductivity profile. Electrical energy is of direct significance mainly in the upper MA, but electrodynamic transport of minor constituents such as smoke particles or CN may be important at other altitudes.

Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet

NASA Astrophysics Data System (ADS)

Zhou, Qiujiao; Qi, Bing; Huang, Jianjun; Pan, Lizhu; Liu, Ying

2016-04-01

The properties of a helium atmospheric-pressure plasma jet (APPJ) are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device. In the glow discharge, we captured the current waveforms at the positions of the three grounded rings. From the current waveforms, the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ. Moreover, the electron density is deduced from a model combining with the time delay and current intensity, which is about 1011 cm-3. In addition, The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings, which is on the order of 107 Hz. The results are helpful for understanding the basic properties of APPJs. supported by National Natural Science Foundation of China (No. 11105093), the Technological Project of Shenzhen, China (No. JC201005280485A), and the Planned S&T Program of Shenzhen, China (No. JC201105170703A)

The Use of the Data Assimilation Research Testbed for Initializing and Evaluating IPCC Decadal Forecasts

NASA Astrophysics Data System (ADS)

Raeder, K.; Anderson, J. L.; Lauritzen, P. H.; Hoar, T. J.; Collins, N.

2010-12-01

DART (www.image.ucar.edu/DAReS/DART) is a general purpose, freely available, ensemble Kalman filter, data assimilation system, which is being used to generate state-of-the-art, partially coupled, ocean-atmosphere re-analyses in support of the decadal predictions planned for the next IPCC report. The resulting gridded product is directly comparable to the state variables output by POP and CAM (oceanic and atmospheric components of NCAR's Community Earth System Model climate model) because those are the assimilating models. Other models could also benefit from comparison against these reanalyses, since the ocean analyses are at the leading edge of ocean state estimation, and the atmospheric analyses are competitive with operational centers'. Such comparisons can reveal model biases and predictability characteristics, and do so in a quantitative way, since the ensemble nature of the analyses provides an objective estimate of the analysis error. The analyses will also be used as initial conditions for the decadal forecasts because they are the most realistic available. The generation of such analyses has revealed errors in model formulation for several versions of the finite volume core CAM, which has led to model improvements in each case. New models can be incorporated into DART in a matter of weeks, allowing them to be compared directly against available observations. The observations currently used in the assimilations include, for the ocean; temperature and salinity from the World Ocean Database (floats, drifters, moorings, autonomous pinipeds, and others), and for the atmosphere; temperature and winds from radiosondes, satellite drift winds, ACARS and aircraft. Observations of ocean currents and atmospheric moisture and pressure are also available. Global Positioning System profiles of atmospheric temperature and moisture are available for recent years. All that is required to add new observations to the suite is the forward operator, which generates an estimate of the observation from the model state. In summary, DART provides a flexible, convenient, rigorous environment for evaluating models in the context of real observations.

Removal of a hydrogenated amorphous carbon film from the tip of a micropipette electrode using direct current corona discharge.

PubMed

Kakuta, Naoto; Okuyama, Naoki; Yamada, Yukio

2010-02-01

Micropipette electrodes are fabricated by coating glass micropipettes first with metal and then with hydrogenated amorphous carbon (a-C:H) as an electrical insulator. Furthermore, at the tip of the micropipette electrode, the deposited a-C:H film needs to be removed to expose the metal-coated surface and hollow for the purposes of electrical measurement and injection. This paper describes a convenient and reliable method for removing the a-C:H film using direct current corona discharge in atmospheric air. The initial film removal occurred at an applied voltage of 1.5-2.0 kV, accompanied by an abrupt increase in the discharge current. The discharge current then became stable at a microampere level in the glow corona mode, and the removed area gradually extended.

The Atmospheric Effects of Stratospheric Aircraft: a First Program Report

NASA Technical Reports Server (NTRS)

Prather, Michael J.; Wesoky, Howard L.; Miake-Lye, Richard C.; Douglass, Anne R.; Turco, Richard P.; Wuebbles, Donald J.; Ko, Malcolm K. W.; Schmeltekopf, Arthur L.

1992-01-01

Studies have indicated that, with sufficient technology development, high speed civil transport aircraft could be economically competitive with long haul subsonic aircraft. However, uncertainty about atmospheric pollution, along with community noise and sonic boom, continues to be a major concern; and this is addressed in the planned 6 yr HSRP begun in 1990. Building on NASA's research in atmospheric science and emissions reduction, the AESA studies particularly emphasizing stratospheric ozone effects. Because it will not be possible to directly measure the impact of an HSCT aircraft fleet on the atmosphere, the only means of assessment will be prediction. The process of establishing credibility for the predicted effects will likely be complex and involve continued model development and testing against climatological patterns. Lab simulation of heterogeneous chemistry and other effects will continue to be used to improve the current models.

Sources and atmospheric transformations of semivolatile organic aerosols

NASA Astrophysics Data System (ADS)

Grieshop, Andrew P.

Fine atmospheric particulate matter (PM2.5) is associated with increased mortality, a fact which led the EPA to promulgate a National Ambient Air Quality Standard (NAAQS) for PM2.5 in 1997. Organic material contributes a substantial portion of the PM2.5 mass; organic aerosols (OA) are either directly emitted (primary OA or POA) or formed via the atmospheric oxidation of volatile precursor compounds as secondary OA (SOA). The relative contributions of POA and SOA to atmospheric OA are uncertain, as are the contributions from various source classes (e.g. motor vehicles, biomass burning). This dissertation first assesses the importance of organic PM within the context of current US air pollution regulations. Most control efforts to date have focused on the inorganic component of PM. Although growing evidence strongly implicates OA, especially which from motor vehicles, in the health effects of PM, uncertain and complex source-receptor relationships for OA discourage its direct control for NAAQS compliance. Analysis of both ambient data and chemical transport modeling results indicate that OA does not play a dominant role in NAAQS violations in most areas of the country under current and likely future regulations. Therefore, new regulatory approaches will likely be required to directly address potential health impacts associated with OA. To help develop the scientific understanding needed to better regulate OA, this dissertation examined the evolution of organic aerosol emitted by combustion systems. The current conceptual model of POA is that it is non-volatile and non-reactive. Both of these assumptions were experimental investigated in this dissertation. Novel dilution measurements were carried out to investigate the gas-particle partitioning of OA at atmospherically-relevant conditions. The results demonstrate that POA from combustion sources is semivolatile. Therefore its gas-particle partitioning depends on temperature and atmospheric concentrations; heating and dilution both cause it to evaporate. Gas-particle partitioning was parameterized using absorptive partitioning theory and the volatility basis-set framework. The dynamics of particle evaporation proved to be much slower than expected and measurements of aerosol composition indicate that particle composition varies with partitioning. These findings have major implications for the measurement and modeling of POA from combustion sources. Source tests need to be conducted at atmospheric concentrations and temperatures. Upon entering the atmosphere, organic aerosol emissions are aged via photochemical reactions. Experiments with dilute wood-smoke demonstrate the dramatic evolution these emissions undergo within hours of emission. Aging produced substantial new OA (doubling or tripling OA levels within hours) and changed particle composition and volatility. These changes are consistent with model predictions based on the partitioning and aging (via gas-phase photochemistry) of semi-volatile species represented with the basis-set framework. Aging of wood-smoke OA made created a much more oxygenated aerosol and formed material spectrally similar to oxygenated OA found widely in the atmosphere. The oxygenated aerosol is also similar that formed with similar experiments conducted with diesel engine emissions. Therefore, aging of emissions from diverse sources may produce chemically similar OA, complicating the establishment of robust source-receptor relationships.

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02032a Click here for additional data file.

PubMed Central

Schwartz, Andrew J.; Walton, Courtney L.; Williams, Kelsey L.; Hieftje, Gary M.

2016-01-01

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-like spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma. PMID:28451101

Direct Temperature Measurements during Netlander Descent on Mars

NASA Astrophysics Data System (ADS)

Colombatti, G.; Angrilli, F.; Ferri, F.; Francesconi, A.; Fulchignoni, M.; Lion Stoppato, P. F.; Saggi, B.

1999-09-01

A new design for a platinum thermoresistance temperature sensor has been developed and tested in Earth's atmosphere and stratosphere. It will be one of the sensors equipping the scientific package ATMIS (Atmospheric and Meteorology Instrument System), which will be devoted to the measurement of the meteorological parameters during both the entry/descent phase and the surface phase, aboard the Netlanders. In particular vertical profiles of temperature, density and pressure will allow the resolution of vertical gradients to investigate the atmospheric structure and dynamics. In view of the future missions to Mars, Netlander represents a unique chance to increase significantly the climate record both in time and in space, doubling the current knowledge of the atmospheric parameters. Furthermore is the only opportunity to conduct direct measurement of temperature and pressure (outside the boundary layer of the airbags used for the landing). The temperature sensor proposed is a platinum thermoresistance, enhancement of HASI TEM (Cassini/Huygens Mission); a substantial improvement of the performances, i.e. a faster dynamic response, has been obtained. Two different prototypes of new design sensor have been built, laboratory test are proceeding and the second one has been already flown aboard a stratospheric balloon.

Extracting atmospheric turbulence and aerosol characteristics from passive imagery

NASA Astrophysics Data System (ADS)

Reinhardt, Colin N.; Wayne, D.; McBryde, K.; Cauble, G.

2013-09-01

Obtaining accurate, precise and timely information about the local atmospheric turbulence and extinction conditions and aerosol/particulate content remains a difficult problem with incomplete solutions. It has important applications in areas such as optical and IR free-space communications, imaging systems performance, and the propagation of directed energy. The capability to utilize passive imaging data to extract parameters characterizing atmospheric turbulence and aerosol/particulate conditions would represent a valuable addition to the current piecemeal toolset for atmospheric sensing. Our research investigates an application of fundamental results from optical turbulence theory and aerosol extinction theory combined with recent advances in image-quality-metrics (IQM) and image-quality-assessment (IQA) methods. We have developed an algorithm which extracts important parameters used for characterizing atmospheric turbulence and extinction along the propagation channel, such as the refractive-index structure parameter C2n , the Fried atmospheric coherence width r0 , and the atmospheric extinction coefficient βext , from passive image data. We will analyze the algorithm performance using simulations based on modeling with turbulence modulation transfer functions. An experimental field campaign was organized and data were collected from passive imaging through turbulence of Siemens star resolution targets over several short littoral paths in Point Loma, San Diego, under conditions various turbulence intensities. We present initial results of the algorithm's effectiveness using this field data and compare against measurements taken concurrently with other standard atmospheric characterization equipment. We also discuss some of the challenges encountered with the algorithm, tasks currently in progress, and approaches planned for improving the performance in the near future.

Evidence for the Maintenance of Slowly Varying Equatorial Currents by Intraseasonal Variability

NASA Astrophysics Data System (ADS)

Greatbatch, Richard J.; Claus, Martin; Brandt, Peter; Matthießen, Jan-Dirk; Tuchen, Franz Philip; Ascani, François; Dengler, Marcus; Toole, John; Roth, Christina; Farrar, J. Thomas

2018-02-01

Recent evidence from mooring data in the equatorial Atlantic reveals that semiannual and longer time scale ocean current variability is close to being resonant with equatorial basin modes. Here we show that intraseasonal variability, with time scales of tens of days, provides the energy to maintain these resonant basin modes against dissipation. The mechanism is analogous to that by which storm systems in the atmosphere act to maintain the atmospheric jet stream. We demonstrate the mechanism using an idealized model setup that exhibits equatorial deep jets. The results are supported by direct analysis of available mooring data from the equatorial Atlantic Ocean covering a depth range of several thousand meters. The analysis of the mooring data suggests that the same mechanism also helps maintain the seasonal variability.

PROPOSED ASTM METHOD FOR THE DETERMINATION OF ASBESTOS IN AIR BY TEM AND INFORMATION ON INTERFERING FIBERS

EPA Science Inventory

The draft of the ASTM Test Method for air entitled: "Airborne Asbestos Concentration in Ambient and Indoor Atmospheres as Determined by Transmission Electron Microscopy Direct Transfer (TEM)" (ASTM Z7077Z) is an adaptation of the International Standard, ISO 10312. It is currently...

Atmospheric Beacons of Life from Exoplanets Around G and K Stars

NASA Technical Reports Server (NTRS)

Airapetian, Vladimir S.; Jackman, Charles H.; Mlynczak, Martin; Danchi, William; Hunt, Linda

2017-01-01

The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets "highlighted" by the magnetic activity from young G and K main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric "beacons of life" create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.

Atmospheric Beacons of Life from Exoplanets Around G and K Stars.

PubMed

Airapetian, Vladimir S; Jackman, Charles H; Mlynczak, Martin; Danchi, William; Hunt, Linda

2017-11-02

The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O 2 ), ozone (O 3 ), water vapor (H 2 O), carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets "highlighted" by the magnetic activity from young G and K main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric "beacons of life" create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.

A New Look at Triton's Atmosphere

NASA Astrophysics Data System (ADS)

Person, Michael

When it was first examined with stellar occultations in the 1990s, Triton's atmosphere was seen to undergo global expansion during the period from 1993 to 1997. This expansion was confirmed as a continuing phenomenon with a stellar occultation observation in 2001 . Unfortunately, as Triton started to pass through a fairly sparse star field, occultation observations have been much more difficult to make. There have been no published occultation data on Triton's atmosphere since the 2001 event, and reported observations in early 2007 had too low of a signal-to-noise ratio to say anything about the atmospheric profile. Thus, it has been over 15 years since the last direct measurement of Triton's expanding atmosphere was made, leaving wide open the question of Triton's current atmospheric state. Is the atmosphere still expanding or is it now collapsing? Are the haze layers seen by Voyager still present? Are the variations seen in the 1990s seasonal or cyclic on shorter time scales due to Triton surface processes? The observation of stellar occultations remains the only way to gain current data on Triton's atmosphere from Earth, and SOFIA's unique ability to be reliably placed in the central flash region of occultation events where the richest dataset is available, and its immunity to low-level weather disturbances make it the ideal platform for updating our knowledge on Triton and beginning to answer these many outstanding questions. We therefore propose to use SOFIA with HIPO, FLITECAM (FLIPO), and the FPI+ to measure temperature, pressure, and particulate haze radial profiles of Triton's atmosphere by observing a stellar occultation which will be visible over the eastern portion of North America in October of 2017. We expect to use FLITECAM/HIPO (FLIPO) Guaranteed Time Observing (GTO) hours for the included observations with the agreement of the FLITECAM and HIPO instrument teams.

The DYNAMO Orbiter Project: High Resolution Mapping of Gravity/Magnetic Fields and In Situ Investigation of Mars Atmospheric Escape

NASA Technical Reports Server (NTRS)

Smrekar, S.; Chassefiere, E.; Forget, F.; Reme, H.; Mazelle, C.; Blelly, P. -L.; Acuna, M.; Connerney, J.; Purucker, M.; Lin, R.

2000-01-01

Dynamo is a small Mars orbiter planned to be launched in 2005 or 2007, in the frame of the NASA/CNES Mars exploration program. It is aimed at improving gravity and magnetic field resolution, in order to better understand the magnetic, geologic and thermal history of Mars, and at characterizing current atmospheric escape, which is still poorly constrained. These objectives are achieved by using a low periapsis orbit, similar to the one used by the Mars Global Surveyor spacecraft during its aerobraking phases. The proposed periapsis altitude for Dynamo of 120-130 km, coupled with the global distribution of periapses to be obtained during one Martian year of operation, through about 5000 low passes, will produce a magnetic/gravity field data set with approximately five times the spatial resolution of MGS. Low periapsis provides a unique opportunity to investigate the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, therefore atmospheric escape, which may have played a crucial role in removing atmosphere, and water, from the planet. There is much room for debate on the importance of current atmosphere escape processes in the evolution of the Martian atmosphere, as early "exotic" processes including hydrodynamic escape and impact erosion are traditionally invoked to explain the apparent sparse inventory of present-day volatiles. Yet, the combination of low surface gravity and the absence of a substantial internally generated magnetic field have undeniable effects on what we observe today. In addition to the current losses in the forms of Jeans and photochemical escape of neutrals, there are solar wind interaction-related erosion mechanisms because the upper atmosphere is directly exposed to the solar wind. The solar wind related loss rates, while now comparable to those of a modest comet, nonetheless occur continuously, with the intriguing possibility of important cumulative and/or enhanced effects over the several billion years of the solar system's life. If the detailed history of the Martian internal field could be traced back, and the current escape processes could be understood well enough to model the expected stronger losses under early Sun conditions, one could go a long way toward constraining this part of the mysterious history of Mars' atmosphere.

Arctic Council Nations Could Encourage Development of Climate Indicator: Flux to the Atmosphere from Arctic Permafrost Carbon

NASA Astrophysics Data System (ADS)

Ekwurzel, B.; Yona, L.; Natali, S.; Holmes, R. M.; Schuur, E.

2015-12-01

Permafrost regions store almost twice the carbon in the atmosphere (Tarnocai et al 2009). As climate warms a proportion of this carbon will be released as carbon dioxide and methane. The Arctic Council may be best suited to harness international scientific collaboration for policy relevant knowledge about the global impacts of permafrost thaw. Scientists in Arctic Council and observer states have historically collaborated on permafrost research (e.g. Permafrost Carbon Network, part of Study of Environmental Arctic Change (SEARCH) project). This work increased knowledge of permafrost carbon pool size and vulnerability. However, data gaps persist across the Arctic. Despite gaps, numerous studies directly inform international policy negotiations aiming to stay below 2° C. Some suggest "permafrost carbon feedback" may comprise 3 to 11% of total allowed emissions through 2100 under a RCP4.5 (Schaefer et al2014). Understanding and accounting for future permafrost atmospheric carbon release requires science and policy coordination that the Arctic Council could incentivize. For example, Council nations could convene scientists and stakeholders to develop a Permafrost-Climate Indicator providing more direct decision support than current permafrost indicators, and identify research needed for a periodic estimate of Arctic permafrost CO2 and CH4 emissions. This presentation covers current challenges scientists and policymakers may face to develop a practical and robust Permafrost Climate Indicator. For example, which timescales are most appropriate for international emissions commitments? Do policy-relevant timescales align with current scientific knowledge? What are the uncertainties and how can they be decreased? We present likely strengths and challenges of a Permafrost Climate Indicator co-developed by scientists and stakeholders. Potential greenhouse gas atmospheric flux from Arctic permafrost carbon may be greater than some nations' United Nations emissions reductions commitments. Investing in better understanding greenhouse gas emissions from thawing permafrost is relevant for all nations and essential to setting global emission targets.

Cold atmospheric pressure air plasma jet for medical applications

NASA Astrophysics Data System (ADS)

Kolb, J. F.; Mohamed, A.-A. H.; Price, R. O.; Swanson, R. J.; Bowman, A.; Chiavarini, R. L.; Stacey, M.; Schoenbach, K. H.

2008-06-01

By flowing atmospheric pressure air through a direct current powered microhollow cathode discharge, we were able to generate a 2cm long plasma jet. With increasing flow rate, the flow becomes turbulent and temperatures of the jet are reduced to values close to room temperature. Utilizing the jet, yeast grown on agar can be eradicated with a treatment of only a few seconds. Conversely, animal studies show no skin damage even with exposures ten times longer than needed for pathogen extermination. This cold plasma jet provides an effective mode of treatment for yeast infections of the skin.

Atmospheric pressure cold plasma as an antifungal therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Peng; Wu Haiyan; Sun Yi

2011-01-10

A microhollow cathode based, direct-current, atmospheric pressure, He/O{sub 2} (2%) cold plasma microjet was used to inactive antifungal resistants Candida albicans, Candida krusei, and Candida glabrata in air and in water. Effective inactivation (>90%) was achieved in 10 min in air and 1 min in water. Antifungal susceptibility tests showed drastic reduction of the minimum inhibitory concentration after plasma treatment. The inactivation was attributed to the reactive oxygen species generated in plasma or in water. Hydroxyl and singlet molecular oxygen radicals were detected in plasma-water system by electron spin resonance spectroscopy. This approach proposed a promising clinical dermatology therapy.

Earth history. Low mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals.

PubMed

Planavsky, Noah J; Reinhard, Christopher T; Wang, Xiangli; Thomson, Danielle; McGoldrick, Peter; Rainbird, Robert H; Johnson, Thomas; Fischer, Woodward W; Lyons, Timothy W

2014-10-31

The oxygenation of Earth's surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth's surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans. Copyright © 2014, American Association for the Advancement of Science.

Exploring the ionic strength effects on the photochemical degradation of pyruvic acid in atmospheric deliquescent aerosol particles

NASA Astrophysics Data System (ADS)

Mekic, Majda; Brigante, Marcello; Vione, Davide; Gligorovski, Sasho

2018-07-01

There is increasing evidence that aqueous-phase atmospheric chemistry is an important source of secondary organic aerosols (SOA), but the related processes are currently not adequately represented in atmospheric chemistry models. Here we show that the absorption spectrum of pyruvic acid (PA) exhibits both an increase of the absorption intensity and a red shift of 13 nm while going from a dilute aqueous phase to a solution containing the inert salt sodium perchlorate (5M NaClO4). If this phenomenon turns out to be more general, many compounds that do not absorb actinic light in clouds and fog could become light absorbers at elevated salt concentrations in aerosol deliquescent particles. Compared to the direct photolysis of PA in dilute aqueous solution, the photolysis rate is increased by three times at high ionic strength (5M NaClO4). Such a considerable enhancement can be rationalized in the framework of the Debye-McAulay approach for reactions of ionic + neutral (or neutral + neutral) species, considering that the PA direct photolysis likely involves interaction between the photogenerated triplet state and water. This is, to our knowledge, the first report of a significant effect of the ionic strength on the rate of an atmospheric photochemical reaction. The phenomenon has important implications for the fate of PA and, potentially, of other organic compounds in atmospheric aerosol deliquescent particles.

Solar system neighbors as proxies for exoplanets; Peering through the atmospheres of Titan and Saturn with Cassini

NASA Astrophysics Data System (ADS)

Teal, Dillon J.; Fortney, Jonathan J.; Line, Michael R.

2016-10-01

A transiting exoplanet is a planet that orbits another star, and periodically passes directly in front of its parent star, blocking out a small fraction of the stellar light. We can study the atmospheres of these planets by looking at the tiny fraction of the star's light that passes through the planet's thin outer atmosphere, called a transmission spectrum. This is one of the few ways to probe an exoplanet's atmosphere with current technology. This field will rapidly expand with the launch of the Transiting Exoplanet Survey System (TESS) in 2017, to find more planets, and the James Webb Space Telescope (JWST) in 2018, to characterize exoplanet atmospheres. The need to validate the models we use to calculate exoplanet atmosphere properties in the regime of high signal-to-noise data has become increasingly important. Thankfully, with the help of NASA's Cassini orbiter we can test our transmission spectra models against transmission spectra of real planetary bodies for which we have "ground truth" measurements. Using the CHIMERA Transmission spectra model of Line et al. (2013a) and the Python multinesting framework pyMultinest, from the Saturn and Titan transmission spectra we retrieve the abundances of the important molecules CH4, CO, CO2, NH3, and C2H2 along with atmospheric temperature, a reference or "surface" pressure, and the cloud pressure. Here we discuss the current status of this work, and potential problems facing our models, including a C-H stretching feature between 3-4 microns and haze scattering.

Assessment of Global Annual Atmospheric Energy Balance from Satellite Observations

NASA Technical Reports Server (NTRS)

Lin, Bing; Stackhouse, Paul; Minnis, Patrick; Wielicki, Bruce A.; Hu, Yongxiang; Sun, Wenbo; Fan, Tai-Fang (Alice); Hinkelman, Laura

2008-01-01

Global atmospheric energy balance is one of the fundamental processes for the earth's climate system. This study uses currently available satellite data sets of radiative energy at the top of atmosphere (TOA) and surface and latent and sensible heat over oceans for the year 2000 to assess the global annual energy budget. Over land, surface radiation data are used to constrain assimilated results and to force the radiation, turbulent heat, and heat storage into balance due to a lack of observation-based turbulent heat flux estimations. Global annual means of the TOA net radiation obtained from both direct measurements and calculations are close to zero. The net radiative energy fluxes into the surface and the surface latent heat transported into the atmosphere are about 113 and 86 Watts per square meter, respectively. The estimated atmospheric and surface heat imbalances are about -8 9 Watts per square meter, values that are within the uncertainties of surface radiation and sea surface turbulent flux estimates and likely systematic biases in the analyzed observations. The potential significant additional absorption of solar radiation within the atmosphere suggested by previous studies does not appear to be required to balance the energy budget the spurious heat imbalances in the current data are much smaller (about half) than those obtained previously and debated at about a decade ago. Progress in surface radiation and oceanic turbulent heat flux estimations from satellite measurements significantly reduces the bias errors in the observed global energy budgets of the climate system.

A Plasma Window for Transmission of Radiation and Particle Beams from Vacuum to Atmosphere for Various Applications

NASA Astrophysics Data System (ADS)

Hershcovitch, Ady

1997-11-01

Many industrial and scientific processes like electron beam melting and welding, material modification by ion implantation, dry etching, and micro-fabrication, as well as generation of synchrotron radiation are performed almost exclusively in vacuum nowadays, since the electron and ion guns and their extractors must be kept at a reasonably high vacuum. Consequently, there are numerous drawbacks, among which are low production rates due to required pumping time, limits the vacuum volume sets on the size of target objects. In a small number of applications like non-vacuum electron beam welding, and various processes involving UV and x-ray radiation, thin vacuum walls or long stages of differential pumping are used. But, the resultant degradations of particle and radiation beams severely limit those applications. A novel apparatus, which utilized a short plasma arc, was successfully used to maintain a pressure of 7.6 x exp(-6) Torr in a vacuum chamber with a 2.36mm aperture to atmosphere, i.e., a plasma was successfully used to "plug" a hole to atmosphere while maintaining a reasonably high vacuum in the chamber. Successful transmission of charged particle beams from a vacuum through the plasma to atmosphere was accomplished. More details can be found in A. Hershcovitch, J. Appl. Physics 78, p. 5283 (1995). In addition to sustaining a vacuum atmosphere interface, the plasma has very strong lensing effect on charged particles. The plasma current generates an azimuthal magnetic field which exerts a radial Lorentz on charged particles moving parallel to the current channel. With proper orientation of the current direction, the Lorentz force is radially inward. This feature can be used to focus in beams to a very small spot size, and to overcome beam dispersion due to scattering by atmospheric atoms and molecules. Relatively hot plasma at the atmosphere boundary rarefies the atmospheric gases to further enhance particle beam propagation to the materials to target. Recent experimental results, with a plasma window coupled to a venturi, show a factor of three further enhancement in vacuum-atmosphere separation.

Fire metrology: Current and future directions in physics-based measurements

Treesearch

Robert L. Kremens; Alistair M.S. Smith; Matthew B. Dickinson

2010-01-01

The robust evaluation of fire impacts on the biota, soil, and atmosphere requires measurement and analysis methods that can characterize combustion processes across a range of temporal and spatial scales. Numerous challenges are apparent in the literature. These challenges have led to novel research to quantify the 1) structure and heterogeneity of the pre-fire...

DISCOVERY OF FOG AT THE SOUTH POLE OF TITAN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, M. E.; Smith, A. L.; Chen, C.

2009-11-20

While Saturn's moon Titan appears to support an active methane hydrological cycle, no direct evidence for surface-atmosphere exchange has yet appeared. The indirect evidence, while compelling, could be misleading. It is possible, for example, that the identified lake features could be filled with ethane, an involatile long-term residue of atmospheric photolysis; the apparent stream and channel features could be ancient remnants of a previous climate; and the tropospheric methane clouds, while frequent, could cause no rain to reach the surface. We report here the detection of fog at the south pole of Titan during late summer using observations from themore » VIMS instrument on board the Cassini spacecraft. While terrestrial fog can form from a variety of causes, most of these processes are inoperable on Titan. Fog on Titan can only be caused by evaporation of nearly pure liquid methane; the detection of fog provides the first direct link between surface and atmospheric methane. Based on the detections presented here, liquid methane appears widespread at the south pole of Titan in late southern summer, and the hydrological cycle on Titan is currently active.« less

Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balazs, Csaba; Conrad, Jan; Farmer, Ben

Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential γ-ray signals from dark matter (DM) annihilation above ~50 GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate γ-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC)more » and direct detection experiments. Here, for DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.« less

Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments

DOE PAGES

Balazs, Csaba; Conrad, Jan; Farmer, Ben; ...

2017-10-04

Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential γ-ray signals from dark matter (DM) annihilation above ~50 GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate γ-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC)more » and direct detection experiments. Here, for DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.« less

Impact of Ocean Acidification on Fluxes of non-CO2 Climate-Active Species: Report from the GESAMP WG38 workshop

NASA Astrophysics Data System (ADS)

Suntharalingam, Parvadha; Gehlen, Marion; Hopkins, Frances; Duce, Robert; Jickells, Tim; Gesamp WG38 Workshop, Participants

2017-04-01

Most investigations of the impact of ocean acidification (OA) have focused on changes in oceanic uptake of anthropogenic CO2, the resulting shifts in carbonate chemical equilibria, and the consequences for marine calcifying organisms. Little attention has been paid to the direct impacts of OA on the ocean sources of a range of other gaseous and aerosol species that are influential in regulating radiative forcing, atmospheric oxidising capacity and atmospheric chemistry. The oceanic processes governing emissions of these species are frequently sensitive to the changes in pH and ocean pCO2 accompanying ocean acidification. Such processes include, for example, metabolic rates of microbial activity, levels of surface primary production, ecosystem composition, and photo-chemical and microbially mediated production/loss pathways for individual species. The direct and indirect influences of these factors on oceanic fluxes of non-CO2 trace-gases and aerosols, and the subsequent feedbacks to climate remain highly uncertain. To address these issues UN/GESAMP Working Group 38, The Atmospheric Input of Chemicals to the Ocean, convened a workshop on this topic at the University of East Anglia in February, 2017. The goals of this workshop are to review and synthesize the current science on the direct impacts of ocean acidification on marine emissions to the atmosphere of key species important for climate, and atmospheric chemistry; and to identify the primary needs for new research to improve process understanding and to quantify the impact of ocean acidification on these marine fluxes (i.e., provide recommendations on the specific laboratory process studies, field measurements and model analyses needed to support targeted research activities on this topic). The results, conclusions, and recommendations of this workshop will be presented.

THE ORIGIN OF NET ELECTRIC CURRENTS IN SOLAR ACTIVE REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalmasse, K.; Aulanier, G.; Démoulin, P.

There is a recurring question in solar physics regarding whether or not electric currents are neutralized in active regions (ARs). This question was recently revisited using three-dimensional (3D) magnetohydrodynamic (MHD) numerical simulations of magnetic flux emergence into the solar atmosphere. Such simulations showed that flux emergence can generate a substantial net current in ARs. Other sources of AR currents are photospheric horizontal flows. Our aim is to determine the conditions for the occurrence of net versus neutralized currents with this second mechanism. Using 3D MHD simulations, we systematically impose line-tied, quasi-static, photospheric twisting and shearing motions to a bipolar potentialmore » magnetic field. We find that such flows: (1) produce both direct and return currents, (2) induce very weak compression currents—not observed in 2.5D—in the ambient field present in the close vicinity of the current-carrying field, and (3) can generate force-free magnetic fields with a net current. We demonstrate that neutralized currents are in general produced only in the absence of magnetic shear at the photospheric polarity inversion line—a special condition that is rarely observed. We conclude that  photospheric flows, as magnetic flux emergence, can build up net currents in the solar atmosphere, in agreement with recent observations. These results thus provide support for eruption models based on pre-eruption magnetic fields that possess a net coronal current.« less

Mapping Global Ocean Surface Albedo from Satellite Observations: Models, Algorithms, and Datasets

NASA Astrophysics Data System (ADS)

Li, X.; Fan, X.; Yan, H.; Li, A.; Wang, M.; Qu, Y.

2018-04-01

Ocean surface albedo (OSA) is one of the important parameters in surface radiation budget (SRB). It is usually considered as a controlling factor of the heat exchange among the atmosphere and ocean. The temporal and spatial dynamics of OSA determine the energy absorption of upper level ocean water, and have influences on the oceanic currents, atmospheric circulations, and transportation of material and energy of hydrosphere. Therefore, various parameterizations and models have been developed for describing the dynamics of OSA. However, it has been demonstrated that the currently available OSA datasets cannot full fill the requirement of global climate change studies. In this study, we present a literature review on mapping global OSA from satellite observations. The models (parameterizations, the coupled ocean-atmosphere radiative transfer (COART), and the three component ocean water albedo (TCOWA)), algorithms (the estimation method based on reanalysis data, and the direct-estimation algorithm), and datasets (the cloud, albedo and radiation (CLARA) surface albedo product, dataset derived by the TCOWA model, and the global land surface satellite (GLASS) phase-2 surface broadband albedo product) of OSA have been discussed, separately.

Atmospheric Wind Relaxations and the Oceanic Response in the California Current Large Marine Ecosystem

NASA Astrophysics Data System (ADS)

Fewings, M. R.; Dorman, C. E.; Washburn, L.; Liu, W.

2010-12-01

On the West Coast of North America in summer, episodic relaxation of the upwelling-favorable winds causes warm water to propagate northward from southern to central California, against the prevailing currents [Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. Similar wind relaxations are an important characteristic of coastal upwelling ecosystems worldwide. Although these wind relaxations have an important influence on coastal ocean dynamics, no description exists of the regional atmospheric patterns that lead to wind relaxations in southern California, or of the regional ocean response. We use QuikSCAT wind stress, North American Regional Reanalysis atmospheric pressure products, water temperature and velocity from coastal ocean moorings, surface ocean currents from high-frequency radars, and MODIS satellite sea-surface temperature and ocean color images to analyze wind relaxation events and the ocean response. We identify the events based on an empirical index calculated from NDBC buoy winds [Melton et al. 2009]. We describe the regional evolution of the atmosphere from the Gulf of Alaska to Baja California over the few days leading up to wind relaxations, and the coastal ocean temperature, color, and current response off southern and central California. We analyze ~100 wind relaxation events in June-September during the QuikSCAT mission, 1999-2009. Our results indicate south-central California wind relaxations in summer are tied to mid-level atmospheric low-pressure systems that form in the Gulf of Alaska and propagate southeastward over 3-5 days. As the low-pressure systems reach southern California, the atmospheric pressure gradient along the coast weakens, causing the surface wind stress to relax to near zero. The weak wind signal appears first at San Diego and propagates northward. QuikSCAT data indicate the relaxed winds extend over the entire Southern California Bight and up to 200 km offshore of central California. Atmospheric dynamics in the Gulf of Alaska influence ocean conditions in central and southern California via these wind relaxations. The ocean response within a few km of the coast involves poleward-flowing currents that transport warm water out of the lees of capes and headlands and counter to the direction of the California Current [Send et al. 1987, Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. A similar response occurs in the Benguela and Canary Current coastal upwelling systems. The ocean response involves both barotropic and baroclinic dynamics and is consistent with existing geophysical models of buoyant, coastally-trapped plumes [Washburn et al., in prep]. Our ongoing work includes i) studying the regional ocean response to determine its spatial extent, time evolution, and ocean-atmosphere coupling dynamics; ii) developing an atmospheric index to predict wind relaxations in southern California based on pressure in the Gulf of Alaska; iii) examining the strength and frequency of wind relaxations over the past 30 years for connections to El Niño and the Pacific Decadal Oscillation; and iv) predicting future variations in wind relaxations and the response of the California Current Large Marine Ecosystem.

[Bio-electrochemical effect on hydrogenotrophic sulfate reduction stimulated by electrical field in the presence of H2 under atmospheric pressure].

PubMed

Xu, Hui-Wei; Zhang, Xu; Yang, Shan-Shan; Li, Guang-He

2009-07-15

Microbial sulfate reduction rate is limited with H2 as electron donor. In order to improve hydrogenotrophic sulfate reduction under normal atmospheric H2 pressure, a bio-electrochemical system with direct current was designed and performed in this study. Results indicates that sulfate reduction rate (SRR) increases with the augment of current intensity under lower current intensity (I < or = 1.50 mA). When optimum current intensity of 1.50 mA is applied, the SRR is 1.7 to 2.1 times higher than that of the control reactor. The synergistic effect of electrochemistry and microbiology on sulfate reduction varies at different current intensity. Under the condition of I < or = 1.50 mA, the most probable mechanism of SRR increase is that electric or magnetic field stimulates the proliferation of sulfate-reducing bacteria (SRB) and the activity of the enzymes. When I is higher than 1.50 mA, the activity of SRB is inhibited, resulting in lower reduction rate compared with that at lower current. If controlling the cathode potential lower than -0.69 V and H2 partial pressure 1.01 x 10(5) Pa, electro-catalytic sulfate reduction process takes place with H2 as reductant in this bio-electrochemical system. However, the overall reduction rate is still lower than that when I = 1.50 mA is applied, and additionally the energy consumption is much higher. Therefore, electric field of low intensity can enhance hydrogenotrophic sulfate reduction in the presence of H2 under atmospheric pressure.

Alternating current corona discharge/atmospheric pressure chemical ionization for mass spectrometry.

PubMed

Habib, Ahsan; Usmanov, Dilshadbek; Ninomiya, Satoshi; Chen, Lee Chuin; Hiraoka, Kenzo

2013-12-30

Although alternating current (ac) corona discharge has been widely used in the fields of material science and technology, no reports have been published on its application to an atmospheric pressure chemical ionization (APCI) ion source. In this work, ac corona discharge for an APCI ion source has been examined for the first time. The ambient atmospheric pressure ac corona discharge (15 kHz, 2.6 kVptp ) was generated by using a stainless steel acupuncture needle. The generated ions were measured using an ion trap mass spectrometer. A comparative study on ac and direct current (dc) corona APCI ion sources was carried out using triacetone triperoxide and trinitrotoluene as test samples. The ac corona discharge gave ion signals as strong as dc corona discharge for both positive and negative ion modes. In addition, softer ionization was obtained with ac corona discharge than with dc corona discharge. The erosion of the needle tip induced by ac corona was less than that obtained with positive mode dc corona. A good 'yardstick' for assessing ac corona is that it can be used for both positive and negative ion modes without changing the polarity of the high-voltage power supply. Thus, ac corona can be an alternative to conventional dc corona for APCI ion sources. Copyright © 2013 John Wiley & Sons, Ltd.

OSOAA: A Vector Radiative Transfer Model of Coupled Atmosphere-Ocean System for a Rough Sea Surface Application to the Estimates of the Directional Variations of the Water Leaving Reflectance to Better Process Multi-angular Satellite Sensors Data Over the Ocean

NASA Technical Reports Server (NTRS)

Chami, Malik; LaFrance, Bruno; Fougnie, Bertrand; Chowdhary, Jacek; Harmel, Tristan; Waquet, Fabien

2015-01-01

In this study, we present a radiative transfer model, so-called OSOAA, that is able to predict the radiance and degree of polarization within the coupled atmosphere-ocean system in the presence of a rough sea surface. The OSOAA model solves the radiative transfer equation using the successive orders of scattering method. Comparisons with another operational radiative transfer model showed a satisfactory agreement within 0.8%. The OSOAA model has been designed with a graphical user interface to make it user friendly for the community. The radiance and degree of polarization are provided at any level, from the top of atmosphere to the ocean bottom. An application of the OSOAA model is carried out to quantify the directional variations of the water leaving reflectance and degree of polarization for phytoplankton and mineral-like dominated waters. The difference between the water leaving reflectance at a given geometry and that obtained for the nadir direction could reach 40%, thus questioning the Lambertian assumption of the sea surface that is used by inverse satellite algorithms dedicated to multi-angular sensors. It is shown as well that the directional features of the water leaving reflectance are weakly dependent on wind speed. The quantification of the directional variations of the water leaving reflectance obtained in this study should help to correctly exploit the satellite data that will be acquired by the current or forthcoming multi-angular satellite sensors.

Charged particle tracking at Titan, and further applications

NASA Astrophysics Data System (ADS)

Bebesi, Zsofia; Erdos, Geza; Szego, Karoly

2016-04-01

We use the CAPS ion data of Cassini to investigate the dynamics and origin of Titan's atmospheric ions. We developed a 4th order Runge-Kutta method to calculate particle trajectories in a time reversed scenario. The test particle magnetic field environment imitates the curved magnetic environment in the vicinity of Titan. The minimum variance directions along the S/C trajectory have been calculated for all available Titan flybys, and we assumed a homogeneous field that is perpendicular to the minimum variance direction. Using this method the magnetic field lines have been calculated along the flyby orbits so we could select those observational intervals when Cassini and the upper atmosphere of Titan were magnetically connected. We have also taken the Kronian magnetodisc into consideration, and used different upstream magnetic field approximations depending on whether Titan was located inside of the magnetodisc current sheet, or in the lobe regions. We also discuss the code's applicability to comets.

Numerical Analysis of the Effect of Active Wind Speed and Direction on Circulation of Sea of Azov Water with and without Allowance for the Water Exchange through the Kerch Strait

NASA Astrophysics Data System (ADS)

Cherkesov, L. V.; Shul'ga, T. Ya.

2018-01-01

The effect of seawater movement through the Kerch Strait for extreme deviations in the level and speed of currents in the Sea of Azov caused by the action of climate wind fields has been studied using the Princeton ocean model (POM), a general three-dimensional nonlinear model of ocean circulation. Formation of the water flow through the strait is caused by the long-term action of the same type of atmospheric processes. The features of the water dynamics under conditions of changing intensity and active wind direction have been studied. Numerical experiments were carried out for two versions of model Sea of Azov basins: closed (without the Kerch Strait) and with a fluid boundary located in the Black Sea. The simulation results have shown that allowance for the strait leads to a significant change in the velocities of steady currents and level deviations at wind speeds greater than 5 m/s. The most significant effect on the parameters of steady-state movements is exerted by the speed of the wind that generates them; allowance for water exchange through the strait is less important. Analysis of the directions of atmospheric circulation has revealed that the response generated by the movement of water through the strait is most pronounced when a southeast wind is acting.

Studies on possible propagation of microbial contamination in planetary clouds

NASA Technical Reports Server (NTRS)

Dimmick, R. L.; Chatigny, M. A.

1973-01-01

Current U.S. planetary quarantine standards based on international agreements require consideration of the probability of contamination (Pc) of the outer planets, Venus, Jupiter, Saturn, etc. One of the key parameters in estimation of the Pc of these planets is the probability of growth (Pg) of terrestrial microorganisms on or near these planets. For example, Jupiter and Saturn appear to have an atmosphere in which some microbial species could metabolize and propagate. This study includes investigation of the likelihood of metabolism and propagation of microbes suspended in dynamic atmospheres. It is directed toward providing experimental information needed to aid in rational estimation of Pg for these outer plants.

Static current-sheet models of quiescent prominences

NASA Technical Reports Server (NTRS)

Wu, F.; Low, B. C.

1986-01-01

A particular class of theoretical models idealize the prominence to be a discrete flat electric-current sheet suspended vertically in a potential magnetic field. The weight of the prominence is supported by the Lorentz force in the current sheet. These models can be extended to have curved electric-current sheets and to vary three-dimensionally. The equation for force balance is 1 over 4 pi (del times B) times Bdel p- p9 z=zero. Using Cartesian coordinates we take, for simplicity, a uniform gravity with constant acceleration g in the direction -z. If we are interested not in the detailed internal structure of the prominence, but in the global magnetic configuration around the prominence, we may take prominence plasma to be cold. Consideration is given to how such equilibrium states can be constructed. To simplify the mathematical problem, suppose there is no electric current in the atmosphere except for the discrete currents in the cold prominence sheet. Let us take the plane z =0 to be the base of the atmosphere and restrict our attention to the domain z greater than 0. The task we have is to solve for a magnetic field which is everywhere potential except on some free surface S, subject to suit able to boundary conditions. The surface S is determined by requiring that it possesses a discrete electric current density such that the Lorentz force on it is everywhere vertically upward to balance the weight of the material m(S). Since the magnetic field is potential in the external atmosphere, the latter is decoupled from the magnetic field and its plane parallel hydrostatic pressure and density can be prescribed.

Static current-sheet models of quiescent prominences

NASA Astrophysics Data System (ADS)

Wu, F.; Low, B. C.

1986-12-01

A particular class of theoretical models idealize the prominence to be a discrete flat electric-current sheet suspended vertically in a potential magnetic field. The weight of the prominence is supported by the Lorentz force in the current sheet. These models can be extended to have curved electric-current sheets and to vary three-dimensionally. The equation for force balance is 1 over 4 pi (del times B) times Bdel p- p9 z=zero. Using Cartesian coordinates we take, for simplicity, a uniform gravity with constant acceleration g in the direction -z. If we are interested not in the detailed internal structure of the prominence, but in the global magnetic configuration around the prominence, we may take prominence plasma to be cold. Consideration is given to how such equilibrium states can be constructed. To simplify the mathematical problem, suppose there is no electric current in the atmosphere except for the discrete currents in the cold prominence sheet. Let us take the plane z =0 to be the base of the atmosphere and restrict our attention to the domain z greater than 0. The task we have is to solve for a magnetic field which is everywhere potential except on some free surface S, subject to suit able to boundary conditions. The surface S is determined by requiring that it possesses a discrete electric current density such that the Lorentz force on it is everywhere vertically upward to balance the weight of the material m(S). Since the magnetic field is potential in the external atmosphere, the latter is decoupled from the magnetic field and its plane parallel hydrostatic pressure and density can be prescribed.

Direct EPP Affects on the Middle Atmosphere

NASA Technical Reports Server (NTRS)

Jackman, Charles H.

2011-01-01

Energetic precipitating particles (EPPs) can cause significant direct constituent changes in the mesosphere and stratosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The HOx increases result in direct ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. The NOx family has a considerably longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone directly, if produced in the stratosphere. Ozone decreases from the EPPs lead to a reduction in atmospheric heating and, subsequent atmospheric cooling. Conversely, EPPs can cause direct atmospheric heating through Joule heating. Measured HOx constituents OH and HO2 showed increases due to solar protons. Observed NOx constituents NO and NO2 were enhanced due to both solar protons and precipitating electrons. Other hydrogen- and nitrogen-ocntaining constituents were also measured to be directly influenced by EPPs, including N2O, HNO3, HO2NO2, N2OS, H2O2, ClONO2, HCl, and HOCl. Observed constituents ClO and CO were directly affected by EPPs as well. Many measurements indicated significant direct ozone decreases. A significant number of satellites housed instruments, which observed direct EPP-caused atmospheric effects, including Nimbus 4 (BUV), Nimbus 7 (SBUV), several NOAA platforms (SBUV/2), SME, UARS (HALOE, CLAES), SCISAT-1 (ACE-FTS), Odin (OSIRIS), Envisat-l (GOMOS, MIPAS, SCIAMACHY), and Aura (MLS). Measurements by rockets and ground-based radar also indicated EPP direct impacts. Atmospheric models have been used with some success in predicting the direct EPP impacts on the mesosphere and stratosphere. A review of the observed direct effects of EPP on the middle atmosphere will be given in this presentation.

Cross-Scale Observational Signatures of Magnetic Reconnection

NASA Technical Reports Server (NTRS)

Savage, Sabrina; Malaspina, David

2014-01-01

Magnetic reconnection is a significant mechanism for energy release across many astrophysical applications. In the solar atmosphere, reconnection is considered a primary contributor of flare evolution and coronal heating. Directly observing reconnection occurring in the solar atmosphere, however, is not trivial considering that the scale size of the diffusion region is magnitudes smaller than the observational capabilities of current instrumentation, and coronal magnetic field measurements are not currently sufficient to capture the process. Meanwhile, reconnection occurring in the Earth's magnetosphere transfers energy from the solar wind through a comparable process, although on vastly different scales. Magnetospheric measurements are made in situ rather than remotely; ergo, comparison of observations between the two regimes allows for potentially significant insight into reconnection as a stochastic and possibly turbulent process. We will present a set of observations from long-duration solar events and compare them to in situ measurements from the magnetosphere.

Phenomena of oscillations in atmospheric pressure direct current glow discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Fu-cheng; Yan, Wen; Wang, De-zhen

2013-12-15

Self-sustained oscillations in a dc glow discharge with a semiconductor layer at atmospheric pressure were investigated by means of a one-dimensional fluid model. It is found that the dc glow discharge initially becomes unstable in the subnormal glow region and gives rise to oscillations of plasma parameters. A variety of oscillations with one or more frequencies have been observed under different conditions. The discharge oscillates between the glow discharge mode and the Townsend discharge mode in the oscillations with large amplitude while operates in the subnormal glow discharge mode all the while in the oscillations with small amplitude. Fourier Transformmore » spectra of oscillations reveal the transition mechanism between different oscillations. The effects of semiconductor conductivity on the oscillation frequency of the dominant mode, gas voltage, as well as the discharge current have also been analyzed.« less

Cross-scale Observational Signatures of Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Savage, S. L.; Malaspina, D.

2014-12-01

Magnetic reconnection is a significant mechanism for energy release across many astrophysical applications. In the solar atmosphere, reconnection is considered a primary contributor of flare evolution and coronal heating. Directly observing reconnection occurring in the solar atmosphere, however, is not trivial considering that the scale size of the diffusion region is magnitudes smaller than the observational capabilities of current instrumentation, and coronal magnetic field measurements are not currently sufficient to capture the process. Meanwhile, reconnection occurring in the Earth's magnetosphere transfers energy from the solar wind through a comparable process, although on vastly different scales. Magnetospheric measurements are made in situ rather than remotely; ergo, comparison of observations between the two regimes allows for potentially significant insight into reconnection as a stochastic and possibly turbulent process. We will present a set of observations from long-duration solar events and compare them to in situ measurements from the magnetosphere.

The Effect of the Leeuwin Current on Offshore Surface Gravity Waves in Southwest Western Australia

NASA Astrophysics Data System (ADS)

Wandres, Moritz; Wijeratne, E. M. S.; Cosoli, Simone; Pattiaratchi, Charitha

2017-11-01

The knowledge of regional wave regimes is critical for coastal zone planning, protection, and management. In this study, the influence of the offshore current regime on surface gravity waves on the southwest Western Australian (SWWA) continental shelf was examined. This was achieved by coupling the three dimensional, free surface, terrain-following hydrodynamic Regional Ocean Modelling System (ROMS) and the third generation wave model Simulating WAves Nearshore (SWAN) using the Coupled Ocean-Atmosphere-WaveSediment Transport (COAWST) model. Different representative states of the Leeuwin Current (LC), a strong pole-ward flowing boundary current with a persistent eddy field along the SWWA shelf edge were simulated and used to investigate their influence on different large wave events. The coupled wave-current simulations were compared to wave only simulations, which represented scenarios in the absence of a background current field. Results showed that the LC and the eddy field significantly impact SWWA waves. Significant wave heights increased (decreased) when currents were opposing (aligning with) the incoming wave directions. During a fully developed LC system significant wave heights were altered by up to ±25% and wave directions by up to ±20°. The change in wave direction indicates that the LC may modify nearshore wave dynamics and consequently alter sediment patterns. Operational regional wave forecasts and hindcasts may give flawed predictions if wave-current interaction is not properly accounted for.

Elevated atmospheric CO2 negatively impacts photosynthesis through radiative forcing and physiology-mediated climate feedback

NASA Astrophysics Data System (ADS)

Zhu, Peng; Zhuang, Qianlai; Ciais, Philippe; Welp, Lisa; Li, Wenyu; Xin, Qinchuan

2017-02-01

Increasing atmospheric CO2 affects photosynthesis involving directly increasing leaf carboxylation rates, stomatal closure, and climatic effects. The direct effects are generally thought to be positive leading to increased photosynthesis, while its climatic effects can be regionally positive or negative. These effects are usually considered to be independent from each other, but they are in fact coupled through interactions between land surface exchanges of gases and heat and the physical climate system. In particular, stomatal closure reduces evapotranspiration and increases sensible heat emissions from ecosystems, leading to decreased atmospheric moisture and precipitation and local warming. We use a coupled earth system model to attribute the influence of the increase in CO2 on gross primary productivity (GPP) during the period of 1930-2011. In our model, CO2 radiative effects cause climate change that has only a negligible effect on global GPP (a reduction of 0.9 ± 2% during the last 80 years) because of opposite responses between tropical and northern biomes. On the other hand, CO2 physiological effects on GPP are both positive, by increased carboxylation rates and water use efficiency (7.1 ± 0.48% increase), and negative, by vegetation-climate feedback reducing precipitation, as a consequence of decreased transpiration and increased sensible heat in areas without water limitation (2.7 ± 1.76% reduction).When considering the coupled atmosphere-vegetation system, negative climate feedback on photosynthesis and plant growth due to the current level of CO2 opposes 29-38% of the gains from direct fertilization effects.

Kinetics of OH + CO reaction under atmospheric conditions

NASA Technical Reports Server (NTRS)

Hynes, A. J.; Wine, P. H.; Ravishankara, A. R.

1986-01-01

A pulsed laser photolysis-pulsed laser-induced fluorescence technique is used to directly measure the temperature, pressure, and H2O concentration dependence on k1 in air. K1 is found to increase linearly with increasing pressure at pressures of not greater than 1 atm, and the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. The rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are shown to be the same at 262 K as at 299 K. The present results significantly reduce the current atmospheric model uncertainties in the temperature dependence under atmospheric conditions, in the third body efficiency of O2, and in the effect of water vapor on k1.

Challenges in tracing the fate and effects of atmospheric polycyclic aromatic hydrocarbon deposition in vascular plants.

PubMed

Desalme, Dorine; Binet, Philippe; Chiapusio, Geneviève

2013-05-07

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants that raise environmental concerns because of their toxicity. Their accumulation in vascular plants conditions harmful consequences to human health because of their position in the food chain. Consequently, understanding how atmospheric PAHs are taken up in plant tissues is crucial for risk assessment. In this review we synthesize current knowledge about PAH atmospheric deposition, accumulation in both gymnosperms and angiosperms, mechanisms of transfer, and ecological and physiological effects. PAHs emitted in the atmosphere partition between gas and particulate phases and undergo atmospheric deposition on shoots and soil. Most PAH concentration data from vascular plant leaves suggest that contamination occurs by both direct (air-leaf) and indirect (air-soil-root) pathways. Experimental studies demonstrate that PAHs affect plant growth, interfering with plant carbon allocation and root symbioses. Photosynthesis remains the most studied physiological process affected by PAHs. Among scientific challenges, identifying specific physiological transfer mechanisms and improving the understanding of plant-symbiont interactions in relation to PAH pollution remain pivotal for both fundamental and applied environmental sciences.

Radio scintillations observed during atmospheric occultations of Voyager: Internal gravity waves at Titan and magnetic field orientations at Jupiter and Saturn. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1983-01-01

The refractive index of planetary atmospheres at microwave frequencies is discussed. Physical models proposed for the refractive irregularities in the ionosphere and neutral atmosphere serve to characterize the atmospheric scattering structures, and are used subsequently to compute theoretical scintillation spectra for comparison with the Voyager occultation measurements. A technique for systematically analyzing and interpreting the signal fluctuations observed during planetary occultations is presented and applied to process the dual-wavelength data from the Voyager radio occultations by Jupiter, Saturn, and Titan. Results concerning the plasma irregularities in the upper ionospheres of Jupiter and Saturn are reported. The measured orientation of the irregularities is used to infer the magnetic field direction at several locations in the ionospheres of these two planets; the occultation measurements conflict with the predictions of Jovian magnetic field models, but generally confirm current models of Saturn's field. Wave parameters, including the vertical fluxes of energy and momentum, are estimated, and the source of the internal gravity waves discovered in Titan's upper atmosphere is considered.

Atmospheric bioaerosols originating from Adélie penguins (Pygoscelis adeliae): Ecological observations of airborne bacteria at Hukuro Cove, Langhovde, Antarctica

NASA Astrophysics Data System (ADS)

Kobayashi, Fumihisa; Maki, Teruya; Kakikawa, Makiko; Noda, Takuji; Mitamura, Hiromichi; Takahashi, Akinori; Imura, Satoshi; Iwasaka, Yasunobu

2016-03-01

The relationship between atmospheric bioaerosols and ecosystems is currently of global importance. Antarctica has an extreme climate, meaning that ecosystem behavior in this region is relatively simple. Direct sampling of atmospheric bioaerosols was performed at an Adélie penguin (Pygoscelis adeliae) colony at Hukuro Cove, Langhovde, Antarctica on 22 January 2013. The aim of the sampling was to reveal the effect of the penguins on the Antarctic ecosystem within the atmospheric bioaerosols. Samples were bio-analyzed using a next-generation sequencing method. Biomass concentrations of Bacilli-class bacteria were 19.4 times higher when sampled leeward of the penguin colony compared with windward sampling. The source of these bacteria was the feces of the penguins. Predicted atmospheric trajectories indicate that the bacteria disperse towards the Southern Ocean. The largest biomass concentration in the windward bacteria was of the Gammaproteobacteria class, which decreased markedly with distance through the penguin colony, being deposited on soil, surface water, and ocean. It is concluded that bioaerosols and ecosystems near the penguin colony strongly influence each other.

Photochemistry, Ion Chemistry, and Haze Formation in Pluto’s Atmosphere

NASA Astrophysics Data System (ADS)

Summers, Michael E.; Stern, S. A.; Gladstone, G. Randal; Young, Leslie A.; Olkin, C. B.; Weaver, H. A.; Cheng, A. F.; Strobel, D. F.; Ennico, K. A.; Kammer, J. A.; Parker, A. H.; Retherford, K. D.; Schindhelm, E.; Singer, K. N.; Steffl, A. J.; Tsang, C. C.; Versteeg, M. H.; Greathouse, T. K.; Linscott, I. R.; Tyler, L. G.; Woods, W. W.; Hinson, D. P.; Parker, J. W.; Renaud, J. P.; Ewell, M.; Lisse, Cary M.

2015-11-01

The detection of ethylene (C2H4) and acetylene (C2H2) in Pluto’s atmosphere provides important ground-truth observations for validating photochemical models of Pluto’s atmosphere. Their detection also confirms the production of precursor chemical compounds involved in the formation of tholins, which are thought to give Pluto’s surface its reddish color. Photochemical models predict many other hydrocarbon and nitrile products, currently undetected, which may also be participants in tholin production on Pluto’s surface or on atmospheric haze particles. The observed atmospheric haze layer extending to altitudes of ~140 km above Pluto’s surface, suggests a global and very robust process of atmospheric particle nucleation, growth, and sedimentation onto Pluto’s surface. The high altitude extent of the haze layer suggests that the nucleation process begins above the expected altitude range where hydrocarbons become supersaturated (below ~30 km altitude). This situation may be analogous to that in Titan’s atmosphere, wherein nucleation and aerosol growth is directly related to large negative ion production. In the case of Pluto, this means that nucleation may occur at altitudes as high as 1200 km altitude where ionization in Pluto’s atmosphere peaks. In this paper we discuss these processes and their implications for haze formation in Pluto’s atmosphere and its deposition onto Pluto’s surface. This work was supported by NASA's New Horizons project.

The development of the time dependence of the nuclear EMP electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eng, C

The nuclear electromagnetic pulse (EMP) electric field calculated with the legacy code CHAP is compared with the field given by an integral solution of Maxwell's equations, also known as the Jefimenko equation, to aid our current understanding on the factors that affect the time dependence of the EMP. For a fair comparison the CHAP current density is used as a source in the Jefimenko equation. At first, the comparison is simplified by neglecting the conduction current and replacing the standard atmosphere with a constant density air slab. The simplicity of the resultant current density aids in determining the factors thatmore » affect the rise, peak and tail of the EMP electric field versus time. The three dimensional nature of the radiating source, i.e. sources off the line-of-sight, and the time dependence of the derivative of the current density with respect to time are found to play significant roles in shaping the EMP electric field time dependence. These results are found to hold even when the conduction current and the standard atmosphere are properly accounted for. Comparison of the CHAP electric field with the Jefimenko electric field offers a direct validation of the high-frequency/outgoing wave approximation.« less

A Review of Atmospheric Ozone and Current Thinking on the Antarctic Ozone Hole.

DTIC Science & Technology

1987-01-01

UNIVERSITY OF CALIFORNIA 0 A Review of Atmospheric ozone and Current Thinking on the Antartic Ozone Hole A thesis submitted in partial satisfaction of the...4. TI TLE (Pit 5,1tlfie) S. TYPE OF REPORT & PFRIOO COVERED A Review of Atmospheric Ozone and Current THESIS/DA/;J.At1AAU00 Thinking on the Antartic ...THESIS A Review of Atmospheric Ozone and Current Thinking on the Antartic Ozone Hole by Randolph Antoine Fix Master of Science in Atmospheric Science

Photochemical Formation of Aerosol in Planetary Atmospheres: Photon and Water Mediated Chemistry of SO_2

NASA Astrophysics Data System (ADS)

Kroll, Jay A.; Donaldson, D. J.; Vaida, Veronica

2016-06-01

Sulfur compounds have been observed in a number of planetary atmospheres throughout our solar system. Our current understanding of sulfur chemistry explains much of what we observe in Earth's atmosphere. However, several discrepancies between modeling and observations of the Venusian atmosphere show there are still problems in our fundamental understanding of sulfur chemistry. This is of particular concern due to the important role sulfur compounds play in the formation of aerosols, which have a direct impact on planetary climates, including Earth's. We investigate the role of water complexes in the hydration of sulfur oxides and dehydration of sulfur acids and will present spectroscopic studies to document such effects. I will present recent work investigating mixtures of SO_2 and water that generate large quantities of aerosol when irradiated with solar UV light, even in the absence of traditional OH chemistry. I will discuss a proposed mechanism for the formation of sulfurous acid (H_2SO_3) and present recent experimental work that supports this proposed mechanism. Additionally, the implications that photon-induced hydration of SO_2 has for aerosol formation in the atmosphere of earth as well as other planetary atmospheres will be discussed.

Changes in atmospheric aerosol loading retrieved from space based measurements during the past decade

NASA Astrophysics Data System (ADS)

Yoon, J.; Burrows, J. P.; Vountas, M.; von Hoyningen-Huene, W.; Chang, D. Y.; Richter, A.; Hilboll, A.

2013-10-01

Atmospheric aerosol, generated from natural and anthropogenic sources, plays a key role in regulating visibility, air quality, and acid deposition. It is directly linked to and impacts on human health. It also reflects and absorbs incoming solar radiation and thereby influences the climate change. The cooling by aerosols is now recognized to have partly masked the atmospheric warming from fossil fuel combustion emissions. The role and potential management of short-lived climate pollutants such as aerosol are currently a topic of much scientific and public debate. Our limited knowledge of atmospheric aerosol and its influence on the Earth's radiation balance has a significant impact on the accuracy and error of current predictions of the future global climate change. In the past decades, environmental legislation in industrialized countries has begun to limit the release of anthropogenic pollutants. In contrast, in Asia as a result of the recent rapid economic development, emissions from industry and traffic have increased dramatically. In this study, the temporal changes/trends of atmospheric aerosols, derived from the satellite instruments MODIS (on board Terra and Aqua), MISR (Terra), and SeaWiFS (OrbView-2) during the past decade, are investigated. Whilst the aerosol optical thickness, AOT, over Western Europe decreases (i.e. by up to about -40% from 2003 to 2008) and parts of North America, a statistically significant increase (about +34% in the same period) over East China is observed and attributed to both the increase in industrial output and the Asian desert dust.

Theory of Radiation Transfer in Neutron Star Atmospheres

NASA Technical Reports Server (NTRS)

Zavlin, Vyacheslav

2006-01-01

The possibility for direct investigation of thermal emission from isolated neutron stars opened about a quarter of century ago with the launch of the first X-ray observatories Einstein and EXOSAT stimulated developing models of the neutron star surface radiation which began at the end of 80's. Confronting observational data with theoretical models of thermal emission allows one to infer the surface temperatures, magnetic fields, chemical composition, and neutron star masses and radii. This information, supplemented with the model equations of state and neutron star cooling models, provides an opportunity to understand the fundamental properties of the superdense matter in the stars' interiors. Almost all available models are based on the assumption that thermal radiation emitted by a neutron star is formed in the superficial star's layers--atmosphere. The neutron star atmospheres are very different from those of usual stars due to the immense gravity and huge magnetic fields. In this presentation we review the current status of the neutron star atmosphere modeling, present most important results, discuss problems and possible future developments.

Indirect chemical effects of methane on climate warming

NASA Astrophysics Data System (ADS)

Lelieveld, Jos; Crutzen, Paul J.

1992-01-01

METHANE concentrations in the atmosphere have increased from about 0.75 to 1.7 p.p.m.v. since pre-industrial times1,2. The current annual rate of increase of about 0.8% yr-1 (ref. 2) is due to increases in industrial and agricultural emissions. This increase in atmospheric methane concentrations not only influences the climate directly, but also indirectly through chemical reactions. Here we show that the climate effects of methane's atmospheric chemistry have previously been overestimated, notably by the Inter-governmental Panel on Climate Change (IPCC)3, largely owing to neglect of the height dependence of certain atmospheric radiative processes. Using available estimates of fossil-fuel-related leaks of methane, our results show that switching from coal and oil to natural gas as an energy source would reduce climate warming. A significant fraction of methane emissions cannot, however, be accounted for by known sources; should leakages from gas production and distribution be underestimated for some countries, then it might be unwise to switch to using natural gas.

Reducing the cost of Ca-based direct air capture of CO2.

PubMed

Zeman, Frank

2014-10-07

Direct air capture, the chemical removal of CO2 directly from the atmosphere, may play a role in mitigating future climate risk or form the basis of a sustainable transportation infrastructure. The current discussion is centered on the estimated cost of the technology and its link to "overshoot" trajectories, where atmospheric CO2 levels are actively reduced later in the century. The American Physical Society (APS) published a report, later updated, estimating the cost of a one million tonne CO2 per year air capture facility constructed today that highlights several fundamental concepts of chemical air capture. These fundamentals are viewed through the lens of a chemical process that cycles between removing CO2 from the air and releasing the absorbed CO2 in concentrated form. This work builds on the APS report to investigate the effect of modifications to the air capture system based on suggestions in the report and subsequent publications. The work shows that reduced carbon electricity and plastic packing materials (for the contactor) may have significant effects on the overall price, reducing the APS estimate from $610 to $309/tCO2 avoided. Such a reduction does not challenge postcombustion capture from point sources, estimated at $80/tCO2, but does make air capture a feasible alternative for the transportation sector and a potential negative emissions technology. Furthermore, air capture represents atmospheric reductions rather than simply avoided emissions.

Assimilation for skin SST in the NASA GEOS atmospheric data assimilation system.

PubMed

Akella, Santha; Todling, Ricardo; Suarez, Max

2017-01-01

The present article describes the sea surface temperature (SST) developments implemented in the Goddard Earth Observing System, Version 5 (GEOS-5) Atmospheric Data Assimilation System (ADAS). These are enhancements that contribute to the development of an atmosphere-ocean coupled data assimilation system using GEOS. In the current quasi-operational GEOS-ADAS, the SST is a boundary condition prescribed based on the OSTIA product, therefore SST and skin SST (Ts) are identical. This work modifies the GEOS-ADAS Ts by modeling and assimilating near sea surface sensitive satellite infrared (IR) observations. The atmosphere-ocean interface layer of the GEOS atmospheric general circulation model (AGCM) is updated to include near surface diurnal warming and cool-skin effects. The GEOS analysis system is also updated to directly assimilate SST-relevant Advanced Very High Resolution Radiometer (AVHRR) radiance observations. Data assimilation experiments designed to evaluate the Ts modification in GEOS-ADAS show improvements in the assimilation of radiance observations that extends beyond the thermal IR bands of AVHRR. In particular, many channels of hyperspectral sensors, such as those of the Atmospheric Infrared Sounder (AIRS), and Infrared Atmospheric Sounding Interferometer (IASI) are also better assimilated. We also obtained improved fit to withheld, in-situ buoy measurement of near-surface SST. Evaluation of forecast skill scores show marginal to neutral benefit from the modified Ts.

Assimilation for Skin SST in the NASA GEOS Atmospheric Data Assimilation System

NASA Technical Reports Server (NTRS)

Akella, Santha; Todling, Ricardo; Suarez, Max

2017-01-01

The present article describes the sea surface temperature (SST) developments implemented in the Goddard Earth Observing System, Version 5 (GEOS) Atmospheric Data Assimilation System (ADAS). These are enhancements that contribute to the development of an atmosphere-ocean coupled data assimilation system using GEOS. In the current quasi-operational GEOS-ADAS, the SST is a boundary condition prescribed based on the OSTIA product, therefore SST and skin SST (Ts) are identical. This work modifies the GEOS-ADAS Ts by modelling and assimilating near sea surface sensitive satellite infrared (IR) observations. The atmosphere-ocean interface layer of the GEOS atmospheric general circulation model (AGCM) is updated to include near-surface diurnal warming and cool-skin effects. The GEOS analysis system is also updated to directly assimilate SST-relevant Advanced Very High Resolution Radiometer (AVHRR) radiance observations. Data assimilation experiments designed to evaluate the Ts modification in GEOS-ADAS show improvements in the assimilation of radiance observations that extend beyond the thermal infrared bands of AVHRR. In particular, many channels of hyperspectral sensors, such as those of the Atmospheric Infrared Sounder (AIRS), and Infrared Atmospheric Sounding Interferometer (IASI) are also better assimilated. We also obtained improved fit to withheld insitu buoy measurement of near-surface SST. Evaluation of forecast skill scores show neutral to marginal benefit from the modified Ts.

First in situ evidence of wakes in the far field behind offshore wind farms.

PubMed

Platis, Andreas; Siedersleben, Simon K; Bange, Jens; Lampert, Astrid; Bärfuss, Konrad; Hankers, Rudolf; Cañadillas, Beatriz; Foreman, Richard; Schulz-Stellenfleth, Johannes; Djath, Bughsin; Neumann, Thomas; Emeis, Stefan

2018-02-01

More than 12 GW of offshore wind turbines are currently in operation in European waters. To optimise the use of the marine areas, wind farms are typically clustered in units of several hundred turbines. Understanding wakes of wind farms, which is the region of momentum and energy deficit downwind, is important for optimising the wind farm layouts and operation to minimize costs. While in most weather situations (unstable atmospheric stratification), the wakes of wind turbines are only a local effect within the wind farm, satellite imagery reveals wind-farm wakes to be several tens of kilometres in length under certain conditions (stable atmospheric stratification), which is also predicted by numerical models. The first direct in situ measurements of the existence and shape of large wind farm wakes by a specially equipped research aircraft in 2016 and 2017 confirm wake lengths of more than tens of kilometres under stable atmospheric conditions, with maximum wind speed deficits of 40%, and enhanced turbulence. These measurements were the first step in a large research project to describe and understand the physics of large offshore wakes using direct measurements, together with the assessment of satellite imagery and models.

Definition and preliminary design of the LAWS (Laser Atmospheric Wind Sounder), volume 2, phase 2

NASA Technical Reports Server (NTRS)

1992-01-01

Accurate knowledge of winds is critical to our understanding of the earth's climate and to our ability to predict climate change. Winds are a fundamental component of highly nonlinear interactions between oceans, land surfaces, and the atmosphere. Interactions at these interfaces are the focus of much climate change research. Although wind information is critical for advancing our understanding, currently most of our description of atmospheric motion is obtained indirectly - i.e., derived from observations of temperature and moisture through geostrophic relationships. Direct measurement of winds over the globe is limited to land-based rawinsonde surface stations and a few ship/aircraft reports. Cloud track winds using satellite imagery are calculated but must be used with great care. The LAWS mission objective, therefore, is to provide diurnal and global direct observations of winds - an observation that will incrementally enhance our knowledge of the earth's climate and physical processes responsible for its change. This document is Volume 2 of the LAWS Phase 2 Final Study Report and describes the definition and preliminary design of the LAWS instrument, together with details of the laser breadboard program conducted during the last 18 months of the program.

Design of a perfluorocarbon tracer based monitoring network to support monitoring verification and accounting of sequestered CO2

NASA Astrophysics Data System (ADS)

Watson, T.; Sullivan, T.

2013-05-01

The levels of CO2 in the atmosphere have been growing since the beginning of the industrial revolution. The current level is 391 ppm. If there are no efforts to mitigate CO2 emissions, the levels will rise to 750 ppm by 2100. Geologic carbon sequestration is one strategy that may be used to begin to reduce emissions. Sequestration will not be effective unless reservoir leak rates are significantly less than 1%. There must be rigorous monitoring protocols in place to ensure sequestration projects meet regulatory and environmental goals. Monitoring for CO2 leakage directly is difficult because of the large background levels and variability of CO2 in the atmosphere. Using tracers to tag the sequestered CO2 can mitigate some of the difficulties of direct measurement but a tracer monitoring network and the levels of tagging need to be carefully designed. Simple diffusion and dispersion models are used to predict the surface and atmospheric concentrations that would be seen by a network monitoring a sequestration site. Levels of tracer necessary to detect leaks from 0.01 to 1% are presented and suggestions for effective monitoring and protection of global tracer utility are presented.

Examining Model Atmospheric Particles Inside and Out

NASA Astrophysics Data System (ADS)

Wingen, L. M.; Zhao, Y.; Fairhurst, M. C.; Perraud, V. M.; Ezell, M. J.; Finlayson-Pitts, B. J.

2017-12-01

Atmospheric particles scatter incoming solar radiation and act as cloud condensation nuclei (CCN), thereby directly and indirectly affecting the earth's radiative balance and reducing visibility. These atmospheric particles may not be uniform in composition. Differences in the composition of a particle's outer surface from its core can arise during particle growth, (photo)chemical aging, and exchange of species with the gas phase. The nature of the surface on a molecular level is expected to impact growth mechanisms as well as their ability to act as CCN. Model laboratory particle systems are explored using direct analysis in real time-mass spectrometry (DART-MS), which is sensitive to surface composition, and contrasted with average composition measurements using high resolution, time-of-flight aerosol mass spectrometry (HR-ToF-AMS). Results include studies of the heterogeneous reactions of amines with solid dicarboxylic acid particles, which are shown to generate aminium dicarboxylate salts at the particle surface, leaving an unreacted core. Combination of both mass spectrometric techniques reveals a trend in reactivity of C3-C7 dicarboxylic acids with amines and allows calculation of the DART probe depth into the particles. The results of studies on additional model systems that are currently being explored will also be reported.

Looking at Earth from space: Direct readout from environmental satellites

NASA Technical Reports Server (NTRS)

1994-01-01

Direct readout is the capability to acquire information directly from meteorological satellites. Data can be acquired from NASA-developed, National Oceanic and Atmospheric Administration (NOAA)-operated satellites, as well as from other nations' meteorological satellites. By setting up a personal computer-based ground (Earth) station to receive satellite signals, direct readout may be obtained. The electronic satellite signals are displayed as images on the computer screen. The images can display gradients of the Earth's topography and temperature, cloud formations, the flow and direction of winds and water currents, the formation of hurricanes, the occurrence of an eclipse, and a view of Earth's geography. Both visible and infrared images can be obtained. This booklet introduces the satellite systems, ground station configuration, and computer requirements involved in direct readout. Also included are lists of associated resources and vendors.

Regional aerosol radiative and hydrological effects over the mid-Atlantic corridor

NASA Astrophysics Data System (ADS)

Creekmore, Torreon N.

A thorough assessment of direct, indirect, and semi-direct influences of aerosols on Earth's energy budget is required to better understand climate and estimate how it may change in the future. Clear-sky surface broadband (measured and modeled) irradiance, spectral aerosol optical depth, heating rate profiles, and non-radiative flux measurements were conducted at a state-of-the-art site, developed by the NOAA-Howard University Center for Atmospheric Sciences (NCAS) program, providing a best estimate of aerosol radiative atmosphere-surface interactions. Methods developed by the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program were applied to: (1) temporally quantify regional aerosol forcing, (2) to derive an empirical equation describing a relationship between aerosol optical depth and normalized diffuse ratio, (3) evaluate aerosol impacts on atmospheric heating, and (4) evaluate how aerosol forcing impacts may possibly reduce latent and sensible fluxes. Measurements were obtained during the period of May--September for the years of 2005, 2006, and 2007. Atmospheric aerosols are among the key uncertainties affecting the Earth's climate and atmospheric radiative processes. Present-day increases in aerosol concentrations directly, indirectly, and semi-directly impact the Earth's energy budget (i.e., cooling the surface and heating the atmosphere), thereby contributing to climate change. The Howard University Beltsville Site (HUBS) has experienced a greater loss in mean normalized aerosol radiative forcing with time, as observations show a decrease from --0.9 in 2005 to --3.1 and --3.4 W/m2 for 2006 and 2007 respectively, in mean net surface irradiance. The mean normalized aerosol radiative forcing estimated for the period considered was --2.5 W/m2. The reduction in surface solar insolation is due to increased scattering and absorption related to increased aerosol burdens v for the period, promoting surface cooling and atmospheric heating. Calculation of radiative flux and heating rates profiles, which are constrained by HUBS observations, were performed by the 1-D Fu-Liou radiative transfer model to investigate the effect of polluted and pristine aerosol conditions on the surface energy budget and hydrological cycle. For HUBS the surface forcing (--14.2 W/m2) and atmospheric forcing (9.9 W/m2) were significantly larger than the TOA (--4.3 W/m2) radiative forcing. Associated aerosol heating, as well as reduced surface insolation, may lead to increasing near surface static stability, and reduced vertical transport of moisture into the atmospheric boundary layer, and over time, a possible spin-down of the hydrological cycle. It is shown that HUBS provides an ideal opportunity for improving measurements and datasets, thus allowing for both the study and understanding of aerosol impacts on the climate system. Further, results show that in order to provide reference quality data and constrain aerosol radiative effects over land, ground-based research sites must conform to HUBS standards of: (1) instrumentation (e.g. passive and active sensors); (2) operational protocols (e.g. calibration and routine cleaning); (3) rigorous cloud screening protocols; and (4) incorporation of ARM QC and modified FFA algorithms. HUBS surface measurements provides the reference quality data necessary and capability required to help enhance measurements and constrain current uncertainties in estimates of aerosol direct effects over land. Incorporating a combined technique of both active and passive instruments reduced the direct radiative forcing estimates by ˜82 W/m2. The analysis of aerosol effects over HUBS helps continue in bridging the gap of applying measurements for improvement of climate simulations by generating observational products, which describes aerosol and radiation field characteristics in detail.

Resolving vorticity-driven lateral fire spread using the WRF-Fire coupled atmosphere-fire numerical model

NASA Astrophysics Data System (ADS)

Simpson, C. C.; Sharples, J. J.; Evans, J. P.

2014-05-01

Fire channelling is a form of dynamic fire behaviour, during which a wildland fire spreads rapidly across a steep lee-facing slope in a direction transverse to the background winds, and is often accompanied by a downwind extension of the active flaming region and extreme pyro-convection. Recent work using the WRF-Fire coupled atmosphere-fire model has demonstrated that fire channelling can be characterised as vorticity-driven lateral fire spread (VDLS). In this study, 16 simulations are conducted using WRF-Fire to examine the sensitivity of resolving VDLS to spatial resolution and atmosphere-fire coupling within the WRF-Fire model framework. The horizontal grid spacing is varied between 25 and 90 m, and the two-way atmosphere-fire coupling is either enabled or disabled. At high spatial resolution, the atmosphere-fire coupling increases the peak uphill and lateral spread rate by a factor of up to 2.7 and 9.5. The enhancement of the uphill and lateral spread rate diminishes at coarser spatial resolution, and VDLS is not modelled for a horizontal grid spacing of 90 m. The laterally spreading fire fronts become the dominant contributors of the extreme pyro-convection. The resolved fire-induced vortices responsible for driving the lateral spread in the coupled simulations have non-zero vorticity along each unit vector direction, and develop due to an interaction between the background winds and vertical return circulations generated at the flank of the fire front as part of the pyro-convective updraft. The results presented in this study demonstrate that both high spatial resolution and two-way atmosphere-fire coupling are required to reproduce VDLS within the current WRF-Fire model framework.

NASA LaRC Workshop on Guidance, Navigation, Controls, and Dynamics for Atmospheric Flight, 1993

NASA Technical Reports Server (NTRS)

Buttrill, Carey S. (Editor)

1993-01-01

This publication is a collection of materials presented at a NASA workshop on guidance, navigation, controls, and dynamics (GNC&D) for atmospheric flight. The workshop was held at the NASA Langley Research Center on March 18-19, 1993. The workshop presentations describe the status of current research in the GNC&D area at Langley over a broad spectrum of research branches. The workshop was organized in eight sessions: overviews, general, controls, military aircraft, dynamics, guidance, systems, and a panel discussion. A highlight of the workshop was the panel discussion which addressed the following issue: 'Direction of guidance, navigation, and controls research to ensure U.S. competitiveness and leadership in aerospace technologies.'

Planet-wide sand motion on mars

USGS Publications Warehouse

Bridges, N.T.; Bourke, M.C.; Geissler, P.E.; Banks, M.E.; Colon, C.; Diniega, S.; Golombek, M.P.; Hansen, C.J.; Mattson, S.; McEwen, A.S.; Mellon, M.T.; Stantzos, N.; Thomson, B.J.

2012-01-01

Prior to Mars Reconnaissance Orbiter data, images of Mars showed no direct evidence for dune and ripple motion. This was consistent with climate models and lander measurements indicating that winds of sufficient intensity to mobilize sand were rare in the low-density atmosphere. We show that many sand ripples and dunes across Mars exhibit movement of as much as a few meters per year, demonstrating that Martian sand migrates under current conditions in diverse areas of the planet. Most motion is probably driven by wind gusts that are not resolved in global circulation models. A past climate with a thicker atmosphere is only required to move large ripples that contain coarse grains. ?? 2012 Geological Society of America.

The Deuterium to Hydrogen Ratio in the Water that Formed the Yellowknife Bay Mudstones in Gale Crater

NASA Technical Reports Server (NTRS)

Mahaffy, Paul R.; Brunner, Anna E.; Webster, Chris R.; Atreya, Sushil K.; Mcadam, Amy Catherine; Stern, Jennifer Claire; Leshin, Laurie Ann; Navarro-Gonzales, Rafael; Jones, J.; Kashyap, Srishti

2014-01-01

A suite of isotope ratios of light elements in the present martian atmosphere (13C/12C, 15N/14N, 18O/16O, 38Ar/36Ar, and D/H) are all substantially enriched in the heavy element suggesting atmospheric loss to space over the past billions of years with preferential loss of the lighter isotope from each pair. In situ measurements from MSL's Sample Analysis at Mars (SAM) instrument [e.g. 1,2,3] have considerably refined previous measurements from the Viking mass spectrometers [e.g. 4], from remote spectroscopic observations [e.g. 5,6], and from martian meteorite studies [e.g. 7,8]. The persistence of habitable environments such as the ancient Yellowknife Bay lake recently revealed by measurements from the Curiosity rover [9] depends on the surface temperatures and the duration of an atmosphere thicker than that at present. Current and planned measurements from orbit with the Mars Express and MAVEN missions respectively intend to study the processes of atmospheric escape including solar wind interaction, sputtering, thermal escape, and dissociative recombination, and determine or refine the current rate of atmospheric loss caused by these and other mechanisms. The goal of these programs is to understand the physical processes sufficiently well so that robust extrapolations over the past billions of years can be made D/H is measured by both the Tunable Laser Spectrometer (TLS) and the Quadrupole Mass Spectrometer (QMS) of the SAM suite. to predict the atmospheric and surface conditions on early Mars. However, the study of the history of martian atmospheric evolution will be greatly facilitated if we are able to also directly measure the isotopic composition of volatiles captured in rocks that are representative of the ancient atmosphere. To date, D/H is one of the most promising candidates for this study since water is the most abundant volatile thermally released from the Yellowknife Bay phylosilicates discovered by the SAM and CheMin experiments of MSL and its

20 Years of Exoplanets: From Surveys Towards Characterization

NASA Astrophysics Data System (ADS)

Rauscher, Emily

2015-11-01

Twenty years ago the discovery of the first planet outside of our solar system ushered in a new subfield of exoplanet study. In the years since, the number of known planets has skyrocketed into the thousands, due to an ever-expanding pool of detection methods, projects and missions, and substantial improvements in technique. These remarkable discoveries have revealed an exoplanet population that is highly diverse, in many cases breaking expectations set by the single example of our own solar system, and providing us with the opportunity to study planets under a wide range of physical conditions. Equally as exciting as the increasing number of known exoplanets, within the last dozen years we have seen the move from exoplanet discovery to characterization we are currently able to measure atmospheric properties of many of the brightest exoplanets. We are now in an era where we can study the diversity of atmospheric conditions for dozens of exoplanets, including measurements of their temperatures, albedos, compositions, and in some cases even more detailed information about their two- or three-dimensional atmospheric structures and circulation patterns. In this talk I will review the current state of theory and observations, the lessons we have learned, and the questions and techniques that direct future work.

Fighting global warming by greenhouse gas removal: destroying atmospheric nitrous oxide thanks to synergies between two breakthrough technologies.

PubMed

Ming, Tingzhen; de Richter, Renaud; Shen, Sheng; Caillol, Sylvain

2016-04-01

Even if humans stop discharging CO2 into the atmosphere, the average global temperature will still increase during this century. A lot of research has been devoted to prevent and reduce the amount of carbon dioxide (CO2) emissions in the atmosphere, in order to mitigate the effects of climate change. Carbon capture and sequestration (CCS) is one of the technologies that might help to limit emissions. In complement, direct CO2 removal from the atmosphere has been proposed after the emissions have occurred. But, the removal of all the excess anthropogenic atmospheric CO2 will not be enough, due to the fact that CO2 outgases from the ocean as its solubility is dependent of its atmospheric partial pressure. Bringing back the Earth average surface temperature to pre-industrial levels would require the removal of all previously emitted CO2. Thus, the atmospheric removal of other greenhouse gases is necessary. This article proposes a combination of disrupting techniques to transform nitrous oxide (N2O), the third most important greenhouse gas (GHG) in terms of current radiative forcing, which is harmful for the ozone layer and possesses quite high global warming potential. Although several scientific publications cite "greenhouse gas removal," to our knowledge, it is the first time innovative solutions are proposed to effectively remove N2O or other GHGs from the atmosphere other than CO2.

New directions: Time for a new approach to modeling surface-atmosphere exchanges in air quality models?

NASA Astrophysics Data System (ADS)

Saylor, Rick D.; Hicks, Bruce B.

2016-03-01

Just as the exchange of heat, moisture and momentum between the Earth's surface and the atmosphere are critical components of meteorological and climate models, the surface-atmosphere exchange of many trace gases and aerosol particles is a vitally important process in air quality (AQ) models. Current state-of-the-art AQ models treat the emission and deposition of most gases and particles as separate model parameterizations, even though evidence has accumulated over time that the emission and deposition processes of many constituents are often two sides of the same coin, with the upward (emission) or downward (deposition) flux over a landscape depending on a range of environmental, seasonal and biological variables. In this note we argue that the time has come to integrate the treatment of these processes in AQ models to provide biological, physical and chemical consistency and improved predictions of trace gases and particles.

The Signature of Southern Hemisphere Atmospheric Circulation Patterns in Antarctic Precipitation

PubMed Central

Thompson, David W. J.; van den Broeke, Michiel R.

2017-01-01

Abstract We provide the first comprehensive analysis of the relationships between large‐scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four patterns of large‐scale Southern Hemisphere climate variability: the southern baroclinic annular mode, the southern annular mode, and the two Pacific‐South American teleconnection patterns. Variations in all four patterns influence the spatial configuration of precipitation over Antarctica, consistent with their signatures in high‐latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled‐climate models are able to reproduce all four patterns of atmospheric variability but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone. PMID:29398735

Rapid direct micromachining of PTFE using MeV ions in an oxygen rich atmosphere

NASA Astrophysics Data System (ADS)

Grime, G. W.; Sofield, C. J.; Gomez-Morilla, I.; Gwilliam, R.; Ynsa, M. D.; Enguita, O.

2005-04-01

We have investigated the mechanism of high rate erosion which is observed when polytetrafluoroethylene (PTFE) is exposed to MeV protons in an oxygen rich atmosphere (e.g. air). Using currents of the order of nA, it is possible to create holes with depths of millimetres and diameter defined by the beam area on the surface with exposure times of minutes. This is not observed in atmospheres of nitrogen, helium or argon nor in vacuum. We propose that the erosion is a result of the formation of a stable gaseous compound following beam induced decomposition of the PTFE (possibly an acyl fluoride) which does not re-deposit in the hole. We present the results of experiments leading to this hypothesis and propose a method for fabricating three-dimensional structures in PTFE with micrometre feature size. This process is the subject of an international patent application.

New particle formation in China: Current knowledge and further directions.

PubMed

Wang, Zhibin; Wu, Zhijun; Yue, Dingli; Shang, Dongjie; Guo, Song; Sun, Junying; Ding, Aijun; Wang, Lin; Jiang, Jingkun; Guo, Hai; Gao, Jian; Cheung, Hing Cho; Morawska, Lidia; Keywood, Melita; Hu, Min

2017-01-15

New particle formation (NPF) studies have been conducted in China since 2004. Formation of new atmospheric aerosol particles has been observed to take place in diverse environments, even under the circumstances of high pre-existing particle loading, challenging the traditional and present understanding of the physicochemical nucleation mechanisms, which have been proposed based on the investigations in clean environments and under laboratory experimental conditions. This paper summarizes the present status and gaps in understanding NPF in China and discusses the main directions opening for future research. Copyright © 2016 Elsevier B.V. All rights reserved.

Does historical wildfire activity alter metal fluxes to northern lakes?

NASA Astrophysics Data System (ADS)

Pelletier, N.; Chetelat, J.; Vermaire, J. C.; Palmer, M.; Black, J.; Pellisey, J.; Tracz, B.; van der Wielen, S.

2017-12-01

Current drought conditions in northwestern Canada are conducive to more frequent and severe wildfires that may mobilize mercury and other metals accumulated in soil and biomass. There is evidence that wildfires can remobilize and transport mercury within and outside catchments by atmospheric volatilization, particulate emissions and catchment soil erosion. However, the effect of fires on mercury fluxes to nearby lake sediments remains unclear. In this study, we use a combination of 10 dated lake sediment cores and four nearby ombrotrophic peatland cores to investigate the effects of wildfires on mercury fluxes to lake sediments. Lakes varying in catchment size and distance from recent fire events were sampled. Mercury concentrations in the environmental archives were measured, and macroscopic charcoal particles (>100 um) were counted at high resolution in the sediments to observe the co-variation of the local fire history and mercury fluxes. Mercury flux recorded in ombrotrophic peat cores provided an estimate of the historical atmospheric mercury flux from local and regional atmospheric deposition. The mercury flux recorded in lake sediments corresponds to the sum of direct atmospheric deposition and catchment transport. In combination, these archives will allow for the partitioning of mercury loading attributable to catchment transport from direct atmospheric deposition. After correcting the fluxes for particle focusing and terragenic elements input, flux from different lakes will be compared based on their catchment size and their temporal and spatial proximity known fire events. Altogether, our preliminary results using these paleolimnological methods will provide new insights on mercury transport processes that are predicted to become more important under a changing climate.

Scattered Light Polarimetry of Exoplanets

NASA Astrophysics Data System (ADS)

Wiktorowicz, S.

2014-12-01

The last decade has witnessed an explosion in atmospheric characterization of spatially unresolved exoplanets using transmission spectra of transiting planets, but understanding has been hampered by degeneracies resolvable through blue optical observations. Here, scattered light is more important than the Wien tail of re-radiated thermal emission. Therefore, the next frontier in exoplanet characterization lies in the direct detection of scattered light. The polarization state of starlight scattered by a planetary atmosphere distinguishes it from the direct light from the host star, and the inherently differential nature of polarimetry reduces systematic effects to the point where ground-based detections are possible. Furthermore, polarimetry is uniquely sensitive to the size distribution, shape, and chemical composition of atmospheric cloud particles as well as to the scattering optical depth. I will review the current state of exoplanet polarimetry, which is dominated not by photon noise but by non-Gaussian systematic effects. Ground-based detection of order ten exoplanet photons relative to the host star's million requires dense orbital phase coverage and therefore long observing programs. However, variability inherent in the host star, interstellar medium, Earth's atmosphere, the telescope, and the instrument at all timescales must be measured and subtracted in order to definitively uncover scattered light from the exoplanet. While polarimetry is in principle sensitive to exoplanets regardless of orbital inclination, repeated observations of transiting exoplanet systems during secondary eclipse events are required to measure the polarimetric variability of the system that cannot be due to the planet. The emergence of scattered light polarimetry as a robust tool for the study of exoplanet atmospheres, and eventually surfaces, therefore requires diligent attention to the role of systematic effects.

Atmospheric Seasonality as an Exoplanet Biosignature

NASA Astrophysics Data System (ADS)

Olson, Stephanie L.; Schwieterman, Edward W.; Reinhard, Christopher T.; Ridgwell, Andy; Kane, Stephen R.; Meadows, Victoria S.; Lyons, Timothy W.

2018-05-01

Current investigations of exoplanet biosignatures have focused on static evidence of life, such as the presence of biogenic gases like O2 or CH4. However, the expected diversity of terrestrial planet atmospheres and the likelihood of both “false positives” and “false negatives” for conventional biosignatures motivate exploration of additional life detection strategies, including time-varying signals. Seasonal variation in atmospheric composition is a biologically modulated phenomenon on Earth that may occur elsewhere because it arises naturally from the interplay between the biosphere and time-variable insolation. The search for seasonality as a biosignature would avoid many assumptions about specific metabolisms and provide an opportunity to directly quantify biological fluxes—allowing us to characterize, rather than simply recognize, biospheres on exoplanets. Despite this potential, there have been no comprehensive studies of seasonality as an exoplanet biosignature. Here, we provide a foundation for further studies by reviewing both biological and abiological controls on the magnitude and detectability of seasonality of atmospheric CO2, CH4, O2, and O3 on Earth. We also consider an example of an inhabited world for which atmospheric seasonality may be the most notable expression of its biosphere. We show that life on a low O2 planet like the weakly oxygenated mid-Proterozoic Earth could be fingerprinted by seasonal variation in O3 as revealed in its UV Hartley–Huggins bands. This example highlights the need for UV capabilities in future direct-imaging telescope missions (e.g., LUVOIR/HabEx) and illustrates the diagnostic importance of studying temporal biosignatures for exoplanet life detection/characterization.

Comparison of model estimated and measured direct-normal solar irradiance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halthore, R.N.; Schwartz, S.E.; Michalsky, J.J.

1997-12-01

Direct-normal solar irradiance (DNSI), the energy in the solar spectrum incident in unit time at the Earth{close_quote}s surface on a unit area perpendicular to the direction to the Sun, depends only on atmospheric extinction of solar energy without regard to the details of the extinction, whether absorption or scattering. Here we report a set of closure experiments performed in north central Oklahoma in April 1996 under cloud-free conditions, wherein measured atmospheric composition and aerosol optical thickness are input to a radiative transfer model, MODTRAN 3, to estimate DNSI, which is then compared with measured values obtained with normal incidence pyrheliometersmore » and absolute cavity radiometers. Uncertainty in aerosol optical thickness (AOT) dominates the uncertainty in DNSI calculation. AOT measured by an independently calibrated Sun photometer and a rotating shadow-band radiometer agree to within the uncertainties of each measurement. For 36 independent comparisons the agreement between measured and model-estimated values of DNSI falls within the combined uncertainties in the measurement (0.3{endash}0.7{percent}) and model calculation (1.8{percent}), albeit with a slight average model underestimate ({minus}0.18{plus_minus}0.94){percent}; for a DNSI of 839Wm{sup {minus}2} this corresponds to {minus}1.5{plus_minus}7.9Wm{sup {minus}2}. The agreement is nearly independent of air mass and water-vapor path abundance. These results thus establish the accuracy of the current knowledge of the solar spectrum, its integrated power, and the atmospheric extinction as a function of wavelength as represented in MODTRAN 3. An important consequence is that atmospheric absorption of short-wave energy is accurately parametrized in the model to within the above uncertainties. {copyright} 1997 American Geophysical Union« less

Changes and variations in the turning angle of Arctic sea ice

NASA Astrophysics Data System (ADS)

Ukita, J.; Honda, M.; Ishizuka, S.

2012-12-01

The motion of sea ice is under influences of forcing from winds and currents and of sea ice properties. In facing rapidly changing Arctic climate we are interested in whether we observe and quantify changes in sea ice conditions reflected in its velocity field. Theoretical consideration on the freedrift model predicts a change in the sea ice turning angle with respect to the direction of forcing wind in association with thinning sea ice thickness. Possible changes in atmospheric and ocean boundary layer conditions may be reflected in the sea ice turning angle through modification of both atmospheric and oceanic Ekman spirals. With these in mind this study examines statistical properties of the turning angle of the Arctic sea ice and compares them with atmospheric/ice/ocean conditions for the period of 1979-2010 on the basis of IABP buoy data. Preliminary results indicate that over this period the turning angle has varying trends depending on different seasons. We found weakly significant (>90% level) changes in the turning angle from August to October with the maximum trend in October. The direction of trends is counter-clockwise with respect to the geostrophic wind direction, which is consistent with the thinning of sea ice. The interannual variability of the turning angle for this peak season of the reduced sea ice cover is not the same as that of the Arctic SIE. However, in recent years the turning angle appears to covary with the surface air temperature, providing supporting evidence for the relationship between the angle and sea ice thickness. In the presentation we will provide results on the relationships between the turning angle and atmospheric and oceanic variables and further discuss their implications.

Atmosphere Impact Losses

NASA Astrophysics Data System (ADS)

Schlichting, Hilke E.; Mukhopadhyay, Sujoy

2018-02-01

Determining the origin of volatiles on terrestrial planets and quantifying atmospheric loss during planet formation is crucial for understanding the history and evolution of planetary atmospheres. Using geochemical observations of noble gases and major volatiles we determine what the present day inventory of volatiles tells us about the sources, the accretion process and the early differentiation of the Earth. We further quantify the key volatile loss mechanisms and the atmospheric loss history during Earth's formation. Volatiles were accreted throughout the Earth's formation, but Earth's early accretion history was volatile poor. Although nebular Ne and possible H in the deep mantle might be a fingerprint of this early accretion, most of the mantle does not remember this signature implying that volatile loss occurred during accretion. Present day geochemistry of volatiles shows no evidence of hydrodynamic escape as the isotopic compositions of most volatiles are chondritic. This suggests that atmospheric loss generated by impacts played a major role during Earth's formation. While many of the volatiles have chondritic isotopic ratios, their relative abundances are certainly not chondritic again suggesting volatile loss tied to impacts. Geochemical evidence of atmospheric loss comes from the {}3He/{}^{22}Ne, halogen ratios (e.g., F/Cl) and low H/N ratios. In addition, the geochemical ratios indicate that most of the water could have been delivered prior to the Moon forming impact and that the Moon forming impact did not drive off the ocean. Given the importance of impacts in determining the volatile budget of the Earth we examine the contributions to atmospheric loss from both small and large impacts. We find that atmospheric mass loss due to impacts can be characterized into three different regimes: 1) Giant Impacts, that create a strong shock transversing the whole planet and that can lead to atmospheric loss globally. 2) Large enough impactors (m_{cap} ≳ √{2} ρ0 (π h R)^{3/2}, r_{cap}˜25 km for the current Earth), that are able to eject all the atmosphere above the tangent plane of the impact site, where h, R and ρ0 are the atmospheric scale height, radius of the target, and its atmospheric density at the ground. 3) Small impactors (m_{min}>4 πρ0 h3, r_{min}˜ 1 km for the current Earth), that are only able to eject a fraction of the atmospheric mass above the tangent plane. We demonstrate that per unit impactor mass, small impactors with r_{min} < r < r_{cap} are the most efficient impactors in eroding the atmosphere. In fact for the current atmospheric mass of the Earth, they are more than five orders of magnitude more efficient (per unit impactor mass) than giant impacts, implying that atmospheric mass loss must have been common. The enormous atmospheric mass loss efficiency of small impactors is due to the fact that most of their impact energy and momentum is directly available for local mass loss, where as in the giant impact regime a lot of energy and momentum is 'wasted' by having to create a strong shock that can transverse the entirety of the planet such that global atmospheric loss can be achieved. In the absence of any volatile delivery and outgassing, we show that the population of late impactors inferred from the lunar cratering record containing 0.1% M_{\\oplus } is able to erode the entire current Earth's atmosphere implying that an interplay of erosion, outgassing and volatile delivery is likely responsible for determining the atmospheric mass and composition of the early Earth. Combining geochemical observations with impact models suggest an interesting synergy between small and big impacts, where giant impacts create large magma oceans and small and larger impacts drive the atmospheric loss.

NEW DIRECTIONS: VOCS AND BIOSPHERE-ATMOSPHERE FEEDBACKS

EPA Science Inventory

Shallcross and Monks [New Directions: a Role For Isoprene in Biosphere-Climate-Chemistry Feedbacks, Atmospheric Environment, Vol. 34 (2000) pp. 1659-1660] recently summarized the importance of biogenic isoprene in a biosphere-atmosphere system under constant change. In this art...

Energetic solar particle events

NASA Technical Reports Server (NTRS)

Fenton, K. B.; Fenton, A. G.; Humble, J. E.

1985-01-01

Studies of the arrival directions of energetic solar particles during ground level enhancements (CLE's) observed by neutron monitors have shown that, in general, in the first hour of the event most of the particles arrive with a distribution of pitch angles peaked about the garden hose field direction in the vicinity of Earth. During the first hour some of the particles arrive from the antisolar direction, while in later stages of the event the intensity becomes more nearly isotropic as a result of scattering of particles in interplanetary space. An attempt is made to determine the arrival directions of the particles during the early stages of the GLE of 16 February 1984 using the data currently available from high latitude neutron monitors near sea level where the cut off is essentially atmospheric (approx. LGV).

Direct Observations of Clouds on Brown Dwarfs: A Spitzer Study of Extreme Cases

NASA Astrophysics Data System (ADS)

Burgasser, Adam; Cruz, Kelle; Cushing, Michael; Kirkpatrick, J. Davy; Looper, Dagny; Lowrance, Patrick; Marley, Mark; Saumon, Didier

2008-03-01

Clouds play a fundamental role in the emergent spectral energy distributions and observed variability of very low mass stars and brown dwarfs, yet hey have only been studied indirectly thus far. Recent indications of a broad silicate grain absorption feature in the 8-11 micron spectra of mid-type L dwarfs, and evidence that the strength of this absorption varies according to broad-band near-infrared color, may finally allow the first direct studies of clouds and condensate grain properties in brown dwarf atmospheres. We propose to observe a sample of 18 ``extreme'' L dwarfs - objects with unusually blue and red near-infrared colors - with IRAC and IRS to study the 8-11 micron feature in detail (including grain size distributions and bulk compositions), and to constrain advanced condensate cloud atmosphere models currently in development. Our program provides a unique examination of the general processes of cloud formation by focusing on the relatively warm photospheres of late-type brown dwarfs.

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

PubMed

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-07

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

Estimation of the Ocean Skin Temperature using the NASA GEOS Atmospheric Data Assimilation System

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Akella, Santha; Todling, Ricardo; Suarez, Max

2016-01-01

This report documents the status of the development of a sea surface temperature (SST) analysis for the Goddard Earth Observing System (GEOS) Version-5 atmospheric data assimilation system (ADAS). Its implementation is part of the steps being taken toward the development of an integrated earth system analysis. Currently, GEOS-ADAS SST is a bulk ocean temperature (from ocean boundary conditions), and is almost identical to the skin sea surface temperature. Here we describe changes to the atmosphere-ocean interface layer of the GEOS-atmospheric general circulation model (AGCM) to include near surface diurnal warming and cool-skin effects. We also added SST relevant Advanced Very High Resolution Radiometer (AVHRR) observations to the GEOS-ADAS observing system. We provide a detailed description of our analysis of these observations, along with the modifications to the interface between the GEOS atmospheric general circulation model, gridpoint statistical interpolation-based atmospheric analysis and the community radiative transfer model. Our experiments (with and without these changes) show improved assimilation of satellite radiance observations. We obtained a closer fit to withheld, in-situ buoys measuring near-surface SST. Evaluation of forecast skill scores corroborate improvements seen in the observation fits. Along with a discussion of our results, we also include directions for future work.

Modeling High-Resolution Coastal Ocean Dynamics with COAMPS: System Overview, Applications and Future Directions

NASA Astrophysics Data System (ADS)

Allard, R. A.; Campbell, T. J.; Edwards, K. L.; Smith, T.; Martin, P.; Hebert, D. A.; Rogers, W.; Dykes, J. D.; Jacobs, G. A.; Spence, P. L.; Bartels, B.

2014-12-01

The Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS®) is an atmosphere-ocean-wave modeling system developed by the Naval Research Laboratory which can be configured to cycle regional forecasts/analysis models in single-model (atmosphere, ocean, and wave) or coupled-model (atmosphere-ocean, ocean-wave, and atmosphere-ocean-wave) modes. The model coupling is performed using the Earth System Modeling Framework (ESMF). The ocean component is the Navy Coastal Ocean Model (NCOM), and the wave components include Simulating WAves Nearshore (SWAN) and WaveWatch-III. NCOM has been modified to include wetting and drying, the effects of Stokes drift current, wave radiation stresses due to horizontal gradients of the momentum flux of surface waves, enhancement of bottom drag in shallow water, and enhanced vertical mixing due to Langmuir turbulence. An overview of the modeling system including ocean data assimilation and specification of boundary conditions will be presented. Results from a high-resolution (10-250m) modeling study from the Surfzone Coastal Oil Pathways Experiment (SCOPE) near Ft. Walton Beach, Florida in December 2013 will be presented. ®COAMPS is a registered trademark of the Naval Research Laboratory

The 1995 scientific assessment of the atmospheric effects of stratospheric aircraft

NASA Technical Reports Server (NTRS)

Stolarski, Richard S.; Baughcum, Steven L.; Brune, William H.; Douglass, Anne R.; Fahey, David W.; Friedl, Randall R.; Liu, Shaw C.; Plumb, R. Alan; Poole, Lamont R.; Wesoky, Howard L.

1995-01-01

This report provides a scientific assessment of our knowledge concerning the impact of proposed high-speed civil transport (HSCT) aircraft on the atmosphere. It comes at the end of Phase 1 of the Atmospheric Effects of Stratospheric Aircraft element of the NASA High-Speed Research Program. The fundamental problem with stratospheric flight is that pollutant residence times are long because the stratosphere is a region of permanent temperature inversion with stable stratification. Using improved two-dimensional assessment models and detailed fleet emissions scenarios, the assessment examines the possible impact of the range of effluents from aircraft. Emphasis is placed on the effects of NO(x) and H2O on the atmospheric ozone content. Measurements in the plume of an in-flight Concorde supersonic transport indicated a large number of small particles. These measurements, coupled with model sensitivity studies, point out the importance of obtaining a more detailed understanding of the fate of sulfur in the HSCT exhaust. Uncertainties in the current understanding of the processes important for determining the overall effects of HSCT's on the atmosphere are discussed and partially quantified. Research directions are identified to improve the quantification of uncertainties and to reduce their magnitude.

A Unified Computational Model for Solar and Stellar Flares

NASA Technical Reports Server (NTRS)

Allred, Joel C.; Kowalski, Adam F.; Carlsson, Mats

2015-01-01

We present a unified computational framework that can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is accelerated in the corona and propagates downward depositing energy and momentum along the way. This rapidly heats the lower stellar atmosphere causing it to explosively expand and dramatically brighten. Our models consist of flux tubes that extend from the sub-photosphere into the corona. We simulate how flare-accelerated charged particles propagate down one-dimensional flux tubes and heat the stellar atmosphere using the Fokker-Planck kinetic theory. Detailed radiative transfer is included so that model predictions can be directly compared with observations. The flux of flare-accelerated particles drives return currents which additionally heat the stellar atmosphere. These effects are also included in our models. We examine the impact of the flare-accelerated particle beams on model solar and dMe stellar atmospheres and perform parameter studies varying the injected particle energy spectra. We find the atmospheric response is strongly dependent on the accelerated particle cutoff energy and spectral index.

Fire Influences on Atmospheric Composition, Air Quality, and Climate

NASA Technical Reports Server (NTRS)

Voulgarakis, Apostolos; Field, Robert D.

2015-01-01

Fires impact atmospheric composition through their emissions, which range from long-lived gases to short-lived gases and aerosols. Effects are typically larger in the tropics and boreal regions but can also be substantial in highly populated areas in the northern mid-latitudes. In all regions, fire can impact air quality and health. Similarly, its effect on large-scale atmospheric processes, including regional and global atmospheric chemistry and climate forcing, can be substantial, but this remains largely unexplored. The impacts are primarily realised in the boundary layer and lower free troposphere but can also be noticeable in upper troposphere/lower stratosphere (UT/LS) region, for the most intense fires. In this review, we summarise the recent literature on findings related to fire impact on atmospheric composition, air quality and climate. We explore both observational and modelling approaches and present information on key regions and on the globe as a whole. We also discuss the current and future directions in this area of research, focusing on the major advances in emission estimates, the emerging efforts to include fire as a component in Earth system modelling and the use of modelling to assess health impacts of fire emissions.

Understanding the Early Evolution of M dwarf Extreme Ultraviolet Radiation

NASA Astrophysics Data System (ADS)

Peacock, Sarah; Barman, Travis; Shkolnik, Evgenya

2015-11-01

The chemistry and evolution of planetary atmospheres depends on the evolution of high-energy radiation emitted by its host star. High levels of extreme ultraviolet (EUV) radiation can drastically alter the atmospheres of terrestrial planets through ionizing, heating, expanding, chemically modifying and eroding them during the first few billion years of a planetary lifetime. While there is evidence that stars emit their highest levels of far and near ultraviolet (FUV; NUV) radiation in the earliest stages of their evolution, we are currently unable to directly measure the EUV radiation. Most previous stellar atmosphere models under-predict FUV and EUV emission from M dwarfs; here we present new models for M stars that include prescriptions for the hot, lowest density atmospheric layers (chromosphere, transition region and corona), from which this radiation is emitted. By comparing our model spectra to GALEX near and far ultraviolet fluxes, we are able to predict the evolution of EUV radiation for M dwarfs from 10 Myr to a few Gyr. This research is the next major step in the HAZMAT (HAbitable Zones and M dwarf Activity across Time) project to analyze how the habitable zone evolves with the evolving properties of stellar and planetary atmospheres.

Soil Moisture Controls on Rainfall and Temperature Variability: A Modeler Searches Through Observational Data

NASA Technical Reports Server (NTRS)

Koster, Randal

2010-01-01

The degree to which atmospheric processes respond to variations in soil moisture - a potentially important but largely untapped element of subseasonal to seasonal prediction - can be determined easily and directly for an atmospheric model but cannot be determined directly for nature through an analysis of observations. In atmospheric models) directions of causality can be artificially manipulated; we can avoid difficulties associated with the fact that atmospheric variations have a much larger impact on land state variations than vice-versa. In nature) on the other hand) the dominant direction of causality (the atmosphere forcing the ground) cannot be artificially "turned off") and the statistics associated with this dominant direction overwhelm those of the feedback signal. Observational data) however) do allow a number of indirect measures of landatmosphere feedback. This seminar reports on a series of joint analyses of observational and model data designed to illuminate the degree of land-atmosphere feedback present in the real world. The indirect measures do in fact suggest that feedback in nature, though small) is significant - enough to warrant the development of realistic land initialization strategies for subseasonal and seasonal forecasts.

Direct Search for Dark Matter with DarkSide

NASA Astrophysics Data System (ADS)

Agnes, P.; Alexander, T.; Alton, A.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Cadonati, L.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cocco, A. G.; Crippa, L.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Deo, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M. Y.; Guardincerri, Y.; Hackett, B.; Herner, K.; Hungerford, E. V.; Ianni, Al; Ianni, An; Jollet, C.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kurlej, A.; Li, P. X.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Ma, Y. Q.; Machulin, I.; Mandarano, A.; Mari, S.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P. D.; Milincic, R.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Nelson, A.; Odrowski, S.; Okounkova, M.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Papp, L.; Parmeggiano, S.; Parsells, R.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Segreto, E.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wojcik, M.; Wright, A.; Xiang, X.; Xu, J.; Yang, C. G.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhu, C.; Zuzel, G.

2015-11-01

The DarkSide experiment is designed for the direct detection of Dark Matter with a double phase liquid Argon TPC operating underground at Laboratori Nazionali del Gran Sasso. The TPC is placed inside a 30 tons liquid organic scintillator sphere, acting as a neutron veto, which is in turn installed inside a 1 kt water Cherenkov detector. The current detector is running since November 2013 with a 50 kg atmospheric Argon fill and we report here the first null results of a Dark Matter search for a (1422 ± 67) kg.d exposure. This result correspond to a 90% CL upper limit on the WIMP-nucleon cross section of 6.1 × 10-44 cm2 (for a WIMP mass of 100 GeV/c2) and it's currently the most sensitive limit obtained with an Argon target.

In vitro antimicrobial effects and mechanisms of direct current air-liquid discharge plasma on planktonic Staphylococcus aureus and Escherichia coli in liquids.

PubMed

Xu, Zimu; Cheng, Cheng; Shen, Jie; Lan, Yan; Hu, Shuheng; Han, Wei; Chu, Paul K

2018-06-01

The direct inactivation effects of an atmospheric pressure direct current (DC) air plasma against planktonic Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in aqueous solution are investigated in vitro. Upon plasma treatment, extensively analyses on cell culturability, metabolic capacity, membrane integrity, surface morphology, cellular proteins, nucleic acids and intracellular reactive oxygen species (ROS) for both bacterial species were carried out and significant antimicrobial effects observed. Compared with the cellular culturability, a sub-lethal viable but non-culturable (VBNC) state was induced while more S. aureus entered this state than E. coli. Damaged bacterial outer structures were observed and the total concentrations of cellular protein and nucleic acid decreased for both bacteria after plasma treatment. The plasma-induced aqueous reactive species (RS) and intracellular ROS might produce detrimental effects to the bacteria, while S. aureus was less susceptible to the discharge after a 20-min exposure compared to E. coli. Copyright © 2018 Elsevier B.V. All rights reserved.

Assimilation for skin SST in the NASA GEOS atmospheric data assimilation system

PubMed Central

Akella, Santha; Todling, Ricardo; Suarez, Max

2018-01-01

The present article describes the sea surface temperature (SST) developments implemented in the Goddard Earth Observing System, Version 5 (GEOS-5) Atmospheric Data Assimilation System (ADAS). These are enhancements that contribute to the development of an atmosphere-ocean coupled data assimilation system using GEOS. In the current quasi-operational GEOS-ADAS, the SST is a boundary condition prescribed based on the OSTIA product, therefore SST and skin SST (Ts) are identical. This work modifies the GEOS-ADAS Ts by modeling and assimilating near sea surface sensitive satellite infrared (IR) observations. The atmosphere-ocean interface layer of the GEOS atmospheric general circulation model (AGCM) is updated to include near surface diurnal warming and cool-skin effects. The GEOS analysis system is also updated to directly assimilate SST-relevant Advanced Very High Resolution Radiometer (AVHRR) radiance observations. Data assimilation experiments designed to evaluate the Ts modification in GEOS-ADAS show improvements in the assimilation of radiance observations that extends beyond the thermal IR bands of AVHRR. In particular, many channels of hyperspectral sensors, such as those of the Atmospheric Infrared Sounder (AIRS), and Infrared Atmospheric Sounding Interferometer (IASI) are also better assimilated. We also obtained improved fit to withheld, in-situ buoy measurement of near-surface SST. Evaluation of forecast skill scores show marginal to neutral benefit from the modified Ts. PMID:29628531

Atmospheric Effect on Remote Sensing of the Earth's Surface

NASA Technical Reports Server (NTRS)

Fraser, R. S.; Kaufman, Y. J. (Principal Investigator)

1985-01-01

Radiative transfer theory (RT) for an atmosphere with a nonuniform surface is the basis for understanding and correcting for the atmospheric effect on remote sensing of surface properties. In the present work the theory is generalized and tested successfully against laboratory and field measurements. There is still a need to generalize the RT approximation for off-nadir directions and to take into account anisotropic reflectance at the surface. The reflectance at the surface. The adjacency effect results in a significant modification of spectral signatures of the surface, and therefore results in modification of classifications, of separability of field classes, and of spatial resolution. For example, the 30 m resolution of the Thematic Mapper is reduced to 100 m by a hazy atmosphere. The adjacency effect depends on several optical parameters of aerosols: optical thickness, depth of aerosol layer, scattering phase function, and absorption. Remote sensing in general depends on these parameter, not just adjacency effects, but they are not known well enough for making accurate atmospheric corrections. It is important to establish methods for estimating these parameters in order to develop correction methods for atmospheric effects. Such estimations can be based on climatological data, which are not available yet, correlations between the optical parameters and meteorological data, and the same satellite measurements of radiances that are used for estimating surface properties. Knowledge about the atmospheric parameters important for remote sensing is being enlarged with current measurements of them.

Current 2-μm dial measurements of atmospheric CO2 and expected results from space using new MCT APDS

NASA Astrophysics Data System (ADS)

Dumas, A.; Gibert, F.; Rothman, J.; Édouart, D.; Le Mounier, F.; Cénac, C.

2017-11-01

In the framework of CO2 monitoring in the Atmospheric Boundary Layer (ABL), a ground-based 2-μm Differential Absorption Lidar (DIAL) has been developed at the Laboratoire de Météorologie Dynamique (LMD) in Palaiseau. In order to derive flux information, this system has been set up with coherent detection, which allows to combine CO2 density measurements with wind velocity measurements. On the other hand, new advances in the field of Mercury Cadmium Tellure (MCT) Avalanche Photodiodes (APDs) open the way for high-precision measurements in direct detection ultimately from space. In this study, we first report on state of the art measurements obtained with the current coherent DIAL system before presenting expected results for a similar laser transmitter equipped with MCT APDs. For this latter part, we use a numerical model which relies on APDs performance data provided by the Laboratoire d'Électronique et de Technologie de l'Information (LETI).

The Evolution of CO2 on Mars

NASA Technical Reports Server (NTRS)

Kahn, R.

1985-01-01

The consequences of the hypothesis that the evolution of CO2 is directly linked to the occurrence of at least transitory pockets of moisture were exposed. The current conditions preclude the existence of open bodies of liquid water and the formation of moisture in disequilibrium is not excluded by any known constraints. The water evaporation rate is inversely proportional to PCO2, and the existence of a limiting value (P*) for which liquid water can form in the Mars environment is postulated. The evolution of PCO2 is controlled largely by relatively rapid aqueous chemistry forming carbon-containing sedimentary rocks, perhaps during early history in open water, but more recently in transitory pockets of moisture in the soil. Once the total atmospheric pressure is reduced to near P*, the occurrence of transitory moisture is inhibited, and atmospheric CO2 is no longer depleted by an efficient mechanism. The role of the carbonate reservoir in the current overall carbon budget on Mars, according to this scheme, is illustrated.

Meteoric Magnesium Ions in the Martian Atmosphere

NASA Technical Reports Server (NTRS)

Pesnell, William Dean; Grebowsky, Joseph

1999-01-01

From a thorough modeling of the altitude profile of meteoritic ionization in the Martian atmosphere we deduce that a persistent layer of magnesium ions should exist around an altitude of 70 km. Based on current estimates of the meteoroid mass flux density, a peak ion density of about 10(exp 4) ions/cm is predicted. Allowing for the uncertainties in all of the model parameters, this value is probably within an order of magnitude of the correct density. Of these parameters, the peak density is most sensitive to the meteoroid mass flux density which directly determines the ablated line density into a source function for Mg. Unlike the terrestrial case, where the metallic ion production is dominated by charge-exchange of the deposited neutral Mg with the ambient ions, Mg+ in the Martian atmosphere is produced predominantly by photoionization. The low ultraviolet absorption of the Martian atmosphere makes Mars an excellent laboratory in which to study meteoric ablation. Resonance lines not seen in the spectra of terrestrial meteors may be visible to a surface observatory in the Martian highlands.

Middle atmosphere electrical structure, dynamics and coupling

NASA Technical Reports Server (NTRS)

Hale, L. C.

1984-01-01

The ram current to ion traps and the insensitivity of ion conductivity to compressibility provide the basis of robust techniques for middle atmosphere measurements. Gerdien condensers are more difficult to implement but provide more information. Mesospheric electrical conductivity shows many orders of magnitude variability, with depressions below gas phase model values indicating dominance by aerosol particles. The mobility of these ions has been directly measured and indicates particles of thousands of AMU. Large mesospheric fields have come into question, and diagnostic measurements show that many such measurements may be artifacts. However, some measurements of V/m fields with symmetrical and redundant sensors appear to be real. These fields complicate the 'mapping' picture of electrical coupling and may also modulate the transport of aerosol particles. They are probably related to neutral atmospheric dynamics and/or the aerosol particles. Lightning couples much more energy to the middle atmosphere and above than previously suspected, primarily in the ELF-UHF range. There are many important unanswered questions in this relatively unexplored frontier area which may be answered with low cost balloon and sounding rocket experiments.

Environmental impacts on the diversity of methane-cycling microbes and their resultant function

PubMed Central

Aronson, Emma L.; Allison, Steven D.; Helliker, Brent R.

2013-01-01

Methane is an important anthropogenic greenhouse gas that is produced and consumed in soils by microorganisms responding to micro-environmental conditions. Current estimates show that soil consumption accounts for 5–15% of methane removed from the atmosphere on an annual basis. Recent variability in atmospheric methane concentrations has called into question the reliability of estimates of methane consumption and calls for novel approaches in order to predict future atmospheric methane trends. This review synthesizes the environmental and climatic factors influencing the consumption of methane from the atmosphere by non-wetland, terrestrial soil microorganisms. In particular, we focus on published efforts to connect community composition and diversity of methane-cycling microbial communities to observed rates of methane flux. We find abundant evidence for direct connections between shifts in the methane-cycling microbial community, due to climate and environmental changes, and observed methane flux levels. These responses vary by ecosystem and associated vegetation type. This information will be useful in process-based models of ecosystem methane flux responses to shifts in environmental and climatic parameters. PMID:23966984

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

PubMed Central

Smits, Kathleen; Eagen, Victoria; Trautz, Andrew

2015-01-01

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages. PMID:26131928

Investigating Mars South Residual CO2 Cap with a Global Climate Model

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Dequaire, J.; Hollingsworth, J. L.; Haberle, R. M.

2016-01-01

The CO2 cycle is one of the three controlling climate cycles on Mars. One aspect of the CO2 cycle that is not yet fully understood is the existence of a residual CO2 ice cap that is offset from the south pole. Previous investigations suggest that the atmosphere may control the placement of the south residual cap (e.g., Colaprete et al., 2005). These investigations show that topographically forced stationary eddies in the south during southern hemisphere winter produce colder atmospheric temperatures and increased CO2 snowfall over the hemisphere where the residual cap resides. Since precipitated CO2 ice produces higher surface albedos than directly deposited CO2 ice, it is plausible that CO2 snowfall resulting from the zonally asymmetric atmospheric circulation produces surface ice albedos high enough to maintain a residual cap only in one hemisphere. The goal of the current work is to further evaluate Colaprete et al.'s hypothesis by investigating model-predicted seasonally varying snowfall patterns in the southern polar region and the atmospheric circulation components that control them.

Electrical measurements in the atmosphere and the Ionosphere over an active thunderstorm. II - Direct current electric fields and conductivity

NASA Technical Reports Server (NTRS)

Holzworth, R. H.; Kelley, M. C.; Siefring, C. L.; Hale, L. C.; Mitchell, J. D.

1985-01-01

On August 9, 1981, a series of three rockets was launched over an air mass thunderstorm off the eastern seaboard of Virginia while simultaneous stratospheric and ground-based electric field measurements were made. The conductivity was substantially lower at most altitudes than the conductivity profiles used by theoretical models. Direct current electric fields over 80 mV/m were measured as far away as 96 km from the storm in the stratosphere at 23 km altitude. No dc electric fields above 75 km altitude could be identified with the thunderstorm, in agreement with theory. However, vertical current densities over 120 pA/sq m were seen well above the classical 'electrosphere' (at 50 or 60 km). Frequent dc shifts in the electric field following lightning transients were seen by both balloon and rocket payloads. These dc shifts are clearly identifiable with either cloud-to-ground (increases) or intercloud (decreases) lightning flashes.

Pulsed microdischarge with inductively coupled plasma mass spectrometry for elemental analysis on solid metal samples.

PubMed

Li, Weifeng; Yin, Zhibin; Cheng, Xiaoling; Hang, Wei; Li, Jianfeng; Huang, Benli

2015-05-05

Pulsed microdischarge employed as source for direct solid analysis was investigated in N2 environment at atmospheric pressure. Compared with direct current (DC) microdischarge, it exhibits advantages with respect to the ablation and emission of the sample. Comprehensive evidence, including voltage-current relationship, current density (j), and electron density (ne), suggests that pulsed microdischarge is in the arc regime while DC microdischarge belongs to glow. Capability in ablating metal samples demonstrates that pulsed microdischarge is a viable option for direct solid sampling because of the enhanced instantaneous energy. Using optical spectrometer, only common emission lines of N2 can be acquired in DC mode, whereas primary atomic and ionic lines of the sample are obtained in the case of pulsed mode. Calculations show a significant difference in N2 vibrational temperatures between DC and pulsed microdischarge. Combined with inductively coupled plasma mass spectrometry (ICPMS), pulsed microdischarge exhibits much better performances in calibration linearity and limits of detection (LOD) than those of DC discharge in direct analysis of samples of different matrices. To improve transmission efficiency, a mixture of Ar and N2 was employed as discharge gas as well as carrier gas in follow-up experiments, facilitating that LODs of most elements reached ng/g.

Observations of the effect of wind on the cooling of active lava flows

USGS Publications Warehouse

Keszthelyi, L.; Harris, A.J.L.; Dehn, J.

2003-01-01

We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahochoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400??C. We currently estimate that the atmospheric heat transfer coefficient is about 45-50 W m-2 K-1 for a 10 m/s wind and a surface temperature ???500??C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.

Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions

USGS Publications Warehouse

Isaksen, Ivar S.A.; Gauss, Michael; Myhre, Gunnar; Walter Anthony, Katey M.; Ruppel, Carolyn

2011-01-01

The magnitude and feedbacks of future methane release from the Arctic region are unknown. Despite limited documentation of potential future releases associated with thawing permafrost and degassing methane hydrates, the large potential for future methane releases calls for improved understanding of the interaction of a changing climate with processes in the Arctic and chemical feedbacks in the atmosphere. Here we apply a “state of the art” atmospheric chemistry transport model to show that large emissions of CH4 would likely have an unexpectedly large impact on the chemical composition of the atmosphere and on radiative forcing (RF). The indirect contribution to RF of additional methane emission is particularly important. It is shown that if global methane emissions were to increase by factors of 2.5 and 5.2 above current emissions, the indirect contributions to RF would be about 250% and 400%, respectively, of the RF that can be attributed to directly emitted methane alone. Assuming several hypothetical scenarios of CH4 release associated with permafrost thaw, shallow marine hydrate degassing, and submarine landslides, we find a strong positive feedback on RF through atmospheric chemistry. In particular, the impact of CH4 is enhanced through increase of its lifetime, and of atmospheric abundances of ozone, stratospheric water vapor, and CO2 as a result of atmospheric chemical processes. Despite uncertainties in emission scenarios, our results provide a better understanding of the feedbacks in the atmospheric chemistry that would amplify climate warming.

Directional time-distance probing of model sunspot atmospheres

NASA Astrophysics Data System (ADS)

Moradi, H.; Cally, P. S.; Przybylski, D.; Shelyag, S.

2015-05-01

A crucial feature not widely accounted for in local helioseismology is that surface magnetic regions actually open a window from the interior into the solar atmosphere, and that the seismic waves leak through this window, reflect high in the atmosphere, and then re-enter the interior to rejoin the seismic wave field normally confined there. In a series of recent numerical studies using translation invariant atmospheres, we utilized a `directional time-distance helioseismology' measurement scheme to study the implications of the returning fast and Alfvén waves higher up in the solar atmosphere on the seismology at the photosphere (Cally & Moradi 2013; Moradi & Cally 2014). In this study, we extend our directional time-distance analysis to more realistic sunspot-like atmospheres to better understand the direct effects of the magnetic field on helioseismic travel-time measurements in sunspots. In line with our previous findings, we uncover a distinct frequency-dependent directional behaviour in the travel-time measurements, consistent with the signatures of magnetohydrodynamic mode conversion. We found this to be the case regardless of the sunspot field strength or depth of its Wilson depression. We also isolated and analysed the direct contribution from purely thermal perturbations to the measured travel times, finding that waves propagating in the umbra are much more sensitive to the underlying thermal effects of the sunspot.

Ion Traps at the Sun: Implications for Elemental Fractionation

NASA Astrophysics Data System (ADS)

Fleishman, Gregory D.; Musset, Sophie; Bommier, Véronique; Glesener, Lindsay

2018-04-01

Why the tenuous solar outer atmosphere, or corona, is much hotter than the underlying layers remains one of the greatest challenges for solar modeling. Detailed diagnostics of the coronal thermal structure come from extreme ultraviolet (EUV) emission. The EUV emission is produced by heavy ions in various ionization states and depends on the amount of these ions and on plasma temperature and density. Any nonuniformity of the elemental distribution in space or variability in time affects thermal diagnostics of the corona. Here we theoretically predict ionized chemical element concentrations in some areas of the solar atmosphere, where the electric current is directed upward. We then detect these areas observationally, by comparing the electric current density with the EUV brightness in an active region. We found a significant excess in EUV brightness in the areas with positive current density rather than negative. Therefore, we report the observational discovery of substantial concentrations of heavy ions in current-carrying magnetic flux tubes, which might have important implications for the elemental fractionation in the solar corona known as the first ionization potential effect. We call such areas of heavy ion concentration the “ion traps.” These traps hold enhanced ion levels until they are disrupted by a flare, whether large or small.

Variations of the Antarctic Circumpolar Current (ACC) in the Kerguelen Sector during the Last Deglaciation : sedimentological and geochemical evidences

NASA Astrophysics Data System (ADS)

Bout-Roumazeilles, V.; Beny, F.; Mazaud, A.; Michel, E.; Crosta, X.; Davies, G. R.; Bory, A. J. M.

2017-12-01

High-resolution sedimentological and geochemical records were obtained from two sediment cores recovered by the French R/V Marion Dufresne during the INDIEN-SUD-ACC cruises near the sub-Antarctic Kerguelen Islands (49°S). This area is ideal to record past oceanic and atmospheric changes in the Southern Ocean because they are currently located in the northern branch of the Antarctic Circumpolar Current and under the direct influence of Southern Hemisphere Westerly wind belt. This study focuses on the last termination, with specific emphasis on the impact of severe climatic events (Heinrich Stadial 1, Antarctic Cold Reversal, Younger Dryas) onto the ocean-atmospheric exchange. Results indicates that most of the sediment is derived from the Kerguelen Plateau, characterized by high smectite content. Periodically, a minor contribution of Antarctica is noticeable. In particular, illite variations suggest fast and short northward incursions of Antarctic Bottom Water, probably formed in the Prydz Bay during the last glaciation. Grainsize repartition combined to magnetic parameters show a southward migration of the ACC and the fronts associated from the beginning of the deglaciation, which is consistent with Southern Hemisphere climate variations. On the opposite, it highlights an asynchronous decrease of the ACC strength, with a large drop during the Antarctic Cold Reversal when atmospheric CO2 increase was slowed down. Thus, at least in the studied area, the ACC strength and the Antarctic Climate were not synchronous during the last deglaciation.

Eddy covariance and lysimeter measurements of moisture fluxes over supraglacial debris

NASA Astrophysics Data System (ADS)

Brock, Benjamin

2015-04-01

Supraglacial debris covers have the potential to evaporate large quantities of water derived from either sub-debris ice melt or precipitation. Currently, knowledge of evaporation and condensation rates in supraglacial debris is limited due to the difficulty of making direct measurements. This paper presents eddy covariance and lysimeter measurements of moisture fluxes made over a 0.2 m debris layer at Miage debris covered glacier, Italian Alps, during the 2013 ablation season. The meteorological data are complimented by reflectometer measurements of volumetric water fraction in the saturated and vadose zones of the debris layer. The lysimeters were designed specifically to mimic the debris cover and were embedded within the debris matrix, level with the surface. Over the ablation season, the latent heat flux is dominated by evaporation, and the flux magnitude closely follows the daily cycle of daytime solar heating and night time radiative cooling of debris. Mean flux values are of the order of 1 kg m-2 day-1, but often higher for short periods following rainfall. Condensation rates are relatively small and restricted to night time and humid conditions when the debris-atmosphere vapour pressure gradient reverses due to relatively warm air overlying cold debris. The reflectometer measurements provide evidence of vertical water movement through capillary rise in the upper part of the fine-grained debris layer, just above the saturated horizon, and demonstrate how debris bulk water content increases after rainfall. The latent heat flux responds directly to changes in wind speed, indicating that atmospheric turbulence can penetrate porous upper debris layers to the saturated horizon. Hence, vertical sorting of debris sediments and antecedent rainfall are important in determining evaporation rates, in addition to current meteorological conditions. Comparison of lysimeter measurements with rainfall data provides an estimate that between 45% and 89% of rainfall is evaporated directly back to the atmosphere. Rainfall evaporation rates increase with debris impermeability and temperature, with highest rates occurring when a shower falls on hot debris. If these point measurements are representative of larger scales, evaporation rates of the order of 1000 tonnes km-2 day-1 are implied, with higher rates following rainfall. This has important implications for downstream runoff, sub-debris ice melt rates (due to consumption of evaporative latent heat energy) and, possibly, convective atmospheric processes.

Technical Report Series on Global Modeling and Data Assimilation. Volume 22; A Coupled Ocean-Atmosphere Radiative Model for Global Ocean Biogeochemical Models

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Suarez, Max J. (Editor)

2002-01-01

An ocean-atmosphere radiative model (OARM) evaluates irradiance availability and quality in the water column to support phytoplankton growth and drive ocean thermodynamics. An atmospheric component incorporates spectral and directional effects of clear and cloudy skies as a function of atmospheric optical constituents, and spectral reflectance across the air-sea interface. An oceanic component evaluates the propagation of spectral and directional irradiance through the water column as a function of water, five phytoplankton groups, and chromophoric dissolved organic matter. It tracks the direct and diffuse streams from the atmospheric component, and a third stream, upwelling diffuse irradiance. The atmospheric component of OARM was compared to data sources at the ocean surface with a coefficient of determination (r2) of 0.97 and a root mean square of 12.1%.

Advanced Detector and Waveform Digitizer for Water Vapor DIAL Systems

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Luck, William S., Jr.; DeYoung, Russell J.

1998-01-01

Measurement of atmospheric water vapor has become a major requirement for understanding moist-air processes. Differential absorption lidar (DIAL) is a technique best suited for the measurement of atmospheric water vapor. NASA Langley Research Center is continually developing improved DIAL systems. One aspect of current development is focused on the enhancement of a DIAL receiver by applying state-of-the-art technology in building a new compact detection system that will be placed directly on the DIAL receiver telescope. The newly developed detection system has the capability of being digitally interfaced with a simple personal computer, using a discrete input/output interface. This has the potential of transmitting digital data over relatively long distances instead of analog signals, which greatly reduces measurement noise. In this paper, we discuss some results from the new compact water vapor DIAL detection system which includes a silicon based avalanche photodiode (APD) detector, a 14-bit, 10-MHz waveform digitizer, a microcontroller and other auxiliary electronics. All of which are contained on a small printed-circuit-board. This will significantly reduce the weight and volume over the current CAMAC system and eventually will be used in a water vapor DIAL system on an unpiloted atmospheric vehicle (UAV) aircraft, or alternatively on an orbiting spacecraft.

Hy-wire measurements of atmospheric potential

NASA Astrophysics Data System (ADS)

Holzworth, Robert H.

1984-02-01

A method of directly measuring the electric potential drop across the lowest portion of the atmosphere by using an apparatus called Hy-wire is described. This tethered balloon-borne system has been operated extensively at altitudes near 0.62 km at which voltages over 150 k V were measured with a high impedance device. Also described are measurements of system parameters such as system capacitance (5.6 pf/m), impedance (1010Ω), and response time (tens of seconds). Hy-wire measurements from an around the-clock experiment at Wallops Island, Va., having a characteristic repetitive diurnal pattern of variability exceeding 40% of the mean, are presented. This diurnal pattern is discussed in terms of both local and global current sources. A demonstration using Hy-wire as a lightning channel model is also presented. These experiments have so far been conducted at mid-latitudes but can also be flown from other locations in an effort to determine whether the lowest atmospheric electric circuit is affected by high altitude and possibly global current systems, and if so how much. The data presented in this paper are not definitive about the source of potential variations. The data are, however, representative of the new Hy-wire technique and demonstrative of the potential usefulness of this technique.

The atmospheric electric global circuit. [thunderstorm activity

NASA Technical Reports Server (NTRS)

Kasemir, H. W.

1979-01-01

The hypothesis that world thunderstorm activity represents the generator for the atmospheric electric current flow in the earth atmosphere between ground and the ionosphere is based on a close correlation between the magnitude and the diurnal variation of the supply current (thunderstorm generator current) and the load current (fair weather air-earth current density integrated over the earth surface). The advantages of using lightning survey satellites to furnish a base for accepting or rejecting the thunderstorm generator hypothesis are discussed.

LEAP: An Innovative Direction Dependent Ionospheric Calibration Scheme for Low Frequency Arrays

NASA Astrophysics Data System (ADS)

Rioja, María J.; Dodson, Richard; Franzen, Thomas M. O.

2018-05-01

The ambitious scientific goals of the SKA require a matching capability for calibration of atmospheric propagation errors, which contaminate the observed signals. We demonstrate a scheme for correcting the direction-dependent ionospheric and instrumental phase effects at the low frequencies and with the wide fields of view planned for SKA-Low. It leverages bandwidth smearing, to filter-out signals from off-axis directions, allowing the measurement of the direction-dependent antenna-based gains in the visibility domain; by doing this towards multiple directions it is possible to calibrate across wide fields of view. This strategy removes the need for a global sky model, therefore all directions are independent. We use MWA results at 88 and 154 MHz under various weather conditions to characterise the performance and applicability of the technique. We conclude that this method is suitable to measure and correct for temporal fluctuations and direction-dependent spatial ionospheric phase distortions on a wide range of scales: both larger and smaller than the array size. The latter are the most intractable and pose a major challenge for future instruments. Moreover this scheme is an embarrassingly parallel process, as multiple directions can be processed independently and simultaneously. This is an important consideration for the SKA, where the current planned architecture is one of compute-islands with limited interconnects. Current implementation of the algorithm and on-going developments are discussed.

Field Observations of Coastal Air-Sea Interaction

NASA Astrophysics Data System (ADS)

Ortiz-Suslow, D. G.; Haus, B. K.; Williams, N. J.; Graber, H. C.

2016-12-01

In the nearshore zone wind, waves, and currents generated from different forcing mechanisms converge in shallow water. This can profoundly affect the physical nature of the ocean surface, which can significantly modulate the exchange of momentum, heat, and mass across the air-sea interface. For decades, the focus of air-sea interaction research has been on the open ocean while the shallow water regime has been relatively under-explored. This bears implications for efforts to understand and model various coastal processes, such as mixing, surface transport, and air-sea gas flux. The results from a recent study conducted at the New River Inlet in North Carolina showed that directly measured air-sea flux parameters, such as the atmospheric drag coefficient, are strong functions of space as well as the ambient conditions (i.e. wind speed and direction). The drag is typically used to parameterize the wind stress magnitude. It is generally assumed that the wind direction is the direction of the atmospheric forcing (i.e. wind stress), however significant wind stress steering off of the azimuthal wind direction was observed and was found to be related to the horizontal surface current shear. The authors have just returned from a field campaign carried out within Monterey Bay in California. Surface observations made from two research vessels were complimented by an array of beach and inland flux stations, high-resolution wind forecasts, and satellite image acquisitions. This is a rich data set and several case studies will be analyzed to highlight the importance of various processes for understanding the air-sea fluxes. Preliminary findings show that interactions between the local wind-sea and the shoaling, incident swell can have a profound effect on the wind stress magnitude. The Monterey Bay coastline contains a variety of topographical features and the importance of land-air-sea interactions will also be investigated.

Current problems in applied mathematics and mathematical modeling

NASA Astrophysics Data System (ADS)

Alekseev, A. S.

Papers are presented on mathematical modeling noting applications to such fields as geophysics, chemistry, atmospheric optics, and immunology. Attention is also given to models of ocean current fluxes, atmospheric and marine interactions, and atmospheric pollution. The articles include studies of catalytic reactors, models of global climate phenomena, and computer-assisted atmospheric models.

Observational Signatures of Magnetic Reconnection

NASA Technical Reports Server (NTRS)

Savage, Sabrina

2014-01-01

Magnetic reconnection is often referred to as the primary source of energy release during solar flares. Directly observing reconnection occurring in the solar atmosphere, however, is not trivial considering that the scale size of the diffusion region is magnitudes smaller than the observational capabilities of current instrumentation, and coronal magnetic field measurements are not currently sufficient to capture the process. Therefore, predicting and studying observationally feasible signatures of the precursors and consequences of reconnection is necessary for guiding and verifying the simulations that dominate our understanding. I will present a set of such observations, particularly in connection with long-duration solar events, and compare them with recent simulations and theoretical predictions.

Electrodynamics of the middle atmosphere: Superpressure balloon program

NASA Technical Reports Server (NTRS)

Holzworth, Robert H.

1987-01-01

In this experiment a comprehensive set of electrical parameters were measured during eight long duration flights in the southern hemisphere stratosphere. These flight resulted in the largest data set ever collected from the stratosphere. The stratosphere has never been electrodynamically sampled in the systematic manner before. New discoveries include short term variability in the planetary scale electric current system, the unexpected observation of stratospheric conductivity variations over thunderstorms and the observation of direct stratospheric conductivity variations following a relatively small solar flare. Major statistical studies were conducted of the large scale current systems, the stratospheric conductivity and the neutral gravity waves (from pressure and temperature data) using the entire data set.

Orbital, tectonic and oceanographic controls on Pliocene climate and atmospheric circulation in Arctic Norway

NASA Astrophysics Data System (ADS)

Panitz, Sina; Salzmann, Ulrich; Risebrobakken, Bjørg; De Schepper, Stijn; Pound, Matthew J.; Haywood, Alan M.; Dolan, Aisling M.; Lunt, Daniel J.

2018-02-01

During the Pliocene Epoch, a stronger-than-present overturning circulation has been invoked to explain the enhanced warming in the Nordic Seas region in comparison to low to mid-latitude regions. While marine records are indicative of changes in the northward heat transport via the North Atlantic Current (NAC) during the Pliocene, the long-term terrestrial climate evolution and its driving mechanisms are poorly understood. We present the first two-million-year-long Pliocene pollen record for the Nordic Seas region from Ocean Drilling Program (ODP) Hole 642B, reflecting vegetation and climate in Arctic Norway, to assess the influence of oceanographic and atmospheric controls on Pliocene climate evolution. The vegetation record reveals a long-term cooling trend in northern Norway, which might be linked to a general decline in atmospheric CO2 concentrations over the studied interval, and climate oscillations primarily controlled by precession (23 kyr), obliquity (54 kyr) and eccentricity (100 kyr) forcing. In addition, the record identifies four major shifts in Pliocene vegetation and climate mainly controlled by changes in northward heat transport via the NAC. Cool temperate (warmer than present) conditions prevailed between 5.03-4.30 Ma, 3.90-3.47 Ma and 3.29-3.16 Ma and boreal (similar to present) conditions predominated between 4.30-3.90 Ma, 3.47-3.29 and after 3.16 Ma. A distinct decline in sediment and pollen accumulation rates at c. 4.65 Ma is probably linked to changes in ocean currents, marine productivity and atmospheric circulation. Climate model simulations suggest that changes in the strength of the Atlantic Meridional Overturning Circulation during the Early Pliocene could have affected atmospheric circulation in the Nordic Seas region, which would have affected the direction of pollen transport from Scandinavia to ODP Hole 642B.

Development and Application of a Wireless Sensor for Space Charge Density Measurement in an Ultra-High-Voltage, Direct-Current Environment

PubMed Central

Xin, Encheng; Ju, Yong; Yuan, Haiwen

2016-01-01

A space charge density wireless measurement system based on the idea of distributed measurement is proposed for collecting and monitoring the space charge density in an ultra-high-voltage direct-current (UHVDC) environment. The proposed system architecture is composed of a number of wireless nodes connected with space charge density sensors and a base station. The space charge density sensor based on atmospheric ion counter method is elaborated and developed, and the ARM microprocessor and Zigbee radio frequency module are applied. The wireless network communication quality and the relationship between energy consumption and transmission distance in the complicated electromagnetic environment is tested. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the UHVDC transmission lines and can accurately measure the space charge density. PMID:27775627

Development and Application of a Wireless Sensor for Space Charge Density Measurement in an Ultra-High-Voltage, Direct-Current Environment.

PubMed

Xin, Encheng; Ju, Yong; Yuan, Haiwen

2016-10-20

A space charge density wireless measurement system based on the idea of distributed measurement is proposed for collecting and monitoring the space charge density in an ultra-high-voltage direct-current (UHVDC) environment. The proposed system architecture is composed of a number of wireless nodes connected with space charge density sensors and a base station. The space charge density sensor based on atmospheric ion counter method is elaborated and developed, and the ARM microprocessor and Zigbee radio frequency module are applied. The wireless network communication quality and the relationship between energy consumption and transmission distance in the complicated electromagnetic environment is tested. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the UHVDC transmission lines and can accurately measure the space charge density.

Estimating Photosynthetically Available Radiation (PAR) at the Earth's surface from satellite observations

NASA Technical Reports Server (NTRS)

Frouin, Robert

1993-01-01

Current satellite algorithms to estimate photosynthetically available radiation (PAR) at the earth' s surface are reviewed. PAR is deduced either from an insolation estimate or obtained directly from top-of-atmosphere solar radiances. The characteristics of both approaches are contrasted and typical results are presented. The inaccuracies reported, about 10 percent and 6 percent on daily and monthly time scales, respectively, are useful to model oceanic and terrestrial primary productivity. At those time scales variability due to clouds in the ratio of PAR and insolation is reduced, making it possible to deduce PAR directly from insolation climatologies (satellite or other) that are currently available or being produced. Improvements, however, are needed in conditions of broken cloudiness and over ice/snow. If not addressed properly, calibration/validation issues may prevent quantitative use of the PAR estimates in studies of climatic change. The prospects are good for an accurate, long-term climatology of PAR over the globe.

Direct search for dark matter with DarkSide

DOE PAGES

Agnes, P.

2015-11-16

Here, the DarkSide experiment is designed for the direct detection of Dark Matter with a double phase liquid Argon TPC operating underground at Laboratori Nazionali del Gran Sasso. The TPC is placed inside a 30 tons liquid organic scintillator sphere, acting as a neutron veto, which is in turn installed inside a 1 kt water Cherenkov detector. The current detector is running since November 2013 with a 50 kg atmospheric Argon fill and we report here the first null results of a Dark Matter search for a (1422 ± 67) kg.d exposure. This result correspond to a 90% CL uppermore » limit on the WIMP-nucleon cross section of 6.1 × 10 -44 cm 2 (for a WIMP mass of 100 GeV/c 2) and it's currently the most sensitive limit obtained with an Argon target.« less

Online coupled regional meteorology-chemistry models in Europe: current status and prospects

NASA Astrophysics Data System (ADS)

Baklanov, A.; Schluenzen, K. H.; Suppan, P.; Baldasano, J.; Brunner, D.; Aksoyoglu, S.; Carmichael, G.; Douros, J.; Flemming, J.; Forkel, R.; Galmarini, S.; Gauss, M.; Grell, G.; Hirtl, M.; Joffre, S.; Jorba, O.; Kaas, E.; Kaasik, M.; Kallos, G.; Kong, X.; Korsholm, U.; Kurganskiy, A.; Kushta, J.; Lohmann, U.; Mahura, A.; Manders-Groot, A.; Maurizi, A.; Moussiopoulos, N.; Rao, S. T.; Savage, N.; Seigneur, C.; Sokhi, R.; Solazzo, E.; Solomos, S.; Sørensen, B.; Tsegas, G.; Vignati, E.; Vogel, B.; Zhang, Y.

2013-05-01

The simulation of the coupled evolution of atmospheric dynamics, pollutant transport, chemical reactions and atmospheric composition is one of the most challenging tasks in environmental modelling, climate change studies, and weather forecasting for the next decades as they all involve strongly integrated processes. Weather strongly influences air quality (AQ) and atmospheric transport of hazardous materials, while atmospheric composition can influence both weather and climate by directly modifying the atmospheric radiation budget or indirectly affecting cloud formation. Until recently, however, due to the scientific complexities and lack of computational power, atmospheric chemistry and weather forecasting have developed as separate disciplines, leading to the development of separate modelling systems that are only loosely coupled. The continuous increase in computer power has now reached a stage that enables us to perform online coupling of regional meteorological models with atmospheric chemical transport models. The focus on integrated systems is timely, since recent research has shown that meteorology and chemistry feedbacks are important in the context of many research areas and applications, including numerical weather prediction (NWP), AQ forecasting as well as climate and Earth system modelling. However, the relative importance of online integration and its priorities, requirements and levels of detail necessary for representing different processes and feedbacks can greatly vary for these related communities: (i) NWP, (ii) AQ forecasting and assessments, (iii) climate and earth system modelling. Additional applications are likely to benefit from online modelling, e.g.: simulation of volcanic ash or forest fire plumes, pollen warnings, dust storms, oil/gas fires, geo-engineering tests involving changes in the radiation balance. The COST Action ES1004 - European framework for online integrated air quality and meteorology modelling (EuMetChem) - aims at paving the way towards a new generation of online integrated atmospheric chemical transport and meteorology modelling with two-way interactions between different atmospheric processes including dynamics, chemistry, clouds, radiation, boundary layer and emissions. As its first task, we summarise the current status of European modelling practices and experience with online coupled modelling of meteorology with atmospheric chemistry including feedback mechanisms and attempt reviewing the various issues connected to the different modules of such online coupled models but also providing recommendations for coping with them for the benefit of the modelling community at large.

Direct multiangle solution for poorly stratified atmospheres

Treesearch

Vladimir Kovalev; Cyle Wold; Alexander Petkov; Wei Min Hao

2012-01-01

The direct multiangle solution is considered, which allows improving the scanning lidar-data-inversion accuracy when the requirement of the horizontally stratified atmosphere is poorly met. The signal measured at zenith or close to zenith is used as a core source for extracting optical characteristics of the atmospheric aerosol loading. The multiangle signals are used...

Measurements of nitric acid, carboxylic acids, and selected aerosol species for the NASA/GTE Pacific Mission - West (PEM-WEST)

NASA Technical Reports Server (NTRS)

Talbot, Robert W.; Dibb, Jack E.

1993-01-01

The research investigation funded through this grant to the University of New Hampshire was performed during a major field expedition conducted by the NASA Tropospheric Chemistry Program. The NASA Global Tropospheric Experiment (GTE) executed an airborne science mission (PEM-WEST A) aboard the NASA Ames DC-8 over the Pacific Ocean during Sep./Oct. 1981. The atmosphere over the central Pacific Ocean is the only major region in the Northern Hemisphere that is relatively free from direct anthropogenic influence. Thus, this environment is ideally suited to study the natural biogeochemical cycles of carbon, nitrogen, ozone, sulfur, and aerosols without serious confounding problems related to anthropogenic emissions. Asian sources account for about 17 percent of the global budgets of nitrogen oxides (NO(x)) and sulfur dioxide (SO2). The Pacific Rim region therefore provides the opportunity to study the anthropogenic impact on natural atmospheric chemical cycles. The PEM-WEST A flights were focused on contrasting the chemistry of 'clean' air over the central Pacific with anthropogenically impacted air advected off the Asian continent. The principal objectives of PEM-WEST A were to investigate the atmospheric chemistry of ozone (O3) and its precursors, and to study important aspects of the atmospheric sulfur cycle over the western Pacific Ocean. Measurements conducted by the University of New Hampshire contributed directly to both of these objectives. Subsequent PEM-WEST field missions are planned by GTE in the mid-1990's to contrast atmospheric chemistry documented during PEM-WEST A with other time periods. This report presents preliminary findings from the PEM-WEST A field mission. Data interpretation is currently ongoing with the goal of manuscript submission of scientific results to a special issue of the Journal of Geophysical Research-Atmospheres in Feb. 1994. The reader is strongly encouraged to review this suite of profession articles to appreciate the overall scientific findings and benefits of the PEM-WEST A field mission.

Mass spectrometry imaging for visualizing organic analytes in food.

PubMed

Handberg, Eric; Chingin, Konstantin; Wang, Nannan; Dai, Ximo; Chen, Huanwen

2015-01-01

The demand for rapid chemical imaging of food products steadily increases. Mass spectrometry (MS) is featured by excellent molecular specificity of analysis and is, therefore, a very attractive method for chemical profiling. MS for food imaging has increased significantly over the past decade, aided by the emergence of various ambient ionization techniques that allow direct and rapid analysis in ambient environment. In this article, the current status of food imaging with MSI is reviewed. The described approaches include matrix-assisted laser desorption/ionization (MALDI), but emphasize desorption atmospheric pressure photoionization (DAPPI), electrospray-assisted laser desorption/ionization (ELDI), probe electrospray ionization (PESI), surface desorption atmospheric pressure chemical ionization (SDAPCI), and laser ablation flowing atmospheric pressure afterglow (LA-FAPA). The methods are compared with regard to spatial resolution; analysis speed and time; limit of detection; and technical aspects. The performance of each method is illustrated with the description of a related application. Specific requirements in food imaging are discussed. © 2014 Wiley Periodicals, Inc.

Atmospheric-pressure plasma decontamination/sterilization chamber

DOEpatents

Herrmann, Hans W.; Selwyn, Gary S.

2001-01-01

An atmospheric-pressure plasma decontamination/sterilization chamber is described. The apparatus is useful for decontaminating sensitive equipment and materials, such as electronics, optics and national treasures, which have been contaminated with chemical and/or biological warfare agents, such as anthrax, mustard blistering agent, VX nerve gas, and the like. There is currently no acceptable procedure for decontaminating such equipment. The apparatus may also be used for sterilization in the medical and food industries. Items to be decontaminated or sterilized are supported inside the chamber. Reactive gases containing atomic and metastable oxygen species are generated by an atmospheric-pressure plasma discharge in a He/O.sub.2 mixture and directed into the region of these items resulting in chemical reaction between the reactive species and organic substances. This reaction typically kills and/or neutralizes the contamination without damaging most equipment and materials. The plasma gases are recirculated through a closed-loop system to minimize the loss of helium and the possibility of escape of aerosolized harmful substances.

Real-time radon monitoring at Stromboli volcano: influence of environmental parameters on 222Rn degassing

NASA Astrophysics Data System (ADS)

Cigolini, C.; Ripepe, M.; Poggi, P.; Laiolo, M.

2008-12-01

Two real-time stations for radon monitoring are currently operative at Stromboli volcano. The 222Rn electronic dosimeters are interfaced with an electronic board connected to a radiomodem for wireless data transfer (through a directional antenna) to a receiving station at the volcano observatory (COA). Radon activity data and enviromental parameters (soil temperature and atmospheric pressure) are sampled every 15 minutes and are instantaneously elaborated and transferred via web so that they can be checked in remote. Collected time series show that there is an overall inverse correlation between radon emissions and seasonal temperature variations. Signal processing analysis show that radon emissions in sectors of diffuse degassing are modulated by tidal forces as well. In addition, radon activities recorded at the summit station, located along the summit fracture zone where the gas flux is concentrated, are positively correlated with changes in atmospheric pressure and confirm the occurrence of the 'atmospheric stack effect'. It is not excluded that this process may play an active role in modulating Stromboli explosivity.

Sampling of atmospheric carbonyl compounds for determination by liquid chromatography after 2,4-dinitrophenylhydrazine labelling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vairavamurthy, A.; Roberts, J.M.; Newman, L.

1991-06-01

Carbonyl compounds are both primary (directly emitted) and secondary (formed in situ) atmospheric species, which play a major role in tropospheric photochemistry. Because of trace concentrations (parts-per-billion and lower), ambient air measurements of carbonyls pose serious analytical problems. Generally, chromatographic approaches combined with chemical derivatization have been used to enhance sensitivity and selectivity in analysis. Currently, the liquid chromatographic method coupled to 2,4-dinitrophenylhydrazine derivatization (DNPH-LC) is in widespread use. Interferences arising from similar compounds are greatly minimized by chromatographic separation; however, those in the air sampling step, especially with ozone, continue to be problematic and remain to be resolved. Wemore » discuss here the different sampling techniques used for time-integrated collection of carbonyls in the DNPH-LC methods. Emphasis is placed on addressing: (1) the principles, advantages, and limitations of sampling techniques; (2) problems associated with reagent blank and sampling instrument; and (3) effects of atmospheric co-pollutants, especially ozone. 58 refs., 8 figs., 3 tabs.« less

Analysis of ELF Radio Atmospherics Radiated by Rocket-Triggered Lightning

NASA Astrophysics Data System (ADS)

Dupree, N. A.; Moore, R. C.; Pilkey, J. T.; Uman, M. A.; Jordan, D. M.; Caicedo, J. A.; Hare, B.; Ngin, T. K.

2014-12-01

Experimental observations of ELF radio atmospherics produced by rocket-triggered lightning flashes are used to analyze Earth-ionosphere waveguide excitation and propagation characteristics. Rocket-triggered lightning experiments are performed at the International Center for Lightning Research and Testing (ICLRT) located at Camp Blanding, Florida. Long-distance ELF observations are performed in California, Greenland, and Antarctica. The lightning current waveforms directly measured at the base of the lightning channel (at the ICLRT) along with pertinent Lightning Mapping Array (LMA) data are used together with the Long Wavelength Propagation Capability (LWPC) code to predict the radio atmospheric (sferic) waveform observed at the receiver locations under various ionospheric conditions. We identify fitted exponential electron density profiles that accurately describe the observed propagation delays, phase delays, and signal amplitudes. The ability to infer ionospheric characteristics using distant ELF observations greatly enhances ionospheric remote sensing capabilities, especially in regard to interpreting observations of transient luminous events (TLEs) and other ionospheric effects associated with lightning.

Atmospheric deposition of methanol over the Atlantic Ocean

PubMed Central

Yang, Mingxi; Nightingale, Philip D.; Beale, Rachael; Liss, Peter S.; Blomquist, Byron; Fairall, Christopher

2013-01-01

In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air–sea methanol transfer along a ∼10,000-km north–south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air–sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at ∼5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface—an important term for improving air–sea gas exchange models. PMID:24277830

Atmospheric deposition of methanol over the Atlantic Ocean.

PubMed

Yang, Mingxi; Nightingale, Philip D; Beale, Rachael; Liss, Peter S; Blomquist, Byron; Fairall, Christopher

2013-12-10

In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air-sea methanol transfer along a ∼10,000-km north-south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air-sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at ∼5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface-an important term for improving air-sea gas exchange models.

Photochemistry of aqueous pyruvic acid

PubMed Central

Griffith, Elizabeth C.; Carpenter, Barry K.; Shoemaker, Richard K.; Vaida, Veronica

2013-01-01

The study of organic chemistry in atmospheric aerosols and cloud formation is of interest in predictions of air quality and climate change. It is now known that aqueous phase chemistry is important in the formation of secondary organic aerosols. Here, the photoreactivity of pyruvic acid (PA; CH3COCOOH) is investigated in aqueous environments characteristic of atmospheric aerosols. PA is currently used as a proxy for α-dicarbonyls in atmospheric models and is abundant in both the gas phase and the aqueous phase (atmospheric aerosols, fog, and clouds) in the atmosphere. The photoreactivity of PA in these phases, however, is very different, thus prompting the need for a mechanistic understanding of its reactivity in different environments. Although the decarboxylation of aqueous phase PA through UV excitation has been studied for many years, its mechanism and products remain controversial. In this work, photolysis of aqueous PA is shown to produce acetoin (CH3CHOHCOCH3), lactic acid (CH3CHOHCOOH), acetic acid (CH3COOH), and oligomers, illustrating the progression from a three-carbon molecule to four-carbon and even six-carbon molecules through direct photolysis. These products are detected using vibrational and electronic spectroscopy, NMR, and MS, and a reaction mechanism is presented accounting for all products detected. The relevance of sunlight-initiated PA chemistry in aqueous environments is then discussed in the context of processes occurring on atmospheric aerosols. PMID:23821751

Mars Climate Orbiter's Investigation of the Atmosphere and Polar Caps

NASA Technical Reports Server (NTRS)

McCleese, D. J.; Moroz, V.; Schofield, T.; Taylor, F.; Zurek, R.

1999-01-01

The Mars Climate Orbiter (MCO) is now on its way to Mars. It carries an atmospheric sounder whose observations will provide a continuous, global data set on weather and climate for a full Martian year. This paper describes the observation strategy and anticipated results from the Pressure Modulator Infrared Radiometer (PMIRR). PMIRR will measure vertical profiles of atmospheric infrared radiance in the 7 to 50 micron wavelength region extending from the surface of Mars to 80-km altitude. The observations have a vertical resolution of 5 km, or one-half the atmospheric scale height. From these radiance profiles we will retrieve profiles of atmospheric temperature, pressure, and the amounts of dust, condensates and water vapor. In addition, PMIRR will measure the radiative balance of the polar regions of Mars in an effort to better understand the short-term climate variability of the planet. The information obtained with PMIRR on MCO will be complementary to data obtained by the Thermal Emission Spectrometer (TES) and Radio Science (RS) experiments on the Mars Global Surveyor. A major emphasis of our research will be the assimilation of PMIRR data into numerical models of the Martian atmosphere. Assimilation schemes, of which several are currently in development, will permit the extension of measurements to spatial and temporal scales and to phenomena (e.g. winds) not observed directly by PMIRR.

The Role of Atmospheric Organic Nitrogen in Forest Nitrogen Cycling

NASA Astrophysics Data System (ADS)

Lockwood, A.; Shepson, P.; Rhodes, D.

2003-12-01

Changes in the global climate and atmosphere cause significant effects to the biosphere. Forests respond to these global changes in various ways which all can affect their ability to store carbon, which in turn impacts climate change. Many temperate latitude forests are nitrogen-limited. A current working hypothesis is that atmospheric nitrogen compounds that are deposited to the canopy may be directly utilized by the plant as a nitrogen source. A significant fraction of atmospheric reactive nitrogen that can be deposited is organic. Organic nitrogen deposition is not well characterized nor have the ecological consequences been assessed. Our hypothesis is that organic nitrogen deposition to the canopy is significant, and that that nitrogen is utilized by trees. Fumigation experiments were conducted with 14N and 15N-labeled organic nitrates (focusing on 1-nitrooxy-3-methyl butane as a surrogate for isoprene nitrates) to determine if and how that nitrogen gets incorporated into the leaves by detecting the 15N-labeled leaf amino acids. This research builds on work completed during past summer intensives as part of the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET), and begins the next stage of research as part of the Biosphere Atmosphere Research & Training program (BART) at the University of Michigan Biological Station (UMBS). The overall goal of the new effort, the Biosphere Exchange of Atmospheric Carbon and Odd Nitrogen (BEACON) program, is to evaluate the interactive roles of the atmosphere and forest in the coupling of the carbon and nitrogen cycles.

The Breath of Planet Earth: Atmospheric Circulation. Assimilation of Surface Wind Observations

NASA Technical Reports Server (NTRS)

Atlas, Robert; Bloom, Stephen; Otterman, Joseph

2000-01-01

Differences in air pressure are a major cause of atmospheric circulation. Because heat excites the movement of atoms, warm temperatures cause, air molecules to expand. Because those molecules now occupy a larger space, the pressure that their weight exerts is decreased. Air from surrounding high-pressure areas is pushed toward the low-pressure areas, creating circulation. This process causes a major pattern of global atmosphere movement known as meridional circulation. In this form of convection, or vertical air movement, heated equatorial air rises and travels through the upper atmosphere toward higher latitudes. Air just above the equator heads toward the North Pole, and air just below the equator moves southward. This air movement fills the gap created where increased air pressure pushes down cold air. The ,cold air moves along the surface back toward the equator, replacing the air masses that rise there. Another influence on atmospheric. circulation is the Coriolis force. Because of the Earth's rotation, large-scale wind currents move in the direction of this axial spin around low-pressure areas. Wind rotates counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. just as the Earth's rotation affects airflow, so too does its surface. In the phenomenon of orographic lifting, elevated topographic features such as mountain ranges lift air as it moves up their surface.

History of Martian Atmosphere and Volatiles Derived From MAVEN Observations

NASA Astrophysics Data System (ADS)

Jakosky, B. M.

2017-12-01

The MAVEN spacecraft has been observing loss of volatiles from the Mars upper atmosphere to space for more than a full Mars year. By understanding the present-day loss rates and the processes that drive loss, we can extrapolate to past epochs and estimate the total amount of gas lost to space through time. The current total loss rate is more than 2 kg/s. With the increased loss rate in the past due to the greater solar EUV flux and solar-wind intensity early in history, we estimate that more than 0.5 bar of CO2 might have been lost to space. This plausibility argument is augmented by observations of the 38Ar/36Ar ratio today that provide a direct indication of the integrated loss through time; the measurements indicate that the majority of atmospheric gas has, in fact, been lost to space. Combined with the lack of carbonates on the surface that can be a reservoir for CO2 from an earlier, thick atmosphere, these results point to loss to space as having been the major process for driving the changes in the atmosphere. Loss to space appears to have been responsible for changing the Martian climate from an early, warm, wet environment to the cold, dry climate that we see today.

Using a simple apparatus to measure direct and diffuse photosynthetically active radiation at remote locations.

PubMed

Cruse, Michael J; Kucharik, Christopher J; Norman, John M

2015-01-01

Plant canopy interception of photosynthetically active radiation (PAR) drives carbon dioxide (CO2), water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM) Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal) of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the potential to support ecological research via a relatively inexpensive method to collect continuous measurements of total, direct beam and diffuse PAR in remote locations.

Using a Simple Apparatus to Measure Direct and Diffuse Photosynthetically Active Radiation at Remote Locations

PubMed Central

Cruse, Michael J.; Kucharik, Christopher J.; Norman, John M.

2015-01-01

Plant canopy interception of photosynthetically active radiation (PAR) drives carbon dioxide (CO2), water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM) Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal) of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the potential to support ecological research via a relatively inexpensive method to collect continuous measurements of total, direct beam and diffuse PAR in remote locations. PMID:25668208

Detecting Super-Thin Clouds With Polarized Light

NASA Technical Reports Server (NTRS)

Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

2014-01-01

We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

Detecting Super-Thin Clouds with Polarized Sunlight

NASA Technical Reports Server (NTRS)

Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

2014-01-01

We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

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

NASA Technical Reports Server (NTRS)

Wolfe, G. M.; Hanisco, T. F.; Arkinson, H. L.; Bui, T. P.; Crounse, J. D.; Dean-Day, J.; Goldstein, A.; Guenther, A.; Hall, S. R.; Huey, G.;

Sample damage during X-ray fluorescence analysis--case study on ammonium salts in atmospheric aerosols.

PubMed

Van Meel, Katleen; Worobiec, Anna; Stranger, Marianne; Van Grieken, René

2008-08-01

Atmospheric aerosols can consist of, amongst others, compounds like NH(4)NO(3) or (NH(4))(2)SO(4). Such components can suffer radiation damage and/or evaporate during EDXRF measurements, providing errors on successively applied analysis. The aim of this work is to investigate the influence of measurements using conventional EDXRF on the volatile compounds and to compare it with the influence of polarized beam EDXRF using secondary targets (and hence indirect irradiation). The effect of different parameters (acquisition time, accelerating voltage, current and medium) on the concentration loss was studied. The measurements performed in vacuum during a long period lead to the highest losses of volatile compounds. The influence of direct irradiation was proved to be larger than the indirect variant.

CURRENT METHODS AND RESEARCH STRATEGIES FOR MODELING ATMOSPHERIC MERCURY

EPA Science Inventory

The atmospheric pathway of the global mercury cycle is known to be the primary source of mercury contamination to most threatened aquatic ecosystems. Current efforts toward numerical modeling of atmospheric mercury are hindered by an incomplete understanding of emissions, atmosp...

Distribution mode and environmental risk of POP pesticides such as endosulfan under the agricultural practice of straw incorporating.

PubMed

Wang, Jie; Li, Li; Liu, Jianguo; Ti, Bowen

2017-01-01

The practice of incorporating post-harvest crop waste is widely used because it maintains soil fertility and avoids environmental pollution from straw burning. However, the practice of straw incorporation may also retain the pesticides that are applied to crop plants, which may pose a potential long term risk to local and regional environments if the applied pesticide is a Persistent, Bioaccumulative, and Toxic (PBT) substance or a Persistent Organic Pollutant (POP). Here we investigate the influence of the "receiving-retention-release" route on the distribution of a POP pesticide (endosulfan) and the associated environmental risk among different environmental compartments. Our study indicates that most endosulfan enters the atmosphere (φ atmosphere  = 64.5-72.5%), which is dominated by the indirect route of volatilization from crop plants (φ atmosphere, indirect  = 54.7-70.3%). In contrast, soil releases are minor (φ soil  = 10.8-20.5%), and are dominated by direct release during application (φ soil, direct  = 8.0-18.0%). Under the practice of straw incorporation, the use of endosulfan posed an environmental risk to agricultural soil. In addition, the atmospheric deposition of endosulfan also posed an environmental risk to sediment. The study highlights the significance of the "receiving-retention-release" route by crop plants in determining the fate of POP pesticides associated with straw incorporation; hence complementing the current methodology for assessing the environmental risk of these compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Venera-D Mission Concept: Evaluation by a Joint Science Definition Team of a Means for the Comprehensive Scientific Exploration of Venus

NASA Astrophysics Data System (ADS)

Senske, D.; Zasova, L. V.; Economou, T.; Eismont, N.; Esposito, L. W.; Gerasimov, M.; Ignatiev, N. I.; Ivanov, M.; Jessup, K. L.; Korablev, O.; Tibor, K.; Limaye, S. S.; Martynov, A.; Ocampo, A.

2016-12-01

Located in the same part of the solar system and formed out of the same protoplanetary material, Venus is Earth's twin. Although these siblings have nearly the same size, mass, and density, the climate of Venus, fueled by a massive CO2 atmosphere has an enormous greenhouse effect with a surface pressure of 90 atm. and a temperature of 470°C. Shrouded in clouds of sulfuric acid, the surface lacks water and has been sculpted by volcanism and deformed by faulting and folding forming rifts and belts of mountains. The lack of an intrinsic magnetic field suggests the planet's interior structure may be different than that of the earth. The study of Venus will aid in better understanding our own world and the possible future evolution of our climate. In particular, the instability of our climate and the increase in amount of greenhouse gases-can our climate be slowly going in Venus' direction? Despite the advancement in understanding achieved from previous and ongoing missions, the key questions concerning the origin and evolution of Venus and its climate cannot be solved by observations from orbit alone. Direct measurements in the atmosphere and on the surface are required. In this regard, a Joint Science Definition Team (JSDT) chartered by NASA and IKI/Roscosmos has been studying a concept for the comprehensive investigation of Venus that would consist of an orbiter (>3 yr. of operation) and a lander (2 hrs. on the surface). The scientific goals of the concept are tied closely to the key objectives established by VEXAG and the NASA Planetary Decadal Survey and include: investigation of the thermal structure and chemical composition of the atmosphere and clouds, abundances and isotopic ratios of the light and noble gases; study of the thermal balance, dynamics, and super-rotation of the atmosphere; determination of the surface mineralogy and elemental composition including key radioactive isotopes; study of potential current volcanic and electrical activity; and study of the plasma environment, magnetosphere, and atmospheric escape. The JSDT is also evaluating technology needs and the potential for innovative flight element augmentations including, free flying aerial platforms, sub-satellites, and drop sondes. The status of the JSDT activity and the context of the mission within past and current Venus exploration will be reported.

Brown dwarf science at Project 1640: the case of HD 19467 B

NASA Astrophysics Data System (ADS)

Aguilar, Jonathan; Crepp, Justin R.; Rice, Emily L.; Pueyo, Laurent; Veicht, Aaron; Nilsson, Ricky; Oppenheimer, Rebecca; Hinkley, Sasha; Brenner, Douglas; Vasisht, Gautam; Cady, Eric; Beichman, Charles A.; Hillenbrand, Lynne; Lockhart, Thomas; Matthews, Christopher T.; Roberts, Lewis C.; Sivaramakrishnan, Anand; Soummer, Remi; Zhai, Chengxing; Giorla, Paige

2015-01-01

Project 1640 is an extreme-AO, coronagraphic, hyperspectral direct-imaging instrument designed to characterize substellar companions in the giant planet to brown dwarf mass regime. It also plays an important role in the TRENDS survey, which targets solar-type stars with Doppler accelerations known to be caused by brown dwarf-sized companions. A recent highlight from TRENDS is HD 19467 B -- this is currently the only directly-imaged benchmark T dwarf known to induce a measurable Doppler acceleration around its host. J- and H-band spectra taken by the Project 1640 integral field spectrograph were fitted against SpeX/IRTF T dwarf standards and synthetic spectra from BT-Settl atmospheric models. Spectral typing classified HD 19467 B as a T5.5±1 brown dwarf with an effective temperature of Teff = 978+20-43 K. The new spectrum helps resolve a previous disagreement about the system age, helping constrain the range of allowed masses for the companion. We expect that new data from the ongoing TRENDS survey will help improve our understanding of brown dwarf atmospheres in high mass ratio systems.

Development and application of gravity-capillary wave fourier analysis for the study of air-sea interaction physics

NASA Astrophysics Data System (ADS)

MacKenzie Laxague, Nathan Jean

Short ocean waves play a crucial role in the physical coupling between the ocean and the atmosphere. This is particularly true for gravity-capillary waves, waves of a scale (O(0.01-0.1) m) such that they are similarly restored to equilibrium by gravitational and interfacial tension (capillary) effects. These waves are inextricably linked to the turbulent boundary layer processes which characterize near-interfacial flows, acting as mediators of the momentum, gas, and heat fluxes which bear greatly on surface material transport, tropical storms, and climatic processes. The observation of these waves and the fluid mechanical phenomena which govern their behavior has long posed challenges to the would-be observer. This is due in no small part to the delicacy of centimeter-scale waves and the sensitivity of their properties to disruption via tactile measurement. With the ever-growing interest in satellite remote sensing, direct observations of short wave characteristics are needed along coastal margins. These zones are characterized by a diversity of physical processes which can affect the short-scale sea surface topography that is directly sensed via radar backscatter. In a related vein, these observations are needed to more fully understand the specific hydrodynamic relationship between young, wind-generated gravity-capillary waves and longer gravity waves. Furthermore, understanding of the full oceanic current profile is hampered by a lack of observations in the near-surface domain (z = O(0.01-0.1) m), where flows can differ greatly from those at depth. Here I present the development of analytical techniques for describing gravity-capillary ocean surface waves in order to better understand their role in the mechanical coupling between the atmosphere and ocean. This is divided amongst a number of research topics, each connecting short ocean surface waves to a physical forcing process via the transfer of momentum. One involves the examination of the sensitivity of short ocean surface waves to atmospheric forcing. Another is the exploration of long wave-short wave interactions and their effects on air-sea interaction vis-a-vis hydrodynamic modulation. The third and final topic is the characterization of the gravity-capillary regime of the wavenumber-frequency spectrum for the purpose of retrieving near-surface, wind-driven current. All of these fit as part of the desire to more fully describe the mechanism by which momentum is transferred across the air-sea interface and to discuss the consequences of this flux in the very near-surface layer of the ocean. Gravity-capillary waves are found to have an outsize share of ocean surface roughness, with short wave spectral peaks showing a connection to turbulent atmospheric stress. Short wave modulation is found to occur strongest at high wavenumbers at the lowest wind speeds, with peak modulation occurring immediately downwind of the long wave crest. Furthermore, short scale roughness enhancement is found to occur upwind of the long wave crest for increasing wind forcing magnitude. Observations of the near-surface current profile show that flows retrieved via this method agree well with the results of camera-tracked dye. Application of this method to data collected in the mouth of the Columbia River (MCR) indicates the presence of a near-surface current component that departs considerably from the tidal flow and orients into the wind stress direction. These observations demonstrate that wind speed-based parameterizations may not be sufficient to estimate wind drift and hold implications for the way in which surface material (e.g., debris or spilled oil) transport is estimated when atmospheric stress is of relatively high magnitude or is steered off the mean wind direction.

Wind Stress Variability Observed Over Coastal Waters

NASA Astrophysics Data System (ADS)

Ortiz-Suslow, D. G.; Haus, B. K.; Laxague, N.; Williams, N. J.; Graber, H. C.

2016-02-01

The wind stress on the ocean surface generates waves, drives currents, and enhances gas exchange; and a significant amount of work has been done to characterize the air-sea momentum flux in terms of bulk oceanographic and atmospheric parameters. However, the majority of this work to develop operational algorithms has been focused on the deep ocean and the suitability of these methods in the coastal regime has not been evaluated. The findings from a two-part field campaign will be presented which highlight the divergence of nearshore wind stress observations from conventional, deep water results. The first set of data comes from a coastal region near a relatively small, natural tidal inlet. A high degree of spatial variability was observed in both the wind stress magnitude and direction, suggestive of coastal processes (e.g., depth-limited wave affects and horizontal current shear) modulating the momentum flux from the atmosphere to the ocean surface. These shallow-water processes are typically not accounted for in conventional parameterizations. Across the experimental domain and for a given wind speed, the stress magnitude was found to be nearly 2.5 times that predicted by conventional methods; also, a high propensity for stress steering off the mean azimuthal wind direction (up to ±70 degrees) was observed and linked to horizontal current gradients produced by the tidal inlet. The preliminary findings from a second data set taken in the vicinity of the macrotidal Columbia River Mouth will also be presented. Compared to the first data set, a similar degree of variability is observed here, but the processes responsible for this are present at a much larger scale. Specifically, the Columbia River Mouth observations were made in the presence of significant swell wave energy and during periods of very high estuarine discharge. The relative angle between the wind and swell direction is expected to be significant with regards to the observed momentum flux. Also, these processes facilitate strong wave-current interaction, which may also affect the surface topography and thus play a role in air-sea exchanges. The Columbia River Mouth system showcases a complex coastal environment and future avenues for investigating these dynamics will be discussed.

Assessment, Validation, and Refinement of the Atmospheric Correction Algorithm for the Ocean Color Sensors. Chapter 19

NASA Technical Reports Server (NTRS)

Wang, Menghua

2003-01-01

The primary focus of this proposed research is for the atmospheric correction algorithm evaluation and development and satellite sensor calibration and characterization. It is well known that the atmospheric correction, which removes more than 90% of sensor-measured signals contributed from atmosphere in the visible, is the key procedure in the ocean color remote sensing (Gordon and Wang, 1994). The accuracy and effectiveness of the atmospheric correction directly affect the remotely retrieved ocean bio-optical products. On the other hand, for ocean color remote sensing, in order to obtain the required accuracy in the derived water-leaving signals from satellite measurements, an on-orbit vicarious calibration of the whole system, i.e., sensor and algorithms, is necessary. In addition, it is important to address issues of (i) cross-calibration of two or more sensors and (ii) in-orbit vicarious calibration of the sensor-atmosphere system. The goal of these researches is to develop methods for meaningful comparison and possible merging of data products from multiple ocean color missions. In the past year, much efforts have been on (a) understanding and correcting the artifacts appeared in the SeaWiFS-derived ocean and atmospheric produces; (b) developing an efficient method in generating the SeaWiFS aerosol lookup tables, (c) evaluating the effects of calibration error in the near-infrared (NIR) band to the atmospheric correction of the ocean color remote sensors, (d) comparing the aerosol correction algorithm using the singlescattering epsilon (the current SeaWiFS algorithm) vs. the multiple-scattering epsilon method, and (e) continuing on activities for the International Ocean-Color Coordinating Group (IOCCG) atmospheric correction working group. In this report, I will briefly present and discuss these and some other research activities.

Asymmetric Magnetic Reconnection in the Solar Atmosphere

NASA Astrophysics Data System (ADS)

Murphy, N. A.; Miralles, M. P.; Ranquist, D. A.; Pope, C. L.; Raymond, J. C.; Lukin, V. S.; McKillop, S.; Shen, C.; Winter, H. D.; Reeves, K. K.; Lin, J.

2013-12-01

Models of solar flares and coronal mass ejections typically predict the development of an elongated current sheet in the wake behind the rising flux rope. In reality, reconnection in these current sheets will be asymmetric along the inflow, outflow, and out-of-plane directions. We perform resistive MHD simulations to investigate the consequences of asymmetry during solar reconnection. We predict several observational signatures of asymmetric reconnection, including flare loops with a skewed candle flame shape, slow drifting of the current sheet into the strong field upstream region, asymmetric footpoint speeds and hard X-ray emission, and rolling motions within the erupting flux rope. There is net plasma flow across the magnetic field null along both the inflow and outflow directions. We compare simulations to SDO/AIA, Hinode/XRT, and STEREO observations of flare loop shapes, current sheet drifting, and rolling motions during prominence eruptions. Simulations of the plasmoid instability with different upstream magnetic fields show that the reconnection rate remains enhanced even during the asymmetric case. The islands preferentially grow into the weak field upstream region. The islands develop net vorticity because the outflow jets impact them obliquely rather than directly. Asymmetric reconnection in the chromosphere occurs when emerging flux interacts with pre-existing overlying flux. We present initial results on asymmetric reconnection in partially ionized chromospheric plasmas. Finally, we discuss how comparisons to observations are necessary to understand the role of three-dimensional effects.

Asymmetric Magnetic Reconnection in the Solar Atmosphere

NASA Astrophysics Data System (ADS)

Murphy, N. A.; Miralles, M. P.; Ranquist, D. A.; Pope, C. L.; Raymond, J. C.; Lukin, V. S.; McKillop, S. C.; Shen, C.; Winter, H. D.; Reeves, K. K.; Lin, J.

2013-12-01

Models of solar flares and coronal mass ejections typically predict the development of an elongated current sheet in the wake behind the rising flux rope. In reality, reconnection in these current sheets will be asymmetric along the inflow, outflow, and out-of-plane directions. We perform resistive MHD simulations to investigate the consequences of asymmetry during solar reconnection. We predict several observational signatures of asymmetric reconnection, including flare loops with a skewed candle flame shape, slow drifting of the current sheet into the strong field upstream region, asymmetric footpoint speeds and hard X-ray emission, and rolling motions within the erupting flux rope. There is net plasma flow across the magnetic field null along both the inflow and outflow directions. We compare simulations to SDO/AIA, Hinode/XRT, and STEREO observations of flare loop shapes, current sheet drifting, and rolling motions during prominence eruptions. Simulations of the plasm! oid instability with different upstream magnetic fields show that the reconnection rate remains enhanced even during the asymmetric case. The islands preferentially grow into the weak field upstream region. The islands develop net vorticity because the outflow jets impact them obliquely rather than directly. Asymmetric reconnection in the chromosphere occurs when emerging flux interacts with pre-existing overlying flux. We present initial results on asymmetric reconnection in partially ionized chromospheric plasmas. Finally, we discuss how comparisons to observations are necessary to understand the role of three-dimensional effects.

Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions

USGS Publications Warehouse

Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.

2013-01-01

Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.

Race to the Top: Transiting Brown Dwarfs and Hot Jupiters

NASA Astrophysics Data System (ADS)

Beatty, Thomas G.

2015-12-01

There are currently twelve known transiting brown dwarfs, nine of which orbit single main-sequence stars. These systems give us one of the only ways in which we may directly measure the masses and radii brown dwarfs, which in turn provides strong constraints on theoretical models of brown dwarf interiors and atmospheres. In addition, the transiting brown dwarfs allow us to forge a link between our understanding of transiting hot Jupiters, and our understanding of the field brown dwarf population. Comparing the two gives us a unique avenue to explore the role and interaction of surface gravity and stellar irradiation in the atmospheres of sub-stellar objects. It also allows us to leverage the detailed spectroscopic information we have for field brown dwarfs to interpret the broadband colors of hot Jupiters. This provides us with insight into the L/T transition in brown dwarfs, and the atmospheric chemistry changes that occur in hot Jupiter atmospheres as they cool. I will discuss recent observational results, with a particular focus on the transiting brown dwarf KELT-1b, and suggest how more of these important systems may be discovered in the future.

Estimating gas exchange of CO2 and CH4 between headwater systems and the atmosphere in Southwest Sweden

NASA Astrophysics Data System (ADS)

Somlai, Celia; Natchimuthu, Sivakiruthika; Bastviken, David; Lorke, Andreas

2015-04-01

Quantifying the role of inland water systems in terms of carbon sinks and sources and their connection to the terrestrial ecosystems and landscapes is fundamental for improving the balance approach of regional and global carbon budgets. Recent research showed that freshwater bodies emit significant amounts of CO2 and CH4 into the atmosphere. The extent of the emissions from small streams and headwaters, however, remains uncertain due to a limited availability of data. Studies have shown that headwater systems receive most of the terrestrial organic carbon, have the highest dissolved CO2 concentration and the highest gas exchange velocities and cover the largest fractional surface area within fluvial networks. The gas exchange between inland waters and the atmosphere is controlled by two factors: the difference between the dissolved gas concentration and its atmospheric equilibrium concentration, and the gas exchange velocity. The direct measurement of the dissolved gas concentration of greenhouse gases can be measured straightforwardly, for example, by gas chromatography from headspace extraction of water sample. In contrast, direct measurement of gas exchange velocity is more complex and time consuming, as simultaneous measurements with a volatile and nonvolatile inert tracer gas are needed. Here we analyze measurements of gas exchange velocities, concentrations and fluxes of dissolved CO2 and CH4, as well as loads of total organic and inorganic carbon in 10 reaches in headwater streams in Southwest Sweden. We compare the gas exchange velocities measured directly through tracer injections with those estimated through various empirical approaches, which are based on modelled and measured current velocity, stream depth and slope. Furthermore, we estimate the resulting uncertainties of the flux estimates. We also present different time series of dissolved CO2, CH4 and O2 concentration, water temperature, barometric pressure, electro conductivity, and pH values measured during the period of tracer injection.

A free-trailing vane flow direction indicator employing a linear output Hall effect transducer

NASA Technical Reports Server (NTRS)

Zell, Peter T.; Mcmahon, Robert D.

1988-01-01

The Hall effect vane (HEV) was developed to measure flow angularity in the NASA 40-by-80-foot and 80-by-120-foot wind tunnels. This indicator is capable of sensing flow direction at air speeds from 5 to 300 knots and over a + or - 40 deg angle range with a resolution of 0.1 deg. A free-trailing vane configuration employing a linear output Hall effect transducer as a shaft angle resolver was used. The current configuration of the HEV is designed primarily for wind tunnel calibration testing; however, other potential applications include atmospheric, flight or ground research testing. The HEV met initial design requirements.

NASA's supercomputing experience

NASA Technical Reports Server (NTRS)

Bailey, F. Ron

1990-01-01

A brief overview of NASA's recent experience in supercomputing is presented from two perspectives: early systems development and advanced supercomputing applications. NASA's role in supercomputing systems development is illustrated by discussion of activities carried out by the Numerical Aerodynamical Simulation Program. Current capabilities in advanced technology applications are illustrated with examples in turbulence physics, aerodynamics, aerothermodynamics, chemistry, and structural mechanics. Capabilities in science applications are illustrated by examples in astrophysics and atmospheric modeling. Future directions and NASA's new High Performance Computing Program are briefly discussed.

Nerve Regeneration in Vitro: Comparative Effects of Direct and Induced Current and NGF. Appendix.

DTIC Science & Technology

1985-11-26

CLASSIFICATION AUTHORITY 3. DISTRIBUTION / AVAILABILIT 0S3W UT16=0 TA11111 2b DECLASSIFICATIONi DOWNGRADING SCHEDULE Ursrce .o. e ulc: 4 PE RFORMING...take place at the surface- water interface of NGF-responsive cells. It had been observed (29, 30) that, under particular circumstances, removal of...days at 39°C in an air-5% CO2 atmosphere in a water - jacketed incubator. In each experiment, a control group (untreated) and a group treated with 2.5s

Fiber-Reinforced Superalloys For Rocket Engines

NASA Technical Reports Server (NTRS)

Lewis, Jack R.; Yuen, Jim L.; Petrasek, Donald W.; Stephens, Joseph R.

1990-01-01

Report discusses experimental studies of fiber-reinforced superalloy (FRS) composite materials for use in turbine blades in rocket engines. Intended to withstand extreme conditions of high temperature, thermal shock, atmospheres containing hydrogen, high cycle fatigue loading, and thermal fatigue, which tax capabilities of even most-advanced current blade material - directionally-solidified, hafnium-modified MAR M-246 {MAR M-246 (Hf) (DS)}. FRS composites attractive combination of properties for use in turbopump blades of advanced rocket engines at temperatures from 870 to 1,100 degrees C.

Electric fields and conductivity in the nighttime E-region - A new magnetosphere-ionosphere-atmosphere coupling effect

NASA Technical Reports Server (NTRS)

Banks, P. M.; Yasuhara, F.

1978-01-01

Calculations have been made of the effects of intense poleward-directed electric fields upon the nighttime ionospheric E-region. The results show the Pedersen and Hall conductivities are substantially changed, thereby decreasing the ionospheric electrical load seen by magnetospheric sources. It appears that relatively large electric fields can exist in the absence of accompanying large field-aligned currents, as long as the underlying ionosphere remains in darkness and/or energetic particle precipitation is absent.

Determination of the Prebomb Southern (Antartic) Ocean Radiocarbon in Organic Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guilderson, T P

2001-02-26

The Southern Hemisphere is an important and unique region of the world's oceans for water-mass formation and mixing, upwelling, nutrient utilization, and carbon export. In fact, one of the primary interests of the oceanographic community is to decipher the climatic record of these processes in the source or sink terms for Southern Ocean surface waters in the CO{sub 2} balance of the atmosphere. Current coupled ocean-atmosphere modeling efforts to trace the input of CO{sub 2} into the ocean imply a strong sink of anthropogenic CO{sub 2} in the southern ocean. However, because of its relative inaccessibility and the difficulty inmore » directly measuring CO{sub 2} fluxes in the Southern Ocean, these results are controversial at best. An accepted diagnostic of the exchange of CO{sub 2} between the atmosphere and ocean is the prebomb distribution of radiocarbon in the ocean and its time-history since atmospheric nuclear testing. Such histories of {sup 14}C in the surface waters of the Southern Ocean do not currently exist, primarily because there are few continuous biological archives (e.g., in corals) such as those that have been used to monitor the {sup 14}C history of the tropics and subtropics. One of the possible long-term archives is the scallop Adamussium collbecki. Although not independently confirmed, relatively crude growth rate estimates of A. collbecki indicate that it has the potential to provide continuous 100 year time-series. We are exploring the suitability of this potential archive.« less

Liquid Hydrocarbon Production from CO2 : Recent Development in Metal-Based Electrocatalysis.

PubMed

Daiyan, Rahman; Lu, Xunyu; Ng, Yun Hau; Amal, Rose

2017-11-23

Rising levels of CO 2 accumulation in the atmosphere have attracted considerable interest in technologies capable of CO 2 capture, storage and conversion. The electrochemical reduction of CO 2 into high-value liquid organic products could be of vital importance to mitigate this issue. The conversion of CO 2 into liquid fuels by using photovoltaic cells, which can readily be integrated in the current infrastructure, will help realize the creation of a sustainable cycle of carbon-based fuel that will promote zero net CO 2 emissions. Despite promising findings, significant challenges still persist that must be circumvented to make the technology profitable for large-scale utilization. With such possibilities, this Minireview presents the current high-performing catalysts for the electrochemical reduction of CO 2 to liquid hydrocarbons, address the limitations and unify the current understanding of the different reaction mechanisms. The Minireview also explores current research directions to improve process efficiencies and production rate and discusses the scope of using photo-assisted electrochemical reduction systems to find stable, highly efficient catalysts that can harvest solar energy directly to convert CO 2 into liquid hydrocarbons. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Portable Ground-Based Atmospheric Monitoring System (PGAMS) for the Calibration and Validation of Atmospheric Correction Algorithms Applied to Aircraft and Satellite Images

NASA Technical Reports Server (NTRS)

Schiller, Stephen; Luvall, Jeffrey C.; Rickman, Doug L.; Arnold, James E. (Technical Monitor)

2000-01-01

Detecting changes in the Earth's environment using satellite images of ocean and land surfaces must take into account atmospheric effects. As a result, major programs are underway to develop algorithms for image retrieval of atmospheric aerosol properties and atmospheric correction. However, because of the temporal and spatial variability of atmospheric transmittance it is very difficult to model atmospheric effects and implement models in an operational mode. For this reason, simultaneous in situ ground measurements of atmospheric optical properties are vital to the development of accurate atmospheric correction techniques. Presented in this paper is a spectroradiometer system that provides an optimized set of surface measurements for the calibration and validation of atmospheric correction algorithms. The Portable Ground-based Atmospheric Monitoring System (PGAMS) obtains a comprehensive series of in situ irradiance, radiance, and reflectance measurements for the calibration of atmospheric correction algorithms applied to multispectral. and hyperspectral images. The observations include: total downwelling irradiance, diffuse sky irradiance, direct solar irradiance, path radiance in the direction of the north celestial pole, path radiance in the direction of the overflying satellite, almucantar scans of path radiance, full sky radiance maps, and surface reflectance. Each of these parameters are recorded over a wavelength range from 350 to 1050 nm in 512 channels. The system is fast, with the potential to acquire the complete set of observations in only 8 to 10 minutes depending on the selected spatial resolution of the sky path radiance measurements

New Remote Sensing Methods for Labeling Disturbance Agents in Appalachian Forests

NASA Astrophysics Data System (ADS)

Hughes, M. J.; Hayes, D. J.

2014-12-01

Forests in the eastern United States are species rich and affected by a variety of disturbance agents such as fire, invasive insects, diseases, and storm events. Millions of hectares of forest are disturbed each year, altering the forest carbon sink and changing forest nutrient cycles. The magnitude and direction of these changes, though, can be different for different disturbance agents. For example, trees that burn in severe fire rapidly release stored carbon into the atmosphere whereas standing deadwood from insect attacks decompose slowly while atmospheric carbon is fixed in regenerating vegetation. The diagnosis and attribution of these processes require accurate and reliable estimates of the extent and frequency of different disturbance agents. Here, a new method is presented that classifies disturbance events identified using time-series analysis of Landsat TM imagery. The method exploits information about changes in the canopy heterogeneity as measured by several texture indices within forest patches. Classifiers were trained using data from the US Forest Service Aerial Detection Surveys and currently differentiate between fires, southern pine beetle, gypsy moth, hemlock woolly adelgid, beech bark disease, anthracnose, and storm events. In addition, the classifier returns a value of 'uncertain' when it is unable to make a clear determination, which is currently approximately 10% of identified disturbances. Classification accuracy for the remainder is 81%, though is variable between agents. For example, the classifier performs well in identifying southern pine beetle and gypsy moth affected areas, but poorly in identifying storms. Reliabilities are similar to accuracies for each agent. The results presented are the first yearly, regional-scale estimates of forest disturbance partitioned by disturbance agent. We find good correspondence with previously described patterns of disturbance and distribution, including direct observational evidence of their predicted periodicities over entire ecoregions. Such estimates are vital for forest monitoring and to better understand the role of the dynamic forest carbon sink in order to reduce uncertainty in atmospheric carbon models. Future work must focus on the inclusion of direct anthropogenic changes such as harvest and urbanization.

Global and regional axial ocean angular momentum signals and length-of-day variations (1985-1996)

NASA Astrophysics Data System (ADS)

Ponte, Rui M.; Stammer, Detlef

2000-07-01

Changes in ocean angular momentum M about the polar axis are related to fluctuations in zonal currents (relative component Mr) and latitudinal shifts in mass (planetary component MΩ). Output from a 1° ocean model is used to calculate global Mr, MΩ, and M time series at 5 day intervals for the period January 1985 to April 1996. The annual cycle in Mr, MΩ, and M is larger than the semiannual cycle, and MΩ amplitudes are nearly twice those of Mr. Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between ω-1 and ω-2) at subseasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing subseasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes, but many local maxima exist because of the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes ~20°S-10°N contribute substantial variability to MΩ, while signals in Mr can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Investigating the Climatology of Mesospheric and Thermospheric Gravity Waves at High Northern Latitudes

NASA Astrophysics Data System (ADS)

Negale, Michael Ray

An important property of the Earth's atmosphere is its ability to support wave motions, and indeed, waves exist throughout the Earth's atmosphere at all times and all locations. What is the importance of these waves? Imagine standing on the beach as water waves come crashing into you. In this case, the waves transport energy and momentum to you, knocking you off balance. Similarly, waves in the atmosphere crash, known as breaking, but what do they crash into? They crash into the atmosphere knocking the atmosphere off balance in terms of the winds and temperatures. Although the Earth's atmosphere is full of waves, they cannot be observed directly; however, their effects on the atmosphere can be observed. Waves can be detected in the winds and temperatures, as mentioned above, but also in pressure and density. In this dissertation, three different studies of waves, known as gravity waves, were performed at three different locations. For these studies, we investigate the size of the waves and in which direction they move. Using specialized cameras, gravity waves were observed in the middle atmosphere (50-70 miles up) over Alaska (for three winter times) and Norway (for one winter time). A third study investigated gravity waves at a much higher altitude (70 miles on up) using radar data from Alaska (for three years). These studies have provided important new information on these waves and how they move through the atmosphere. This in turn helps to understand in which direction these waves are crashing into the atmosphere and therefore, which direction the energy and momentum are going. Studies such as these help to better forecast weather and climate.

Implementation and Simulation Results using Autonomous Aerobraking Development Software

NASA Technical Reports Server (NTRS)

Maddock, Robert W.; DwyerCianciolo, Alicia M.; Bowes, Angela; Prince, Jill L. H.; Powell, Richard W.

2011-01-01

An Autonomous Aerobraking software system is currently under development with support from the NASA Engineering and Safety Center (NESC) that would move typically ground-based operations functions to onboard an aerobraking spacecraft, reducing mission risk and mission cost. The suite of software that will enable autonomous aerobraking is the Autonomous Aerobraking Development Software (AADS) and consists of an ephemeris model, onboard atmosphere estimator, temperature and loads prediction, and a maneuver calculation. The software calculates the maneuver time, magnitude and direction commands to maintain the spacecraft periapsis parameters within design structural load and/or thermal constraints. The AADS is currently tested in simulations at Mars, with plans to also evaluate feasibility and performance at Venus and Titan.

A dc non-thermal atmospheric-pressure plasma microjet

NASA Astrophysics Data System (ADS)

Zhu, WeiDong; Lopez, Jose L.

2012-06-01

A direct current (dc), non-thermal, atmospheric-pressure plasma microjet is generated with helium/oxygen gas mixture as working gas. The electrical property is characterized as a function of the oxygen concentration and show distinctive regions of operation. Side-on images of the jet were taken to analyze the mode of operation as well as the jet length. A self-pulsed mode is observed before the transition of the discharge to normal glow mode. Optical emission spectroscopy is employed from both end-on and side-on along the jet to analyze the reactive species generated in the plasma. Line emissions from atomic oxygen (at 777.4 nm) and helium (at 706.5 nm) were studied with respect to the oxygen volume percentage in the working gas, flow rate and discharge current. Optical emission intensities of Cu and OH are found to depend heavily on the oxygen concentration in the working gas. Ozone concentration measured in a semi-confined zone in front of the plasma jet is found to be from tens to ˜120 ppm. The results presented here demonstrate potential pathways for the adjustment and tuning of various plasma parameters such as reactive species selectivity and quantities or even ultraviolet emission intensities manipulation in an atmospheric-pressure non-thermal plasma source. The possibilities of fine tuning these plasma species allows for enhanced applications in health and medical related areas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newsom, R. K.; Sivaraman, C.; Shippert, T. R.

Wind speed and direction, together with pressure, temperature, and relative humidity, are the most fundamental atmospheric state parameters. Accurate measurement of these parameters is crucial for numerical weather prediction. Vertically resolved wind measurements in the atmospheric boundary layer are particularly important for modeling pollutant and aerosol transport. Raw data from a scanning coherent Doppler lidar system can be processed to generate accurate height-resolved measurements of wind speed and direction in the atmospheric boundary layer.

Aerosol growth in Titan’s ionosphere

PubMed Central

Lavvas, Panayotis; Yelle, Roger V.; Koskinen, Tommi; Bazin, Axel; Vuitton, Véronique; Vigren, Erik; Galand, Marina; Wellbrock, Anne; Coates, Andrew J.; Wahlund, Jan-Erik; Crary, Frank J.; Snowden, Darci

2013-01-01

Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan’s upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere. PMID:23382231

Aerosol growth in Titan's ionosphere.

PubMed

Lavvas, Panayotis; Yelle, Roger V; Koskinen, Tommi; Bazin, Axel; Vuitton, Véronique; Vigren, Erik; Galand, Marina; Wellbrock, Anne; Coates, Andrew J; Wahlund, Jan-Erik; Crary, Frank J; Snowden, Darci

2013-02-19

Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere.

Atmospheric chemistry: Description of the area of performance and a working plan

NASA Astrophysics Data System (ADS)

Kirchhoff, Volker W. J. H.

1986-11-01

INPE's program in Atmospheric Chemistry Research is described. Research in this area is concerned with atmospheric gases and their chemical reactions, production and loss rates, and their interactions with the biosphere. Atmospheric chemistry includes concepts in Physics, Chemistry, Meteorology, and Biology, which gives it a strong interdisciplinary character. The interaction of some of the atmospheric gases with the biosphere, such as ozone, is very strong and direct. Studying atmospheric chemistry is, therefore, of direct interest to man and the quality of life. Details are described to define the objectives of study, in particular those of our research program at INPE. A working plan is proposed in order to reach the defined goals. Owing to the large anthropogenic interference in the balance of the natural atmosphere it is anticipated that a better understanding of Atmospheric Chemistry will be the great scientific challenge of the next decade.

Kinetics of the current response in TlBr detectors under a high dose rate of {gamma}-ray irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gazizov, I. M., E-mail: gazizov@isotop.dubna.ru; Zaletin, V. M.; Kukushkin, V. M.

2012-03-15

The kinetics of the photocurrent response in doped and undoped TlBr samples subjected to irradiation with {gamma}-ray photons from a {sup 137}Cs source with the dose rate 0.033 to 3.84 Gy/min are studied. The crystals were grown by the directional crystallization of the melt method using the Bridgman-Stockbarger technique. The Pb impurity mass fraction introduced into the doped TlBr crystals was 1-10 ppm and amounted to 150 ppm for the Ca impurity. The crystals were grown in a vacuum, in bromine vapors, in a hydrogen atmosphere, and in air. Decay of the photocurrent is observed for extrinsic semiconductor crystals dopedmore » with bivalent cations (irrespective of the growth atmosphere), and also for crystals grown in hydrogen and crystals grown in an excess of thallium. The time constant of photocurrent decay {tau} amounted to 30-1400 s and was proportional to resistivity. It is shown that the current response can be related to photolysis in the TlBr crystals during irradiation with {gamma}-ray photons. The energy of hole traps responsible for a slow increase in the photo-current has been estimated and found to be equal to 0.6-0.85 eV.« less

A 10-year climatology of pollen aerosol for the continental United States: implications for aerosol-climate interactions

NASA Astrophysics Data System (ADS)

Wozniak, M. C.

2016-12-01

Our current understanding of biological particles and their role in the climate system is uncertain. Pollen, a primary biological aerosol particle, has been understudied in the context of climate and atmospheric science because of its coarse size (10-100 µm). Local coarse grain pollen concentrations can reach up to 10,000 grains m-3, and when ruptured by wet or turbulent atmospheric conditions, can produce fine particles (sub-pollen particles, 10-1000 nm) that may increase pollen's lifetime in the atmosphere. Therefore, pollen contributes to both coarse and fine particle loads in the atmosphere that may have climatic impacts. During peak pollen emissions season, what impacts does pollen have on aerosol concentrations in the atmosphere and their indirect forcing? Here we use a model of accurately timed and scaled pollen and sub-pollen particle emissions with climate-dependent phenological dates for four plant functional types (deciduous broadleaf, evergreen needleleaf, grass and ragweed) that dominate emissions across the continental United States. Terrestrial pollen emissions are coupled with the land component of a regional climate model (RegCM4-CLM), and are transported as atmospheric tracers that are allowed interact with radiation and clouds, accounting for the direct and indirect effects of pollen. A ten-year climatology of pollen emissions and climate interactions is calculated for both pollen grains and sub-pollen particles. Its implications for the local and overall radiation budget, aerosol-cloud-precipitation interactions and regional climate are discussed.

Mars 2020 Entry, Descent, and Landing Instrumentation 2 (MEDLI2) Sensor Suite

NASA Technical Reports Server (NTRS)

Hwang, Helen; Wright, Henry; Kuhl, Chris; Schoenenberger, Mark; White, Todd; Karlgaard, Chris; Mahzari, Milad; Oishi, Tomo; Pennington, Steve; Trombetta, Nick;

Development of new tsunami detection algorithms for high frequency radars and application to tsunami warning in British Columbia, Canada

NASA Astrophysics Data System (ADS)

Grilli, S. T.; Guérin, C. A.; Shelby, M. R.; Grilli, A. R.; Insua, T. L.; Moran, P., Jr.

2016-12-01

A High-Frequency (HF) radar was installed by Ocean Networks Canada in Tofino, BC, to detect tsunamis from far- and near-field seismic sources; in particular, from the Cascadia Subduction Zone. This HF radar can measure ocean surface currents up to a 70-85 km range, depending on atmospheric conditions, based on the Doppler shift they cause in ocean waves at the Bragg frequency. In earlier work, we showed that tsunami currents must be at least 0.15 m/s to be directly detectable by a HF radar, when considering environmental noise and background currents (from tide/mesoscale circulation). This limits a direct tsunami detection to shallow water areas where currents are sufficiently strong due to wave shoaling and, hence, to the continental shelf. It follows that, in locations with a narrow shelf, warning times using a direct inversion method will be small. To detect tsunamis in deeper water, beyond the continental shelf, we proposed a new algorithm that does not require directly inverting currents, but instead is based on observing changes in patterns of spatial correlations of the raw radar signal between two radar cells located along the same wave ray, after time is shifted by the tsunami propagation time along the ray. A pattern change will indicate the presence of a tsunami. We validated this new algorithm for idealized tsunami wave trains propagating over a simple seafloor geometry in a direction normally incident to shore. Here, we further develop, extend, and validate the algorithm for realistic case studies of seismic tsunami sources impacting Vancouver Island, BC. Tsunami currents, computed with a state-of-the-art long wave model are spatially averaged over cells aligned along individual wave rays, located within the radar sweep area, obtained by solving the wave geometric optic equation; for long waves, such rays and tsunami propagation times along those are only function of the seafloor bathymetry, and hence can be precalculated for different incident tsunami directions. A model simulating the radar backscattered signal in space and time as a function of simulated tsunami currents is applied to the sweep area. Numerical experiments show that the new algorithm can detect a realistic tsunami further offshore than a direct detection method. Correlation thresholds for tsunami detection will be derived from the results.

THE FIRST SPECTRUM OF THE COLDEST BROWN DWARF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skemer, Andrew J.; Morley, Caroline V.; Fortney, Jonathan J.

2016-08-01

The recently discovered brown dwarf WISE 0855 presents the first opportunity to directly study an object outside the solar system that is nearly as cold as our own gas giant planets. However, the traditional methodology for characterizing brown dwarfs—near-infrared spectroscopy—is not currently feasible, as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5–5.2 μ m spectrum, the same bandpass long used to study Jupiter’s deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter’s. The spectrum quality ismore » high enough to allow for the investigation of dynamical and chemical processes that have long been studied in Jupiter’s atmosphere, but now on an extrasolar world.« less

Local Measurement of Tropospheric HO(x)

NASA Technical Reports Server (NTRS)

Crosley, David R.

1994-01-01

In March of 1992 a workshop sponsored by NASA and NSF was held at SRI International to assess the current ability to measure atmospheric OH and HO2. The measurement techniques reviewed during the workshop for detection of OH included five laser-induced fluorescence schemes, five laser-based adsorption techniques, and four non-laser methods. Six instruments or instrument concepts for HO2 detection, including chemical amplification, conversion to OH with subsequent OH detection, or direct spectroscopic detection of the HO2 were also discussed. The conclusions from the workshop identify several measurement techniques for OH and HO2 that are ready for field tests. These have the ability to measure the radicals with sufficient sensitivity and accuracy to form meaningful comparison with atmospheric model predictions. The workshop conclusions also include recommendations for informal and formal intercomparison protocols.

Quantifying sources and sinks of reactive gases in the lower atmosphere using airborne flux observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfe, Glenn; Hanisco, T. F.; Atkinson, H. L.

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 measurementmore » of fundamental process rates, airborne fluxes offer a new tool to improve biogenic and anthropogenic emissions inventories, photochemical mechanisms, and deposition parameterizations.« less

Atmosphere-Ionosphere Electrodynamic Coupling

NASA Astrophysics Data System (ADS)

Sorokin, V. M.; Chmyrev, V. M.

Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally observed effects as excitation of plasma density inhomogeneities, field-aligned currents, and ULF/ELF emissions and the modification of electron and ion altitude profiles in the upper ionosphere. The electrodynamic model of the ionosphere modification under the influence of some natural and man-made processes in the atmosphere is also discussed. The model is based on the satellite and ground measurements of electromagnetic field and plasma perturbations and on the data on atmospheric radioactivity and soil gas injection into the atmosphere.

Impacts of Aerosol Direct Effects on the South Asian Climate: Assessment of Radiative Feedback Processes Using Model Simulations and Satellite/Surface Measurements

NASA Technical Reports Server (NTRS)

Wang, Sheng-Hsiang; Gautam, Ritesh; Lau, William K. M.; Tsay, Si-Chee; Sun, Wen-Yih; Kim, Kyu-Myong; Chern, Jiun-Dar; Hsu, Christina; Lin, Neng-Huei

2011-01-01

Current assessment of aerosol radiative effect is hindered by our incomplete knowledge of aerosol optical properties, especially absorption, and our current inability to quantify physical and microphysical processes. In this research, we investigate direct aerosol radiative effect over heavy aerosol loading areas (e.g., Indo-Gangetic Plains, South/East Asia) and its feedbacks on the South Asian climate during the pre-monsoon season (March-June) using the Purdue Regional Climate Model (PRCM) with prescribed aerosol data derived by the NASA Goddard Earth Observing System Model (GEOS-5). Our modeling domain covers South and East Asia (60-140E and 0-50N) with spatial resolutions of 45 km in horizontal and 28 layers in vertical. The model is integrated from 15 February to 30 June 2008 continuously without nudging (i.e., only forced by initial/boundary conditions). Two numerical experiments are conducted with and without the aerosol-radiation effects. Both simulations are successful in reproducing the synoptic patterns on seasonal-to-interannual time scales and capturing a pre-monsoon feature of the northward rainfall propagation over Indian region in early June which shown in Tropical Rainfall Measuring Mission (TRMM) observation. Preliminary result suggests aerosol-radiation interactions mainly alter surface-atmosphere energetics and further result in an adjustment of the vertical temperature distribution in lower atmosphere (below 700 hPa). The modifications of temperature and associated rainfall and circulation feedbacks on the regional climate will be discussed in the presentation.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

PubMed

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-04-06

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO₃ solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

DEVELOPING ATMOSPHERIC RETRIEVAL METHODS FOR DIRECT IMAGING SPECTROSCOPY OF GAS GIANTS IN REFLECTED LIGHT. I. METHANE ABUNDANCES AND BASIC CLOUD PROPERTIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupu, Roxana E.; Marley, Mark S.; Zahnle, Kevin

Upcoming space-based coronagraphic instruments in the next decade will perform reflected light spectroscopy and photometry of cool directly imaged extrasolar giant planets. We are developing a new atmospheric retrieval methodology to help assess the science return and inform the instrument design for such future missions, and ultimately interpret the resulting observations. Our retrieval technique employs a geometric albedo model coupled with both a Markov chain Monte Carlo Ensemble Sampler ( emcee ) and a multimodal nested sampling algorithm ( MultiNest ) to map the posterior distribution. This combination makes the global evidence calculation more robust for any given model andmore » highlights possible discrepancies in the likelihood maps. As a proof of concept, our current atmospheric model contains one or two cloud layers, methane as a major absorber, and a H{sub 2}–He background gas. This 6-to-9 parameter model is appropriate for Jupiter-like planets and can be easily expanded in the future. In addition to deriving the marginal likelihood distribution and confidence intervals for the model parameters, we perform model selection to determine the significance of methane and cloud detection as a function of expected signal-to-noise ratio in the presence of spectral noise correlations. After internal validation, the method is applied to realistic spectra of Jupiter, Saturn, and HD 99492c, a model observing target. We find that the presence or absence of clouds and methane can be determined with high confidence, while parameter uncertainties are model dependent and correlated. Such general methods will also be applicable to the interpretation of direct imaging spectra of cloudy terrestrial planets.« less

Artificial Intelligence in planetary spectroscopy

NASA Astrophysics Data System (ADS)

Waldmann, Ingo

2017-10-01

The field of exoplanetary spectroscopy is as fast moving as it is new. Analysing currently available observations of exoplanetary atmospheres often invoke large and correlated parameter spaces that can be difficult to map or constrain. This is true for both: the data analysis of observations as well as the theoretical modelling of their atmospheres.Issues of low signal-to-noise data and large, non-linear parameter spaces are nothing new and commonly found in many fields of engineering and the physical sciences. Recent years have seen vast improvements in statistical data analysis and machine learning that have revolutionised fields as diverse as telecommunication, pattern recognition, medical physics and cosmology.In many aspects, data mining and non-linearity challenges encountered in other data intensive fields are directly transferable to the field of extrasolar planets. In this conference, I will discuss how deep neural networks can be designed to facilitate solving said issues both in exoplanet atmospheres as well as for atmospheres in our own solar system. I will present a deep belief network, RobERt (Robotic Exoplanet Recognition), able to learn to recognise exoplanetary spectra and provide artificial intelligences to state-of-the-art atmospheric retrieval algorithms. Furthermore, I will present a new deep convolutional network that is able to map planetary surface compositions using hyper-spectral imaging and demonstrate its uses on Cassini-VIMS data of Saturn.

Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

NASA Astrophysics Data System (ADS)

Amarsi, A. M.; Lind, K.; Asplund, M.; Barklem, P. S.; Collet, R.

2016-12-01

As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves. We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally and temporally averaged 3D STAGGER model atmospheres.

Particle transport model sensitivity on wave-induced processes

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Ricker, Marcel; Krüger, Oliver; Breivik, Oyvind; Stanev, Emil; Schrum, Corinna

2017-04-01

Different effects of wind waves on the hydrodynamics in the North Sea are investigated using a coupled wave (WAM) and circulation (NEMO) model system. The terms accounting for the wave-current interaction are: the Stokes-Coriolis force, the sea-state dependent momentum and energy flux. The role of the different Stokes drift parameterizations is investigated using a particle-drift model. Those particles can be considered as simple representations of either oil fractions, or fish larvae. In the ocean circulation models the momentum flux from the atmosphere, which is related to the wind speed, is passed directly to the ocean and this is controlled by the drag coefficient. However, in the real ocean, the waves play also the role of a reservoir for momentum and energy because different amounts of the momentum flux from the atmosphere is taken up by the waves. In the coupled model system the momentum transferred into the ocean model is estimated as the fraction of the total flux that goes directly to the currents plus the momentum lost from wave dissipation. Additionally, we demonstrate that the wave-induced Stokes-Coriolis force leads to a deflection of the current. During the extreme events the Stokes velocity is comparable in magnitude to the current velocity. The resulting wave-induced drift is crucial for the transport of particles in the upper ocean. The performed sensitivity analyses demonstrate that the model skill depends on the chosen processes. The results are validated using surface drifters, ADCP, HF radar data and other in-situ measurements in different regions of the North Sea with a focus on the coastal areas. The using of a coupled model system reveals that the newly introduced wave effects are important for the drift-model performance, especially during extremes. Those effects cannot be neglected by search and rescue, oil-spill, transport of biological material, or larva drift modelling.

Formation and fate of gaseous and particulate mutagens and carcinogens in real and simulated atmospheres.

PubMed Central

Pitts, J N

1983-01-01

The growing use of coal for heating and electric power generation and diesel engines in light duty motor vehicles will increase not only the existing atmospheric concentrations of criteria pollutants such as NO2, SO2, O3 and fine particulates, but also the concentrations of a number of highly reactive gaseous copollutants such as HONO, HONO2, PAN and the nitrate radical, NO3. These gaseous noncriteria pollutants are of interest not only because of their roles in the chemistry of the "clean" and polluted troposphere, including "acid rain," but also because they may pose health risks disproportionate to their relatively low ambient concentrations, and through complex heterogeneous reactions, they may serve as precursors or catalysts in the formation of "nonclassical" particulate mutagens and carcinogens such as certain nitroarenes associated with combustion generated particulate polycyclic organic matter (POM). Results of research efforts to establish current ambient levels of these noncriteria pollutants and to develop an understanding of their sources, formation and sinks are reported here. First, long pathlength (greater than or equal to 1 km) infrared and UV-visible spectroscopic studies of ambient levels of gaseous HONO, NO3, HONO2, PAN, HCHO and HCOOH in southern California atmospheres are described, and data given on their ambient concentrations. Second, an integrated chemical/microbiological investigation is described. It is directed toward identifying the nature of direct-acting mutagens found in extracts of diesel and ambient POM, as well as those formed upon exposure of environmentally relevant PAH to simulated natural and polluted atmospheres. The identification of certain of these mutagens, including a newly identified class of mutagenic PAH-lactones is discussed, along with the mechanisms of their formation and fate in the natural and polluted troposphere. PMID:6337822

Direct Detection of Polarized, Scattered Light from Exoplanets

NASA Astrophysics Data System (ADS)

Laughlin, Gregory

We propose to radically advance the state of exoplanet characterization, which lags dramatically behind exoplanet discovery. We propose to directly detect scattered light from the atmospheres of close-in, highly eccentric, and extended/non-spherical exoplanets and thereby determine the following: orbital inclination (and therefore masses free of the M sin i mass ambiguity), geometric albedo, presence or lack of hazes and cloud layers, and scattering particle size and composition. Such measurements are crucial to the understanding of exoplanet atmospheres, because observations with NASA s Hubble, Spitzer, and Kepler space telescopes present the following questions: 1) Do exoplanets have highly reflective haze layers? 2) How does the upper atmospheric composition differ between exoplanets with and without thermal inversions? 3) What are the optical manifestations of the extreme heating of highly eccentric exoplanets? 4) Are the atmospheres of certain exoplanets truly escaping their Roche lobes? Using the POLISH2 polarimeter developed by the Postdoctoral Associate (Wiktorowicz) for the Lick 3-m telescope, we propose to monitor the linear polarization state of exoplanet host stars at the part per million level. POLISH2 consistently delivers nearly photon shot noise limited measurements with this precision. In addition, the simultaneous full-Stokes measurements of POLISH2 and the equatorial mount of the Lick 3-m telescope ensure that systematic effects are mitigated to the part per million level. Indeed, we find the accuracy of the POLISH2 polarimeter to be 0.1 parts per million. This instrument and telescope represent the highest precision polarimeter in the world for exoplanet research. We present potential detection of polarized, scattered light from the HD 189733b, Tau Boo b, and WASP-12b exoplanets. We propose to observe hot Jupiters on circular orbits, highly eccentric exoplanets, exoplanets with extended or non-spherical scattering surfaces, and 55 Cnc e, the super-Earth with the highest expected polarimetric signal-to- noise ratio. These exoplanets should all produce detectable polarization, and they present unique opportunities to study the atmospheres of wildly different exoplanets. Extending the PI s (Laughlin) Monte Carlo ray-tracing code, and utilizing the Co-I s (Fortney) experience in modeling exoplanet atmospheres, we propose to fund a graduate student to model the polarization data obtained from POLISH2 and invert the above variables. This is because they affect the amplitude and shape of the periodic variability in the polarization state of light from the system. Indeed, the discovery of spherical, sulfuric acid droplets suspended in the Venusian atmosphere was made forty years ago with Mie scattering models to fit polarimetric measurements. The PI s ray-tracing code, which has been used to model the rapid heating of the eccentric HD 80606b exoplanet, currently includes Rayleigh scattering and alkali metal absorption in a self-consistent manner. The direct detection of exoplanets as well as characterization of their atmospheric compositions and structure is directly related to the goals of the Origins program and to the NASA 2010 Science Plan, which emphasizes exploration of exoplanets and exoplanetary systems.

Impact of maritime traffic on polycyclic aromatic hydrocarbons, metals and particulate matter in Venice air.

PubMed

Gregoris, Elena; Barbaro, Elena; Morabito, Elisa; Toscano, Giuseppa; Donateo, Antonio; Cesari, Daniela; Contini, Daniele; Gambaro, Andrea

2016-04-01

Harbours are important hubs for economic growth in both tourism and commercial activities. They are also an environmental burden being a source of atmospheric pollution often localized near cities and industrial complexes. The aim of this study is to quantify the relative contribution of maritime traffic and harbour activities to atmospheric pollutant concentration in the Venice lagoon. The impact of ship traffic was quantified on various pollutants that are not directly included in the current European legislation for shipping emission reduction: (i) gaseous and particulate PAHs; (ii) metals in PM10; and (iii) PM10 and PM2.5. All contributions were correlated with the tonnage of ships during the sampling periods and results were used to evaluate the impact of the European Directive 2005/33/EC on air quality in Venice comparing measurements taken before and after the application of the Directive (year 2010). The outcomes suggest that legislation on ship traffic, which focused on the issue of the emissions of sulphur oxides, could be an efficient method also to reduce the impact of shipping on primary particulate matter concentration; on the other hand, we did not observe a significant reduction in the contribution of ship traffic and harbour activities to particulate PAHs and metals. Graphical abstract Impact of maritime traffic on polycyclic aromatic hydrocarbons, metals and particulate matter and evaluation of the effect of an European Directive on air quality in Venice.

Sunspot rotation. II. Effects of varying the field strength and twist of an emerging flux tube

NASA Astrophysics Data System (ADS)

Sturrock, Z.; Hood, A. W.

2016-09-01

Context. Observations of flux emergence indicate that rotational velocities may develop within sunspots. However, the dependence of this rotation on sub-photospheric field strength and twist remains largely unknown. Aims: We investigate the effects of varying the initial field strength and twist of an emerging sub-photospheric magnetic flux tube on the rotation of the sunspots at the photosphere. Methods: We consider a simple model of a stratified domain with a sub-photospheric interior layer and three overlying atmospheric layers. A twisted arched flux tube is inserted in the interior and is allowed to rise into the atmosphere. To achieve this, the magnetohydrodynamic equations are solved using the Lagrangian-remap code, Lare3d. We perform a parameter study by independently varying the sub-photospheric magnetic field strength and twist. Results: Altering the initial magnetic field strength and twist of the flux tube significantly affects the tube's evolution and the rotational motions that develop at the photosphere. The rotation angle, vorticity, and current show a direct dependence on the initial field strength. We find that an increase in field strength increases the angle through which the fieldlines rotate, the length of the fieldlines extending into the atmosphere, and the magnetic energy transported to the atmosphere. This also affects the amount of residual twist in the interior. The length of the fieldlines is crucial as we predict the twist per unit length equilibrates to a lower value on longer fieldlines. No such direct dependence is found when we modify the twist of the magnetic field owing to the complex effect this has on the tension force acting on the tube. However, there is still a clear ordering in quantities such as the rotation angle, helicity, and free energy with higher initial twist cases being related to sunspots that rotate more rapidly, transporting more helicity and magnetic energy to the atmosphere.

Trace gas concentrations, intertropical convergence, atmospheric fronts, and ocean currents in the tropical Pacific

NASA Technical Reports Server (NTRS)

Wilkniss, P. E.; Rodgers, E. B.; Swinnerton, J. W.; Larson, R. E.; Lamontagne, R. A.

1979-01-01

Descriptions of the intertropical convergence zones (ITCZ) in the tropical Pacific have been obtained from shipboard measurements of Rn-222, CO, and CH4 in combination with conventional meteorological data and satellite images. The intertropical convergence zone is marked by light shifting waves near an area of heavy cloud cover and precipitation, and appears to be located north and south of the south equatorial current. A 'second' ITCZ with the same atmospheric features was encountered just north of the south equatorial current in the Southern Hemisphere. Atmospheric Rn-222 increases north of the ITCZ and serves as a sensitive indicator for this atmospheric boundary.

Multijunction solar cell design revisited: disruption of current matching by atmospheric absorption bands: Disruption of current matching by atmospheric absorption bands

DOE PAGES

McMahon, William E.; Friedman, Daniel J.; Geisz, John F.

2017-05-23

This paper re-examines the impact of atmospheric absorption bands on series-connected multijunction cell design, motivated by the numerous local efficiency maxima that appear as the number of junctions is increased. Some of the local maxima are related to the bottom subcell bandgap and are already well understood: As the bottom subcell bandgap is varied, a local efficiency maximum is produced wherever the bottom cell bandgap crosses an atmospheric absorption band. The optimal cell designs at these local maxima are generally current matched, such that all subcells have nearly the same short-circuit current. We systematically describe additional local maxima that occurmore » wherever an upper subcell bandgap encounters an atmospheric absorption band. Moreover, these local maxima are not current matched and become more prevalent as the number of junctions increases, complicating the solution space for five-junction and six-junction designs. A systematic framework for describing this complexity is developed, and implications for numerical convergence are discussed.« less

Multijunction solar cell design revisited: disruption of current matching by atmospheric absorption bands: Disruption of current matching by atmospheric absorption bands

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMahon, William E.; Friedman, Daniel J.; Geisz, John F.

This paper re-examines the impact of atmospheric absorption bands on series-connected multijunction cell design, motivated by the numerous local efficiency maxima that appear as the number of junctions is increased. Some of the local maxima are related to the bottom subcell bandgap and are already well understood: As the bottom subcell bandgap is varied, a local efficiency maximum is produced wherever the bottom cell bandgap crosses an atmospheric absorption band. The optimal cell designs at these local maxima are generally current matched, such that all subcells have nearly the same short-circuit current. We systematically describe additional local maxima that occurmore » wherever an upper subcell bandgap encounters an atmospheric absorption band. Moreover, these local maxima are not current matched and become more prevalent as the number of junctions increases, complicating the solution space for five-junction and six-junction designs. A systematic framework for describing this complexity is developed, and implications for numerical convergence are discussed.« less

Volatility of organic aerosol: evaporation of ammonium sulfate/succinic acid aqueous solution droplets.

PubMed

Yli-Juuti, Taina; Zardini, Alessandro A; Eriksson, Axel C; Hansen, Anne Maria K; Pagels, Joakim H; Swietlicki, Erik; Svenningsson, Birgitta; Glasius, Marianne; Worsnop, Douglas R; Riipinen, Ilona; Bilde, Merete

2013-01-01

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol.

Volatility of Organic Aerosol: Evaporation of Ammonium Sulfate/Succinic Acid Aqueous Solution Droplets

PubMed Central

2013-01-01

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol. PMID:24107221

Air Purification Pavement Surface Coating by Atmospheric Pressure Cold Plasma

NASA Astrophysics Data System (ADS)

Westergreen, Joe; Pedrow, Patrick; Shen, Shihui; Jobson, Bertram

2011-10-01

This study develops an atmospheric pressure cold plasma (APCP) reactor to produce activated radicals from precursor molecules, and to immobilize nano titanium dioxide (TiO2) powder to substrate pavement materials. TiO2 has photocatalytic properties and under UV light can be used to oxidize and remove volatile organic compounds (VOCs) and nitrogen oxides (NOx) from the atmosphere. Although TiO2 treated paving materials have great potential to improve air quality, current techniques to adhere TiO2 to substrate materials are either not durable or reduce direct contact of TiO2 with UV light, reducing the photocatalytic effect. To solve this technical difficulty, this study introduces APCP techniques to transportation engineering to coat TiO2 to pavement. Preliminary results are promising and show that TiO2 can be incorporated successfully into an APCP environment and can be immobilized at the surface of the asphalt substrate. The TiO2 coated material with APCP shows the ability to reduce nitrogen oxides when exposed to UV light in an environmental chamber. The plasma reactor utilizes high voltage streamers as the plasma source.

The Use of Indirect Estimates of Soil Moisture to Initialize Coupled Models and its Impact on Short-Term and Seasonal Simulations

NASA Technical Reports Server (NTRS)

Lapenta, William M.; Crosson, William; Dembek, Scott; Lakhtakia, Mercedes

1998-01-01

It is well known that soil moisture is a characteristic of the land surface that strongly affects the partitioning of outgoing radiation into sensible and latent heat which significantly impacts both weather and climate. Detailed land surface schemes are now being coupled to mesoscale atmospheric models in order to represent the effect of soil moisture upon atmospheric simulations. However, there is little direct soil moisture data available to initialize these models on regional to continental scales. As a result, a Soil Hydrology Model (SHM) is currently being used to generate an indirect estimate of the soil moisture conditions over the continental United States at a grid resolution of 36 Km on a daily basis since 8 May 1995. The SHM is forced by analyses of atmospheric observations including precipitation and contains detailed information on slope soil and landcover characteristics.The purpose of this paper is to evaluate the utility of initializing a detailed coupled model with the soil moisture data produced by SHM.

Radiative Cooling: Principles, Progress, and Potentials

PubMed Central

Hossain, Md. Muntasir

2016-01-01

The recent progress on radiative cooling reveals its potential for applications in highly efficient passive cooling. This approach utilizes the maximized emission of infrared thermal radiation through the atmospheric window for releasing heat and minimized absorption of incoming atmospheric radiation. These simultaneous processes can lead to a device temperature substantially below the ambient temperature. Although the application of radiative cooling for nighttime cooling was demonstrated a few decades ago, significant cooling under direct sunlight has been achieved only recently, indicating its potential as a practical passive cooler during the day. In this article, the basic principles of radiative cooling and its performance characteristics for nonradiative contributions, solar radiation, and atmospheric conditions are discussed. The recent advancements over the traditional approaches and their material and structural characteristics are outlined. The key characteristics of the thermal radiators and solar reflectors of the current state‐of‐the‐art radiative coolers are evaluated and their benchmarks are remarked for the peak cooling ability. The scopes for further improvements on radiative cooling efficiency for optimized device characteristics are also theoretically estimated. PMID:27812478

The importance of Titan's current mass loss processes to understanding the evolution of Titan's atmosphere

NASA Astrophysics Data System (ADS)

Mandt, Kathleen; Waite, J. Hunter, Jr.; Bell, Jared; Mousis, Olivier

2010-04-01

Current isotopic ratios in planetary atmospheres have played an important role in determining how that atmosphere has evolved over geologic time scales (e.g. Donahue et al. 1997, Lunine et al. 1999). The current 12C/13C ratio in methane is a particularly useful indicator of Titan's atmospheric evolutionary history (Mandt et al. 2009). Primordial 12C/13C ratios throughout the solar system are limited to 89.01+4.45-2.67. (Alexander et al. 2007, Martins et al. 2008), while the methane 12C/13C ratio measured by GCMS and CIRS are 82.3+/-1.0 and 76.6+/-2.7 respectively (Niemann et al. 2005, Nixon et al. 2008). This is well below the primordial range, suggesting fractionation of the isotopes by atmospheric processes. A number of atmospheric mass loss processes can fractionate the isotopes over geologic time scales. Photochemistry and escape are of particular importance (Donahue et al 1997, Mandt et al. 2009). Measurements of the 12C/13C ratios in C2 hydrocarbons show evidence of fractionation due to photochemistry (Nixon et al. 2008) that is most likely due to a kinetic isotope effect (KIE). A KIE is a mildly efficient fractionating process in which reactions involving 12C occur 1.04 times faster than reactions involving 13C. A moderate time scale, on the order of 50 to 400 million years, is required to change the 12C/13C ratio of the atmospheric methane inventory. The exact length of this time scale depends directly on the methane photochemical loss rate. Titan's photochemistry is extremely complex, and although the total photochemical loss rate is photon-limited (Lorenz et al. 1997), the literature provides a range of loss rates between 4.9 x 10^9 cm-2s-1 (Wilson and Atreya 2004) and 3.4 x 10^10 cm-2s-1 (Lebonnois et al. 2003). This range can alter the time scale for fractionation in the carbon isotopes by as much as a factor of 8. INMS measurements of the methane 12C/13C ratio in the upper atmosphere show that atmospheric escape is a more efficient fractionating process than photochemistry (Mandt et al. 2009). The literature provides a range of possible values for the methane escape rates that depend on the input parameters to upper atmospheric models (Bell et al. 2010). The escape rate of methane could be as little as 2.75 x 10^7 cm-2s-1 (de la Haye et al. 2007) or as great as 3.0 x 10^9 cm-2s-1 (Yelle et al. 2008). This range of loss rates can alter the time scale for fractionation by as much as a factor of 5. Although the photochemical fractionation is less efficient than the escape rate, variance in its value has a greater impact on the time required to fractionate the isotopes because the magnitude of the photochemical loss is much greater than that of the escape rate. Thus, a better quantification of both mass loss rates is key to understanding the evolutionary history of Titan's atmosphere.

Biomolecular damage induced by ionizing radiation: the direct and indirect effects of low-energy electrons on DNA.

PubMed

Alizadeh, Elahe; Orlando, Thomas M; Sanche, Léon

2015-04-01

Many experimental and theoretical advances have recently allowed the study of direct and indirect effects of low-energy electrons (LEEs) on DNA damage. In an effort to explain how LEEs damage the human genome, researchers have focused efforts on LEE interactions with bacterial plasmids, DNA bases, sugar analogs, phosphate groups, and longer DNA moieties. Here, we summarize the current understanding of the fundamental mechanisms involved in LEE-induced damage of DNA and complex biomolecule films. Results obtained by several laboratories on films prepared and analyzed by different methods and irradiated with different electron-beam current densities and fluencies are presented. Despite varied conditions (e.g., film thicknesses and morphologies, intrinsic water content, substrate interactions, and extrinsic atmospheric compositions), comparisons show a striking resemblance in the types of damage produced and their yield functions. The potential of controlling this damage using molecular and nanoparticle targets with high LEE yields in targeted radiation-based cancer therapies is also discussed.

Effect of Annealing Processes on Cu-Zr Alloy Film for Copper Metallization

NASA Astrophysics Data System (ADS)

Wang, Ying; Li, Fu-yin; Tang, Bin-han

2017-12-01

The effect of two different annealing processes on the microstructure and barrier-forming ability of Cu-Zr alloy films has been investigated. Cu-Zr alloy films were deposited directly onto SiO2/Si substrates via direct current magnetron sputtering and subsequently annealed by the vacuum annealing process (VAP) or rapid annealing process under argon atmosphere at temperatures 350°C, 450°C, and 550°C. Then, the microstructure, interface characteristics, and electrical properties of the samples were measured. After annealing, the samples showed a preferential (111) crystal orientation, independent of the annealing process. After two annealing methods, Zr aggregated at the Cu-Zr/SiO2 interface and no serious interdiffusion occurred between Cu and Si. The leakage current measurements revealed that the samples annealed by VAP show a higher reliability. According to the results, the vacuum annealing has better barrier performance than the rapid annealing when used for the fabrication of Cu-based interconnects.

The improvement of the analytical performance of direct current atmospheric pressure glow discharge generated in contact with the small-sized liquid cathode after the addition of non-ionic surfactants to electrolyte solutions.

PubMed

Gręda, Krzysztof; Jamróz, Piotr; Pohl, Paweł

2013-04-15

A low power direct current atmospheric glow discharge sustained in the open to air atmosphere in contact with a small-sized flowing liquid cathode was used as an excitation source in optical emission spectrometry. The composition of electrolyte solutions served as the liquid cathode was modified by the addition of non-ionic surfactants, namely Triton x-45, Triton x-100, Triton x-405 and Triton x-705. The effect of the concentration of each surfactant was thoroughly studied on the emission characteristic of molecular bands identified in spectra, atomic emission lines of 16 metals studied and the background level. It was found that the presence of both heavy surfactants results in a significant increase in the net intensity of analytical lines of metals and a notable reduction of the intensity of bands of diatomic molecules and the background. In conditions considered to be a compromise for all metals, selected figures of merit for this excitation source combined with the optical emission spectrometry detection were determined. Limits of detection for all metals were within the range of 0.0003-0.05 mg L(-1), the precision was better than 6%, while calibration curves were linear over 2 orders of the magnitude of the concentration or more, e.g., for K, Li, Mg, Na and Rb. The discharge system with the liquid cathode modified by the addition of the surfactant found its application in the determination of Ca, Cu, Fe, K, Mg, Mn, Na and Zn in selected environmental samples, i.e., waters, soils and spruce needles, with the quite good precision and the accuracy comparable to that for measurements with flame atomic absorption spectrometry (FAAS) and flame atomic emission spectrometry (FAES). Copyright © 2013 Elsevier B.V. All rights reserved.

Comparison of observation level versus 24-hour average atmospheric loading corrections in VLBI analysis

NASA Astrophysics Data System (ADS)

MacMillan, D. S.; van Dam, T. M.

2009-04-01

Variations in the horizontal distribution of atmospheric mass induce displacements of the Earth's surface. Theoretical estimates of the amplitude of the surface displacement indicate that the predicted surface displacement is often large enough to be detected by current geodetic techniques. In fact, the effects of atmospheric pressure loading have been detected in Global Positioning System (GPS) coordinate time series [van Dam et al., 1994; Dong et al., 2002; Scherneck et al., 2003; Zerbini et al., 2004] and very long baseline interferometery (VLBI) coordinates [Rabble and Schuh, 1986; Manabe et al., 1991; van Dam and Herring, 1994; Schuh et al., 2003; MacMillan and Gipson, 1994; and Petrov and Boy, 2004]. Some of these studies applied the atmospheric displacement at the observation level and in other studies, the predicted atmospheric and observed geodetic surface displacements have been averaged over 24 hours. A direct comparison of observation level and 24 hour corrections has not been carried out for VLBI to determine if one or the other approach is superior. In this presentation, we address the following questions: 1) Is it better to correct geodetic data at the observation level rather than applying corrections averaged over 24 hours to estimated geodetic coordinates a posteriori? 2) At the sub-daily periods, the atmospheric mass signal is composed of two components: a tidal component and a non-tidal component. If observation level corrections reduce the scatter of VLBI data more than a posteriori correction, is it sufficient to only model the atmospheric tides or must the entire atmospheric load signal be incorporated into the corrections? 3) When solutions from different geodetic techniques (or analysis centers within a technique) are combined (e.g., for ITRF2008), not all solutions may have applied atmospheric loading corrections. Are any systematic effects on the estimated TRF introduced when atmospheric loading is applied?

A four-dimensional primitive equation model for coupled coastal-deep ocean studies

NASA Technical Reports Server (NTRS)

Haidvogel, D. B.

1981-01-01

A prototype four dimensional continental shelf/deep ocean model is described. In its present form, the model incorporates the effects of finite amplitude topography, advective nonlinearities, and variable stratification and rotation. The model can be forced either directly by imposed atmospheric windstress and surface pressure distributions, and energetic mean currents imposed by the exterior oceanic circulation; or indirectly by initial distributions of shoreward propagation mesoscale waves and eddies. To avoid concerns over the appropriate specification of 'open' boundary conditions on the cross-shelf and seaward model boundaries, a periodic channel geometry (oriented along-coast) is used. The model employs a traditional finite difference expansion in the cross-shelf direction, and a Fourier (periodic) representation in the long-shelf coordinate.

Dual liquid and gas chromatograph system

DOEpatents

Gay, D.D.

A chromatographic system is described that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a nontransparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extreme low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

Dual liquid and gas chromatograph system

DOEpatents

Gay, Don D.

1985-01-01

A chromatographic system that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a non-transparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extremely low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

Megahertz organic/polymer diodes

DOEpatents

Katz, Howard Edan; Sun, Jia; Pal, Nath Bhola

2012-12-11

Featured is an organic/polymer diode having a first layer composed essentially of one of an organic semiconductor material or a polymeric semiconductor material and a second layer formed on the first layer and being electrically coupled to the first layer such that current flows through the layers in one direction when a voltage is applied in one direction. The second layer is essentially composed of a material whose characteristics and properties are such that when formed on the first layer, the diode is capable of high frequency rectifications on the order of megahertz rectifications such as for example rectifications at one of above 100KHz, 500KhZ, IMHz, or 10 MHz. In further embodiments, the layers are arranged so as to be exposed to atmosphere.

High Relative Abundance of Biofuel Sourced Ethanol in Precipitation in the US and Brazil Determined Using Compound Specific Stable Carbon Isotopes

NASA Astrophysics Data System (ADS)

Shimizu, M. S.; Felix, J. D. D.; Casas, M.; Avery, G. B., Jr.; Kieber, R. J.; Mead, R. N.; Willey, J. D.; Lane, C.

2017-12-01

Ethanol biofuel production and consumption have increased exponentially over the last two decades to help reduce greenhouse gas emissions. Currently, 85% of global ethanol production and consumption occurs in the US and Brazil. Increasing biofuel ethanol usage in these two countries enhances emissions of uncombusted ethanol to the atmosphere contributing to poor air quality. Although measurements of ethanol in the air and the precipitation reveal elevated ethanol concentrations in densely populated cities, other sources such as natural vegetation can contribute to emission to the atmosphere. Previous modeling studies indicated up to 12% of atmospheric ethanol is from anthropogenic emissions. Only one gas phase study in southern Florida attempted to constrain the two sources through direct isotopic measurements. The current study used a stable carbon isotope method to constrain sources of ethanol in rainwater from the US and Brazil. A method was developed using solid phase microextraction (SPME) with subsequent analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Stable carbon isotope signatures (δ13C) of vehicle ethanol emission sources for both the US (-9.8‰) and Brazil (-12.7‰) represented C4 plants as feedstock (corn and sugarcane) for biofuel production. An isotope mixing model using biofuel from vehicles (C4 plants) and biogenic (C3 plants) end-members was implemented to estimate ethanol source apportionment in the rain. We found that stable carbon isotope ratio of ethanol in the rain ranged between -22.6‰ and -12.7‰. Our results suggest that the contribution of biofuel to atmospheric ethanol can be higher than previously estimated. As biofuel usage increasing globally, it is essential to determine the relative abundance of anthropogenic ethanol in other areas of the world.

Effect of Mineralogy on Dissolution and Speciation of Iron Containing Mineral Oxides in Atmospheric Aerosol Dust

NASA Astrophysics Data System (ADS)

Hettiarachchi, E.; Rubasinghege, G. R. S.; Reynolds, R. L.; Goldstein, H. L.; Moskowitz, B. M.

2017-12-01

Iron is one of the important trace elements for the life. Though it is the fourth most abundant element in the terrestrial crust, given higher pH ( 8.5) in the ocean, the direct dissolution of iron from the Earth crust is limited. Despite this limitation, ocean contains about 2 nM of dissolved iron that is 20-fold greater. Therefore, it is hypothesized most iron comes to the ocean via atmosphere, and dissolution occurs in the acidic atmospheric environments. The current work focuses on the effect of minerology on atmospheric processing of Fe-containing mineral dust using four authentic dust samples, collected from different parts of the world, along with three model systems, hematite (α-Fe2O3), magnetite (Fe3O4) and ilmenite (FeTiO3). Here, spectroscopic methods are combined with batch reactor studies to investigate total iron dissolution and speciation, with a specific focus on source material i.e. particle size, mineralogy, and environmental conditions, i.e. pH, temperature and solar flux. Our data suggests that the presence of Ti metal enhances the dissolution of iron regardless the total %Fe in the mineral. The surface area normalized total iron dissolution in ilmenite, under the dark conditions, in the presence of nitric acid (HNO3) is 3-fold higher than that of hematite. In authentic samples, similar effects were observed for samples containing %Ti. Further, 74% of the dissolved iron in ilmenite remained as Fe(II), bioavailable iron, whereas it was only 60% for magnetite and 8% for hematite. In this study, these results were used to interpret similar trends observed for authentic dust samples with high magnetite content. Thus, the findings of the current study highlight important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.

Global and Regional Axial Ocean Angular Momentum Signals and Length-of-day Variations (1985-1996)

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Stammer, Detlef

2000-01-01

Changes in ocean angular momentum M about the polar axis are related to fluctuations in zonal currents (relative component M(sub tau) and latitudinal shifts in mass (planetary component M(sub Omega). Output from a 1 deg. ocean model is used to calculate global M(sub tau), (sub Omega), and M time series at 5 day intervals for the period January 1985 to April 1996. The annual cycle in M(sub tau), M(sub Omega), and M is larger than the semiannual cycle, and M(sub Omega) amplitudes are nearly twice those of M(sub tau). Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between omega(sup -1) and omega(sup -2) at sub-seasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing sub-seasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes, but many local maxima exist because of the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes approx. 20 deg. S - 10 deg. N contribute substantial variability to M(sub Omega), while signals in M(sub tau) can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Global and Regional Axial Ocean Angular Momentum Signals and Length-of-Day Variations (1985-1996)

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Stammer, Detlef

1999-01-01

Changes in ocean angular momentum about the polar axis (M) are related to fluctuations in zonal currents (relative component M(sub r)) and latitudinal shifts in mass (planetary component M(sub Omega)). Output from a 1 deg ocean model is used to calculate global M(sub r), M(sub Omega), and M time series at 5-day intervals for the period January 1985-April 1996. The annual cycle in M(sub r), M(sub Omega), and M is larger than the semiannual cycle, and M(sub Omega) amplitudes are nearly twice those of M(sub r). Year-to-year modulation of the seasonal cycle is present, but interannual variability is weak. The spectrum of M is red (background slope between omega(sup (-1) and omega(sup -2)) at subseasonal periods, implying a white or blue spectrum for the external torque on the ocean. Comparisons with previous studies indicate the importance of direct atmospheric forcing in inducing subseasonal M signals, relative to instabilities and other internal sources of rapid oceanic signals. Regional angular momentum estimates show that seasonal variability tends to be larger at low latitudes but there are many local maxima due to the spatial structure of zonal current and mass variability. At seasonal timescales, latitudes approximately 20 S - 10 N contribute substantial variability to M(sub Omega), while signals in M(sub r) can be traced to Antarctic Circumpolar Current transports and associated circulation. Variability in M is found to be small when compared with similar time series for the atmosphere and the solid Earth, but ocean signals are significantly coherent with atmosphere-solid Earth residuals, implying a measurable oceanic impact on length-of-day variations.

Establishing a Network of faint DA white dwarfs as Spectrophotometric Standards

NASA Astrophysics Data System (ADS)

Saha, Abhijit; Narayan, Gautham; Holberg, Jay; Matheson, Thomas; Olszewski, Edward; Stubbs, Christopher; Bohlin, Ralph; Sabbi, Elena; Deustua, Susana; Rest, Armin; Axelrod, Tim; MacKenty, John W.; Camarota, Larry; Gilliland, Ron

2015-08-01

Systematic uncertainties in photometric calibration are the dominant source of error in current type Ia supernova dark energy studies, as well as other forefront cosmology efforts, e.g. photo-redshift determinations for weak lensing mass tomography. Current and next-generation ground-based all-sky surveys require a network of calibration stars with 1) known SEDs (to properly and unambiguously take into account filter differences), and 2) that are on a common photometric zeropoint scale across the sky to sub-percent accuracy. We are using a combination of HST panchromatic photometry and ground based spectroscopy to establish such an essential network of faint primary photometric standards, exploiting the well-understood spectral energy distributions of DA white dwarf stars that are free from the complications of observing through the Earth's time-variable atmosphere. The Balmer features in the spectra are used to deduce the two parameters (temperature and log(g)) from which we model the spectral energy distribution (SED) from these stars which have pure hydrogen atmospheres. By comparing against panchromatic broadband HST photometry, and allowing for an achromatic zero-point adjustment and mild scaling of the interstellar reddening, we find that model prediction and observation agree to a few milli-mag. By combining the zero-point and reddening adjustments with the modeled SED, for each star we obtain the incident SED above the terrestrial atmosphere, thus establishing these objects as spectrophotometric standards. We are pursuing 23 objects between 16 and 19 mag spread over the sky uniformly around the equator and northern mid-latitudes, with plans to extend this to southern latitudes. This precision photometric heritage from HST will benefit essentially all existing and upcoming survey projects, and in prticular, directly addresses one of the current barriers to understanding the nature of dark energy.

Atmospheric pollutants in peri-urban forests of Quercus ilex: evidence of pollution abatement and threats for vegetation.

PubMed

García-Gómez, Héctor; Aguillaume, Laura; Izquieta-Rojano, Sheila; Valiño, Fernando; Àvila, Anna; Elustondo, David; Santamaría, Jesús M; Alastuey, Andrés; Calvete-Sogo, Héctor; González-Fernández, Ignacio; Alonso, Rocío

2016-04-01

Peri-urban vegetation is generally accepted as a significant remover of atmospheric pollutants, but it could also be threatened by these compounds, with origin in both urban and non-urban areas. To characterize the seasonal and geographical variation of pollutant concentrations and to improve the empirical understanding of the influence of Mediterranean broadleaf evergreen forests on air quality, four forests of Quercus ilex (three peri-urban and one remote) were monitored in different areas in Spain. Concentrations of nitrogen dioxide (NO2), ammonia (NH3), nitric acid (HNO3) and ozone (O3) were measured during 2 years in open areas and inside the forests and aerosols (PM10) were monitored in open areas during 1 year. Ozone was the only air pollutant expected to have direct phytotoxic effects on vegetation according to current thresholds for the protection of vegetation. The concentrations of N compounds were not high enough to directly affect vegetation but could be contributing through atmospheric N deposition to the eutrophization of these ecosystems. Peri-urban forests of Q. ilex showed a significant below-canopy reduction of gaseous concentrations (particularly NH3, with a mean reduction of 29-38%), which indicated the feasibility of these forests to provide an ecosystem service of air quality improvement. Well-designed monitoring programs are needed to further investigate air quality improvement by peri-urban ecosystems while assessing the threat that air pollution can pose to vegetation.

Field-wind Distribution and Eruption Columns: Colima Volcano, México.

NASA Astrophysics Data System (ADS)

Fonseca, R.; Martin, A. L.; Perez, I.

2006-12-01

Colima Volcano (19º51'N 103º62'W) is characterized by explosive behaviour. Recently this volcano has shown an increase in explosive activity suggesting the possibility of a subplinian event in the next future like the ones occurred in 1818 and 1913. They were characterized by eruptive columns higher than 20 Km. Considering the possibility of a new explosive event we carried out a wind study based on the radiosonde balloon data set (1980-1995) with 15 atmospheric levels. This data set was collected by Global Gridded Upper Air Statistics (GGUAS) of the European Centre for Médium Range Weather Forecast (ECMRWF). The data was processed with a cinematic model for the study of global atmospheric wind circulation. In this model the current function (vorticity) and a potential function (convergency and/or divergency) was calculated with the Poison equation, utilizing a spectral numeric model. Dominant wind direction in January-May and October-December is toward the East with variations to the East/South East. On the contrary during July-September the dominant wind direction is toward the West, South-West, North-East; East and North-East. The fluctuations related to anticyclonic circulation occur in May, July, September and November at the altitude between 5 and 18 Km. The wind model allows identification of the wind horizontal circulation during the whole year at different atmospheric levels. Moreover, the perturbations of the normal circulation have also been identified. These results are applied to an a ash fall map for ash-fall hazard zonification.

CentNet—A deployable 100-station network for surface exchange research

NASA Astrophysics Data System (ADS)

Oncley, S.; Horst, T. W.; Semmer, S.; Militzer, J.; Maclean, G.; Knudson, K.

2014-12-01

Climate, air quality, atmospheric composition, surface hydrology, and ecological processes are directly affected by the Earth's surface. Complexity of this surface exists at multiple spatial scales, which complicates the understanding of these processes. NCAR/EOL currently provides a facility to the research community to make direct eddy-covariance flux observations to quantify surface-atmosphere interactions. However, just as model resolution has continued to increase, there is a need to increase the spatial density of flux measurements to capture the wide variety of scales that contribute to exchange processes close to the surface. NCAR/EOL now has developed the CentNet facility, that is envisioned to have on the order of 100 surface flux stations deployable for periods of months to years. Each station would measure standard meteorological variables, all components of the surface energy balance (including turbulence fluxes and radiation), atmospheric composition, and other quantities to characterize the surface. Thus, CentNet can support observational research in the biogeosciences, hydrology, urban meteorology, basic meteorology, and turbulence. CentNet has been designed to be adaptable to a wide variety of research problems while keeping operations manageable. Tower infrastructure has been designed to be lightweight, easily deployed, and with a minimal set-up footprint. CentNet uses sensor networks to increase spatial sampling at each station. The data system saves every sample on site to retain flexibility in data analysis. We welcome guidance on development and funding priorities as we build CentNet.

Large unexplained suite of chemically reactive compounds present in ambient air due to biomass fires.

PubMed

Kumar, V; Chandra, B P; Sinha, V

2018-01-12

Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s -1 to 64 s -1 ) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.

NEPTUNE'S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES.

PubMed

Simon, Amy A; Rowe, Jason F; Gaulme, Patrick; Hammel, Heidi B; Casewell, Sarah L; Fortney, Jonathan J; Gizis, John E; Lissauer, Jack J; Morales-Juberias, Raul; Orton, Glenn S; Wong, Michael H; Marley, Mark S

2016-02-01

Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired nine months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune's zonal wind profile, and confirms observed cloud feature variability. Although Neptune's clouds vary in location and intensity on short and long timescales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extrasolar planet variability measurements. In particular we suggest that the balance between large, relatively stable, atmospheric features and smaller, more transient, clouds controls the character of substellar atmospheric variability. Atmospheres dominated by a few large spots may show inherently greater light curve stability than those which exhibit a greater number of smaller features.

Photochemistry in the Atmospheres of Denver and Mexico City

NASA Astrophysics Data System (ADS)

Cantrell, C. A.

2016-12-01

The composition of atmospheres in and downwind of urban centers has been the subject of study for decades. While early campaigns involved measurements exclusively from the ground, more recent studies have included airborne-based observations. Improved understanding has hinged critically on the development of instrumentation for better qualitifcation of pollutants, and measurement of previously unobserved species in the gas and particulate phases. Comprehensive, well-planned studies have, over time, led to more detailed understanding of chemical transformations and thus improved model representations and directions for further research. This presentation focuses on findings from two case studies of urban atmospheres, namely the MILAGRO study in the Mexico City metropolitan area and the FRAPPE study in the Denver metropolitan region. Both studies made use of extensive ground-based networks and multiple aircraft platforms. The data collected during these studies have been combined with numerical models to derive assessments of the evolution of atmospheric composition due to photochemistry, mixing, and surface processes. Here, analysis of MILAGRO data focuses on the evolution of outflow downwind of the urban region. In FRAPPE, the focus is the possible role of oil and gas exploration on urban air quality. These findings are used to assess the accuracy of current numerical models to reproduce observations, and to point toward areas possibly needing further study.

Evidence from the Pacific troposphere for large global sources of oxygenated organic compounds

NASA Astrophysics Data System (ADS)

Singh, H.; Chen, Y.; Staudt, A.; Jacob, D.; Blake, D.; Heikes, B.; Snow, J.

2001-04-01

The presence of oxygenated organic compounds in the troposphere strongly influences key atmospheric processes. Such oxygenated species are, for example, carriers of reactive nitrogen and are easily photolysed, producing free radicals-and so influence the oxidizing capacity and the ozone-forming potential of the atmosphere-and may also contribute significantly to the organic component of aerosols. But knowledge of the distribution and sources of oxygenated organic compounds, especially in the Southern Hemisphere, is limited. Here we characterize the tropospheric composition of oxygenated organic species, using data from a recent airborne survey conducted over the tropical Pacific Ocean (30°N to 30°S). Measurements of a dozen oxygenated chemicals (carbonyls, alcohols, organic nitrates, organic pernitrates and peroxides), along with several C2-C8 hydrocarbons, reveal that abundances of oxygenated species are extremely high, and collectively, oxygenated species are nearly five times more abundant than non-methane hydrocarbons in the Southern Hemisphere. Current atmospheric models are unable to correctly simulate these findings, suggesting that large, diffuse, and hitherto-unknown sources of oxygenated organic compounds must therefore exist. Although the origin of these sources is still unclear, we suggest that oxygenated species could be formed via the oxidation of hydrocarbons in the atmosphere, the photochemical degradation of organic matter in the oceans, and direct emissions from terrestrial vegetation.

Polarized scattered light from self-luminous exoplanets. Three-dimensional scattering radiative transfer with ARTES

NASA Astrophysics Data System (ADS)

Stolker, T.; Min, M.; Stam, D. M.; Mollière, P.; Dominik, C.; Waters, L. B. F. M.

2017-11-01

Context. Direct imaging has paved the way for atmospheric characterization of young and self-luminous gas giants. Scattering in a horizontally-inhomogeneous atmosphere causes the disk-integrated polarization of the thermal radiation to be linearly polarized, possibly detectable with the newest generation of high-contrast imaging instruments. Aims: We aim to investigate the effect of latitudinal and longitudinal cloud variations, circumplanetary disks, atmospheric oblateness, and cloud particle properties on the integrated degree and direction of polarization in the near-infrared. We want to understand how 3D atmospheric asymmetries affect the polarization signal in order to assess the potential of infrared polarimetry for direct imaging observations of planetary-mass companions. Methods: We have developed a three-dimensional Monte Carlo radiative transfer code (ARTES) for scattered light simulations in (exo)planetary atmospheres. The code is applicable to calculations of reflected light and thermal radiation in a spherical grid with a parameterized distribution of gas, clouds, hazes, and circumplanetary material. A gray atmosphere approximation is used for the thermal structure. Results: The disk-integrated degree of polarization of a horizontally-inhomogeneous atmosphere is maximal when the planet is flattened, the optical thickness of the equatorial clouds is large compared to the polar clouds, and the clouds are located at high altitude. For a flattened planet, the integrated polarization can both increase or decrease with respect to a spherical planet which depends on the horizontal distribution and optical thickness of the clouds. The direction of polarization can be either parallel or perpendicular to the projected direction of the rotation axis when clouds are zonally distributed. Rayleigh scattering by submicron-sized cloud particles will maximize the polarimetric signal whereas the integrated degree of polarization is significantly reduced with micron-sized cloud particles as a result of forward scattering. The presence of a cold or hot circumplanetary disk may also produce a detectable degree of polarization (≲1%) even with a uniform cloud layer in the atmosphere.

High-efficiency solar cells fabricated from direct-current magnetron sputtered n-indium tin oxide onto p-InP grown by atmospheric pressure metalorganic vapor phase epitaxy

NASA Technical Reports Server (NTRS)

Li, X.; Wanlass, M. W.; Gessert, T. A.; Emery, K. A.; Coutts, T. J.

1989-01-01

An attempt is made to improve device efficiencies by depositing indium tin oxide onto epitaxially grown p-InP on p(+)-InP substrates. This leads to a reduction in the device series resistance, high-quality reproducible surfaces, and an improvement in the transport properties of the base layer. Moreover, many of the facets associated with badly characterized bulk liquid encapsulated Czochralski substrates used in previous investigations are removed in this way.

An Adaptive H infinity Control Algorithm for Jitter Control and Target Tracking in a Directed Energy Weapon

DTIC Science & Technology

2012-05-16

large size and lack of efficiency of current technology after initial review. In the 1990’s the Air Force designed and produced a high- altitude ...Forden, G.E., "The airborne laser," Spectrum, IEEE , vol.34, no.9, pp.40-49, Sep 1997 10 altitude of 40,000 ft. the atmosphere was much clearer...distance remains the same. OT-5 provides a relative position of beam center on the detector. Two voltage outputs are given corresponding to x-axis location

Development of flame resistant treatment for nomex fibrous structures

NASA Technical Reports Server (NTRS)

Toy, M. S.

1978-01-01

Technology which renders aramid fibrous structures flame resistant through chemical modification was developed. The project scaled up flame resistant treatment from laboratory fabric swatches of a few inches to efficiently producing ten yards of commercial width (41 inches) aromatic polyamide. The radiation intensity problem of the processor was resolved. Further improvement of the processor cooling system was recommended for two reasons: (1) To advance current technology of flame proofing Nomex fabric to higher oxygen enriched atmospheres; and (2) To adapt the processor for direct applicability to low cost commercial fabrics.

Characterising exoplanet atmospheres with SPHERE: the HR 8799 system with Exo-REM and NEMESIS

NASA Astrophysics Data System (ADS)

Baudino, J.-L.; Bonnefoy, M.; Vigan, A.; Irwin, P. J.

2017-12-01

The characterisation of the exoplanets evolved recently thanks to the beginning of the second generation of direct imaging instruments, especially with SPHERE. The resolution and wavelength range available currently give access to an increase of accuracy and on the number of physical parameters that can be constrain. One of the first target of SPHERE was the HR 8799 system. The four planets was characterised using four different forward models including Exo-REM. We complete this paper buy using NEMESIS, a retrieval code.

Satellite Estimates of the Direct Radiative Forcing of Biomass Burning Aerosols Over South America and Africa

NASA Technical Reports Server (NTRS)

Christopher, Sundar A.; Wang, Min; Kliche, Donna V.; Berendes, Todd; Welch, Ronald M.; Yang, S.K.

1997-01-01

Atmospheric aerosol particles, both natural and anthropogenic are important to the earth's radiative balance. Therefore it is important to provide adequate validation information on the spatial, temporal and radiative properties of aerosols. This will enable us to predict realistic global estimates of aerosol radiative effects more confidently. The current study utilizes 66 AVHRR LAC (Local Area Coverage) and coincident Earth Radiation Budget Experiment (ERBE) images to characterize the fires, smoke and radiative forcings of biomass burning aerosols over four major ecosystems of South America.

OPERA neutrino oscillation search: Status and perspectives

NASA Astrophysics Data System (ADS)

Gornushkin, Yu.

2016-07-01

OPERA is a long-baseline neutrino experiment at the Gran Sasso laboratory (LNGS) designed to search for ν_{{μ}}^{} → ν_{{τ}}^{} oscillations in a direct appearance mode on an event by event basis. OPERA took data in 2008-2012 with the CNGS neutrino beam from CERN. The data analysis is ongoing, with the goal of establishing ν_{{τ}}^{} appearance with a high significance. Complementary studies of the ν_{{μ}}^{} → ν_{{e}}^{} oscillations and atmospheric muons fluxes were performed as well. Current results of the experiment are presented and perspectives discussed.

Experimental Analysis of Pseudospark Sourced Electron Beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Pal, U. N.; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.

2011-12-01

The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

Spectral analysis of extinguished sunlight

NASA Astrophysics Data System (ADS)

Zagury, Frédéric; Goutail, Florence

2003-08-01

SAOZ (Système d'Analyse par Observation Zénitale) is a balloon-borne experiment which determines the column density of several molecular species from the visible spectrum of sunlight. We will use sequence of spectra collected during a sunset to discuss atmospheric extinction, and the nature of the radiation field in the atmosphere. The radiation field in the atmosphere is, from daylight to sunset, and with a clear sky, dominated by light coming from the direction of the sun. This light is composed of direct sunlight (extinguished by the gas), and of sunlight forward-scattered by aerosols. As the sun sets, aerosol scattering is first perceived towards the UV. It progressively replaces direct sunlight over all of the spectrum. Our analysis permits fixing the main parameters of each component of the radiation field at any time. The fits we find for the extinction of sunlight in the atmosphere must also apply to starlight. Thus, the present work can be used in astronomy to correct ground-based spectral observations for extinction in the atmosphere.

Spatial Representativeness Error in the Ground-Level Observation Networks for Black Carbon Radiation Absorption

NASA Astrophysics Data System (ADS)

Wang, Rong; Andrews, Elisabeth; Balkanski, Yves; Boucher, Olivier; Myhre, Gunnar; Samset, Bjørn Hallvard; Schulz, Michael; Schuster, Gregory L.; Valari, Myrto; Tao, Shu

2018-02-01

There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that strongly absorbs solar radiation. The observation-constrained estimate, which is several times larger than the bottom-up estimate, is influenced by the spatial representativeness error due to the mesoscale inhomogeneity of the aerosol fields and the relatively low resolution of global chemistry-transport models. Here we evaluated the spatial representativeness error for two widely used observational networks (AErosol RObotic NETwork and Global Atmosphere Watch) by downscaling the geospatial grid in a global model of BC aerosol absorption optical depth to 0.1° × 0.1°. Comparing the models at a spatial resolution of 2° × 2° with BC aerosol absorption at AErosol RObotic NETwork sites (which are commonly located near emission hot spots) tends to cause a global spatial representativeness error of 30%, as a positive bias for the current top-down estimate of global BC direct radiative forcing. By contrast, the global spatial representativeness error will be 7% for the Global Atmosphere Watch network, because the sites are located in such a way that there are almost an equal number of sites with positive or negative representativeness error.

Perfluorocarboxylic acid (PFCA) atmospheric formation and transport to the Arctic.

NASA Astrophysics Data System (ADS)

Pike-thackray, C.; Selin, N. E.

2015-12-01

Perfluorocarboxylic acids (PFCAs) are highly persistent and toxic environmental contaminants that have been found in remote locations such as the Arctic, far from emission sources. These persistent organic pollutants are emitted directly to the atmosphere as well as being produced by the degradation of precursor compounds in the atmosphere, but recent trends towards increasing precursor emissions and decreasing direct emissions raise the importance of production in the atmosphere. Our work aims to improve understanding of the atmospheric degradation of fluorotelomer precursor compounds to form the long-chain PFCAs PFOA (C8) and PFNA (C9).Using the atmospheric chemical transport model GEOS-Chem, which uses assimilated meteorology to simulate the atmospheric transport of trace gas species, we investigate the interaction of the atmospheric formation of PFCAs and the atmospheric transport of their precursor species. Our simulations are a first application of the GEOS-Chem framework to PFCA chemistry. We highlight the importance of the spatial and temporal variability of background atmospheric chemical conditions experienced during transport. We find that yields and formation times of PFOA and PFNA respond differently and strongly to the photochemical conditions of the atmosphere, such as the abundance of NO, HO2, and other photochemical species.

Current Status and Challenges of Atmospheric Data Assimilation

NASA Astrophysics Data System (ADS)

Atlas, R. M.; Gelaro, R.

2016-12-01

The issues of modern atmospheric data assimilation are fairly simple to comprehend but difficult to address, involving the combination of literally billions of model variables and tens of millions of observations daily. In addition to traditional meteorological variables such as wind, temperature pressure and humidity, model state vectors are being expanded to include explicit representation of precipitation, clouds, aerosols and atmospheric trace gases. At the same time, model resolutions are approaching single-kilometer scales globally and new observation types have error characteristics that are increasingly non-Gaussian. This talk describes the current status and challenges of atmospheric data assimilation, including an overview of current methodologies, the difficulty of estimating error statistics, and progress toward coupled earth system analyses.

Ocean-Wave Dynamics Analysis during Hurricane Ida and Norida Using a Fully Coupled Modeling System

NASA Astrophysics Data System (ADS)

Olabarrieta, M.; Warner, J. C.; Armstrong, B. N.

2010-12-01

Extreme storms, such as hurricanes and extratropical storms play a dominant role in shaping the beaches of the East and Gulf Coasts of the United States. Future tropical depressions will be more intense than in the present climate (Assessment Report of IPCC, 2007) and therefore coastal areas are likely to become more susceptible to their effects. The major damage caused by these extreme events is associated with the duration of the storm, storm intensity, waves, and the total water levels reached during the storm. Numerical models provide a useful approach to study the spatial and temporal distribution of these parameters. However, the correct estimation of the total water levels and wind wave heights through numerical modeling requires accurate representation of the air-sea interface dynamics. These processes are highly complex due to the variable interactions between winds, ocean waves and currents near the sea surface. In the present research we use the COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modeling system (Warner et al., 2010) to address the key role of the atmosphere-ocean-wave interactions during Hurricane Ida and its posterior evolution to NorIda, November 2009. This northeastern storm was one of the most costly in the past two decades and likely in the top five of the past century. One interesting aspect of the considered period is that it includes two very different atmospheric extreme conditions, a hurricane and a northeastern storm, developed in regions with very different oceanographic characteristics. By performing a suite of numerical runs we are able to isolate the effect of the interaction terms between the atmosphere (WRF model), the ocean (ROMS model) and the wave propagation and generation model (SWAN). Special attention is given to the role of the ocean surface roughness and high resolution SST fields on the atmospheric boundary layers dynamics and consequently these effects on the wind wave generation, surface currents and storm surge. The effects of ocean currents on wind wave generation and propagations are also analyzed. The model results are compared to different data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the NDBC and the National Tidal Database respectively. The results identified that the inclusion of the ocean roughness on the atmospheric module greatly improves the wind intensity estimation and therefore also the wind waves and the storm surge amplitude. For example, during the passage of Ida through the Gulf of Mexico the wind speeds are reduced due to the wave induced ocean roughness, resulting in better agreement with the measured winds. During NorIda, the effect of the surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. Three different ocean roughness closure models are analyzed, with the wave-age based closure model providing the best results. Ocean currents are also shown to affect wave spectral characteristics through the generation and propagation processes. Changes within 15% on the significant wave height are detected in areas affected by the main oceanic currents: the Gulf Stream and the Loop Current.

Direct observation of OH production from the ozonolysis of olefins

NASA Astrophysics Data System (ADS)

Donahue, Neil M.; Kroll, Jesse H.; Anderson, James G.; Demerjian, Kenneth L.

Ozone olefin reactions may be a significant source of OH in the urban atmosphere, but current evidence for OH production is indirect and contested. We report the first direct observation of OH radicals from the reaction of ozone with a series of olefins (ethene, isoprene, trans-2-butene and 2,3 dimethyl-2-butene) in 4-6 torr of nitrogen. Using LIF to directly observe the steady-state of OH produced by the initial ozone-olefin reaction and subsequently destroyed by the OH-olefin reaction, we are able to establish OH yields broadly consistent with indirect values. The identification of the OH is unequivocal, and there is no indication that it is produced by a secondary process. To support these observations, we present a complete ab-initio potential energy surface for the O3-ethene reaction, extending from the reactants to available products.

Highlights of Recent Developments in the International GPS Service and Perspectives for Future Directions

NASA Technical Reports Server (NTRS)

Neilan, R.; Reigber, C.; Springer, T.; Beutler, G.; Kouba, J.

1999-01-01

In December 1998, the IGS Governing Board officially changed the name of this IAG service from 'International GPS Service for Geodynamics to simply the 'International GPS Service'. This change of name reflects the fact that today the IGS supports numerous scientific projects outside the traditional geodetic and geodynamic disciplines. A number of IGS projects and working groups have been established, each concentrating on a particular science application, such as the ionosphere, atmosphere, reference frame, precise time transfer, etc. These activities are enabled and simulated by the IGS and directly contribute to the continuing development of the service. The IGS is currently poised to respond to evolving user requirements that focus on timeliness and reliability of data and products, particularly in support of a slate of Low Earth Orbiter missions over the next decade. Perspectives on the future of the IGS will be developed based on current directions as well as anticipated external influences, such as GPS satellite modernization, GLONASS, availability of global communications, and plans for the European GALILEO (Global Navigation Satellite System - GNSS). We will address development of user friendly interfaces and IGS product tutorials.

Atmospheric circulation of extrasolar giant planets

NASA Astrophysics Data System (ADS)

Showman, A. P.

2012-12-01

Of the many known extrasolar planets, over 100 have orbital semi-major axes less than 0.1 AU, and a significant fraction of these hot Jupiters and Neptunes are known to transit their stars, allowing them to be characterized with the Spitzer, Hubble, and groundbased telescopes. The stellar flux incident on these planets is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared light curves, spectra, albedo, and atmospheric composition, and recent Spitzer infrared light curves show evidence for dynamical meteorology in these planets' atmospheres. Here, I will survey basic dynamical ideas and detailed 3D numerical models that illuminate the atmospheric circulation of these exotic, tidally locked planets. These models suggest that, generally, the circulation will be characterized by broad, fast zonal jets, with day-night temperature contrasts at the photosphere that may vary from small in some cases to large in others. I will discuss the dynamical mechanisms for maintaining the fast zonal jets that develop in these models, as well as the mechanisms for controlling the temperature patterns, including the day-night temperature contrasts. These mechanisms help to explain current observations, and they predict regime transitions for how the wind and temperature patterns should vary with the incident stellar flux, strength of atmospheric drag, and other parameters. These transitions are observable and in some cases are already becoming evident in the data. I will also compare the circulation of the hot Jupiters to that of young, massive giant planets being directly imaged around other stars, which will be the subject of a new observational vanguard over the next decade. To emphasize the similarities as well as differences, I will ground this discussion in our understanding of the more familiar atmospheric dynamical regime of Earth, as well as our "local" giant planets Jupiter, Saturn, Uranus, and Neptune.

Atmospheric circulation of extrasolar giant planets

NASA Astrophysics Data System (ADS)

Showman, A. P.

2011-12-01

Of the many known extrasolar planets, nearly 200 have orbital semi-major axes less than 0.1 AU, and a significant fraction of these hot Jupiters and Neptunes are known to transit their stars, allowing them to be characterized with the Spitzer, Hubble, and groundbased telescopes. The stellar flux incident on these planets is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared light curves, spectra, albedo, and atmospheric composition, and recent Spitzer infrared light curves show evidence for dynamical meteorology in these planets' atmospheres. Here, I will survey basic dynamical ideas and detailed 3D numerical models that illuminate the atmospheric circulation of these exotic, tidally locked planets. These models suggest that, generally, the circulation will be characterized by broad, fast zonal jets, with day-night temperature contrasts at the photosphere that may vary from small in some cases to large in others. I will discuss the dynamical mechanisms for maintaining the fast zonal jets that develop in these models, as well as the mechanisms for controlling the temperature patterns, including the day-night temperature contrasts. These mechanisms help to explain current observations, and they predict regime transitions for how the wind and temperature patterns should vary with the incident stellar flux, strength of atmospheric drag, and other parameters. These transitions are observable and in some cases are already becoming evident in the data. I will also compare the circulation of the hot Jupiters to that of young, massive giant planets being directly imaged around other stars, which will be the subject of a new observational vanguard over the next decade. To emphasize the similarities as well as differences, I will ground this discussion in our understanding of the more familiar atmospheric dynamical regime of Earth, as well as our "local" giant planets Jupiter, Saturn, Uranus, and Neptune.

Wildland Fire Forecasting: Predicting Wildfire Behavior, Growth, and Feedbacks on Weather

NASA Astrophysics Data System (ADS)

Coen, J. L.

2005-12-01

Recent developments in wildland fire research models have represented more complex of fire behavior. The cost has been to increase the computational requirements. When operational constraints are included, such as the need to produce such forecasts faster than real time, the challenge becomes a balance of how much complexity (with corresponding gains in realism) and accuracy can be achieved in producing the quantities of interest while meeting the specified operational constraints. Current field tools are calculator or Palm-Pilot based algorithms such as BEHAVE and BEHAVE Plus that produce timely estimates of instantaneous fire spread rates, flame length, and fire intensity at a point using readily estimated inputs of fuel model, terrain slope, and atmospheric wind speed at a point. At the cost of requiring a PC and slower calculation, FARSITE represents two-dimensional fire spread and adds capabilities including a parameterized representation of crown fire ignition, This work describes how a coupled atmosphere-fire model previously used as a research tool has been adapted for production of real-time forecasts of fire growth and its interactions with weather over a domain focusing on Colorado during summer 2004. The coupled atmosphere-wildland fire-environment (CAWFE) model composed of a 3-dimensional atmospheric prediction model that has been two-way coupled with an empirical fire spread model. The models are connected in that atmospheric conditions (and fuel conditions influenced by the atmosphere) affect the rate and direction of fire propagation, which releases sensible and latent heat (i.e. thermal and water vapor fluxes) to the atmosphere that in turn alter the winds and atmospheric structure around the fire. Thus, it can represent time and spatially-varying weather and the fire feedbacks on the atmospheric which are at the heart of sudden changes in fire behavior and examples of extreme fire behavior such as blow ups, which are now not predictable with current tools. Thus, although this work shows that is it possible to perform more detailed simulations in real time, fire behavior forecasting remains a challenging problem. This is due to challenges in weather prediction, particularly at fine spatial and temporal scales considered "nowcasting" (0-6 hrs), uncertainties in fire behavior even with known meteorological conditions, limitations in quantitative datasets on fuel properties such as fuel loading, and verification. This work describes efforts to advance these capabilities with input from remote sensing data on fuel characteristics and dynamic steering and object-based verification with remotely sensed fire perimeters.

Oxidation of mercury by bromine in the subtropical Pacific free troposphere

NASA Astrophysics Data System (ADS)

Gratz, L. E.; Ambrose, J. L.; Jaffe, D. A.; Shah, V.; Jaeglé, L.; Stutz, J.; Festa, J.; Spolaor, M.; Tsai, C.; Selin, N. E.; Song, S.; Zhou, X.; Weinheimer, A. J.; Knapp, D. J.; Montzka, D. D.; Flocke, F. M.; Campos, T. L.; Apel, E.; Hornbrook, R.; Blake, N. J.; Hall, S.; Tyndall, G. S.; Reeves, M.; Stechman, D.; Stell, M.

2015-12-01

Mercury is a global toxin that can be introduced to ecosystems through atmospheric deposition. Mercury oxidation is thought to occur in the free troposphere by bromine radicals, but direct observational evidence for this process is currently unavailable. During the 2013 Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks campaign, we measured enhanced oxidized mercury and bromine monoxide in a free tropospheric air mass over Texas. We use trace gas measurements, air mass back trajectories, and a chemical box model to confirm the origin and chemical history of the sampled air mass. We find the presence of elevated oxidized mercury to be consistent with oxidation of elemental mercury by bromine atoms in this subsiding upper tropospheric air mass within the subtropical Pacific High, where dry atmospheric conditions are conducive to oxidized mercury accumulation. Our results support the role of bromine as the dominant oxidant of mercury in the upper troposphere.

Wind Turbine Gust Prediction Using Remote Sensing Data

NASA Astrophysics Data System (ADS)

Towers, Paul; Jones, Bryn

2013-11-01

Offshore wind energy is a growing energy source as governments around the world look for environmentally friendly solutions to potential future energy shortages. In order to capture more energy from the wind, larger turbines are being designed, leading to the structures becoming increasingly vulnerable to damage caused by violent gusts of wind. Advance knowledge of such gusts will enable turbine control systems to take preventative action, reducing turbine maintenance costs. We present a system which can accurately forecast the velocity profile of an oncoming wind, given only limited spatial measurements from light detection and ranging (LiDAR) units, which are currently operational in industry. Our method combines nonlinear state estimation techniques with low-order models of atmospheric boundary-layer flows to generate flow-field estimates. We discuss the accuracy of our velocity profile predictions by direct comparison to data derived from large eddy simulations of the atmospheric boundary layer.

The effects of atmospheric cloud radiative forcing on climate

NASA Technical Reports Server (NTRS)

Randall, David A.

1989-01-01

In order to isolate the effects of atmospheric cloud radiative forcing (ACRF) on climate, the general circulation of an ocean-covered earth called 'Seaworld' was simulated using the Colorado State University GCM. Most current climate models, however, do not include an interactive ocean. The key simplifications in 'Seaworld' are the fixed boundary temperature with no land points, the lack of mountains and the zonal uniformity of the boundary conditions. Two 90-day 'perpetual July' simulations were performed and analyzed the last sixty days of each. The first run included all the model's physical parameterizations, while the second omitted the effects of clouds in both the solar and terrestrial radiation parameterizations. Fixed and identical boundary temperatures were set for the two runs, and resulted in differences revealing the direct and indirect effects of the ACRF on the large-scale circulation and the parameterized hydrologic processes.

Miniature Low-Noise G-Band I-Q Receiver

NASA Technical Reports Server (NTRS)

Kangaslahti, Pekka P.; Pukala, David M.; Gaier, Todd C.; Tanner, Alan B.; O'Dwyer, Ian J.; Lambrigtsen, Bjom H.; Soria, Mary M.; Owen, Heather R.; Lai, Richard; Mei, Xiaobing

2010-01-01

Weather forecasting, hurricane tracking, and atmospheric science applications depend on humidity sounding of atmosphere. Current instruments provide these measurements from groundbased, airborne, and low Earth orbit (LEO) satellites by measuring radiometric temperature on the flanks of the 183-GHz water vapor line. Miniature, low-noise receivers have been designed that will enable these measurements from a geostationary, thinned array sounder, which is based on hundreds of low-noise receivers that convert the 180-GHz signal directly to baseband in-phase and in-quadrature signals for digitization and correlation. The developed receivers provide a noise temperature of 450 K from 165 to 183 GHz (NF = 4.1 dB), and have a mass of 3 g while consuming 24 mW of power. These are the most sensitive broadband I-Q receivers at this frequency range that operate at room temperature, and are significantly lower in mass and power consumption than previously reported receivers.

Acetonitrile Ion Suppression in Atmospheric Pressure Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Colizza, Kevin; Mahoney, Keira E.; Yevdokimov, Alexander V.; Smith, James L.; Oxley, Jimmie C.

2016-11-01

Efforts to analyze trace levels of cyclic peroxides by liquid chromatography/mass spectrometry gave evidence that acetonitrile suppressed ion formation. Further investigations extended this discovery to ketones, linear peroxides, esters, and possibly many other types of compounds, including triazole and menadione. Direct ionization suppression caused by acetonitrile was observed for multiple adduct types in both electrospray ionization and atmospheric pressure chemical ionization. The addition of only 2% acetonitrile significantly decreased the sensitivity of analyte response. Efforts to identify the mechanism were made using various nitriles. The ion suppression was reduced by substitution of an acetonitrile hydrogen with an electron-withdrawing group, but was exacerbated by electron-donating or steric groups adjacent to the nitrile. Although current theory does not explain this phenomenon, we propose that polar interactions between the various functionalities and the nitrile may be forming neutral aggregates that manifest as ionization suppression.

Cold atmospheric pressure plasma for treatment of chronic wounds: drug or medical device?

PubMed

Kramer, A; Conway, B R; Meissner, K; Scholz, F; Rauch, B H; Moroder, A; Ehlers, A; Meixner, A J; Heidecke, C-D; Partecke, L I; Kietzmann, M; Assadian, O

2017-08-02

The use of cold atmospheric pressure plasma (CAPP) as a new therapeutic option to aid the healing of chronic wounds appears promising. Currently, uncertainty exists regarding their classification as medical device or medical drug. Because the classification of CAPP has medical, legal, and economic consequences as well as implications for the level of preclinical and clinical testing, the correct classification is not an academic exercise, but an ethical need. A multidisciplinary team of physicians, surgeons, pharmacists, physicists and lawyers has analysed the physical and technical characteristics as well as legal conditions of the biological action of CAPP. It was concluded that the mode of action of the locally generated CAPP, with its main active components being different radicals, is pharmacological and not physical in nature. Depending on the intended use, CAPP should be classified as a drug, which is generated by use of a medical device directly at the point of therapeutic application.

Bio-Decontamination of Water and Surfaces by DC Discharges in Atmospheric Air

NASA Astrophysics Data System (ADS)

Machala, Zdenko; Tarabová, Barbora; Pelach, Michal; Šipoldová, Zuzana; Hensel, Karol; Janda, Mário; Šikurová, Libuša

Two types of DC-driven atmospheric air discharges, including a streamer corona and a transient spark with short high current pulses of limited energy, were employed for bio-decontamination of water and various surfaces (agar plates, plastic foils, human teeth) contaminated by bacteria or spores (Salmonella typhimurium, Bacillus cereus). Both discharges generate cold non-equilibrium plasma. The discharges combined with the electro-spraying of the treated water through the needle electrode lead to fast and efficient bio-decontamination. Experiments comparing direct and indirect plasma effects, oxidation stress measurements in the cell membranes, and chemical changes induced in the treated water enable assessment of the plasma agents being responsible for microbial inactivation. Radicals and reactive oxygen species seem to be dominant biocidal agents, although deeper understanding of the plasma-induced water chemistry and of the temporal evolution of the bio-inactivation processes is needed.

Sensitivity of clear-sky direct radiative effect of the aerosol to micro-physical properties by using 6SV radiative transfer model: preliminary results

NASA Astrophysics Data System (ADS)

Bassani, Cristiana; Tirelli, Cecilia; Manzo, Ciro; Pietrodangelo, Adriana; Curci, Gabriele

2015-04-01

The aerosol micro-physical properties are crucial to analyze their radiative impact on the Earth's radiation budget [IPCC, 2007]. The 6SV model, last generation of the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) radiative transfer code [Kotchenova et al., 2007; Vermote et al., 1997] has been used to perform physically-based atmospheric correction of hyperspectral airborne and aircraft remote sensing data [Vermote et al., 2009; Bassani et al. 2010; Tirelli et al., 2014]. The atmospheric correction of hyperspectral data has been shown to be sensitive to the aerosol micro-physical properties, as reported in Bassani et al., 2012. The role of the aerosol micro-physical properties on the accuracy of the atmospheric correction of hyperspectral data acquired over water and land targets is investigated within the framework of CLAM-PHYM (Coasts and Lake Assessment and Monitoring by PRISMA HYperspectral Mission) and PRIMES (Synergistic use of PRISMA products with high resolution meteo-chemical simulations and their validation on ground and from satellite) projects, both funded by Italian Space Agency (ASI). In this work, the results of the radiative field of the Earth/Atmosphere coupled system simulated by using 6SV during the atmospheric correction of hyperspectral data are presented. The analysis of the clear-sky direct radiative effect is performed considering the aerosol micro-physical properties used to define the aerosol model during the atmospheric correction process. In particular, the AERONET [Holben et al., 1998] and FLEXAOD [Curci et al., 2014] micro-physical properties are used for each image to evaluate the contribution of the size distribution and refractive index of the aerosol type on the surface reflectance and on the direct radiative forcing. The results highlight the potential of the hyperspectral remote sensing data for atmospheric studies as well as for environmental studies. Currently, the future hyperspectral missions, such as the PRISMA mission, are an opportunity to study the aerosol radiative effects. IPCC, 2007. Climate Change 2007: the Physical Science Basis. ISBN 978 0521 88009-1 Hardback; 978 0521 70596-7 Paperback. Kotchenova and Vermote, 2007. Appl. Opt. doi:10.1364/AO.46.004455. Vermote et al., 1997. IEEE Trans. Geosci. Remote Sens. doi:10.1109/36.581987. Vermote and Kotchenova, 2009. J. Geophys. Res. doi:10.1029/2007JD009662. Bassani et al., 2010. Sensors. doi:10.3390/s100706421. Bassani et al., 2012. Atmos. Meas. Tech. doi:10.5194/amt-5-1193-2012. Tirelli,C. et al., 2014. AGU2014, 15-19 September 2014. Holben et al., 1998. Rem. Sens. Environ. doi:10.1016/S0034-4257(98)00031-5 Curci et al., 2014. Atmos. Environ. doi:10.1016/j.atmosenv.2014.09.009

Bias in modeled bi-directional NH3 fluxes associated with temporal averaging of atmospheric NH3 concentrations

EPA Science Inventory

Direct flux measurements of NH3 are expensive, time consuming, and require detailed supporting measurements of soil, vegetation, and atmospheric chemistry for interpretation and model parameterization. It is therefore often necessary to infer fluxes by combining measurements of...

Observing Recent Changes in the Large-Scale Arctic Energy Budget

NASA Astrophysics Data System (ADS)

Porter, D. F.; Serreze, M.; Cassano, J.

2008-12-01

Changes in the large-scale energy budget of the Arctic are examined using a variety of next-generation reanalysis and observational data. An effort is made to construct a best-guess of the current arctic energy budget using a variety of atmospheric data. For the period of 2000-2005, monthly means from the Clouds and the Earth's Radiant Energy System (CERES) data represents the current most-reliable top of atmosphere radiation budget. The remaining components of the energy budget system in the arctic polar cap (defined as 70 degrees North latitude circle), comprising of the vertically-integrated storage and horizontal transports of energy, and net heat transfers between the atmosphere and the subsurface column, are diagnosed using the Japanese 25-year Reanalysis Project (JRA-25) and the NCEP/NCAR Reanalysis (NRA). The as then record-setting minimum sea-ice extent during the 2005 melt season is used as a marker of recent changes occurring in the arctic climate system. However, changes in each reanalysis differs than the satellite observations. In one example, when compared to the 2000-2005 climatology, CERES shows a shift in the peak TOA radiation from July to June in 2005, a change that is absent in the reanalyses and directly attributable to the early and pronounced albedo reduction. An earlier peak in TOA radiation can strongly modulate the flux energy convergence from lower latitudes through circulation changes. Here, the energy budget framework provides a simplified view of the pathway through which changes of key component parings occur.

GENESIS: new self-consistent models of exoplanetary spectra

NASA Astrophysics Data System (ADS)

Gandhi, Siddharth; Madhusudhan, Nikku

2017-12-01

We are entering the era of high-precision and high-resolution spectroscopy of exoplanets. Such observations herald the need for robust self-consistent spectral models of exoplanetary atmospheres to investigate intricate atmospheric processes and to make observable predictions. Spectral models of plane-parallel exoplanetary atmospheres exist, mostly adapted from other astrophysical applications, with different levels of sophistication and accuracy. There is a growing need for a new generation of models custom-built for exoplanets and incorporating state-of-the-art numerical methods and opacities. The present work is a step in this direction. Here we introduce GENESIS, a plane-parallel, self-consistent, line-by-line exoplanetary atmospheric modelling code that includes (a) formal solution of radiative transfer using the Feautrier method, (b) radiative-convective equilibrium with temperature correction based on the Rybicki linearization scheme, (c) latest absorption cross-sections, and (d) internal flux and external irradiation, under the assumptions of hydrostatic equilibrium, local thermodynamic equilibrium and thermochemical equilibrium. We demonstrate the code here with cloud-free models of giant exoplanetary atmospheres over a range of equilibrium temperatures, metallicities, C/O ratios and spanning non-irradiated and irradiated planets, with and without thermal inversions. We provide the community with theoretical emergent spectra and pressure-temperature profiles over this range, along with those for several known hot Jupiters. The code can generate self-consistent spectra at high resolution and has the potential to be integrated into general circulation and non-equilibrium chemistry models as it is optimized for efficiency and convergence. GENESIS paves the way for high-fidelity remote sensing of exoplanetary atmospheres at high resolution with current and upcoming observations.

An absolute photometric system at 10 and 20 microns

NASA Technical Reports Server (NTRS)

Rieke, G. H.; Lebofsky, M. J.; Low, F. J.

1985-01-01

Two new direct calibrations at 10 and 20 microns are presented in which terrestrial flux standards are referred to infrared standard stars. These measurements give both good agreement and higher accuracy when compared with previous direct calibrations. As a result, the absolute calibrations at 10 and 20 microns have now been determined with accuracies of 3 and 8 percent, respectively. A variety of absolute calibrations based on extrapolation of stellar spectra from the visible to 10 microns are reviewed. Current atmospheric models of A-type stars underestimate their fluxes by about 10 percent at 10 microns, whereas models of solar-type stars agree well with the direct calibrations. The calibration at 20 microns can probably be determined to about 5 percent by extrapolation from the more accurate result at 10 microns. The photometric system at 10 and 20 microns is updated to reflect the new absolute calibration, to base its zero point directly on the colors of A0 stars, and to improve the accuracy in the comparison of the standard stars.

The sequestration switch: removing industrial CO2 by direct ocean absorption.

PubMed

Ametistova, Lioudmila; Twidell, John; Briden, James

2002-04-22

This review paper considers direct injection of industrial CO2 emissions into the mid-water oceanic column below 500 m depth. Such a process is a potential candidate for switching atmospheric carbon emissions directly to long term sequestration, thereby relieving the intermediate atmospheric burden. Given sufficient research justification, the argument is that harmful impact in both the Atmosphere and the biologically rich upper marine layer could be reduced. The paper aims to estimate the role that active intervention, through direct ocean CO2 storage, could play and to outline further research and assessment for the strategy to be a viable option for climate change mitigation. The attractiveness of direct ocean injection lies in its bypassing of the Atmosphere and upper marine region, its relative permanence, its practicability using existing technologies and its quantification. The difficulties relate to the uncertainty of some fundamental scientific issues, such as plume dynamics, lowered pH of the exposed waters and associated ecological impact, the significant energy penalty associated with the necessary engineering plant and the uncertain costs. Moreover, there are considerable uncertainties regarding related international marine law. Development of the process would require acceptance of the evidence for climate change, strict requirements for large industrial consumers of fossil fuel to reduce CO2 emissions into the Atmosphere and scientific evidence for the overall beneficial impact of ocean sequestration.

Modeling Planetary Atmospheric Energy Deposition By Energetic Ions

NASA Astrophysics Data System (ADS)

Parkinson, Christopher; Bougher, Stephen; Gronoff, Guillaume; Barthelemy, Mathieu

2016-07-01

The structure, dynamics, chemistry, and evolution of planetary upper atmospheres are in large part determined by the available sources of energy. In addition to the solar EUV flux, the solar wind and solar energetic particle (SEP) events are also important sources. Both of these particle populations can significantly affect an atmosphere, causing atmospheric loss and driving chemical reactions. Attention has been paid to these sources from the standpoint of the radiation environment for humans and electronics, but little work has been done to evaluate their impact on planetary atmospheres. At unmagnetized planets or those with crustal field anomalies, in particular, the solar wind and SEPs of all energies have direct access to the atmosphere and so provide a more substantial energy source than at planets having protective global magnetic fields. Additionally, solar wind and energetic particle fluxes should be more significant for planets orbiting more active stars, such as is the case in the early history of the solar system for paleo-Venus and Mars. Therefore quantification of the atmospheric energy input from the solar wind and SEP events is an important component of our understanding of the processes that control their state and evolution. We have applied a full Lorentz motion particle transport model to study the effects of particle precipitation in the upper atmospheres of Mars and Venus. Such modeling has been previously done for Earth and Mars using a guiding center precipitation model. Currently, this code is only valid for particles with small gyroradii in strong uniform magnetic fields. There is a clear necessity for a Lorentz formulation, hence, a systematic study of the ionization, excitation, and energy deposition has been conducted, including a comparison of the influence relative to other energy sources (namely EUV photons). The result is a robust examination of the influence of energetic ion transport on the Venus and Mars upper atmosphere which will be discussed in this presentation.

Solar Effects of Low-Earth Orbit objects in ORDEM 3.0

NASA Technical Reports Server (NTRS)

Vavrin, A. B.; Anz-Meador, P.; Kelley, R. L.

2014-01-01

Variances in atmospheric density are directly related to the variances in solar flux intensity between 11- year solar cycles. The Orbital Debris Engineering Model (ORDEM 3.0) uses a solar flux table as input for calculating orbital lifetime of intact and debris objects in Low-Earth Orbit. Long term projections in solar flux activity developed by the NASA Orbital Debris Program Office (ODPO) extend the National Oceanic and Atmospheric Administration Space Environment Center (NOAA/SEC) daily historical flux values with a 5-year projection. For purposes of programmatic scheduling, the Q2 2009 solar flux table was chosen for ORDEM 3.0. Current solar flux activity shows that the current solar cycle has entered a period of lower solar flux intensity than previously forecasted in 2009. This results in a deviation of the true orbital debris environment propagation in ORDEM 3.0. In this paper, we present updated orbital debris populations in LEO using the latest solar flux values. We discuss the effects on recent breakup events such as the FY-1C anti-satellite test and the Iridium 33 / Cosmos 2251 accidental collision. Justifications for chosen solar flux tables are discussed.

Observing Human-induced Linkages between Urbanization and Earth's Climate System

NASA Technical Reports Server (NTRS)

Shepherd, J. Marshall; Jin, Menglin

2004-01-01

Urbanization is one of the extreme cases of land use change. Most of world s population has moved to urban areas. Although currently only 1.2% of the land is considered urban, the spatial coverage and density of cities are expected to rapidly increase in the near future. It is estimated that by the year 2025, 60% of the world s population will live in cities. Human activity in urban environments also alters atmospheric composition; impacts components of the water cycle; and modifies the carbon cycle and ecosystems. However, our understanding of urbanization on the total Earth-climate system is incomplete. Better understanding of how the Earth s atmosphere-ocean-land-biosphere components interact as a coupled system and the influence of the urban environment on this climate system is critical. The goal of the 2003 AGU Union session Human-induced climate variations on urban areas: From observations to modeling was to bring together scientists from interdisciplinary backgrounds to discuss the data, scientific approaches and recent results on observing and modeling components of the urban environment with the intent of sampling our current stand and discussing future direction on this topic. Herein, a summary and discussion of the observations component of the session are presented.

Microplasma-based flowing atmospheric-pressure afterglow (FAPA) source for ambient desorption-ionization mass spectrometry.

PubMed

Zeiri, Offer M; Storey, Andrew P; Ray, Steven J; Hieftje, Gary M

2017-02-01

A new direct-current microplasma-based flowing atmospheric pressure afterglow (FAPA) source was developed for use in ambient desorption-ionization mass spectrometry. The annular-shaped microplasma is formed in helium between two concentric stainless-steel capillaries that are separated by an alumina tube. Current-voltage characterization of the source shows that this version of the FAPA operates in the normal glow-discharge regime. A glass surface placed in the path of the helium afterglow reaches temperatures of up to approximately 400 °C; the temperature varies with distance from the source and helium flow rate through the source. Solid, liquid, and vapor samples were examined by means of a time-of-flight mass spectrometer. Results suggest that ionization occurs mainly through protonation, with only a small amount of fragmentation and adduct formation. The mass range of the source was shown to extend up to at least m/z 2722 for singly charged species. Limits of detection for several small organic molecules were in the sub-picomole range. Examination of competitive ionization revealed that signal suppression occurs only at high (mM) concentrations of competing substances. Copyright © 2016 Elsevier B.V. All rights reserved.

Triggers and Manifestations of Flare Energy Release in the Low Atmosphere

NASA Astrophysics Data System (ADS)

Kosovichev, A. G.; Sharykin, I. N.; Sadykov, V. M.; Vargas, S.; Zimovets, I. V.

2016-12-01

The main goal is to understand triggers and manifestations of the flare energy release in the lower layers of the solar atmosphere (the photosphere and chromosphere) using high-resolution optical observations and magnetic field measurements. As a case study we present results for an M-class flare. We analyze optical images, HMI Dopplergrams and vector magnetograms, and use Non-Linear Force-Free Field (NLFFF) extrapolation for reconstruction of the magnetic topology. The NLFFF modelling reveals interaction of oppositely directed magnetic flux-tubes in the Polarity Inversion Line (PIL). These two interacting magnetic flux tubes are observed as a compact sheared arcade along the PIL in the high-resolution broad-band continuum images from New Solar Telescope (NST). In the vicinity of the PIL, the NST H-alpha observations reveal formation of a thin three-ribbon structure corresponding to the small-scale photospheric magnetic arcade. Magnetic reconnection is triggered by two interacting magnetic flux tubes with forming current sheet extended along the PIL. Presented observational results evidence in favor of location of the primary energy release site in the dense chromosphere where plasma is partially ionized in the region of strong electric currents concentrated near the polarity inversion line.

Diagnostics of an AC driven atmospheric pressure non-thermal plasma jet and its use for radially directed jet array

NASA Astrophysics Data System (ADS)

Zhu, W.; Wang, R.

2017-08-01

An alternating current atmospheric pressure plasma jet is generated with noble gas or noble gas/oxygen admixture as working gas. A "core plasma filament" is observed at the center of the dielectric tube and extends to the plasma jet at higher peak-to-peak voltages. This type of plasma jet is believed to be of the same nature with the reported plasma bullet driven by pulsed DC power sources. Double current probes are used to assess the speed of the plasma bullet and show that the speed is around 104-105 m/s. The time dependence of the downstream bullet speed is attributed to the gas heating and in turn the increase of the reduced electric field E/N. Optical emission spectra show the dependence of helium and oxygen emission intensities on the concentration of oxygen additive in the carrier gas, with peak values found at 0.5% O2. Multiple radial jets are realized on dielectric tubes of different sizes. As a case study, one of these multi-jet devices is used to treat B. aureus on the inner surface of a plastic beaker and is shown to be more effective than a single jet.

The atmosphere of Pluto as observed by New Horizons

NASA Astrophysics Data System (ADS)

Gladstone, G. Randall; Stern, S. Alan; Ennico, Kimberly; Olkin, Catherine B.; Weaver, Harold A.; Young, Leslie A.; Summers, Michael E.; Strobel, Darrell F.; Hinson, David P.; Kammer, Joshua A.; Parker, Alex H.; Steffl, Andrew J.; Linscott, Ivan R.; Parker, Joel Wm.; Cheng, Andrew F.; Slater, David C.; Versteeg, Maarten H.; Greathouse, Thomas K.; Retherford, Kurt D.; Throop, Henry; Cunningham, Nathaniel J.; Woods, William W.; Singer, Kelsi N.; Tsang, Constantine C. C.; Schindhelm, Eric; Lisse, Carey M.; Wong, Michael L.; Yung, Yuk L.; Zhu, Xun; Curdt, Werner; Lavvas, Panayotis; Young, Eliot F.; Tyler, G. Leonard; Bagenal, F.; Grundy, W. M.; McKinnon, W. B.; Moore, J. M.; Spencer, J. R.; Andert, T.; Andrews, J.; Banks, M.; Bauer, B.; Bauman, J.; Barnouin, O. S.; Bedini, P.; Beisser, K.; Beyer, R. A.; Bhaskaran, S.; Binzel, R. P.; Birath, E.; Bird, M.; Bogan, D. J.; Bowman, A.; Bray, V. J.; Brozovic, M.; Bryan, C.; Buckley, M. R.; Buie, M. W.; Buratti, B. J.; Bushman, S. S.; Calloway, A.; Carcich, B.; Conard, S.; Conrad, C. A.; Cook, J. C.; Cruikshank, D. P.; Custodio, O. S.; Ore, C. M. Dalle; Deboy, C.; Dischner, Z. J. B.; Dumont, P.; Earle, A. M.; Elliott, H. A.; Ercol, J.; Ernst, C. M.; Finley, T.; Flanigan, S. H.; Fountain, G.; Freeze, M. J.; Green, J. L.; Guo, Y.; Hahn, M.; Hamilton, D. P.; Hamilton, S. A.; Hanley, J.; Harch, A.; Hart, H. M.; Hersman, C. B.; Hill, A.; Hill, M. E.; Holdridge, M. E.; Horanyi, M.; Howard, A. D.; Howett, C. J. A.; Jackman, C.; Jacobson, R. A.; Jennings, D. E.; Kang, H. K.; Kaufmann, D. E.; Kollmann, P.; Krimigis, S. M.; Kusnierkiewicz, D.; Lauer, T. R.; Lee, J. E.; Lindstrom, K. L.; Lunsford, A. W.; Mallder, V. A.; Martin, N.; McComas, D. J.; McNutt, R. L.; Mehoke, D.; Mehoke, T.; Melin, E. D.; Mutchler, M.; Nelson, D.; Nimmo, F.; Nunez, J. I.; Ocampo, A.; Owen, W. M.; Paetzold, M.; Page, B.; Pelletier, F.; Peterson, J.; Pinkine, N.; Piquette, M.; Porter, S. B.; Protopapa, S.; Redfern, J.; Reitsema, H. J.; Reuter, D. C.; Roberts, J. H.; Robbins, S. J.; Rogers, G.; Rose, D.; Runyon, K.; Ryschkewitsch, M. G.; Schenk, P.; Sepan, B.; Showalter, M. R.; Soluri, M.; Stanbridge, D.; Stryk, T.; Szalay, J. R.; Tapley, M.; Taylor, A.; Taylor, H.; Umurhan, O. M.; Verbiscer, A. J.; Versteeg, M. H.; Vincent, M.; Webbert, R.; Weidner, S.; Weigle, G. E.; White, O. L.; Whittenburg, K.; Williams, B. G.; Williams, K.; Williams, S.; Zangari, A. M.; Zirnstein, E.

2016-03-01

Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. Whereas the lower atmosphere (at altitudes of less than 200 kilometers) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen (N2) dominates the atmosphere (at altitudes of less than 1800 kilometers or so), whereas methane (CH4), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6) are abundant minor species and likely feed the production of an extensive haze that encompasses Pluto. The cold upper atmosphere shuts off the anticipated enhanced-Jeans, hydrodynamic-like escape of Pluto's atmosphere to space. It is unclear whether the current state of Pluto's atmosphere is representative of its average state - over seasonal or geologic time scales.

The atmosphere of Pluto as observed by New Horizons.

PubMed

Gladstone, G Randall; Stern, S Alan; Ennico, Kimberly; Olkin, Catherine B; Weaver, Harold A; Young, Leslie A; Summers, Michael E; Strobel, Darrell F; Hinson, David P; Kammer, Joshua A; Parker, Alex H; Steffl, Andrew J; Linscott, Ivan R; Parker, Joel Wm; Cheng, Andrew F; Slater, David C; Versteeg, Maarten H; Greathouse, Thomas K; Retherford, Kurt D; Throop, Henry; Cunningham, Nathaniel J; Woods, William W; Singer, Kelsi N; Tsang, Constantine C C; Schindhelm, Eric; Lisse, Carey M; Wong, Michael L; Yung, Yuk L; Zhu, Xun; Curdt, Werner; Lavvas, Panayotis; Young, Eliot F; Tyler, G Leonard

2016-03-18

Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. Whereas the lower atmosphere (at altitudes of less than 200 kilometers) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen (N2) dominates the atmosphere (at altitudes of less than 1800 kilometers or so), whereas methane (CH4), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6) are abundant minor species and likely feed the production of an extensive haze that encompasses Pluto. The cold upper atmosphere shuts off the anticipated enhanced-Jeans, hydrodynamic-like escape of Pluto's atmosphere to space. It is unclear whether the current state of Pluto's atmosphere is representative of its average state--over seasonal or geologic time scales. Copyright © 2016, American Association for the Advancement of Science.

Determining Atmospheric Pressure Using a Water Barometer

ERIC Educational Resources Information Center

Lohrengel, C. Frederick, II; Larson, Paul R.

2012-01-01

The atmosphere is an envelope of compressible gases that surrounds Earth. Because of its compressibility and nonuniform heating by the Sun, it is in constant motion. The atmosphere exerts pressure on Earth's surface, but that pressure is in constant flux. This experiment allows students to directly measure atmospheric pressure by measuring the…

Spectroscopic database

NASA Technical Reports Server (NTRS)

Husson, N.; Barbe, A.; Brown, L. R.; Carli, B.; Goldman, A.; Pickett, H. M.; Roche, A. E.; Rothman, L. S.; Smith, M. A. H.

1985-01-01

Several aspects of quantitative atmospheric spectroscopy are considered, using a classification of the molecules according to the gas amounts in the stratosphere and upper troposphere, and reviews of quantitative atmospheric high-resolution spectroscopic measurements and field measurements systems are given. Laboratory spectroscopy and spectral analysis and prediction are presented with a summary of current laboratory spectroscopy capabilities. Spectroscopic data requirements for accurate derivation of atmospheric composition are discussed, where examples are given for space-based remote sensing experiments of the atmosphere: the ATMOS (Atmospheric Trace Molecule) and UARS (Upper Atmosphere Research Satellite) experiment. A review of the basic parameters involved in the data compilations; a summary of information on line parameter compilations already in existence; and a summary of current laboratory spectroscopy studies are used to assess the data base.

The Influence of Anthropogenic Sources on Fluxes of Secondary Organic Aerosol Precursors From a Deciduous Forest in the Southeastern United States

NASA Astrophysics Data System (ADS)

Saylor, R. D.; Stein, A. F.

2012-12-01

The dynamic, bi-directional exchange of trace chemical species between forests and the atmosphere has important impacts on both the forest ecosystem and atmospheric composition, with potentially profound consequences on air quality, climate and global ecosystem functioning. Forests are a dominant source of biogenic volatile organic compound (BVOC) emissions into the earth's atmosphere and thus play an important role in the formation of secondary organic aerosol (SOA). To arrive at a better scientific understanding of the complex chemical and physical processes of forest-atmosphere exchange and provide a platform for robust analysis of field measurements of these processes, a process-level, multiphase model of the atmospheric chemistry and physics of forest canopies is being developed. This model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS) is being used to investigate various aspects of forest-atmosphere exchange and chemistry including gas, aqueous and aerosol phases. ACCESS currently includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer, detailed chemical reactions, mixing with the background atmosphere and bi-directional exchange between the atmosphere and the canopy and the forest floor. The Walker Branch Watershed (WBW) is a dedicated ecosystem research area on the U. S. Department of Energy's Oak Ridge Reservation in eastern Tennessee. The 97.5 ha watershed has been the site of long-term ecosystem and atmospheric research activities since the mid-1960's. A flux tower located within the watershed (35°57'30"N, 84°17'15"W; 365 m above mean sea level) and 10 km southwest of Oak Ridge, Tennessee, has served as a focal point for previous atmospheric turbulence and chemical flux measurements and the canopy morphology of the forest surrounding the flux tower has been extensively documented. The forest is broadleaf deciduous consisting of chestnut oak (Quercus prinus), tulip poplar (Liriodendron tulipifera), white oak (Quercus alba), red oak (Quercus rubra), red maple (Acer rubrum), and various hickory species (Carya sp.) in order of decreasing biomass density. At the time of isoprene flux measurements made at the tower in 1999, the stand was approximately 50 years old, the overstory canopy height was 24 m, and the whole canopy leaf area index was 4.9 m2 leaf/m2 ground area. In this presentation, the model formulation is described and results from the application of ACCESS to the WBW forest are presented and compared to measurements made at the site to investigate the influence of background anthropogenic sources on above canopy fluxes of SOA precursors in an isoprene emission dominated landscape in the unique atmospheric chemical environment of the southeastern United States. In particular, levels of background NOx concentrations are found to significantly influence both the magnitude and chemical composition of fluxes of SOA precursors from the canopy.

Solar-terrestrial coupling through atmospheric electricity

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

Current status of quantitative rotational spectroscopy for atmospheric research

NASA Technical Reports Server (NTRS)

Drouin, Brian J.; Wlodarczak, Georges; Colmont, Jean-Marcel; Rohart, Francois

2004-01-01

Remote sensing of rotational transitions in the Earth's atmosphere has become an important method for the retrieval of geophysical temperatures, pressures and chemical composition profiles that requires accurate spectral information. This paper highlights the current status of rotational data that are useful for atmospheric measurements, with a discussion of the types the rotational lineshape measurements that are not generally available in either online repository.

Lidar instruments for ESA Earth observation missions

NASA Astrophysics Data System (ADS)

Hélière, Arnaud; Armandillo, Errico; Durand, Yannig; Culoma, Alain; Meynart, Roland

2017-11-01

The idea of deploying a lidar system on an Earthorbiting satellite stems from the need for continuously providing profiles of our atmospheric structure with high accuracy and resolution and global coverage. Interest in this information for climatology, meteorology and the atmospheric sciences in general is huge. Areas of application range from the determination of global warming and greenhouse effects, to monitoring the transport and accumulation of pollutants in the different atmospheric regions (such as the recent fires in Southeast Asia), to the assessment of the largely unknown microphysical properties and the structural dynamics of the atmosphere itself. Spaceborne lidar systems have been the subject of extensive investigations by the European Space Agency since mid 1970's, resulting in mission and instrument concepts, such as ATLID, the cloud backscatter lidar payload of the EarthCARE mission, ALADIN, the Doppler wind lidar of the Atmospheric Dynamics Mission (ADM) and more recently a water vapour Differential Absorption Lidar considered for the WALES mission. These studies have shown the basic scientific and technical feasibility of spaceborne lidars, but they have also demonstrated their complexity from the instrument viewpoint. As a result, the Agency undertook technology development in order to strengthen the instrument maturity. This is the case for ATLID, which benefited from a decade of technology development and supporting studies and is now studied in the frame of the EarthCARE mission. ALADIN, a Direct Detection Doppler Wind Lidar operating in the Ultra -Violet, will be the 1st European lidar to fly in 2007 as payload of the Earth Explorer Core Mission ADM. WALES currently studied at the level of a phase A, is based upon a lidar operating at 4 wavelengths in near infrared and aims to profile the water vapour in the lower part of the atmosphere with high accuracy and low bias. Lastly, the European Space Agency is extending the lidar instrument field for Earth Observation by initiating feasibility studies of a spaceborne concept to monitor atmospheric CO2 and other greenhouse gases. The purpose of this paper is to present the instruments concept and related technology/instrument developments that are currently running at the European Space Agency. The paper will also outline the development planning proposed for future lidar systems.

Ground-based instrumentation for measurements of atmospheric conduction current and electric field at the South Pole

NASA Technical Reports Server (NTRS)

Byrne, G. J.; Benbrook, J. R.; Bering, E. A.; Few, A. A.; Morris, G. A.; Trabucco, W. J.; Paschal, E. W.

1993-01-01

Attention is given to instruments constructed to measure the atmospheric conduction current and the atmospheric electric field - two fundamental parameters of the global-electric circuit. The instruments were deployed at the Amundsen-Scott South Pole Station in January 1991 and are designed to operate continuously for up to one year without operator intervention. The atmospheric current flows into one hemisphere, through the electronics where it is measured, and out the other hemisphere. The electric field is measured by a field mill of the rotating dipole type. Sample data from the first days of operation at the South Pole indicate variations in the global circuit over time scales from minutes to hours to days.

Atmospheric sampling glow discharge ionization source

DOEpatents

McLuckey, Scott A.; Glish, Gary L.

1989-01-01

An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles

PubMed Central

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-01-01

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO3 solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system. PMID:28773393

Complex monitoring and alert network for electromagnetic, infrasound, acoustic seismotectonic phenomena

NASA Astrophysics Data System (ADS)

-Emilian Toader, Victorin; Moldovan, Iren-Adelina; Constantin, Ionescu

2014-05-01

The Romanian seismicity recorded in 2013 three important events: the largest seismic "silence", the shortest sequence of two earthquakes greater than 4.8R in less than 14 days after the "Romanian National Institute for Earth Physics" (NIEP) developed a digital network, and a very high crustal activity in Galati area. We analyze the variations of the telluric currents and local magnetic field, variations of the atmospheric electrostatic field, infrasound, temperature, humidity, wind speed and direction, atmospheric pressure, variations in the earth crust with inclinometers and animal behavior. The general effect is the first high seismic energy discontinuity that could be a precursor factor. Since 1977 Romania did not register any important earthquake that would generate a sense of fear among the population. In parallel with the seismic network NIEP developed a magneto-telluric, bioseismic, VLF and acoustic network. A large frequency spectrum is covered for mechanical vibration, magnetic and electric field with ground and air sensors. Special software was designed for acquisition, analysis and real time alert using internet direct connection, web page, email and SMS. Many examples show the sensitivity of telluric current, infrasound, acoustic records (from air-ground), and the effect of tectonic stress on the magnetic field or ground deformation. The next update of the multidisciplinary monitoring network will include measurement of ionization, radon emission, sky color, solar radiation and extension of infrasound and VL/LF equipment. NOAA Space Weather satellites transmit solar activity magnetic field data, X ray flux, electron, and proton flux information useful for complex analysis.

Induced charging of shuttle orbiter by high electron-beam currents

NASA Technical Reports Server (NTRS)

Liemohn, H. B.

1977-01-01

Emission of high-current electron beams that was proposed for some Spacelab payloads required substantial return currents to the orbiter skin in order to neutralize the beam charge. Since the outer skin of the vehicle was covered with approximately 1200 sq m of thermal insulation which has the dielectric quality of air and an electrical conductivity that was estimated by NASA at 10 to the -9 power to 10 to the -10 power mhos/m, considerable transient charging and local potential differences were anticipated across the insulation. The theory for induced charging of spacecraft due to operation of electron guns was only developed for spherical metal vehicles and constant emission currents, which were not directly applicable to the orbiter situation. Field-aligned collection of electron return current from the ambient ionosphere at orbiter altitudes provides up to approximately 150 mA on the conducting surfaces and approximately 2.4 A on the dielectric thermal insulation. Local ionization of the neutral atmosphere by energetic electron bombardment or electrical breakdown may provide somewhat more return current.

Ground and CHAMP observations of field-aligned current circuits generated by lower atmospheric disturbances and expectations to the SWARM to clarify their three dimensional structure

NASA Astrophysics Data System (ADS)

Iyemori, Toshihiko; Nakanishi, Kunihito; Aoyama, Tadashi; Lühr, Hermann

2014-05-01

Acoustic gravity waves propagated to the ionosphere cause dynamo currents in the ionosphere. They divert along geomagnetic field lines of force to another hemisphere accompanying electric field and then flow in the ionosphere of another hemisphere by the electric field forming closed current circuits. The oscillating current circuits with the period of acoustic waves generate magnetic variations on the ground, and they are observed as long period geomagnetic pulsations. This effect has been detected during big earthquakes, strong typhoons, tornados etc. On a low-altitude satellite orbit, the spatial distribution (i.e., structure) of the current circuits along the satellite orbit should be detected as temporal magnetic oscillations, and the effect is confirmed by a CHAMP data analysis. On the spatial structure, in particular, in the longitudinal direction, it has been difficult to examine by a single satellite or from ground magnetic observations. The SWARM satellites will provide an unique opportunity to clarify the three dimensional structure of the field-aligned current circuits.

The Greenhouse Effect - Re-examination of the Impact of an Increase in Carbon Dioxide in the Atmosphere

NASA Astrophysics Data System (ADS)

Underwood, T. G.

2017-12-01

Examination of the radiation budget at the surface of the Earth shows that there are three factors affecting the surface temperature; the amount of solar radiation absorbed by the atmosphere and by the surface respectively, and the amount of leakage of infrared radiation emitted from the surface directly into space. If there were no leakage, the upwelling infrared radiation from the Earth's surface would be equal to the incoming solar radiation absorbed by the atmosphere plus twice the solar radiation absorbed by the surface. This results from the summation of a sequence of equal upward and downward re-emissions of infrared radiation absorbed by the atmosphere following the initial absorption of solar radiation. At current levels of solar absorption, this would result in total upwelling radiation of approximately 398.6 W/m2, or a maximum surface temperature of 16.4°C. Allowing for leakage of infrared radiation through the atmospheric window, the resulting emission from the Earth's surface is reduced to around 396 W/m2, corresponding to the current average global surface temperature of around 15.9°C. Absorption of solar and infrared radiation by greenhouse gases is determined by the absorption bands for the respective gases and their concentrations. Absorption of incoming solar radiation is largely by water vapor and ozone, and an increase in absorption would reduce not increase the surface temperature. Moreover, it is probable that all emitted infrared radiation that can be absorbed by greenhouse gases, primarily water vapor, with a small contribution from carbon dioxide and ozone, is already fully absorbed, and the leakage of around 5.5 % corresponds to the part of the infrared red spectrum that is not absorbed by greenhouse gases. The carbon dioxide absorption bands, which represent a very small percentage of the infrared spectrum, are most likely fully saturated. In these circumstances, increased concentrations of greenhouse gases, and carbon dioxide in particular, will have no effect on the emitted radiation. The surface temperature is probably at the thermodynamic limit for the current luminosity of the sun. Satellite based measurements since 1979 suggest that any global warming over the past 150 years may be due to an increase in total solar irradiance, which we are still a decade or two from being able to confirm.

Modeling the Performance of Direct-Detection Doppler Lidar Systems in Real Atmospheres

NASA Technical Reports Server (NTRS)

McGill, Matthew J.; Hart, William D.; McKay, Jack A.; Spinhirne, James D.

1999-01-01

Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems has assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar systems: the double-edge and the multi-channel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only about 10-20% compared to nighttime performance, provided a proper solar filter is included in the instrument design.

Command generator tracker based direct model reference adaptive tracking guidance for Mars atmospheric entry

NASA Astrophysics Data System (ADS)

Li, Shuang; Peng, Yuming

2012-01-01

In order to accurately deliver an entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance is essential. This paper addresses the issue of Mars atmospheric entry guidance using the command generator tracker (CGT) based direct model reference adaptive control to reduce the adverse effect of the bounded uncertainties on atmospheric density and aerodynamic coefficients. Firstly, the nominal drag acceleration profile meeting a variety of constraints is planned off-line in the longitudinal plane as the reference model to track. Then, the CGT based direct model reference adaptive controller and the feed-forward compensator are designed to robustly track the aforementioned reference drag acceleration profile and to effectively reduce the downrange error. Afterwards, the heading alignment logic is adopted in the lateral plane to reduce the crossrange error. Finally, the validity of the guidance algorithm proposed in this paper is confirmed by Monte Carlo simulation analysis.

Evidence of water vapor in excess of saturation in the atmosphere of Mars.

PubMed

Maltagliati, L; Montmessin, F; Fedorova, A; Korablev, O; Forget, F; Bertaux, J-L

2011-09-30

The vertical distribution of water vapor is key to the study of Mars' hydrological cycle. To date, it has been explored mainly through global climate models because of a lack of direct measurements. However, these models assume the absence of supersaturation in the atmosphere of Mars. Here, we report observations made using the SPICAM (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars) instrument onboard Mars Express that provide evidence of the frequent presence of water vapor in excess of saturation, by an amount far surpassing that encountered in Earth's atmosphere. This result contradicts the widespread assumption that atmospheric water on Mars cannot exist in a supersaturated state, directly affecting our long-term representation of water transport, accumulation, escape, and chemistry on a global scale.

Giant Impacts and Earth's Primordial Atmosphere

NASA Astrophysics Data System (ADS)

Agnor, C.; Asphaug, E.

2002-09-01

Estimates of Earth's accretion timescale based on modeling (e.g. Wetherill 1990) and isotopic evidence (Halliday and Porcelli 2000) indicate that the Earth formed in 25-100 Myr. At least a portion of this accretion took place in the presence of the solar nebula. While the problem of nailing down the nebular lifetime remains open, observations of dust disks surrounding young stars and meteoritic evidence suggest that the gas disk existed and was involved in making planetary material for 10 Myr (e.g. Podosek & Cassen 1994, Trilling et al. 2001). The persistence of a remnant of the nebula's original gas disk during terrestrial planet accretion is certainly plausible. The existence of this remnant nebula has dynamical (Agnor & Ward 2002, Kominami & Ida 2002) and geochemical (Porcelli & Pepin 2000) implications for terrestrial planet formation. Nakazawa et al. (1985) explored the structure of Earth's primordial atmosphere as the solar nebula was dissipating. They found that even for low surface densities of nebular gas ( σ gas ~ 1 g cm-2 or ~0.1% of the minimum mass nebula), Earth can capture a significant primordial atmosphere directly from the nebula (i.e. total mass up to a few lunar masses, or ~ 105 times the current atmosphere). Such a massive primordial atmosphere may have played a dynamical role in the formation of the Moon (e.g. models of lunar capture have employed aerodynamic drag in Earth's atmosphere as the primary mechanism for reducing the Moon's orbital energy, Nakazawa et al. 1983). Conversely, the formation of the Moon may have played a role in removing Earth's primordial atmosphere. Giant impacts have been suggested as one possible mechanism that could accomplish global atmospheric removal (Ahrens 1993). We are using smooth particle hydrodynamics (SPH) to model the removal of Earth's primordial atmosphere via giant impact. We employ initial conditions similar to recent works on lunar formation (e.g. Canup & Asphaug 2001) but also include ideal gas atmospheres on the colliding bodies. In addition to exploring the hydrodynamics and efficiency of atmospheric removal via giant impact, we also examine the influence of Earth's protoatmosphere on the ejecta velocity distribution and formation of the proto-lunar disk.

VICI (Venus In Situ Composition Investigations): The Next Step in Understanding Venus Climate Evolution

NASA Astrophysics Data System (ADS)

Glaze, L. S.; Garvin, J. B.

2017-12-01

Venus provides a natural laboratory to explore an example of terrestrial planet evolution that may be cosmically ubiquitous. By better understanding the composition of the Venus atmosphere and surface, we can better constrain the efficiency of the Venusian greenhouse. VICI is a proposed NASA New Frontiers mission that delivers two landers to Venus on two separate Venus fly-bys. Following six orbital remote sensing missions to Venus (since 1978), VICI would be the first mission to land on the Venus surface since 1985, and the first U.S. mission to enter the Venus atmosphere in 49 years. The four major VICI science objectives are: Atmospheric origin and evolution: Understand the origin of the Venus atmosphere, how it has evolved, including how recently Venus lost its oceans, and how and why it is different from the atmospheres of Earth and Mars, through in situ measurements of key noble gases, nitrogen, and hydrogen. Atmospheric composition and structure: Reveal the unknown chemical processes and structure in Venus' deepest atmosphere that dominate the current climate through two comprehensive, in situ vertical profiles. Surface properties and geologic evolution: For the first time ever, explore the tessera from the surface, specifically to test hypotheses of ancient content-building cycles, erosion, and links to past climates using multi-point mineralogy, elemental chemistry, imaging and topography. Surface-atmosphere interactions: Characterize Venus' surface weathering environment and provide insight into the sulfur cycle at the surface-atmosphere interface by integrating rich atmospheric composition and structure datasets with imaging, surface mineralogy, and elemental rock composition. VICI is designed to study Venus' climate history through detailed atmospheric composition measurements not possible on earlier missions. In addition, VICI images the tessera surface during descent enabling detailed topography to be generated. Finally, VICI makes multiple elemental chemistry measurements, including depth profiles through the weathering rind and subsurface, and the first ever direct mineralogy measurements on the Venus surface. VICI's payloads build on the success of the Mars Science Laboratory (MSL) by carrying the same instrumentation that has delivered high-impact science results on Mars.

Direct synthesis of few-layer graphene supported platinum nanocatalyst for methanol oxidation

NASA Astrophysics Data System (ADS)

Tan, Hong; Ma, Xiaohui; Sheng, Leimei; An, Kang; Yu, Liming; Zhao, Hongbin; Xu, Jiaqiang; Ren, Wei; Zhao, Xinluo

2014-11-01

High-crystalline few-layer graphene supported Pt nanoparticles have been synthesized by arc discharge evaporation of carbon electrodes containing Pt element. A high-temperature treatment under hydrogen atmosphere has been carried out to obtain a new type of Pt/graphene catalyst for methanol oxidation in direct methanol fuel cell. The morphology and structure characterizations of as-grown few-layer graphene supported Pt nanoparticles and Pt/graphene catalysts have been studied by Raman spectroscopy, scanning electron microscopy with energy-dispersive spectroscopy, and high-resolution transmission electron microscopy. Cyclic voltammograms and chronoamperometric curves show that our present Pt/graphene catalysts have larger current density for methanol oxidation, higher tolerance to carbon monoxide poisoning, and better stability during the operating procedure, compared to commercial Pt/C catalysts.

Hypersonic Flight Mechanics. [for atmospheric entry trajectories

NASA Technical Reports Server (NTRS)

Busemann, A.; Vinh, N. X.; Culp, R. D.

1976-01-01

The effects of aerodynamic forces on trajectories at orbital speeds are discussed in terms of atmospheric models. The assumptions for the model are spherical symmetry, nonrotating, and an exponential atmosphere. The equations of flight, and the performance in extra-atmospheric flight are discussed along with the return to the atmosphere, and the entry. Solutions of the exact equations using directly matched asymptotic expansions are presented.

Positive direct current corona discharges in single wire-duct electrostatic precipitators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yehia, Ashraf, E-mail: yehia30161@yahoo.com; Department of Physics, Faculty of Science, Assiut University, Assiut 71516, Arab Republic of Egypt; Abdel-Fattah, E.

This paper is aimed to study the characteristics of the positive dc corona discharges in single wire-duct electrostatic precipitators. Therefore, the corona discharges were formed inside dry air fed single wire-duct reactor under positive dc voltage at the normal atmospheric conditions. The corona current-voltage characteristics curves have been measured in parallel with the ozone concentration generated inside the reactor under different discharge conditions. The corona current-voltage characteristics curves have agreed with a semi empirical equation derived from the previous studies. The experimental results of the ozone concentration generated inside the reactor were formulated in the form of an empirical equationmore » included the different parameters that were studied experimentally. The obtained equations are valid to expect both the current-voltage characteristics curves and the corresponding ozone concentration that generates with the positive dc corona discharges inside single wire-duct electrostatic precipitators under any operating conditions in the same range of the present study.« less

Origin and evolution of planetary atmospheres

NASA Technical Reports Server (NTRS)

Pollack, J. B.; Yung, Y. L.

1980-01-01

The current understanding of the origin and evolution of the atmospheres of solar system objects is reviewed. Physical processes that control this evolution are described in an attempt to develop a set of general principles that can help guide studies of specific objects. Particular emphasis is placed on the planetary and satellite atmospheres of the inner solar system objects; current hypotheses on the origin and evolution of these objects are critically considered.

Atmosphere: Change is in the Air

Science.gov Websites

Forces of Change Main Arctic Atmosphere El Niño Current Conditions DIG IT! Share | Smithsonian Atmosphere: Change is in the Air Explore Earth's changing atmosphere. Discover how our ever-changing everything that breathes. This web site incorporates images and information from the Atmosphere: Change is in

ROLE OF LEAF SURFACE WATER IN THE BI-DIRECTIONAL AMMONIA EXCHANGE BETWEEN THE ATMOSPHERE AND TERRESTRIAL BIOSPHERE

EPA Science Inventory

A field experiment was conducted to study the ammonia exchange between plants and the atmosphere in a soybean field in Duplin County, North Carolina during the summer of 2002. Measurements indicate that the net canopy-scale ammonia exchange is bi-directional and has a significant...

Atmospheric circulation of brown dwarfs and directly imaged extrasolar giant planets with active clouds

NASA Astrophysics Data System (ADS)

Tan, Xianyu; Showman, Adam

2016-10-01

Observational evidence have suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys for brown dwarfs showed that near-IR brightness variability is common for L and T dwarfs. Directly imaged EGPs share similar observations, and can be viewed as low-gravity versions of BDs. Clouds are believed to play the major role in shaping the thermal structure, dynamics and near-IR flux of these atmospheres. So far, only a few studies have been devoted to atmospheric circulation and the implications for observations of BDs and directly EGPs, and yet no global model includes a self-consistent active cloud formation. Here we present preliminary results from the first global circulation model applied to BDs and directly imaged EGPs that can properly treat absorption and scattering of radiation by cloud particles. Our results suggest that horizontal temperature differences on isobars can reach up to a few hundred Kelvins, with typical horizontal length scale of the temperature and cloud patterns much smaller than the radius of the object. The combination of temperature anomaly and cloud pattern can result in moderate disk-integrated near-IR flux variability. Wind speeds can reach several hundred meters per second in cloud forming layers. Unlike Jupiter and Saturn, we do not observe stable zonal jet/banded patterns in our simulations. Instead, our simulated atmospheres are typically turbulent and dominated by transient vortices. The circulation is sensitive to the parameterized cloud microphysics. Under some parameter combinations, global-scale atmospheric waves can be triggered and maintained. These waves induce global-scale temperature anomalies and cloud patterns, causing large (up to several percent) disk-integrated near-IR flux variability. Our results demonstrate that the commonly observed near-IR brightness variability for BDs and directly imaged EGPs can be explained by the typical cloud-induced turbulent circulation, and in particular, the large flux variability for some objects can be attributed to the global-scale patterns of temperature anomaly and cloud formation caused by atmospheric waves.

Reconstruction of 137Cs activity in the ocean following the Fukushima Daiichi Nuclear Power Plant Accident

NASA Astrophysics Data System (ADS)

Tsumune, Daisuke; Aoyama, Michio; Tsubono, Takaki; Tateda, Yutaka; Misumi, Kazuhiro; Hayami, Hiroshi; Toyoda, Yasuhiro; Maeda, Yoshiaki; Yoshida, Yoshikatsu; Uematsu, Mitsuo

2014-05-01

A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant following the earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways, direct release from the accident site and atmospheric deposition. We reconstructed spatiotemporal variability of 137Cs activity in the ocean by the comparison model simulations and observed data. We employed a regional scale and the North Pacific scale oceanic dispersion models, an atmospheric transport model, a sediment transport model, a dynamic biological compartment model for marine biota and river runoff model to investigate the oceanic contamination. Direct releases of 137Cs were estimated for more than 2 years after the accident by comparing simulated results and observed activities very close to the site. The estimated total amounts of directly released 137Cs was 3.6±0.7 PBq. Directly release rate of 137Cs decreased exponentially with time by the end of December 2012 and then, was almost constant. The daily release rate of 137Cs was estimated to be 3.0 x 1010 Bq day-1 by the end of September 2013. The activity of directly released 137Cs was detectable only in the coastal zone after December 2012. Simulated 137Cs activities attributable to direct release were in good agreement with observed activities, a result that implies the estimated direct release rate was reasonable, while simulated 137Cs activities attributable to atmospheric deposition were low compared to measured activities. The rate of atmospheric deposition onto the ocean was underestimated because of a lack of measurements of dose rate and air activity of 137Cs over the ocean when atmospheric deposition rates were being estimated. Observed 137Cs activities attributable to atmospheric deposition in the ocean helped to improve the accuracy of simulated atmospheric deposition rates. Although there is no observed data of 137Cs activity in the ocean from 11 to 21 March 2011, observed data of marine biota should reflect the history of 137Cs activity in this early period. The comparisons between simulated 137Cs activity of marine biota by a dynamic biological compartment and observed data also suggest that simulated 137Cs activity attributable to atmospheric deposition was underestimated in this early period. In addition, river runoff model simulations suggest that the river flux of 137Cs to the ocean was effective to the 137Cs activity in the ocean in this early period. The sediment transport model simulations suggests that the inventory of 137Cs in sediment was less than 10

The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic.

PubMed

Galbán-Malagón, Cristóbal; Berrojalbiz, Naiara; Ojeda, María-José; Dachs, Jordi

2012-05-29

Semivolatile persistent organic pollutants have the potential to reach remote environments, such as the Arctic Ocean, through atmospheric transport and deposition. Here we show that this transport of polychlorinated biphenyls to the Arctic Ocean is strongly retarded by the oceanic biological pump. A simultaneous sampling of atmospheric, seawater and plankton samples was performed in July 2007 in the Greenland Current and Atlantic sector of the Arctic Ocean. The atmospheric concentrations declined during atmospheric transport over the Greenland Current with estimated half-lives of 1-4 days. These short half-lives can be explained by the high air-to-water net diffusive flux, which is similar in magnitude to the estimated settling fluxes in the water column. Therefore, the decrease of atmospheric concentrations is due to sequestration of atmospheric polychlorinated biphenyls by enhanced air-water diffusive fluxes driven by phytoplankton uptake and organic carbon settling fluxes (biological pump).

Analysis of entry accelerometer data: A case study of Mars Pathfinder

NASA Astrophysics Data System (ADS)

Withers, Paul; Towner, M. C.; Hathi, B.; Zarnecki, J. C.

2003-08-01

Accelerometers are regularly flown on atmosphere-entering spacecraft. Using their measurements, the spacecraft trajectory and the vertical structure of density, pressure, and temperature in the atmosphere through which it descends can be calculated. We review the general procedures for trajectory and atmospheric structure reconstruction and outline them here in detail. We discuss which physical properties are important in atmospheric entry, instead of working exclusively with the dimensionless numbers of fluid dynamics. Integration of the equations of motion governing the spacecraft trajectory is carried out in a novel and general formulation. This does not require an axisymmetric gravitational field or many of the other assumptions that are present in the literature. We discuss four techniques - head-on, drag-only, acceleration ratios, and gyroscopes - for constraining spacecraft attitude, which is the critical issue in the trajectory reconstruction. The head-on technique uses an approximate magnitude and direction for the aerodynamic acceleration, whereas the drag-only technique uses the correct magnitude and an approximate direction. The acceleration ratios technique uses the correct magnitude and an indirect way of finding the correct direction and the gyroscopes technique uses the correct magnitude and a direct way of finding the correct direction. The head-on and drag-only techniques are easy to implement and require little additional information. The acceleration ratios technique requires extensive and expensive aerodynamic modelling. The gyroscopes technique requires additional onboard instrumentation. The effects of errors are briefly addressed. Our implementations of these trajectory reconstruction procedures have been verified on the Mars Pathfinder dataset. We find inconsistencies within the published work of the Pathfinder science team, and in the PDS archive itself, relating to the entry state of the spacecraft. Our atmospheric structure reconstruction, which uses only a simple aerodynamic database, is consistent with the PDS archive to about 4%. Surprisingly accurate profiles of atmospheric temperatures can be derived with no information about the spacecraft aerodynamics. Using no aerodynamic information whatsoever about Pathfinder, our profile of atmospheric temperature is still consistent with the PDS archive to about 8%. As a service to the community, we have placed simplified versions of our trajectory and atmospheric structure computer programmes online for public use.

Observations of a cycle of intense coastal upwelling and downwelling at the research site of the Shirshov Institute of Oceanology in the Black Sea

NASA Astrophysics Data System (ADS)

Zatsepin, A. G.; Silvestrova, K. P.; Kuklev, S. B.; Piotoukh, V. B.; Podymov, O. I.

2016-03-01

The paper presents the results of joint analysis of the response of vertical temperature and current velocity profile distributions in the coastal zone of the Gelendzhik region of the Black Sea to strong wind forcing in the third ten-day period of September 2013. This forcing was caused by the propagation of an atmospheric cyclone, which first initiated coastal upwelling that was later replaced by downwelling. We formulate a criterion for the development of full coastal upwelling and demonstrate its efficiency. We assume that frequent events of incomplete coastal upwelling and downwelling are associated with changes in the water dynamics (variations in the intensity and direction of the alongshore current) generally not related to local wind forcing.

Cosmic Carbon Chemistry: From the Interstellar Medium to the Early Earth

PubMed Central

Ehrenfreund, Pascale; Cami, Jan

2010-01-01

Astronomical observations have shown that carbonaceous compounds in the gas and solid state, refractory and icy are ubiquitous in our and distant galaxies. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly large number of molecules that are used in contemporary biochemistry on Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites, and interplanetary dust particles. In this article we review the current knowledge of abundant organic material in different space environments and investigate the connection between presolar and solar system material, based on observations of interstellar dust and gas, cometary volatiles, simulation experiments, and the analysis of extraterrestrial matter. Current challenges in astrochemistry are discussed and future research directions are proposed. PMID:20554702

Wave and Current Measurements From the Coastal Storms Program (CSP) Buoy 41012 off St. Augustine, FL

NASA Astrophysics Data System (ADS)

Crout, R. L.

2008-05-01

The Coastal Storms Program (CSP) is a NOAA program that involves several different branches within NOAA. Components of the National Ocean Service, the National Weather Service, the National Marine Fisheries Service, and the Office of Oceanic and Atmospheric Research participate in CSP, which is administered by the Coastal Services Center. CSP selects an area where an impact in support of the NOAA Societal Goals can be made. The first area selected was the northeast coast of Florida in 2002. In addition to coastal water level stations and modeling efforts, a 3-meter discuss buoy (WMO 41012) was deployed off the coast of St. Augustine, FL in approximately 38 meters of water. In addition to the normal complement of meteorological sensors, Buoy 41012 contained a sensor to measure directional waves at hourly intervals, a temperature-conductivity sensor to measure near-surface temperature and salinity, and a current profiler to obtain near-surface to near-bottom currents at hourly intervals. These data on the continental shelf provide a view of the oceanography on the inner margin of the Gulf Stream. The data are served over the National Data Buoy Center's web page and over the Global Telecommunications System. The waves and currents during the period from September 2005 through December 2007 are related to coastal storms, hurricanes, tides, and Gulf Stream intrusions. During several late fall and winter periods the waves exceeded 4.5 meters. The on-offshore component of the currents appears to be tidally driven, however, predominant on- and off-shore flows are observed in response to storms and Gulf Stream intrusions. The primary component of the flow is aligned alongshore and although the tidal influence is obvious, extended periods of northward and southward currents are observed. Currents approaching 2 knots are observed at various times during the period that the buoy has been active. The high currents appear to be in response to strong wind events (atmospheric frontal passages) and Gulf Stream intrusions.

FRAM telescope - monitoring of atmospheric extinction and variable star photometry

NASA Astrophysics Data System (ADS)

Jurysek, J.; Honkova, K.; Masek, M.

2015-02-01

The FRAM (F/(Ph)otometric Robotic Atmospheric Monitor) telescope is a part of the Pierre Auger Observatory (PAO) located near town Malargüe in Argentina. The main task of the FRAM telescope is the continuous night - time monitoring of the atmospheric extinction and its wavelength dependence. The current methodology of the measurement of a atmospheric extinction and for instrumentation properties also allows simultaneous observation of other interesting astronomical targets. The current observations of the FRAM telescope are focused on the photometry of eclipsing binaries, positional refinement of minor bodies of the Solar system and observations of optical counterparts of gamma ray bursts. In this contribution, we briefly describe the main purpose of the FRAM telescope for the PAO and we also present its current astrono mical observing program.

A new dynamical atmospheric ionizing radiation (AIR) model for epidemiological studies

NASA Technical Reports Server (NTRS)

De Angelis, G.; Clem, J. M.; Goldhagen, P. E.; Wilson, J. W.

2003-01-01

A new Atmospheric Ionizing Radiation (AIR) model is currently being developed for use in radiation dose evaluation in epidemiological studies targeted to atmospheric flight personnel such as civilian airlines crewmembers. The model will allow computing values for biologically relevant parameters, e.g. dose equivalent and effective dose, for individual flights from 1945. Each flight is described by its actual three dimensional flight profile, i.e. geographic coordinates and altitudes varying with time. Solar modulated primary particles are filtered with a new analytical fully angular dependent geomagnetic cut off rigidity model, as a function of latitude, longitude, arrival direction, altitude and time. The particle transport results have been obtained with a technique based on the three-dimensional Monte Carlo transport code FLUKA, with a special procedure to deal with HZE particles. Particle fluxes are transformed into dose-related quantities and then integrated all along the flight path to obtain the overall flight dose. Preliminary validations of the particle transport technique using data from the AIR Project ER-2 flight campaign of measurements are encouraging. Future efforts will deal with modeling of the effects of the aircraft structure as well as inclusion of solar particle events. Published by Elsevier Ltd on behalf of COSPAR.

Metal concentrations in homing pigeon lung tissue as a biomonitor of atmospheric pollution.

PubMed

Cui, Jia; Halbrook, Richard S; Zang, Shuying; Han, Shuang; Li, Xinyu

2018-03-01

Atmospheric pollution in urban areas is a major worldwide concern with potential adverse impacts on wildlife and humans. Biomonitoring can provide direct evidence of the bioavailability and bioaccumulation of toxic metals in the environment that is not available with mechanical air monitoring. The current study continues our evaluation of the usefulness of homing pigeon lung tissue as a biomonitor of atmospheric pollution. Homing pigeons (1-2, 5-6, and 9-10+ year old (yo)) collected from Guangzhou during 2015 were necropsied and concentrations of cadmium (Cd), lead (Pb), and mercury (Hg) were measured in lung tissue. Lung Cd and Pb concentrations were significantly greater in 9-10+-year-old pigeons compared with those in other age groups, indicating their bioavailability and bioaccumulation. Lung Pb and Cd concentrations measured in 5-yo pigeons collected from Guangzhou during 2015 were significantly lower than concentrations reported in 5-yo homing pigeons collected from Guangzhou during 2011 and correlated with concentrations measured using mechanical air monitoring. In addition to temporal differences, spatial differences in concentrations of Cd, Pb, and Hg reported in ambient air samples and in pigeon lung tissues collected from Beijing and Guangzhou are discussed.

Exhaust gas treatment in testing nuclear rocket engines

NASA Astrophysics Data System (ADS)

Zweig, Herbert R.; Fischler, Stanley; Wagner, William R.

1993-01-01

With the exception of the last test series of the Rover program, Nuclear Furnace 1, test-reactor and rocket engine hydrogen gas exhaust generated during the Rover/NERVA program was released directly to the atmosphere, without removal of the associated fission products and other radioactive debris. Current rules for nuclear facilities (DOE Order 5480.6) are far more protective of the general environment; even with the remoteness of the Nevada Test Site, introduction of potentially hazardous quantities of radioactive waste into the atmosphere must be scrupulously avoided. The Rocketdyne treatment concept features a diffuser to provide altitude simulation and pressure recovery, a series of heat exchangers to gradually cool the exhaust gas stream to 100 K, and an activated charcoal bed for adsorption of inert gases. A hydrogen-gas fed ejector provides auxiliary pumping for startup and shutdown of the engine. Supplemental filtration to remove particulates and condensed phases may be added at appropriate locations in the system. The clean hydrogen may be exhausted to the atmosphere and flared, or the gas may be condensed and stored for reuse in testing. The latter approach totally isolates the working gas from the environment.

Radiation pressure driving of a dusty atmosphere

NASA Astrophysics Data System (ADS)

Tsang, Benny T.-H.; Milosavljević, Miloš

2015-10-01

Radiation pressure can be dynamically important in star-forming environments such as ultra-luminous infrared and submillimetre galaxies. Whether and how radiation drives turbulence and bulk outflows in star formation sites is still unclear. The uncertainty in part reflects the limitations of direct numerical schemes that are currently used to simulate radiation transfer and radiation-gas coupling. An idealized setup in which radiation is introduced at the base of a dusty atmosphere in a gravitational field has recently become the standard test for radiation-hydrodynamics methods in the context of star formation. To a series of treatments featuring the flux-limited diffusion approximation as well as a short-characteristics tracing and M1 closure for the variable Eddington tensor approximation, we here add another treatment that is based on the implicit Monte Carlo radiation transfer scheme. Consistent with all previous treatments, the atmosphere undergoes Rayleigh-Taylor instability and readjusts to a near-Eddington-limited state. We detect late-time net acceleration in which the turbulent velocity dispersion matches that reported previously with the short-characteristics-based radiation transport closure, the most accurate of the three preceding treatments. Our technical result demonstrates the importance of accurate radiation transfer in simulations of radiative feedback.

European nitrogen policies, nitrate in rivers and the use of the INCA model

NASA Astrophysics Data System (ADS)

Skeffington, R.

This paper is concerned with nitrogen inputs to European catchments, how they are likely to change in future, and the implications for the INCA model. National N budgets show that the fifteen countries currently in the European Union (the EU-15 countries) probably have positive N balances - that is, N inputs exceed outputs. The major sources are atmospheric deposition, fertilisers and animal feed, the relative importance of which varies between countries. The magnitude of the fluxes which determine the transport and retention of N in catchments is also very variable in both space and time. The most important of these fluxes are parameterised directly or indirectly in the INCA Model, though it is doubtful whether the present version of the model is flexible enough to encompass short-term (daily) variations in inputs or longer-term (decadal) changes in soil parameters. As an aid to predicting future changes in deposition, international legislation relating to atmospheric N inputs and nitrate in rivers is reviewed briefly. Atmospheric N deposition and fertiliser use are likely to decrease over the next 10 years, but probably not sufficiently to balance national N budgets.

Effect of land-use change and management on biogenic volatile organic compound emissions--selecting climate-smart cultivars.

PubMed

Rosenkranz, Maaria; Pugh, Thomas A M; Schnitzler, Jörg-Peter; Arneth, Almut

2015-09-01

Land-use change (LUC) has fundamentally altered the form and function of the terrestrial biosphere. Increasing human population, the drive for higher living standards and the potential challenges of mitigating and adapting to global environmental change mean that further changes in LUC are unavoidable. LUC has direct consequences on climate not only via emissions of greenhouse gases and changing the surface energy balance but also by affecting the emission of biogenic volatile organic compounds (BVOCs). Isoprenoids, which dominate global BVOC emissions, are highly reactive and strongly modify atmospheric composition. The effects of LUC on BVOC emissions and related atmospheric chemistry have been largely ignored so far. However, compared with natural ecosystems, most tree species used in bioenergy plantations are strong BVOC emitters, whereas intensively cultivated crops typically emit less BVOCs. Here, we summarize the current knowledge on LUC-driven BVOC emissions and how these might affect atmospheric composition and climate. We further discuss land management and plant-breeding strategies, which could be taken to move towards climate-friendly BVOC emissions while simultaneously maintaining or improving key ecosystem functions such as crop yield under a changing environment. © 2014 John Wiley & Sons Ltd.

Multiple-element semiquantitative analysis of one-milligram geochemical samples by D.C. arc emission spectrography

USGS Publications Warehouse

Rait, N.

1981-01-01

A modified method is described for a 1-mg sample multi-element semiquantitative spectrographic analysis. This method uses a direct-current arc source, carbon instead of graphite electrodes, and an 80% argon-20% oxygen atmosphere instead of air. Although this is a destructive method, an analysis can be made for 68 elements in all mineral and geochemical samples. Carbon electrodes have been an aid in improving the detection limits of many elements. The carbon has a greater resistance to heat conductance and develops a better tip, facilitating sample volatilization and counter balancing the cooling effect of a flow of the argon-oxygen mixture around the anode. Where such an argon-oxygen atmosphere is used instead of air, the cyanogen band lines are greatly diminished in intensity, and thus more spectral lines of analysis elements are available for use; the spectral background is also lower. The main advantage of using the carbon electrode and the 80% argon-20% oxygen atmosphere is the improved detection limits of 36 out of 68 elements. The detection limits remain the same for 23 elements, and are not as good for only nine elements. ?? 1981.

Emergence of magnetic flux from the convection zone into the corona

NASA Astrophysics Data System (ADS)

Archontis, V.; Moreno-Insertis, F.; Galsgaard, K.; Hood, A.; O'Shea, E.

2004-11-01

Numerical experiments of the emergence of magnetic flux from the uppermost layers of the solar interior to the photosphere and its further eruption into the low atmosphere and corona are carried out. We use idealized models for the initial stratification and magnetic field distribution below the photosphere similar to those used for multidimensional flux emergence experiments in the literature. The energy equation is adiabatic except for the inclusion of ohmic and viscous dissipation terms, which, however, become important only at interfaces and reconnection sites. Three-dimensional experiments for the eruption of magnetic flux both into an unmagnetized corona and into a corona with a preexisting ambient horizontal field are presented. The shocks preceding the rising plasma present the classical structure of nonlinear Lamb waves. The expansion of the matter when rising into the atmosphere takes place preferentially in the horizontal directions: a flattened (or oval) low plasma-β ball ensues, in which the field lines describe loops in the corona with increasing inclination away from the vertical as one goes toward the sides of the structure. Magnetograms and velocity field distributions on horizontal planes are presented simultaneously for the solar interior and various levels in the atmosphere. Since the background pressure and density drop over many orders of magnitude with increasing height, the adiabatic expansion of the rising plasma yields very low temperatures. To avoid this, the entropy of the rising fluid elements should be increased to the high values of the original atmosphere via heating mechanisms not included in the present numerical experiments. The eruption of magnetic flux into a corona with a preexisting magnetic field pointing in the horizontal direction yields a clear case of essentially three-dimensional reconnection when the upcoming and ambient field systems come into contact. The coronal ambient field is chosen at time t=0 perpendicular to the direction of the tube axis and thus, given the twist of the magnetic tube, almost anti-parallel to the field lines at the upper boundary of the rising plasma ball. A thin, dome-shaped current layer is formed at the interface between the two flux systems, in which ohmic dissipation and heating are taking place. The reconnection proceeds by merging successive layers on both sides of the reconnection site; however, this occurs not only at the cusp of the interface, but, also, gradually along its sides in the direction transverse to the ambient magnetic field. The topology of the magnetic field in the atmosphere is thereby modified: the reconnected field lines typically are part of the flanks of the tube below the photosphere but then join the ambient field system in the corona and reach the boundaries of the domain as horizontal field lines.

Direct Linearization and Adjoint Approaches to Evaluation of Atmospheric Weighting Functions and Surface Partial Derivatives: General Principles, Synergy and Areas of Application

NASA Technical Reports Server (NTRS)

Ustino, Eugene A.

2006-01-01

This slide presentation reviews the observable radiances as functions of atmospheric parameters and of surface parameters; the mathematics of atmospheric weighting functions (WFs) and surface partial derivatives (PDs) are presented; and the equation of the forward radiative transfer (RT) problem is presented. For non-scattering atmospheres this can be done analytically, and all WFs and PDs can be computed analytically using the direct linearization approach. For scattering atmospheres, in general case, the solution of the forward RT problem can be obtained only numerically, but we need only two numerical solutions: one of the forward RT problem and one of the adjoint RT problem to compute all WFs and PDs we can think of. In this presentation we discuss applications of both the linearization and adjoint approaches

Atmospheric Signature of the Agulhas Current

NASA Astrophysics Data System (ADS)

Nkwinkwa Njouodo, Arielle Stela; Koseki, Shunya; Keenlyside, Noel; Rouault, Mathieu

2018-05-01

Western boundary currents play an important role in the climate system by transporting heat poleward and releasing it to the atmosphere. While their influence on extratropical storms and oceanic rainfall is becoming appreciated, their coastal influence is less known. Using satellite and climate reanalysis data sets and a regional atmospheric model, we show that the Agulhas Current is a driver of the observed band of rainfall along the southeastern African coast and above the Agulhas Current. The Agulhas current's warm core is associated with sharp gradients in sea surface temperature and sea level pressure, a convergence of low-level winds, and a co-located band of precipitation. Correlations among wind convergence, sea level pressure, and sea surface temperature indicate that these features show high degree of similarity to those in the Gulf Stream region. Model experiments further indicate that the Agulhas Current mostly impacts convective rainfall.

Titan Atmospheric Entry Radiative Heating

NASA Technical Reports Server (NTRS)

Brandis, A. M; Cruden, B. A.

2017-01-01

Detailed spectrally and spatially resolved radiance has been measured in the Electric Arc Shock Tube for conditions relevant to Titan entry, varying atmospheric composition, free-stream density (equivalent to altitude) and shock velocity. Permutations in atmospheric composition include 1.1, 2, 5 and 8.6 CH4 by mole with a balance of N2 and 1.5 CH4 0.5 Ar 98 N2 by mole, which is consistent with the current understanding of Titan's atmosphere. The effect of gas impurities identified in previous shock tube studies were also examined by testing in pure N2 and deliberate addition of air to the CH4N2 mixtures. The test campaign measured radiation at velocities from 4.7 kms to 8 kms and free-stream pressures from 0.1 to 0.47 Torr. These conditions cover a range of potential trajectories for flight missions, including a direct ballistic trajectory, a fly by or an extremely high speed entry. Radiances measured in this work are substantially larger compared to that reported both in past EAST test campaigns and other shock tube facilities. Depending on the metric used for comparison, the discrepancy can be as high as an order of magnitude. Potential causes for the discrepancy, such as the effect of oxygen due to Air leakage, gas composition and purity are discussed. The present work provides a new benchmark set of data to replace those published in previous studies.

Atmospheric propagation and combining of high-power lasers.

PubMed

Nelson, W; Sprangle, P; Davis, C C

2016-03-01

In this paper, we analyze beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations that occur on subnanosecond time scales. Coherently combining these high-power lasers would involve instruments capable of precise phase control and operation at rates greater than ∼10  GHz. To the best of our knowledge, this technology does not currently exist. This presents a challenging problem when attempting to phase lock high-power lasers that is not encountered when phase locking low-power lasers, for example, at milliwatt power levels. Regardless, we demonstrate that even if instruments are developed that can precisely control the phase of high-power lasers, coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Through simulations, we find that coherent beam combining in moderate turbulence and over multikilometer propagation distances has little advantage over incoherent combining. Additionally, in cases of strong turbulence and multikilometer propagation ranges, we find nearly indistinguishable intensity profiles and virtually no difference in the energy on the target between coherently and incoherently combined laser beams. Consequently, we find that coherent beam combining at the transmitter plane is ineffective under typical atmospheric conditions.

NEPTUNE’S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES

PubMed Central

Rowe, Jason F.; Gaulme, Patrick; Hammel, Heidi B.; Casewell, Sarah L.; Fortney, Jonathan J.; Gizis, John E.; Lissauer, Jack J.; Morales-Juberias, Raul; Orton, Glenn S.; Wong, Michael H.; Marley, Mark S.

2017-01-01

Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired nine months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune’s zonal wind profile, and confirms observed cloud feature variability. Although Neptune’s clouds vary in location and intensity on short and long timescales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extrasolar planet variability measurements. In particular we suggest that the balance between large, relatively stable, atmospheric features and smaller, more transient, clouds controls the character of substellar atmospheric variability. Atmospheres dominated by a few large spots may show inherently greater light curve stability than those which exhibit a greater number of smaller features. PMID:28127087

[Research progress and direction of atmospheric brown carbon].

PubMed

Yan, Cai-Qing; Zheng, Mei; Zhang, Yuan-Hang

2014-11-01

Organic aerosol is one of the most important components of atmospheric aerosols. In recent years, organic aerosol has been found and proved to be light absorbing in UV-Visible region. Light absorbing organic carbon (also named as brown carbon) has been one of the forefronts in the field of atmospheric research. Its light absorption contributions to radiative forcing, regional air quality, and global climate change have drawn much attention. Regional air pollution is complex in China. Frequent visibility decline and severe regional haze episodes occurred since January 2013. Previous studies showed high amount of estimated columnar light-absorbing organic carbon in China, and according to current research findings, major sources of fine particulate matter in China (e. g. biomass burning and fossil fuel combustion) were also recognized as the main sources for brown carbon. Considering the high abundance of brown carbon in atmosphere, there is a great need to reconsider and reevaluate contributions of organic aerosol to light absorption, especially its role in haze formation and radiative forcing. However, up to now, basic researches on light absorbing organic carbon are still limited in China. This study aimed to elucidate the need for basic research on brown carbon, summarize previous studies and research progress from different aspects such as sources, composition, measurement, mass concentration distribution, optical property, radiative forcing of brown carbon, point out the existing problems and deficiencies, and put forward suggestions for future study.

The Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Garratt, J. R.

1994-05-01

A comprehensive and lucid account of the physics and dynamics of the lowest one to two kilometers of the Earth's atmosphere in direct contact with the Earth's surface, known as the atmospheric boundary layer (ABL). Dr. Garratt emphasizes the application of the ABL problems to numerical modeling of the climate, which makes this book unique among recent texts on the subject. He begins with a brief introduction to the ABL before leading to the development of mean and turbulence equations and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modeling of the ABL is crucially dependent for its realism on the surface boundary conditions, so chapters four and five deal with aerodynamic and energy considerations, with attention given to both dry and wet land surfaces and the sea. The author next treats the structure of the clear-sky, thermally stratified ABL, including the convective and stable cases over homogeneous land, the marine ABL, and the internal boundary layer at the coastline. Chapter seven then extends this discussion to the cloudy ABL. This is particularly relevant to current research because the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic have been identified as key players in the climate system. In the final chapters, Dr. Garratt summarizes the book's material by discussing appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate stimulation.

Propagation of an Airy beam through the atmosphere.

PubMed

Ji, Xiaoling; Eyyuboğlu, Halil T; Ji, Guangming; Jia, Xinhong

2013-01-28

In this paper, the effect of thermal blooming of an Airy beam propagating through the atmosphere is examined, and the effect of atmospheric turbulence is not considered. The changes of the intensity distribution, the centroid position and the mean-squared beam width of an Airy beam propagating through the atmosphere are studied by using the four-dimensional (4D) computer code of the time-dependent propagation of Airy beams through the atmosphere. It is shown that an Airy beam can't retain its shape and the structure when the Airy beam propagates through the atmosphere due to thermal blooming except for the short propagation distance, or the short time, or the low beam power. The thermal blooming results in a central dip of the center lobe, and causes the center lobe to spread and decrease. In contrast with the center lobe, the side lobes are less affected by thermal blooming, such that the intensity maximum of the side lobe may be larger than that of the center lobe. However, the cross wind can reduce the effect of thermal blooming. When there exists the cross wind velocity vx in x direction, the dependence of centroid position in x direction on vx is not monotonic, and there exists a minimum, but the centroid position in y direction is nearly independent of vx.

Net uptake of atmospheric CO2 by coastal submerged aquatic vegetation

PubMed Central

Tokoro, Tatsuki; Hosokawa, Shinya; Miyoshi, Eiichi; Tada, Kazufumi; Watanabe, Kenta; Montani, Shigeru; Kayanne, Hajime; Kuwae, Tomohiro

2014-01-01

‘Blue Carbon’, which is carbon captured by marine living organisms, has recently been highlighted as a new option for climate change mitigation initiatives. In particular, coastal ecosystems have been recognized as significant carbon stocks because of their high burial rates and long-term sequestration of carbon. However, the direct contribution of Blue Carbon to the uptake of atmospheric CO2 through air-sea gas exchange remains unclear. We performed in situ measurements of carbon flows, including air-sea CO2 fluxes, dissolved inorganic carbon changes, net ecosystem production, and carbon burial rates in the boreal (Furen), temperate (Kurihama), and subtropical (Fukido) seagrass meadows of Japan from 2010 to 2013. In particular, the air-sea CO2 flux was measured using three methods: the bulk formula method, the floating chamber method, and the eddy covariance method. Our empirical results show that submerged autotrophic vegetation in shallow coastal waters can be functionally a sink for atmospheric CO2. This finding is contrary to the conventional perception that most near-shore ecosystems are sources of atmospheric CO2. The key factor determining whether or not coastal ecosystems directly decrease the concentration of atmospheric CO2 may be net ecosystem production. This study thus identifies a new ecosystem function of coastal vegetated systems; they are direct sinks of atmospheric CO2. PMID:24623530

Global Reference Atmosphere Model (GRAM)

NASA Technical Reports Server (NTRS)

Woodrum, A. W.

1989-01-01

GRAM series of four-dimensional atmospheric model validated by years of data. GRAM program, still available. More current are Gram 86, which includes atmospheric data from 1986 and runs on DEC VAX, and GRAM 88, which runs on IBM 3084. Program generates altitude profiles of atmospheric parameters along any simulated trajectory through atmosphere, and also useful for global circulation and diffusion studies.

Rainbows, polarization, and the search for habitable planets.

PubMed

Bailey, Jeremy

2007-04-01

Current proposals for the characterization of extrasolar terrestrial planets rest primarily on the use of spectroscopic techniques. While spectroscopy is effective in detecting the gaseous components of a planet's atmosphere, it provides no way of detecting the presence of liquid water, the defining characteristic of a habitable planet. In this paper, I investigate the potential of an alternative technique for characterizing the atmosphere of a planet using polarization. By looking for a polarization peak at the "primary rainbow" scattering angle, it is possible to detect the presence of liquid droplets in a planet's atmosphere and constrain the nature of the liquid through its refractive index. Single scattering calculations are presented to show that a well-defined rainbow scattering peak is present over the full range of likely cloud droplet sizes and clearly distinguishes the presence of liquid droplets from solid particles such as ice or dust. Rainbow scattering has been used in the past to determine the nature of the cloud droplets in the Venus atmosphere and by the POLarization and Directionality of Earth Reflectances (POLDER) instrument to distinguish between liquid and ice clouds in the Earth atmosphere. While the presence of liquid water clouds does not guarantee the presence of water at the surface, this technique could complement spectroscopic techniques for characterizing the atmospheres of potential habitable planets. The disk-integrated rainbow peak for Earth is estimated to be at a degree of polarization of 12.7% or 15.5% for two different cloud cover scenarios. The observation of this rainbow peak is shown to be feasible with the proposed Terrestrial Planet Finder Coronograph mission in similar total integration times to those required for spectroscopic characterization.

Atmospheric oscillations comparison on long term tropospheric delay time series derived from ray-tracing and GPS

NASA Astrophysics Data System (ADS)

Nikolaidou, Thalia; Santos, Marcelo

2017-04-01

The caused time delay induced by the atmosphere on the GNSS signals (NAD), depends primarily on the amount of atmosphere the signal traverses till it reaches to the Earth's surface and can exceed t 20 m for low elevation angles (around 3 degrees). For a particular ray i.e. satellite/quasar-antenna link, the delay depends on the atmospheric parameters of total pressure, temperature, and the partial pressure of water vapor. Because of that, numerical weather models (NWM) have already proven beneficial for atmospheric modelling and geodesy. By direct raytracing, inside NWM, the VMF1 and the University of New Brunswick VMF1 (UNB-VMF1) (Urquhart et al. 2011), access the 3D variation of the meteorological parameters that determine the delay thus being the state-the-art mapping functions used today. The raytracing procedure is capable of providing NADs delays for any point on the Earth's surface. In this study we study the impact of regional numerical weather models, with high spatial and temporal resolution, namely 25km and 6h. These models outweigh the currently used NWM by having about 2.6 times better spatial resolution. Raytracing through such NWM, using the independent raytracing algorithm develop at UNB (Nievinski, 2009), we acquire superior quality NADs with regional application. We ray-trace for the International GNSS service (IGS) network stations for a time span of 11 years. Benchmarking against the IGS troposphere product is performed to access the accuracy of our results. A periodicity analysis is conducted to examine the signature of atmospheric oscillations on the NAD time series. In order to recognize the NAD periodicities, we compared our product against the GPS-derived IGS troposphere product. Systematic effects within each single technique are identified and long-term NAD stability is accessed.

Potential role of sea spray generation in the atmospheric transport of perfluorocarboxylic acids.

PubMed

Webster, Eva; Ellis, David A

2010-08-01

The observed environmental concentrations of perfluorooctanoic acid (PFOA) and its conjugate base (PFO) in remote regions such as the Arctic have been primarily ascribed to the atmospheric transport and degradation of fluorotelomer alcohols (FTOHs) and to direct PFO transport in ocean currents. These mechanisms are each capable of only partially explaining observations. Transport within marine aerosols has been proposed and may explain transport over short distances but will contribute little over longer distances. However, PFO(A) has been shown to have a very short half-life in aqueous aerosols and thus sea spray was proposed as a mechanism for the generation of PFOA in the gas phase from PFO in a water body. Using the observed PFO concentrations in oceans of the Northern Hemisphere and estimated spray generation rates, this mechanism is shown to have the potential for contributing large amounts of PFOA to the atmosphere and may therefore contribute significantly to the concentrations observed in remote locations. Specifically, the rate of PFOA release into the gas phase from oceans in the Northern Hemisphere is calculated to be potentially comparable to global stack emissions to the atmosphere. The subsequent potential for atmospheric degradation of PFOA and its global warming potential are considered. Observed isomeric ratios and predicted atmospheric concentrations due to FTOH degradation are used to elucidate the likely relative importance of transport pathways. It is concluded that gas phase PFOA released from oceans may help to explain observed concentrations in remote regions. The model calculations performed in the present study strongly suggest that oceanic aerosol and gas phase field monitoring is of vital importance to obtain a complete understanding of the global dissemination of PFCAs. Copyright 2010 SETAC

Atmospheric Composition Change: Climate-Chemistry Interactions

NASA Technical Reports Server (NTRS)

Isaksen, I.S.A.; Granier, C.; Myhre, G.; Bernsten, T. K.; Dalsoren, S. B.; Gauss, S.; Klimont, Z.; Benestad, R.; Bousquet, P.; Collins, W.;

Direct Effects of Atmospheric CO2 Enrichment on Plants and Ecosystems: An Updated Bibliographic Data Base (1980-1994)

DOE Data Explorer

Cushman, R. M. [CDIAC, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (USA); Strain, Boyd R. [Department of Botany, Duke University, Durham, NC (USA); Cure, Jennifer D. [Department of Botany, Duke University, Durham, NC (USA)

1994-06-01

The printed publication provides bibliographic citations and abstracts on recent literature concerning the direct effects of elevated atmospheric concentrations of carbon dioxide (CO2) on plants and ecosystems. The report is an update to Direct Effects of Atmospheric CO{sub 2} Enrichment on Plants and Ecosystems: A Bibliography with Abstracts (ORNL/CDIC-13), also by Boyd R. Strain and Jennifer D. Cure, which was published in 1986. The updated bibliography provides complete bibliographic citations, abstracts, keywords, and common and scientific plant names for approximately 800 references published between 1980 and 1994 (half the cited references were published in 1990 or later). The data base is available as bibliographic files in several formats.

The Type-2 Fuzzy Logic Controller-Based Maximum Power Point Tracking Algorithm and the Quadratic Boost Converter for Pv System

NASA Astrophysics Data System (ADS)

Altin, Necmi

2018-05-01

An interval type-2 fuzzy logic controller-based maximum power point tracking algorithm and direct current-direct current (DC-DC) converter topology are proposed for photovoltaic (PV) systems. The proposed maximum power point tracking algorithm is designed based on an interval type-2 fuzzy logic controller that has an ability to handle uncertainties. The change in PV power and the change in PV voltage are determined as inputs of the proposed controller, while the change in duty cycle is determined as the output of the controller. Seven interval type-2 fuzzy sets are determined and used as membership functions for input and output variables. The quadratic boost converter provides high voltage step-up ability without any reduction in performance and stability of the system. The performance of the proposed system is validated through MATLAB/Simulink simulations. It is seen that the proposed system provides high maximum power point tracking speed and accuracy even for fast changing atmospheric conditions and high voltage step-up requirements.

Low temperature fabrication of VO x thin films for uncooled IR detectors by direct current reactive magnetron sputtering method

NASA Astrophysics Data System (ADS)

Dai, Jun; Wang, Xingzhi; He, Shaowei; Huang, Ying; Yi, Xinjian

2008-03-01

Vanadium oxide films have been fabricated on Si3N4-film-coated silicon substrates by direct current reactive magnetron sputtering method. Conditions of deposition are optimized making use of parameters such as sputtering time, dc power, oxygen partial pressure and substrate temperature. X-ray diffraction indicates that the film is a mixture of VO2, V2O3, and V3O5. Four-probe measurement shows that the VOx thin film owns high temperature coefficient of resistance (TCR ∼-2.05%/°C) and suitable square resistance 18.40 kΩ/□ (measured at 25 °C), indicating it is a well candidate material for uncooled IR detectors. In addition, IR absorption in the wavelength of 2-16 μm has been characterized. It is worth noting that the films are sputtered at a relatively low temperature of 210 °C in a controlled Ar/O2 atmosphere. Compared to traditional craft, this method needs no post-anneal at high temperature (400-500 °C).

Rapid changes in the permafrost soil carbon pool in response to warming

NASA Astrophysics Data System (ADS)

Schuur, E.; Plaza, C.; Pegoraro, E.; Bracho, R. G.; Celis, G.; Crummer, K. G.; Hutchings, J. A.; Hicks Pries, C.; Mauritz, M.; Natali, S.; Salmon, V. G.; Schaedel, C.; Webb, E.

2017-12-01

Current evidence suggests that 5 to 15% of the vast pool of soil carbon stored in northern permafrost zone ecosystems could be emitted as greenhouse gases by 2100 under the current path of global warming. Despite this forecasted release of billions of tons of additional carbon to the atmosphere that would accelerate climate change, direct measurements of change in soil carbon remain scarce and are not typically part of planned Arctic research and observation networks. This is largely because of ground subsidence that occurs as high-ice permafrost (perennially-frozen) soils begin to thaw. Profound physical alterations to the soil profile confound the application of traditional methods for quantifying carbon pool changes to fixed depths or using soil horizons. These issues can be overcome if carbon is quantified in relation to a fixed ash content, which uses the relatively stable mineral component of soil as a metric for pool comparisons through time. Here we apply this approach and show a 26% (95% confidence interval: 12, 39) loss in soil carbon over five years across both experimentally warmed and ambient tundra ecosystems at a site in Alaska where permafrost is degrading due to climate change. Losses were primarily concentrated in the middle of the soil profile, whereas any soil carbon losses from the surface were likely replaced with new carbon inputs from increased plant productivity. These surprisingly large losses overwhelmed increased plant biomass carbon uptake and were not fully detected by measurements of ecosystem-atmosphere carbon dioxide exchange. This research highlights the potential to directly detect changes in the soil carbon pool of this rapidly transforming landscape, and that current methodologies for quantifying ecosystem carbon dynamics may be underestimating soil losses. It also points to the need to make repeat soil carbon pool measurements at sentinel sites across permafrost regions, as this feedback to climate change may be occurring faster than previously thought.

Aerosol Optical Depth Retrievals From High-Resolution Commercial Satellite Imagery Over Areas of High Surface Reflectance

NASA Astrophysics Data System (ADS)

Vincent, D. A.; Nielsen, K. E.; Durkee, P. A.; Reid, J. S.

2005-12-01

The advancement and proliferation of high-resolution commercial imaging satellites presents a new opportunity for overland aerosol characterization. Current aerosol optical depth retrieval methods typically fail over areas with high surface reflectance, such as urban areas and deserts, since the upwelling radiance due to scattering by aerosols is small compared to the radiance resulting from surface reflection. The method proposed here uses shadows cast on the surface to exploit the differences between radiance from the adjacent shaded and unshaded areas of the scene. Shaded areas of the scene are primarily illuminated by diffuse irradiance that is scattered downward from the atmosphere, while unshaded areas are illuminated by both diffuse and direct solar irradiance. The first-order difference between the shaded and unshaded areas is the direct component. Given uniform surface reflectance for the shaded and unshaded areas, the difference in reflected radiance measured by a satellite sensor is related to the direct transmission of solar radiation and inversely proportional to total optical depth. Using an iterative approach, surface reflectance and mean aerosol reflectance can be partitioned to refine the retrieved total optical depth. Aerosol optical depth can then be determined from its contribution to the total atmospheric optical depth (following correction for molecular Rayleigh scattering). Intitial results based on QuickBird imagery and AERONET data collected during the United Arab Emirates Unified Aerosol Experiment (UAE2) indicate that aerosol optical depth retrievals are possible in the visible and near-infrared region with an accuracy of ~0.04.

Assessment of atmospheric trace metal deposition in urban environments using direct and indirect measurement methodology and contributions from wet and dry depositions

NASA Astrophysics Data System (ADS)

Omrani, Mehrazin; Ruban, Véronique; Ruban, Gwenaël; Lamprea, Katerine

2017-11-01

Bulk Atmospheric Deposition (BAD), Wet Atmospheric Deposition (WAD) and Dry Atmospheric Deposition (DAD) were all measured within an urban residential area in Nantes (France) over a 9-month period (27 February - 10 December 2014). The objectives of this study were to compare 2 methods for measuring dry and wet atmospheric depositions in the urban environment (DAD and WAD: direct method; BAD and WAD: indirect one), and to characterize as well the variations and relative contributions of these depositions. Trace metals (As, Cd, Cr, Cu, Ni, Pt and V) were used to carry out these comparison and quantification. BAD was collected with two open polyethylene containers (72 × 54 × 21 cm), while WAD was collected by means of an automated rainwater collector and DAD was determined from both air measurements (recorded by an air sampler) and 7Be deposition velocities. The comparison based on a detailed evaluation of uncertainties showed a significant difference between the direct and indirect methods. Dry and wet depositions varied widely from one month to the next. Zn and Cu were the most abundant elements in both dry and wet depositions. The mean contribution of DAD to the bulk atmospheric deposition during this 9-month study was significant for Zn, Cu and V (about 25%) as well as for Pb (approx. 60%). For this relatively unpolluted urban residential catchment, the contribution of atmospheric deposition to global load at the catchment outlet was low, between 10% and 20% for Zn, Cu, V and Pb, 25% for Cr and about 30% for Ni. For other urban sites exhibiting high atmospheric pollution however, the atmospheric contribution to the global pollution load could be much greater. An accurate and representative estimation of DAD thus proves critical.

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venkattraman, Ayyaswamy

2013-11-15

The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential andmore » the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.« less

Wave-Current Interactions in a wind-jet region

NASA Astrophysics Data System (ADS)

Ràfols, Laura; Grifoll, Manel; Espino, Manuel; Cerralbo, Pablo; Sairouní, Abdel; Bravo, Manel; Sánchez-Arcilla, Agustín

2017-04-01

The Wave-Current Interactions (WCI) are investigated examining the influences of coupling two numerical models. The Regional Ocean Model System (ROMS; Shchepetkin and McWilliams, 2005) and the Simulating Waves Nearshore (SWAN; Booij et al. 1999) are used in a high resolution domain (350 m). For the initial and boundary conditions, data from the IBI-MFC products have been used and the atmospheric forcing fields have been obtained from the Catalan Meteorological Service (SMC). Results from uncoupled numerical models are compared with one-way and two-way coupling simulations. The study area is located at the northern margin of the Ebro Shelf (NW Mediterranean Sea), where episodes of strong cross-shelf wind occur. The results show that during these episodes, the water currents obtained in the two-way simulation have better agreement with the observations compared with the other simulations. Additionally, when the water currents are considered, the wave energy (and thus the significant wave heigh) decrease when the current flows in the same direction as waves propagate. The relative importance of the different terms of the momentum balance equation is also analyzed.

Characterization of thunderstorm induced Maxwell current densities in the middle atmosphere

NASA Technical Reports Server (NTRS)

Baginski, Michael Edward

1989-01-01

Middle atmospheric transient Maxwell current densities generated by lightning induced charge perturbations are investigated via a simulation of Maxwell's equations. A time domain finite element analysis is employed for the simulations. The atmosphere is modeled as a region contained within a right circular cylinder with a height of 110 km and radius of 80 km. A composite conductivity profile based on measured data is used when charge perturbations are centered about the vertical axis at altitudes of 6 and 10 km. The simulations indicate that the temporal structure of the Maxwell current density is relatively insensitive to altitude variation within the region considered. It is also shown that the electric field and Maxwell current density are not generally aligned.

Earth-atmosphere system and surface reflectivities in arid regions from LANDSAT multispectral scanner measurements

NASA Technical Reports Server (NTRS)

Otterman, J.; Fraser, R. S.

1976-01-01

Programs for computing atmospheric transmission and scattering solar radiation were used to compute the ratios of the Earth-atmosphere system (space) directional reflectivities in the vertical direction to the surface reflectivity, for the four bands of the LANDSAT multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa and Central America from the spectral radiance levels measured by the LANDSAT MSS. From these space reflectivities, surface vertical reflectivities were computed applying the pertinent graphs. These surface reflectivities were used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory measurements.

Impact of Sulfur Hazes on the Reflected Light Spectra of Giant Exoplanets

NASA Astrophysics Data System (ADS)

Gao, Peter; Marley, Mark S.; Zahnle, Kevin; Robinson, Tyler D.; Lewis, Nikole K.

2017-01-01

Recent work has shown that photochemical hazes composed of elemental sulfur and its allotropes may arise in the atmospheres of warm and temperate giant exoplanets due to the photolysis of H2S. We investigate the impact such a haze would have on an exoplanet's geometric albedo spectrum using a suite of established radiative-convective, cloud, and albedo models, and how this may impact future direct imaging missions, such as WFIRST. For Jupiter-massed planets, photochemical destruction of H2S results in the production of ~1 ppmv of S8 between 100 and 0.1 mbar. The S8 mixing ratio is largely independent of the stellar UV flux, vertical mixing rates, and atmospheric temperature for expected ranges of those values, such that the S8 haze mass is dependent only on the S8 supersaturation, controlled by the local temperature. Nominal haze masses are found to drastically alter a planet's geometric albedo spectrum: whereas a clear atmosphere is dark at wavelengths between 0.5 and 1 μm due to molecular absorption, the addition of a sulfur haze boosts the albedo there to ~0.7 due to its purely scattering nature. Strong absorption by the haze shortward of 0.4 μm results in albedos <0.1, contrasting the high albedos produced by Rayleigh scattering in a clear atmosphere. These dramatic alteration in the geometric albedo spectra will lead to substantial color changes for hazy planets away from that expected for more Jupiter-like planets. For this reason colors are unlikely to provide definitive identification of warm Jupiter-like planets. The albedo change due to a sulfur haze is largely independent of the location of the haze in the atmosphere, but is a strong function of the haze optical depth as controlled by its column number density and mean particle size, though the absorption feature at short wavelengths remains robust. Detection of such a haze by future direct imaging missions like WFIRST is possible, though discriminating between a sulfur haze and any other reflective material, such as water ice, will require observations shortward of 0.4 μm, which is currently beyond WFIRST's grasp.

Day-to-day variability of midlatitude ionospheric currents due to magnetospheric and lower atmospheric forcing

NASA Astrophysics Data System (ADS)

Yamazaki, Y.; Häusler, K.; Wild, J. A.

2016-07-01

As known from previous studies on the solar quiet (Sq) variation of the geomagnetic field, the strength and pattern of ionospheric dynamo currents change significantly from day to day. The present study investigates the relative importance of two sources that contribute to the day-to-day variability of the ionospheric currents at middle and low latitudes. One is high-latitude electric fields that are caused by magnetospheric convection, and the other is atmospheric waves from the lower atmosphere. Global ionospheric current systems, commonly known as Sq current systems, are simulated using the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model. Simulations are run for 1-30 April 2010 with a constant solar energy input but with various combinations of high-latitude forcing and lower atmospheric forcing. The model well reproduces geomagnetic perturbations on the ground, when both forcings are taken into account. The contribution of high-latitude forcing to the total Sq current intensity (Jtotal) is generally smaller than the contribution of wave forcing from below 30 km, except during active periods (Kp≥4), when Jtotal is enhanced due to the leakage of high-latitude electric fields to lower latitudes. It is found that the penetration electric field drives ionospheric currents at middle and low latitudes not only on the dayside but also on the nightside, which has an appreciable effect on the Dst index. It is also found that quiet time day-to-day variability in Jtotal is dominated by symmetric-mode migrating diurnal and semidiurnal tidal winds at 45-60° latitude at ˜110 km.

Nonhydrostatic icosahedral atmospheric model (NICAM) for global cloud resolving simulations

NASA Astrophysics Data System (ADS)

Satoh, M.; Matsuno, T.; Tomita, H.; Miura, H.; Nasuno, T.; Iga, S.

2008-03-01

A new type of ultra-high resolution atmospheric global circulation model is developed. The new model is designed to perform "cloud resolving simulations" by directly calculating deep convection and meso-scale circulations, which play key roles not only in the tropical circulations but in the global circulations of the atmosphere. Since cores of deep convection have a few km in horizontal size, they have not directly been resolved by existing atmospheric general circulation models (AGCMs). In order to drastically enhance horizontal resolution, a new framework of a global atmospheric model is required; we adopted nonhydrostatic governing equations and icosahedral grids to the new model, and call it Nonhydrostatic ICosahedral Atmospheric Model (NICAM). In this article, we review governing equations and numerical techniques employed, and present the results from the unique 3.5-km mesh global experiments—with O(10 9) computational nodes—using realistic topography and land/ocean surface thermal forcing. The results show realistic behaviors of multi-scale convective systems in the tropics, which have not been captured by AGCMs. We also argue future perspective of the roles of the new model in the next generation atmospheric sciences.

An Overview of Snow Photochemistry: Evidence, Mechanisms and Impacts

NASA Technical Reports Server (NTRS)

Grannas, A. M.; Jones, A. E.; Dibb, J.; Ammann, M.; Anastasio, C.; Beine, H. J.; Bergin, M.; Bottenheim, J.; Boxe, C. S.; Carver, G.;

Spatial Representativeness Error in the Ground‐Level Observation Networks for Black Carbon Radiation Absorption

PubMed Central

Andrews, Elisabeth; Balkanski, Yves; Boucher, Olivier; Myhre, Gunnar; Samset, Bjørn Hallvard; Schulz, Michael; Schuster, Gregory L.; Valari, Myrto; Tao, Shu

2018-01-01

Abstract There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that strongly absorbs solar radiation. The observation‐constrained estimate, which is several times larger than the bottom‐up estimate, is influenced by the spatial representativeness error due to the mesoscale inhomogeneity of the aerosol fields and the relatively low resolution of global chemistry‐transport models. Here we evaluated the spatial representativeness error for two widely used observational networks (AErosol RObotic NETwork and Global Atmosphere Watch) by downscaling the geospatial grid in a global model of BC aerosol absorption optical depth to 0.1° × 0.1°. Comparing the models at a spatial resolution of 2° × 2° with BC aerosol absorption at AErosol RObotic NETwork sites (which are commonly located near emission hot spots) tends to cause a global spatial representativeness error of 30%, as a positive bias for the current top‐down estimate of global BC direct radiative forcing. By contrast, the global spatial representativeness error will be 7% for the Global Atmosphere Watch network, because the sites are located in such a way that there are almost an equal number of sites with positive or negative representativeness error. PMID:29937603

Atmospheric Pressure Plasma Jet for Chem/Bio Warfare Decontamination

NASA Astrophysics Data System (ADS)

Herrmann, Hans W.; Henins, Ivars; Park, Jaeyoung; Selwyn, Gary S.

1999-11-01

Atmospheric Pressure Plasma Jet (APPJ) technology may provide a much needed method of CBW decontamination which, unlike traditional decon methods, is dry and nondestructive to sensitive equipment and materials. The APPJ discharge uses a high-flow feedgas consisting primarily of an inert carrier gas, such as He, and a small amount of a reactive additive, such as O2, which flows between capacitively-coupled electrodes powered at 13.56 MHz. The plasma generates highly reactive metastable and atomic species of oxygen which are then directed onto a contaminated surface. The reactive effluent of the APPJ has been shown to effectively neutralize VX nerve agent as well as simulants for anthrax and mustard blister agent. Research efforts are now being directed towards reducing He consumption and increasing the allowable stand-off distance. Recent results demonstrate that by replacing the O2 reactive additive with CO2, ozone formation is greatly reduced. This has the result of extending the lifetime of atomic oxygen by an order of magnitude or more. A recirculating APP Decon Chamber which combines heat, vacuum, forced convection and reactivity is currently being developed for enhanced decontamination of sensitive equipment. Several techniques are also being evaluated for use in an APP Decon Jet for decontamination of items which cannot be placed inside a chamber.

High-Speed Operation of Interband Cascade Lasers

NASA Technical Reports Server (NTRS)

Soibel, Alexander; Hill, Cory J.; Keo, Sam A.; Wright, Malcom W.; Farr, William H.; Yang, Rui Q.; Liu, H. C.

2010-01-01

Optical sources operating in the atmospheric window of 3-5 microns are of particular interest for the development of free-space optical communication link. It is more advantageous to operate the free-space optical communication link in 3-5-microns atmospheric transmission window than at the telecom wavelength of 1.5 m due to lower optical scattering, scintillation, and background radiation. However, the realization of optical communications at the longer wavelength has encountered significant difficulties due to lack of adequate optical sources and detectors operating in the desirable wavelength regions. Interband Cascade (IC) lasers are novel semiconductor lasers that have a great potential for the realization of high-power, room-temperature optical sources in the 3-5-microns wavelength region, yet no experimental work, until this one, was done on high-speed direct modulation of IC lasers. Here, highspeed interband cascade laser, operating at wavelength 3.0 m, has been developed and the first direct measurement of the laser modulation bandwidth has been performed using a unique, highspeed quantum well infrared photodetector (QWIP). The developed laser has modulation bandwidth exceeding 3 GHz. This constitutes a significant increase of the IC laser modulation bandwidth over currently existing devices. This result has demonstrated suitability of IC lasers as a mid-IR light source for multi-GHz free-space optical communications links

Atmospheric sampling glow discharge ionization source

DOEpatents

McLuckey, S.A.; Glish, G.L.

1989-07-18

An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

A dynamics based view of atmosphere-fire interactions

Treesearch

Brian E. Potter

2002-01-01

Current research on severe fire interactions with the atmosphere focuses largely on examination of correlations between fire growth and various atmospheric properties, and on the development of indices based on these correlations. The author proposes that progress requires understanding the physics and atmospheric dynamics behind the correlations. A conceptual 3-stage...

Plasma density enhancements created by the ionization of the Earth's upper atmosphere by artificial electron beams

NASA Technical Reports Server (NTRS)

Neubert, Torsten; Banks, Peter M.

1990-01-01

Analytical calculations and experimental observations relating to the interaction with the Earth's upper atmosphere of electron beams emitted from low altitude spacecraft are presented. The problem is described by two coupled nonlinear differential equations in the up-going (along a magnetic field line) and down-going differential energy flux. The equations are solved numerically, using the MSIS atmospheric model and the IRI ionospheric model. The results form the model compare well with recent observations from the CHARGE 2 sounding rocket experiment. Two aspects of the beam-neutral atmosphere interaction are discussed. First, the limits on the electron beam current that can be emitted from a spacecraft without substantial spacecraft charging are investigated. This is important because the charging of the spacecraft to positive potentials limits the current and the escape energy of the beam electrons and thereby limits the ionization of the neutral atmosphere. As an example, we find from CHARGE 2 observations and from the model calculations that below about 180 km, secondary electrons generated through the ionization of the neutral atmosphere by 1 to 10 keV electron beams from sounding rockets, completely balance the beam current, thereby allowing the emission of very high beam currents. Second, the amount of plasma production in the beam-streak is discussed. Results are shown for selected values of the beam energy, spacecraft velocity, and spacecraft altitude.

Exploring the Longwave Radiative Effects of Dust Aerosols

NASA Technical Reports Server (NTRS)

Hansell, Richard A., Jr.

2012-01-01

Dust aerosols not only affect air quality and visibility where they pose a significant health and safety risk, but they can also play a role in modulating the energy balance of the Earth-atmosphere system by directly interacting with local radiative fields. Consequently, dust aerosols can impact regional climate patterns such as changes in precipitation and the evolution of the hydrological cycle. Assessing the direct effect of dust aerosols at the solar wavelengths is fairly straightforward due in part to the relatively large signal-to-noise ratio in broadband irradiance measurements. The longwave (LW) impacts, on the other hand, are rather difficult to ascertain since the measured dust signal level (10 Wm-2) is on the same order as the instrumental uncertainties. Moreover, compared to the shortwave (SW), limited experimental data on the LW optical properties of dust makes it a difficult challenge for constraining the LW impacts. Owing to the strong absorption features found in many terrestrial minerals (e.g., silicates and clays), the LW effects, although much smaller in magnitude compared to the SW, can still have a sizeable impact on the energetics of the Earth-atmosphere system, which can potentially trigger changes in the heat and moisture surface budgets, and dynamics of the atmosphere. The current endeavor is an integral part of an on-going research study to perform detailed assessments of dust direct aerosol radiative effects (DARE) using comprehensive global datasets from NASA Goddards mobile ground-based facility (cf. http://smartlabs.gsfc.nasa.gov/) during previous field experiments near key dust source regions. Here we examine and compare the results from two of these studies: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years. The former study focused on transported Saharan dust at Sal Island (16.73N, 22.93W), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye China (39.082N, 100.276E), a semi-arid region between the Taklimakan and Gobi deserts. NASA Goddards Giovanni system is used to help map out the spatial distribution of retrieved aerosol optical depths across the latter desert regions. 1-D radiative transfer model constrained by local measurements, including spectral photometry/interferometry and lidar for characterizing the spatiotemporal variability in dust properties and atmospheric conditions, is employed to evaluate the local instantaneous LW DARE of dust both at the surface and at the top of the atmosphere along with heating rate profiles for cloud-free atmospheres. The efficiency in LW DARE and its significance relative to the diurnally averaged SW effects are explored and compared in both studies. Found to be non-negligible, LW DARE is an important component in the study of regional climate variation with important implications for more detailed global assessments.

Scintillation of astigmatic dark hollow beams in weak atmospheric turbulence.

PubMed

Cai, Yangjian; Eyyuboğlu, Halil T; Baykal, Yahya

2008-07-01

The scintillation properties of astigmatic dark hollow beams (DHBs) in weak atmospheric turbulence were investigated in detail. An explicit expression for the on-axis scintillation index of an astigmatic DHB propagating in weak atmospheric turbulence was derived. It was found that the scintillation index value of an astigmatic DHB with suitable astigmatism (i.e., ratio of the beam waist size in the x direction to that in the y direction), dark size, beam waist size, and wavelength can be smaller than that of a stigmatic DHB and that of stigmatic and astigmatic flat-topped, annular, and Gaussian beams in weak atmospheric turbulence particularly at long propagation ranges. Our results will be useful in long-distance free-space optical communications.

The impact of exospheric neutral dynamics on ring current decay

NASA Astrophysics Data System (ADS)

Ilie, R.; Liemohn, M. W.; Skoug, R. M.; Funsten, H. O.; Gruntman, M.; Bailey, J. J.; Toth, G.

2015-12-01

The geocorona plays an important role in the energy budget of the Earth's inner magnetosphere since charge exchange of energetic ions with exospheric neutrals makes the exosphere act as an energy sink for ring current particles. Long-term ring current decay following a magnetic storm is mainly due to these electron transfer reactions, leading to the formation energetic neutral atoms (ENAs) that leave the ring current system on ballistic trajectories. The number of ENAs emitted from a given region of space depends on several factors, such as the energy and species of the energetic ion population in that region and the density of the neutral gas with which the ions undergo charge exchange. However, the density and structure of the exosphere are strongly dependent on changes in atmospheric temperature and density as well as charge exchange with the ions of plasmaspheric origin, which depletes the geocorona (by having a neutral removed from the system). Moreover, the radiation pressure exerted by solar far-ultraviolet photons pushes the geocoronal hydrogen away from the Earth in an anti-sunward direction to form a tail of neutral hydrogen. TWINS ENA images provide a direct measurement of these ENA losses and therefore insight into the dynamics of the ring current decay through interactions with the geocorona. We assess the influence of geocoronal neutrals on ring current formation and decay by analysis of the predicted ENA emissions using 6 different geocoronal models and simulations from the HEIDI ring current model during storm time. Comparison with TWINS ENA images shows that the location of the peak ENA enhancements is highly dependent on the distribution of geocoronal hydrogen density. We show that the neutral dynamics has a strong influence on the time evolution of the ring current populations as well as on the formation of energetic neutral atoms.

Constraining Hesperian martian PCO2 from mineral analysis at Gale crater

NASA Astrophysics Data System (ADS)

Bristow, T.; Haberle, R. M.; Blake, D. F.; Vaniman, D. T.; Grotzinger, J. P.; Siebach, K. L.; Des Marais, D. J.; Rampe, E. B.; Eigenbrode, J. L.; Sutter, B.; Fairén, A. G.; Mischna, M.; Vasavada, A. R.

2016-12-01

Carbon dioxide is an essential atmospheric component in martian climate models that attempt to reconcile a faint young sun with widespread evidence of liquid water at the planet's surface in the Noachian and Early Hesperian. Current estimates of ancient martian CO2 levels, derived from global inventories of carbon, and orbital detections of Noachian and Early Hesperian clay mineral-bearing terrains indicate CO2 levels that are unable to support warm and wet conditions. These estimates are subject to various sources of uncertainty however. Mineral and contextual sedimentary environmental data collected by the Mars Science Laboratory rover Curiosity in Gale Crater provide a more direct means of estimating the atmospheric partial pressure of CO2 (PCO2) coinciding with a long-lived lake system in Gale crater at 3.5 Ga. Results from a reaction-transport model, which simulates mineralogy observed within the Sheepbed member at Yellowknife Bay by coupling mineral equilibria with carbonate precipitation kinetics and rates of sedimentation, indicate atmospheric levels in the 10's mbar range. At such low PCO2 levels, climate models are unable to warm Hesperian Mars anywhere near the freezing point of water and other gases are required to raise atmospheric pressure to prevent lakes from boiling away. Thus, lacustrine features of Gale formed in a cold environment by a mechanism yet to be determined, or the climate models lack an essential component that would serve to elevate surface temperatures, at least temporally and/or locally, on Hesperian Mars. Our results also impose restrictions on the potential role of atmospheric CO2 in inferred warmer conditions of the Noachian.

Spatial and seasonal variations of Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) in the Arctic atmosphere.

PubMed

Su, Yushan; Hung, Hayley; Blanchard, Pierrette; Patton, Gregory W; Kallenborn, Roland; Konoplev, Alexei; Fellin, Phil; Li, Henrik; Geen, Charles; Stern, Gary; Rosenberg, Bruno; Barrie, Leonard A

2006-11-01

Weekly high-volume air samples were collected between 2000 and 2003 at six Arctic sites, i.e., Alert, Kinngait, and Little Fox Lake (LFL) in Canada, Point Barrow in Alaska, Valkarkai in Russia, and Zeppelin in Norway. Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were quantified in all samples. Comparison showed that alpha-HCH and HCB were homogeneously distributed in the circumpolar atmosphere and uniform throughout the seasons. However, significantly higher atmospheric concentrations of alpha-HCH and HCB and strongertemperature dependence of alpha-HCH and gamma-HCH were found at LFL in Yukon (YK), which is unique among the sites by virtue of its high altitude and low latitude, resulting in higher precipitation rates and summer temperatures. Strong temperature dependence of alpha- and gamma-HCH at this location suggests that secondary emissions, i.e., re-evaporation from surfaces, were more important at this site than others. It is hypothesized that a higher precipitation rate at LFL facilitated the transfer of alpha-HCH from the atmosphere to surface media when technical HCH was still in use worldwide. On the other hand, higher temperature at LFL enhanced reevaporation to the atmosphere after the global ban of technical HCH. In contrast to alpha-HCH and HCB, larger spatial and seasonal differences were seen for gamma-HCH (a currently used pesticide), which likely reflect the influence of different primary contaminant sources on different Arctic locations. Fugacity ratios suggest a net deposition potential of HCB from air to seawater, whereas seawater/air exchange direction of alpha-HCH varies in the circumpolar environment.

P21C-2113: Constraining Hesperian Martian PCO2 from Mineral Analysis at Gale Crater

NASA Technical Reports Server (NTRS)

Bristow, Thomas; Haberle, Robert Michael; Blake, David Frederick; Vaniman, David T.; Grotzinger, John P.; Siebach, Kirsten L.; Des Marais, David J.; Rampe, Elizabeth B.; Eigenbrode, Jennifer L.; Sutter, Brad;

New methodology for adjusting rotating shadowband irradiometer measurements

NASA Astrophysics Data System (ADS)

Vignola, Frank; Peterson, Josh; Wilbert, Stefan; Blanc, Philippe; Geuder, Norbert; Kern, Chris

2017-06-01

A new method is developed for correcting systematic errors found in rotating shadowband irradiometer measurements. Since the responsivity of photodiode-based pyranometers typically utilized for RST sensors is dependent upon the wavelength of the incident radiation and the spectral distribution of the incident radiation is different for the Direct Normal Trradiance and the Diffuse Horizontal Trradiance, spectral effects have to be considered. These cause the most problematic errors when applying currently available correction functions to RST measurements. Hence, direct normal and diffuse contributions are analyzed and modeled separately. An additional advantage of this methodology is that it provides a prescription for how to modify the adjustment algorithms to locations with different atmospheric characteristics from the location where the calibration and adjustment algorithms were developed. A summary of results and areas for future efforts are then discussed.

Volatility of aerosols in the western European environment. Interim report No. 1 thru 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jennings, S.G.

1987-10-01

The volatility apparatus to be used in the proposed work is being currently assembled at the Atmospheric Sciences Laboratory, White Sands Missile Range, New Mexico. When the volatility apparatus is constructed and tested it will be shipped to University College Galway. It is then planned to carry out field-volatility measurements of the ambient aerosol, primarily for the unmodified maritime air mass and secondly for the partially modified European continental air mass. Continuous measurements for periods up to some weeks spanning all four seasons are planned. In preparation for these measurements, a digital readout facility was acquired for the IM 146more » velocity and direction transmitter to be used for recording wind speed and direction. The measurement system was electronically processed to facilitate continuous recording on a microcomputer.« less

A discrete spherical harmonics method for radiative transfer analysis in inhomogeneous polarized planar atmosphere

NASA Astrophysics Data System (ADS)

Tapimo, Romuald; Tagne Kamdem, Hervé Thierry; Yemele, David

2018-03-01

A discrete spherical harmonics method is developed for the radiative transfer problem in inhomogeneous polarized planar atmosphere illuminated at the top by a collimated sunlight while the bottom reflects the radiation. The method expands both the Stokes vector and the phase matrix in a finite series of generalized spherical functions and the resulting vector radiative transfer equation is expressed in a set of polar directions. Hence, the polarized characteristics of the radiance within the atmosphere at any polar direction and azimuthal angle can be determined without linearization and/or interpolations. The spatial dependent of the problem is solved using the spectral Chebyshev method. The emergent and transmitted radiative intensity and the degree of polarization are predicted for both Rayleigh and Mie scattering. The discrete spherical harmonics method predictions for optical thin atmosphere using 36 streams are found in good agreement with benchmark literature results. The maximum deviation between the proposed method and literature results and for polar directions \\vert μ \\vert ≥0.1 is less than 0.5% and 0.9% for the Rayleigh and Mie scattering, respectively. These deviations for directions close to zero are about 3% and 10% for Rayleigh and Mie scattering, respectively.

Obliquity variation in a Mars climate evolution model

NASA Technical Reports Server (NTRS)

Tyler, D.; Haberle, Robert M.

1993-01-01

The existence of layered terrain in both polar regions of Mars is strong evidence supporting a cyclic variation in climate. It has been suggested that periods of net deposition have alternated with periods of net erosion in creating the layered structure that is seen today. The cause for this cyclic climatic behavior is variation in the annually averaged latitudinal distribution of solar insolation in response to obliquity cycles. For Mars, obliquity variation leads to major climatological excursion due to the condensation and sublimation of the major atmospheric constituent, CO2. The atmosphere will collapse into the polar caps, or existing caps will rapidly sublimate into the atmosphere, dependent upon the polar surface heat balance and the direction of the change in obliquity. It has been argued that variations in the obliquity of Mars cause substantial departures from the current climatological values of the surface pressure and the amount of CO2 stored in both the planetary regolith and polar caps. In this new work we have modified the Haberle et al. model to incorporate variable obliquity by allowing the polar and equatorial insolation to become functions of obliquity, which we assume to vary sinusoidally in time. As obliquity varies in the model, there can be discontinuities in the time evolution of the model equilibrium values for surface pressure, regolith, and polar cap storage. The time constant, tau r, for the regolith to find equilibrium with the climate is estimated--depending on the depth, thermal conductivity, and porosity of the regolith--between 10(exp 4) and 10(exp 6) yr. Thus, using 2000-yr timesteps to move smoothly through the 0.1250 m.y. obliquity cycles, we have an atmosphere/regolith system that cannot be assumed in equilibrium. We have dealt with this problem by limiting the rate at which CO2, can move between the atmosphere and regolith, mimicking the diffusive nature and effects of the temperature and pressure waves, by setting the time rate of change of regolith storage proportional to the difference between equilibrium storage and current storage.

Paleogene events in Central Eurasia: their role in the flora and vegetation cover evolution, migration of phytochore boundaries, and climate changes

NASA Astrophysics Data System (ADS)

Akhmetiev, M. A.; Zaporozhets, N. I.

2014-05-01

The flora and vegetation of Central Eurasia evolved in the Paleogene to a significant extent in line with the scenario similar to the Late Cretaceous one. The position of high-rank phytochores was controlled by the global climatic zonality, while development stages of the flora depended on interaction between the Arctic and Tethyan water masses and direction of atmospheric flows and were determined by principal geological and paleogeographic events in the Paleogene history of Central Eurasia. Five main stages are definable in development of the Paleogene flora: (1) early-middle Danian with the wide distribution of temperate-thermophilic floras in the middle and high latitudes and their westward and southward expansion from the Pacific and Arctic regions of the Boreal realm; (2) Late Paleocene-Early Eocene with the maximal advancement of the Tethyan flora to the high latitudes and northward migration of phytochore boundaries in response to intense water exchange between the Tethys and Atlantic oceans with its trade currents and atmospheric heat transfer directly from the tropical zone in absence of the Alpine-Himalayan orogen; (3) Lutetian with development of subtropical monsoon-type floras under influence of the water mass exchange between the Arctic Basin and Peritethys with the monsoon-induced currents and atmospheric heat transfer from the Peritethys under conditions of the restricted connection between the Central Asia basins and Tethys; (4) (?) late Lutetian-Priabonian reflecting the climate inversion due to isolation of the West Siberian Sea from the Arctic Basin against the background of its continuing connection with the Peritethys; the formation of the semiclosed West Siberian Sea at that time was accompanied by development of a climate with humid winters, hot dry summers, and deficiency of average annual precipitation in the middle latitudes of Central Eurasia, where luxuriant subtropical Quercus-Laurus forests with Castanopsis that prevailed at the preceding stage were replaced by sclerophyllous arboreal-frutescent maquis; (5) Oligocene marked by the formation of the temperate deciduous mesophyllous coniferous-broad-leaved Turgai flora after definitive desiccation of the West Siberian Sea and Turgai Seaway due to global regression induced by glaciation (transition from the "warm" to "cold" biosphere).

Accelerated Test Method for Corrosion Protective Coatings Project

NASA Technical Reports Server (NTRS)

Falker, John; Zeitlin, Nancy; Calle, Luz

2015-01-01

This project seeks to develop a new accelerated corrosion test method that predicts the long-term corrosion protection performance of spaceport structure coatings as accurately and reliably as current long-term atmospheric exposure tests. This new accelerated test method will shorten the time needed to evaluate the corrosion protection performance of coatings for NASA's critical ground support structures. Lifetime prediction for spaceport structure coatings has a 5-year qualification cycle using atmospheric exposure. Current accelerated corrosion tests often provide false positives and negatives for coating performance, do not correlate to atmospheric corrosion exposure results, and do not correlate with atmospheric exposure timescales for lifetime prediction.

Extensive middle atmosphere (20-120 KM) modification in the Global Reference Atmospheric Model (GRAM-90)

NASA Technical Reports Server (NTRS)

Justus, C. G.; Johnson, Dale

1990-01-01

The Global Reference Atmospheric Model (GRAM) is currently available in the 'GRAM-88' version (Justus, et al., 1986; 1988), which includes relatively minor upgrades and changes from the 'MOD-3' version (Justus, et al., 1980). Currently a project is underway to use large amounts of data, mostly collected under the Middle Atmosphere Program (MAP) to produce a major upgrade of the program planned for release as the GRAM-90 version. The new data and program revisions will particularly affect the 25-90 km height range. Sources of data and preliminary results are described here in the form of cross-sectional plots.

Efficient Radiative Transfer for Dynamically Evolving Stratified Atmospheres

NASA Astrophysics Data System (ADS)

Judge, Philip G.

2017-12-01

We present a fast multi-level and multi-atom non-local thermodynamic equilibrium radiative transfer method for dynamically evolving stratified atmospheres, such as the solar atmosphere. The preconditioning method of Rybicki & Hummer (RH92) is adopted. But, pressed for the need of speed and stability, a “second-order escape probability” scheme is implemented within the framework of the RH92 method, in which frequency- and angle-integrals are carried out analytically. While minimizing the computational work needed, this comes at the expense of numerical accuracy. The iteration scheme is local, the formal solutions for the intensities are the only non-local component. At present the methods have been coded for vertical transport, applicable to atmospheres that are highly stratified. The probabilistic method seems adequately fast, stable, and sufficiently accurate for exploring dynamical interactions between the evolving MHD atmosphere and radiation using current computer hardware. Current 2D and 3D dynamics codes do not include this interaction as consistently as the current method does. The solutions generated may ultimately serve as initial conditions for dynamical calculations including full 3D radiative transfer. The National Center for Atmospheric Research is sponsored by the National Science Foundation.

Biomagnetic Monitoring of Atmospheric Pollution: A Review of Magnetic Signatures from Biological Sensors.

PubMed

Hofman, Jelle; Maher, Barbara A; Muxworthy, Adrian R; Wuyts, Karen; Castanheiro, Ana; Samson, Roeland

2017-06-20

Biomagnetic monitoring of atmospheric pollution is a growing application in the field of environmental magnetism. Particulate matter (PM) in atmospheric pollution contains readily measurable concentrations of magnetic minerals. Biological surfaces, exposed to atmospheric pollution, accumulate magnetic particles over time, providing a record of location-specific, time-integrated air quality information. This review summarizes current knowledge of biological material ("sensors") used for biomagnetic monitoring purposes. Our work addresses the following: the range of magnetic properties reported for lichens, mosses, leaves, bark, trunk wood, insects, crustaceans, mammal and human tissues; their associations with atmospheric pollutant species (PM, NO x , trace elements, PAHs); the pros and cons of biomagnetic monitoring of atmospheric pollution; current challenges for large-scale implementation of biomagnetic monitoring; and future perspectives. A summary table is presented, with the aim of aiding researchers and policy makers in selecting the most suitable biological sensor for their intended biomagnetic monitoring purpose.

Atmospheric Infrasound during a Large Wildfire

NASA Astrophysics Data System (ADS)

Vance, Alexis; Elbing, Brian

2017-11-01

Numerous natural and manmade sources generate infrasound, including tornado producing storms, human heart, hurricanes, and volcanoes. Infrasound is currently being studied as part of Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD MAP), which is a multi-university collaboration focused on development and implementation of unmanned aircraft systems (UAS) and integration with sensors for atmospheric measurements. To support this effort a fixed infrasonic microphone located in Stillwater, Oklahoma has been monitoring atmospheric emissions since September of 2016. While severe storm systems is the primary focus of this work, the system also captures a wide range of infrasonic sources from distances in excess of 300 miles due to an acoustic ceiling and weak atmospheric absorption. The current presentation will focus on atmospheric infrasound observations during a large wildfire on the Kansas-Oklahoma border that occurred between March 6-22, 2017. This work was supported by NSF Grant 1539070.

Solar Cell Short Circuit Current Errors and Uncertainties During High Altitude Calibrations

NASA Technical Reports Server (NTRS)

Snyder, David D.

2012-01-01

High altitude balloon based facilities can make solar cell calibration measurements above 99.5% of the atmosphere to use for adjusting laboratory solar simulators. While close to on-orbit illumination, the small attenuation to the spectra may result in under measurements of solar cell parameters. Variations of stratospheric weather, may produce flight-to-flight measurement variations. To support the NSCAP effort, this work quantifies some of the effects on solar cell short circuit current (Isc) measurements on triple junction sub-cells. This work looks at several types of high altitude methods, direct high altitude meas urements near 120 kft, and lower stratospheric Langley plots from aircraft. It also looks at Langley extrapolation from altitudes above most of the ozone, for potential small balloon payloads. A convolution of the sub-cell spectral response with the standard solar spectrum modified by several absorption processes is used to determine the relative change from AMO, lscllsc(AMO). Rayleigh scattering, molecular scatterin g from uniformly mixed gases, Ozone, and water vapor, are included in this analysis. A range of atmosph eric pressures are examined, from 0. 05 to 0.25 Atm to cover the range of atmospheric altitudes where solar cell calibrations a reperformed. Generally these errors and uncertainties are less than 0.2%

Representation of Dissolved Organic Carbon in the JULES Dynamic Global Vegetation Model

NASA Astrophysics Data System (ADS)

Nakhavali, Mahdi; Friedlingstein, Pierre; Guenet, Bertrand; Ciais, Philip

2017-04-01

Current global models of the carbon cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, hence not considering lateral transport of carbon from the continent to the oceans. This also means that such models implicitly consider that all the CO2 which is not respired to the atmosphere is stored on land, hence overestimating the land sink of carbon. Moving toward a boundless carbon cycle that is integrating the whole continuum from land to ocean to atmosphere is needed in order to better understand Earth's carbon cycle and to make more reliable projection of its future. Here we present an original representation of Dissolved Organic Carbon (DOC) processes in the Joint UK Land Environment Simulator (JULES). The standard version of JULES represent energy, water and carbon cycles and exchanges with the atmosphere, but only account for water run-off, not including export of carbon from terrestrial ecosystems to the aquatic environments. The aim of the project is to include in JULES a representation of DOC production in terrestrial soils, due to incomplete decomposition of organic matter, its decomposition to the atmosphere, and its export to the river network by leaching. In new developed version of JULES (JULES-DOCM), DOC pools, based on their decomposition rate, are classified into labile and recalcitrant within 3 meters of soil. Based on turnover rate, DOC coming from plant material pools and microbial biomass is directed to labile pool, while DOC from humus is directed to recalcitrant pool. Both of these pools have free (dissolved) and locked (adsorbed) form where just the free pool is subjected to decomposition and leaching. DOC production and decomposition are controlled by rate modifiers (moisture, temperature, vegetation fraction and decomposition rate) at each soil layer. Decomposed DOC is released to the atmosphere following a fixed carbon use efficiency. Leaching accounts for both surface (runoff) and subsurface (groundwater) components and is parameterized as Top soil leaching (from top 20cm) and Bottom soil leaching (down to 3 meters) depending on DOC concentration and runoff leaving that layer. The model parameters are calibrated against specific sites (Brasschaat, Hainich and Carlow) for which observations of DOC concentration and leaching are available. Tuning is performed optimizing parameters such as DOC labile and recalcitrant resident time, DOC vertical distribution and CUE. Once this calibration has been performed at the site level, the model is used for global simulations with the major historical forcing (climate, atmospheric CO2 and land-use changes) in order to estimate the changes of DOC export and their attribution to anthropogenic activities.

Simulation studies of reconstruction of hadron shower direction in INO ICAL detector

NASA Astrophysics Data System (ADS)

Devi, M. M.; Dighe, A.; Indumathi, D.; Lakshmi, S. M.

2018-03-01

The proposed Iron Calorimeter (ICAL) at India-based Neutrino Observatory (INO) will be a 50 kt magnetised iron detector for the detection of atmospheric neutrinos. The atmospheric neutrinos interact via both charged current (CC) and neutral current (NC) interactions with the target iron to produce the detectable final state particles. While CC νμ (bar nuμ) leave a muon track and a hadron shower in the detector, the NC will leave only a hadron shower apart from the secondary invisible neutrino. A GEANT4 based simulation studies to reconstruct hadron showers in CC and NC, using two techniques namely the Orientation Matrix Method (OMM) and the Raw Hit Method (RHM) are presented here. While OMM requires information about the interaction vertex obtained from muon track reconstruction, RHM requires only the shower hit positions and timings and no vertex information and hence can be used for NC events as well. Hadrons from neutrino events generated with NUANCE neutrino generator are analysed. For hadrons in the energy range 0.5-15 GeV produced in CC νμ and bar nuμ interactions, a Δθ'h resolution of around 19o-9o (around 20.5o-12o) is obtained in the |cosθ'h|=[0.8, 1] bin with OMM (RHM). For NC events in the same true energy and direction bins, Δθ'h resolution varies from around 20.5o-13o, from RHM only. OMM (RHM) gives a resolution of about 55o-20o (38o-14o) for the angle between the muon and the hadron shower, βμ h', in the [E'had;cos θ'h] range [0.5-15 GeV; [0.8,1.0

Tunable Ionization Modes of a Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source.

PubMed

Badal, Sunil P; Michalak, Shawn D; Chan, George C-Y; You, Yi; Shelley, Jacob T

2016-04-05

Plasma-based ambient desorption/ionization sources are versatile in that they enable direct ionization of gaseous samples as well as desorption/ionization of analytes from liquid and solid samples. However, ionization matrix effects, caused by competitive ionization processes, can worsen sensitivity or even inhibit detection all together. The present study is focused on expanding the analytical capabilities of the flowing atmospheric-pressure afterglow (FAPA) source by exploring additional types of ionization chemistry. Specifically, it was found that the abundance and type of reagent ions produced by the FAPA source and, thus, the corresponding ionization pathways of analytes, can be altered by changing the source working conditions. High abundance of proton-transfer reagent ions was observed with relatively high gas flow rates and low discharge currents. Conversely, charge-transfer reagent species were most abundant at low gas flows and high discharge currents. A rather nonpolar model analyte, biphenyl, was found to significantly change ionization pathway based on source operating parameters. Different analyte ions (e.g., MH(+) via proton-transfer and M(+.) via charge-transfer) were formed under unique operating parameters demonstrating two different operating regimes. These tunable ionization modes of the FAPA were used to enable or enhance detection of analytes which traditionally exhibit low-sensitivity in plasma-based ADI-MS analyses. In one example, 2,2'-dichloroquaterphenyl was detected under charge-transfer FAPA conditions, which were difficult or impossible to detect with proton-transfer FAPA or direct analysis in real-time (DART). Overall, this unique mode of operation increases the number and range of detectable analytes and has the potential to lessen ionization matrix effects in ADI-MS analyses.

Redesign of the Human Metabolic Simulator

NASA Technical Reports Server (NTRS)

Duffield, Bruce; Jeng, Frank; Lange, Kevin

2004-01-01

The National Aeronautics and Space Administration (NASA) is currently building a Human Metabolic Simulator (HMS) at the Johnson Space Center as part of the Advanced Life Support Air Revitalization Technology Evaluation Facility (ARTEF). The purpose of ARTEF is to evaluate Environmental Control and Life Support System Technologies for Advanced Missions. The HMS is needed to reproduce the primary metabolic effects of human respiration on an enclosed atmosphere when humans cannot be present and the impact of human presence on the system is required. A HMS was designed, built and successfully operated in 2000 but larger crew size requirements and the expense of upgrade of the current system necessitate redesign. This paper addresses the redesign. Several concepts were considered, ranging from chemical oxidation of a hydrocarbon like ethanol or ethyl acetate to carbon dioxide and water, oxidation of an iron-containing compound, or by using a fuel cell. For reasons of cost, simplicity, safety and other factors, the concept chosen includes: a molecular sieve packaged as an industrial oxygen concentrator to remove oxygen from the atmosphere, with direct carbon dioxide, water and heat injection. The water injection is done via heating water to steam with a heat exchanger and thermal effects are handled by directly adding heat to the air stream with a second heat exchanger. Both heat exchangers are supplied by a hot oil loop. The amount of oxygen removal, carbon dioxide addition, water addition and heat addition were calculated using metabolic profiles for respiration and heat, calculated using a series of empirical equations developed for International Space Station (ISS). Sketches of the Human Metabolic Simulator and the hot oil bath loop used to supply heat to the heat exchangers are included

Exploring the influence of surface waves in the carbon dioxide transfer velocity between the ocean and atmosphere in the coastal region

NASA Astrophysics Data System (ADS)

Ocampo-Torres, Francisco Javier; Francisco Herrera, Carlos; Gutiérrez-Loza, Lucía; Osuna, Pedro

2016-04-01

Field measurements have been carried out in order to better understand the possible influence of ocean surface waves in the transfer of carbon dioxide between the ocean and atmosphere in the coastal zone. The CO2 fluxes are being analysed and results are shown in a contribution by Gutiérrez-Loza et al., in this session. Here we try to highlight the findings regarding the transfer velocity (kCO2) once we have incorporated direct measurements of carbon dioxide concentration in the water side. In this study direct measurements of CO2 fluxes were obtained with an eddy covariance tower located in the shoreline equipped with an infrared open-path gas analyzer (LI-7500, LI-COR) and a sonic anemometer (R3-100 Professional Anemometer, Gill Instruments), both at about 13 m above the mean sea level, and sampling at 20 Hz. For some period of time simultaneous information of waves was recorded with a sampling rate of 2 Hz using an Acoustic Doppler Current Profiler (Workhorse Sentinel, Teledyne RD Instruments) at 10 m depth and 350 m away from the tower. Besides, recently the concentration of CO2 in water has also been recorded making use of a SAMI-CO2 instrument. A subtle effect of the wave field is detected in the estimated kCO2. Looking into details of the surface currents being detected very near the air-sea interface through an ADPC, a certain association can be found with the gas transfer velocity. Furthermore, some of the possible effects of breaking wave induced turbulence in the coastal zone is to be addressed. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from CB-2011-01-168173 CONACYT project is greatly acknowledged.

The influence of stabilizers on the production of gold nanoparticles by direct current atmospheric pressure glow microdischarge generated in contact with liquid flowing cathode.

PubMed

Dzimitrowicz, Anna; Jamroz, Piotr; Greda, Krzysztof; Nowak, Piotr; Nyk, Marcin; Pohl, Pawel

Gold nanoparticles (Au NPs) were prepared by direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between a miniature argon flow microjet and a flowing liquid cathode. The applied discharge system was operated in a continuous flow liquid mode. The influence of various stabilizers added to the solution of the liquid cathode, i.e., gelatin (GEL), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA), as well as the concentration of the Au precursor (chloroauric acid, HAuCl 4 ) in the solution on the production growth of Au NPs was investigated. Changes in the intensity of the localized surface plasmon resonance (LSPR) band in UV/Vis absorption spectra of solutions treated by dc-μAPGD and their color were observed. The position and the intensity of the LSPR band indicated that relatively small nanoparticles were formed in solutions containing GEL as a capping agent. In these conditions, the maximum of the absorption LSPR band was at 531, 534, and 535 nm, respectively, for 50, 100, and 200 mg L -1 of Au. Additionally, scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyze the structure and the morphology of obtained Au NPs. The shape of Au NPs was spherical and uniform. Their mean size was ca. 27, 73, and 92 nm, while the polydispersity index was 0.296, 0.348, and 0.456 for Au present in the solution of the flowing liquid cathode at a concentration of 50, 100, and 200 mg L -1 , respectively. The production rate of synthesized Au NPs depended on the precursor concentration with mean values of 2.9, 3.5, and 5.7 mg h -1 , respectively.

The influence of stabilizers on the production of gold nanoparticles by direct current atmospheric pressure glow microdischarge generated in contact with liquid flowing cathode

NASA Astrophysics Data System (ADS)

Dzimitrowicz, Anna; Jamroz, Piotr; Greda, Krzysztof; Nowak, Piotr; Nyk, Marcin; Pohl, Pawel

2015-04-01

Gold nanoparticles (Au NPs) were prepared by direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between a miniature argon flow microjet and a flowing liquid cathode. The applied discharge system was operated in a continuous flow liquid mode. The influence of various stabilizers added to the solution of the liquid cathode, i.e., gelatin (GEL), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA), as well as the concentration of the Au precursor (chloroauric acid, HAuCl4) in the solution on the production growth of Au NPs was investigated. Changes in the intensity of the localized surface plasmon resonance (LSPR) band in UV/Vis absorption spectra of solutions treated by dc-μAPGD and their color were observed. The position and the intensity of the LSPR band indicated that relatively small nanoparticles were formed in solutions containing GEL as a capping agent. In these conditions, the maximum of the absorption LSPR band was at 531, 534, and 535 nm, respectively, for 50, 100, and 200 mg L-1 of Au. Additionally, scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyze the structure and the morphology of obtained Au NPs. The shape of Au NPs was spherical and uniform. Their mean size was ca. 27, 73, and 92 nm, while the polydispersity index was 0.296, 0.348, and 0.456 for Au present in the solution of the flowing liquid cathode at a concentration of 50, 100, and 200 mg L-1, respectively. The production rate of synthesized Au NPs depended on the precursor concentration with mean values of 2.9, 3.5, and 5.7 mg h-1, respectively.

Solar Wind Ablation of Terrestrial Planet Atmospheres

NASA Technical Reports Server (NTRS)

Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

2009-01-01

Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

Progress Towards the Remote Sensing of Aircraft Icing Hazards

NASA Technical Reports Server (NTRS)

Reehorst, Andrew; Brinker, David; Politovich, Marcia; Serke, David; Ryerson, Charles; Pazmany, Andrew; Solheim, Fredrick

2009-01-01

NASA has teamed with the FAA, DoD, industry, and academia for research into the remote detection and measurement of atmospheric conditions leading to aircraft icing hazards. The ultimate goal of this effort is to provide pilots, controllers, and dispatchers sufficient information to allow aircraft to avoid or minimize their exposure to the hazards of in-flight icing. Since the hazard of in-flight icing is the outcome of aircraft flight through clouds containing supercooled liquid water and strongly influenced by the aircraft s speed and configuration and by the length of exposure, the hazard cannot be directly detected, but must be inferred based upon the measurement of conducive atmospheric conditions. Therefore, icing hazard detection is accomplished through the detection and measurement of liquid water in regions of measured sub-freezing air temperatures. The icing environment is currently remotely measured from the ground with a system fusing radar, lidar, and multifrequency microwave radiometer sensors. Based upon expected ice accretion severity for the measured environment, a resultant aircraft hazard is then calculated. Because of the power, size, weight, and view angle constraints of airborne platforms, the current ground-based solution is not applicable for flight. Two current airborne concepts are based upon the use of either multifrequency radiometers or multifrequency radar. Both ground-based and airborne solutions are required for the future since groundbased systems can provide hazard detection for all aircraft in airport terminal regions while airborne systems will be needed to provide equipped aircraft with flight path coverage between terminal regions.

Remote Sounding of the Earth's Atmospheric Limb From a Micro-Satellite Platform: a Feasibility Study of the ALTIUS Mission

NASA Astrophysics Data System (ADS)

Vrancken, D.; Paijmans, B.; Fussen, D.; Neefs, E.; Loodts, N.; Dekemper, E.; Vahellemont, F.; Devos, L.; Moelans, W.; Nevejans, D.; Schroeven-Deceuninck, H.; Bernaerts, D.; Zender, J.

2008-08-01

There is more and more interest in the understanding and the monitoring of the physics and chemistry of the Earth's atmosphere and its impact on the climate change. Currently a significantly high number of sounders provide the required data to monitor the changes in atmosphere composition, but a dramatic drop in operational atmosphere monitoring missions is expected around 2010. This drop is mainly visible in sounders capable of a high vertical resolution. Currently, instruments on ENVISAT and METOP provide relevant data but this is envisaged to be insufficient to ensure full spatial and temporal coverage and redundancy in the measurement data set. ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) is a remote sounding experiment proposed by the Belgian Institute for Space Aeronomy (BIRA/IASB) for which a feasibility study was initiated with BELSPO (Belgian Science Policy) and ESA support. The main objective of this study phase was to establish a mission concept, to define the required payload and to establish a satellite platform design. The study was led by the BIRA/IASB team and performed in close collaboration with OIP (payload developer) and Verhaert Space (spacecraft developer). The mission scenario includes bright limb observations in basically all directions, solar occultations around the terminator passages and star occultations during eclipse. These observation modes allow imaging the atmosphere with a high vertical resolution. The spacecraft will be operated in a 10:00 sun-synchronous orbit at an altitude of 695 km, allowing a 3-day revisit time. The envisaged payload for the ALTIUS mission is an imaging spectrometer, observing in the UV, the VIS and the NIR spectral ranges. For each spectral range, an AOTF (Acousto-Optical Tunable Filter) will permit to perform observations of selectable small wavelength domains. A typical set of 10 wavelengths will be recorded within 1 second. The different operational modes impose a high agility capability on the platform. Furthermore, the quasi- continuous monitoring by the payload will drive the design of the platform in terms of power and downlink capabilities. The mission will be performed using a derivative of the PROBA platform, developed by Verhaert Space. This paper will present the mission requirements for the ALTIUS mission, the envisaged instrument, the spacecraft concept design and the related mission analysis.

Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

NASA Astrophysics Data System (ADS)

Hussain, S.; Qazi, H. I. A.; Badar, M. A.

2014-03-01

An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

Observation and Characterization of a Cosmic Muon Neutrino Flux from the Northern Hemisphere Using Six Years of IceCube Data

NASA Astrophysics Data System (ADS)

Aartsen, M. G.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glagla, M.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, B.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Holzapfel, K.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Jurkovic, M.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kemp, J.; Kheirandish, A.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Leuner, J.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Meli, A.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Mohrmann, L.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schimp, M.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stahlberg, M.; Stanev, T.; Stasik, A.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Turcati, A.; Unger, E.; Usner, M.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Veenkamp, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Weaver, Ch.; Weiss, M. J.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; Icecube Collaboration

2016-12-01

The IceCube Collaboration has previously discovered a high-energy astrophysical neutrino flux using neutrino events with interaction vertices contained within the instrumented volume of the IceCube detector. We present a complementary measurement using charged current muon neutrino events where the interaction vertex can be outside this volume. As a consequence of the large muon range the effective area is significantly larger but the field of view is restricted to the Northern Hemisphere. IceCube data from 2009 through 2015 have been analyzed using a likelihood approach based on the reconstructed muon energy and zenith angle. At the highest neutrino energies between 194 {TeV} and 7.8 {PeV} a significant astrophysical contribution is observed, excluding a purely atmospheric origin of these events at 5.6σ significance. The data are well described by an isotropic, unbroken power-law flux with a normalization at 100 {TeV} neutrino energy of ({0.90}-0.27+0.30)× {10}-18 {{GeV}}-1 {{cm}}-2 {{{s}}}-1 {{sr}}-1 and a hard spectral index of γ =2.13+/- 0.13. The observed spectrum is harder in comparison to previous IceCube analyses with lower energy thresholds which may indicate a break in the astrophysical neutrino spectrum of unknown origin. The highest-energy event observed has a reconstructed muon energy of (4.5+/- 1.2) {PeV} which implies a probability of less than 0.005 % for this event to be of atmospheric origin. Analyzing the arrival directions of all events with reconstructed muon energies above 200 {TeV} no correlation with known γ-ray sources was found. Using the high statistics of atmospheric neutrinos we report the current best constraints on a prompt atmospheric muon neutrino flux originating from charmed meson decays which is below 1.06 in units of the flux normalization of the model in Enberg et al.

Do contemporary (1980-2015) emissions determine the elemental carbon deposition trend at Holtedahlfonna glacier, Svalbard?

NASA Astrophysics Data System (ADS)

Ruppel, Meri M.; Soares, Joana; Gallet, Jean-Charles; Isaksson, Elisabeth; Martma, Tõnu; Svensson, Jonas; Kohler, Jack; Pedersen, Christina A.; Manninen, Sirkku; Korhola, Atte; Ström, Johan

2017-10-01

The climate impact of black carbon (BC) is notably amplified in the Arctic by its deposition, which causes albedo decrease and subsequent earlier snow and ice spring melt. To comprehensively assess the climate impact of BC in the Arctic, information on both atmospheric BC concentrations and deposition is essential. Currently, Arctic BC deposition data are very scarce, while atmospheric BC concentrations have been shown to generally decrease since the 1990s. However, a 300-year Svalbard ice core showed a distinct increase in EC (elemental carbon, proxy for BC) deposition from 1970 to 2004 contradicting atmospheric measurements and modelling studies. Here, our objective was to decipher whether this increase has continued in the 21st century and to investigate the drivers of the observed EC deposition trends. For this, a shallow firn core was collected from the same Svalbard glacier, and a regional-to-meso-scale chemical transport model (SILAM) was run from 1980 to 2015. The ice and firn core data indicate peaking EC deposition values at the end of the 1990s and lower values thereafter. The modelled BC deposition results generally support the observed glacier EC variations. However, the ice and firn core results clearly deviate from both measured and modelled atmospheric BC concentration trends, and the modelled BC deposition trend shows variations seemingly independent from BC emission or atmospheric BC concentration trends. Furthermore, according to the model ca. 99 % BC mass is wet-deposited at this Svalbard glacier, indicating that meteorological processes such as precipitation and scavenging efficiency have most likely a stronger influence on the BC deposition trend than BC emission or atmospheric concentration trends. BC emission source sectors contribute differently to the modelled atmospheric BC concentrations and BC deposition, which further supports our conclusion that different processes affect atmospheric BC concentration and deposition trends. Consequently, Arctic BC deposition trends should not directly be inferred based on atmospheric BC measurements, and more observational BC deposition data are required to assess the climate impact of BC in Arctic snow.

Massive remobilization of permafrost carbon during post-glacial warming

PubMed Central

Tesi, T.; Muschitiello, F.; Smittenberg, R. H.; Jakobsson, M.; Vonk, J. E.; Hill, P.; Andersson, A.; Kirchner, N.; Noormets, R.; Dudarev, O.; Semiletov, I.; Gustafsson, Ö

2016-01-01

Recent hypotheses, based on atmospheric records and models, suggest that permafrost carbon (PF-C) accumulated during the last glaciation may have been an important source for the atmospheric CO2 rise during post-glacial warming. However, direct physical indications for such PF-C release have so far been absent. Here we use the Laptev Sea (Arctic Ocean) as an archive to investigate PF-C destabilization during the last glacial–interglacial period. Our results show evidence for massive supply of PF-C from Siberian soils as a result of severe active layer deepening in response to the warming. Thawing of PF-C must also have brought about an enhanced organic matter respiration and, thus, these findings suggest that PF-C may indeed have been an important source of CO2 across the extensive permafrost domain. The results challenge current paradigms on the post-glacial CO2 rise and, at the same time, serve as a harbinger for possible consequences of the present-day warming of PF-C soils. PMID:27897191

Effect of vertical canopy architecture on transpiration, thermoregulation and carbon assimilation

DOE PAGES

Banerjee, Tirtha; Linn, Rodman Ray

2018-04-11

Quantifying the impact of natural and anthropogenic disturbances such as deforestation, forest fires and vegetation thinning among others on net ecosystem—atmosphere exchanges of carbon dioxide, water vapor and heat—is an important aspect in the context of modeling global carbon, water and energy cycles. The absence of canopy architectural variation in horizontal and vertical directions is a major source of uncertainty in current climate models attempting to address these issues. This work demonstrates the importance of considering the vertical distribution of foliage density by coupling a leaf level plant biophysics model with analytical solutions of wind flow and light attenuation inmore » a horizontally homogeneous canopy. It is demonstrated that plant physiological response in terms of carbon assimilation, transpiration and canopy surface temperature can be widely different for two canopies with the same leaf area index (LAI) but different leaf area density distributions, under several conditions of wind speed, light availability, soil moisture availability and atmospheric evaporative demand.« less

Global terrestrial biogeochemistry: Perturbations, interactions, and time scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braswell, B.H. Jr.

1996-12-01

Global biogeochemical processes are being perturbed by human activity, principally that which is associated with industrial activity and expansion of urban and agricultural complexes. Perturbations have manifested themselves at least since the beginning of the 19th Century, and include emissions of CO{sub 2} and other pollutants from fossil fuel combustion, agricultural emissions of reactive nitrogen, and direct disruption of ecosystem function through land conversion. These perturbations yield local impacts, but there are also global consequences that are the sum of local-scale influences. Several approaches to understanding the global-scale implications of chemical perturbations to the Earth system are discussed. The lifetimemore » of anthropogenic CO{sub 2} in the atmosphere is an important concept for understanding the current and future commitment to an altered atmospheric heat budget. The importance of the terrestrial biogeochemistry relative to the lifetime of excess CO{sub 2} is demonstrated using dynamic, aggregated models of the global carbon cycle.« less

Effect of vertical canopy architecture on transpiration, thermoregulation and carbon assimilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Tirtha; Linn, Rodman Ray

Quantifying the impact of natural and anthropogenic disturbances such as deforestation, forest fires and vegetation thinning among others on net ecosystem—atmosphere exchanges of carbon dioxide, water vapor and heat—is an important aspect in the context of modeling global carbon, water and energy cycles. The absence of canopy architectural variation in horizontal and vertical directions is a major source of uncertainty in current climate models attempting to address these issues. This work demonstrates the importance of considering the vertical distribution of foliage density by coupling a leaf level plant biophysics model with analytical solutions of wind flow and light attenuation inmore » a horizontally homogeneous canopy. It is demonstrated that plant physiological response in terms of carbon assimilation, transpiration and canopy surface temperature can be widely different for two canopies with the same leaf area index (LAI) but different leaf area density distributions, under several conditions of wind speed, light availability, soil moisture availability and atmospheric evaporative demand.« less

Microprocessors as a tool in determining correlation between sferics and tornado genesis: an update

DOE Office of Scientific and Technical Information (OSTI.GOV)

Witte, D.R.

1980-09-01

Sferics - atmospheric electromagnetic radiation - can be directly correlated, it is believed, to the genesis of tornadoes and other severe weather. Sferics are generated by lightning and other atmospheric disturbances that are not yet entirely understood. The recording and analysis of the patterns in which sferics events occur, it is hoped, will lead to accurate real-time prediction of tornadoes and other severe weather. Collection of the tremendous amount of sferics data generated by one storm system becomes cumbersome when correlation between at least two stations is necessary for triangulation. Microprocessor-based computing systems have made the task of data collectionmore » and manipulation inexpensive and manageable. The original paper on this subject delivered at MAECON '78 dealt with hardware interfacing. Presented were hardware and software tradeoffs, as well as design and construction techniques to yield a cost effective system. This updated paper presents an overview of where the data comes from, how it is collected, and some current manipulation and interpretation techniques used.« less

Massive remobilization of permafrost carbon during post-glacial warming

NASA Astrophysics Data System (ADS)

Tesi, T.; Muschitiello, F.; Smittenberg, R. H.; Jakobsson, M.; Vonk, J. E.; Hill, P.; Andersson, A.; Kirchner, N.; Noormets, R.; Dudarev, O.; Semiletov, I.; Gustafsson, Ö.

2016-11-01

Recent hypotheses, based on atmospheric records and models, suggest that permafrost carbon (PF-C) accumulated during the last glaciation may have been an important source for the atmospheric CO2 rise during post-glacial warming. However, direct physical indications for such PF-C release have so far been absent. Here we use the Laptev Sea (Arctic Ocean) as an archive to investigate PF-C destabilization during the last glacial-interglacial period. Our results show evidence for massive supply of PF-C from Siberian soils as a result of severe active layer deepening in response to the warming. Thawing of PF-C must also have brought about an enhanced organic matter respiration and, thus, these findings suggest that PF-C may indeed have been an important source of CO2 across the extensive permafrost domain. The results challenge current paradigms on the post-glacial CO2 rise and, at the same time, serve as a harbinger for possible consequences of the present-day warming of PF-C soils.

Fast Coherent Differential Imaging for Exoplanet Imaging

NASA Astrophysics Data System (ADS)

Gerard, Benjamin; Marois, Christian; Galicher, Raphael; Veran, Jean-Pierre; Macintosh, B.; Guyon, O.; Lozi, J.; Pathak, P.; Sahoo, A.

2018-06-01

Direct detection and detailed characterization of exoplanets using extreme adaptive optics (ExAO) is a key science goal of future extremely large telescopes and space observatories. However, quasi-static wavefront errors will limit the sensitivity of this endeavor. Additional limitations for ground-based telescopes arise from residual AO-corrected atmospheric wavefront errors, generating short-lived aberrations that will average into a halo over a long exposure, also limiting the sensitivity of exoplanet detection. We develop the framework for a solution to both of these problems using the self-coherent camera (SCC), to be applied to ground-based telescopes, called Fast Atmospheric SCC Technique (FAST). Simulations show that for typical ExAO targets the FAST approach can reach ~100 times better in raw contrast than what is currently achieved with ExAO instruments if we extrapolate for an hour of observing time, illustrating that the sensitivity improvement from this method could play an essential role in the future ground-based detection and characterization of lower mass/colder exoplanets.

FAST TRACK COMMUNICATION: Plasma agents in bio-decontamination by dc discharges in atmospheric air

NASA Astrophysics Data System (ADS)

Machala, Zdenko; Chládeková, Lenka; Pelach, Michal

2010-06-01

Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents.

Anthropogenic combustion iron as a complex climate forcer.

PubMed

Matsui, Hitoshi; Mahowald, Natalie M; Moteki, Nobuhiro; Hamilton, Douglas S; Ohata, Sho; Yoshida, Atsushi; Koike, Makoto; Scanza, Rachel A; Flanner, Mark G

2018-04-23

Atmospheric iron affects the global carbon cycle by modulating ocean biogeochemistry through the deposition of soluble iron to the ocean. Iron emitted by anthropogenic (fossil fuel) combustion is a source of soluble iron that is currently considered less important than other soluble iron sources, such as mineral dust and biomass burning. Here we show that the atmospheric burden of anthropogenic combustion iron is 8 times greater than previous estimates by incorporating recent measurements of anthropogenic magnetite into a global aerosol model. This new estimation increases the total deposition flux of soluble iron to southern oceans (30-90 °S) by 52%, with a larger contribution of anthropogenic combustion iron than dust and biomass burning sources. The direct radiative forcing of anthropogenic magnetite is estimated to be 0.021 W m -2 globally and 0.22 W m -2 over East Asia. Our results demonstrate that anthropogenic combustion iron is a larger and more complex climate forcer than previously thought, and therefore plays a key role in the Earth system.

Plasma Clouds and Snowplows: Bulk Plasma Escape from Mars Observed by MAVEN

NASA Technical Reports Server (NTRS)

Halekas, J. S.; Brain, D. A.; Ruhunusiri, S.; McFadden, J. P.; Mitchell, D. L.; Mazelle, C.; Connerney, J. E. P.; Harada, Y.; Hara, T.; Espley, J. R.;

Fire safety applications for spacecraft

NASA Technical Reports Server (NTRS)

Friedman, Robert; Olson, Sandra L.

1989-01-01

Fire safety for spacecraft is reviewed by first describing current practices, many of which are adapted directly from aircraft. Then, current analyses and experimental knowledge in low-gravity combustion, with implications for fire safety are discussed. In orbiting spacecraft, the detection and suppression of flames are strongly affected by the large reduction in buoyant flows under low gravity. Generally, combustion intensity is reduced in low gravity. There are some notable exceptions, however, one example being the strong enhancement of flames by low-velocity ventilation flows in space. Finally, the future requirements in fire safety, particularly the needs of long-duration space stations in fire prevention, detection, extinguishment, and atmospheric control are examined. The goal of spacecraft fire-safety investigations is the establishment of trade-offs that promote maximum safety without hampering the useful human and scientific activities in space.

Inter-Longitude Astronomy (ILA) Project: Current Highlights And Perspectives. I. Magnetic vs. Non-Magnetic Interacting Binary Stars

NASA Astrophysics Data System (ADS)

Andronov, I. L.; Antoniuk, K. A.; Baklanov, A. V.; Breus, V. V.; Burwitz, V.; Chinarova, L. L.; Chochol, D.; Dubovsky, P. A.; Han, W.; Hegedus, T.; Henden, A.; Hric, L.; Chun-Hwey, Kim; Yonggi, Kim; Kolesnikov, S. V.; Kudzej, I.; Liakos, A.; Niarchos, P. G.; Oksanen, A.; Patkos, L.; Petrik, K.; Pit', N. V.; Shakhovskoy, N. M.; Virnina, N. A.; Yoon, J.; Zola, S.

2010-12-01

We present a review of highlights of our photometric and photo-polarimetric monitoring and mathematical modeling of interacting binary stars of different types classical, asynchronous, intermedi ate polars with 25 timescales corresponding to differ ent physical mechanisms and their combinations (part "Polar"); negative and positive superhumpers in nova- like and dwarf novae stars ("Superhumper"); symbiotic ("Symbiosis"); eclipsing variables with and without ev idence for a current mass transfer ("Eclipser") with a special emphasis on systems with a direct impact of the stream into the gainor star's atmosphere, which we propose to call "Impactors", or V361 Lyr-type stars. Other parts of the ILA project are "Stellar Bell" (pul sating variables of different types and periods - M, SR, RV Tau, RR Lyr, Delta Sct) and "New Variable".

The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

NASA Astrophysics Data System (ADS)

Watson, Andrew J.; Naveira Garabato, Alberto C.

2006-02-01

Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO2. Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and ~2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air-sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO2 could then be explained as a natural consequence of the connection between the air-sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO2. Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO2 in such a formulation.

Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system

USGS Publications Warehouse

Olabarrieta, Maitane; Warner, John C.; Armstrong, Brandy N.; Zambon, Joseph B.; He, Ruoying

2012-01-01

The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system was used to investigate atmosphere–ocean–wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor’Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor’easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor’Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness-based parameterization (OOST) provided the best results for wind and wave growth prediction. However, the best agreement between the measured (CODAR) and computed surface currents and storm surge values was obtained with the wave steepness-based roughness parameterization (TY2001), although the differences obtained with respect to DGHQ were not significant. The influence of sea surface temperature (SST) fields on the atmospheric boundary layer dynamics was examined; in particular, we evaluated how the SST affects wind wave generation, surface currents and storm surges. The integrated hydrograph and integrated wave height, parameters that are highly correlated with the storm damage potential, were found to be highly sensitive to the ocean surface roughness parameterization.

Estimation of shortwave direct aerosol radiative forcing at four locations on the Indo-Gangetic plains: Model results and ground measurement

NASA Astrophysics Data System (ADS)

Bibi, Humera; Alam, Khan; Bibi, Samina

2017-08-01

This study provides observational results of aerosol optical and radiative characteristics over four locations in IGP. Spectral variation of Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP) were analysed using AErosol RObotic NETwork (AERONET) data. The analysis revealed that coarse particles were dominant in summer and pre-monsoon, while fine particles were more pronounced in winter and post-monsoon. Furthermore, the spatio-temporal variations of Shortwave Direct Aerosol Radiative Forcing (SDARF) and Shortwave Direct Aerosol Radiative Forcing Efficiency (SDARFE) at the Top Of Atmosphere (TOA), SURface (SUR) and within ATMosphere (ATM) were calculated using SBDART model. The atmospheric Heating Rate (HR) associated with SDARFATM were also computed. It was observed that the monthly averaged SDARFTOA and SDARFSUR were found to be negative leading to positive SDARFATM during all the months over all sites. The increments in net atmospheric forcing lead to maximum HR in November-December and May. The seasonal analysis of SDARF revealed that SDARFTOA and SDARFSUR were negative during all seasons. The SW atmospheric absorption translates to highest atmospheric HR during summer over Karachi and during pre-monsoon over Lahore, Jaipur and Kanpur. Like SDARF, the monthly and seasonal variations of SDARFETOA and SDARFESUR were found to be negative, resulting in positive atmospheric forcing. Additionally, to compare the model estimated forcing against AERONET derived forcing, the regression analysis of AERONET-SBDART forcing were carried out. It was observed that SDARF at SUR and TOA showed relatively higher correlation over Lahore, moderate over Jaipur and Kanpur and lower over Karachi. Finally, the analysis of National Oceanic and Atmospheric Administration Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed that air masses were arriving from multiple source locations.

The Mega Mesospheric Parachute

NASA Technical Reports Server (NTRS)

Kloesel, Kurt J.; Oberto, Robert; Kinsey, Robert

2005-01-01

The current understanding and modeling of the upper reaches of the atmosphere is incomplete. Upper atmospheric interactions with the lower atmosphere, effects of ionizing radiation, high altitude cloud phenomena, and the dynamical interaction with the magnetosphere require greater definition. The scientific objective of obtaining a greater understanding of the upper atmosphere can be achieved by designing, implementing, testing, and utilizing a facility that provides long period in-situ measurements of the mesosphere. Current direct sub-sonic measurements of the upper atmosphere are hampered by the approximately one minute sub-sonic observation window of a ballistic sounding rocket regardless of the launch angle. In-situ measurements at greater than transonic speeds impart energy into the molecular atmospheric system and distort the true atmospheric chemistry. A long duration, sub-sonic capability will significantly enhance our ability to observe and measure: (1) mesospheric lightning phenomena (sprites and blue jets) (2) composition, structure and stratification of noctilucent clouds (3) physics of seasonal radar echoes, gravity wave phenomena (4) chemistry of mesospheric gaseous ratio mixing (5) mesospheric interaction of ionizing radiation (6) dynamic electric and magnetic fields This new facility will also provide local field measurements which complement those that can be obtained through external measurements from satellite and ground-based platforms. The 400 foot (approximately 130 meter) diameter lightweight mega-mesospheric parachute system, deployed with a sounding rocket, is proposed herein as a method to increase sub-sonic mesospheric measurement time periods by more than an order of magnitude. The report outlines a multi-year evolving science instrumentation suite in parallel with the development of the mega meso-chute facility. The developmental issues surrounding the meso-chute are chiefly materials selection (thermal and structural) and deployment mechanism physics. Three mission cases were conceived and developed to include cost and schedules estimates. Each scenario has increasing scientific utility with paralleling launch weight, parachute hang-time, deployment altitude, and parachute size: (1) Case #1: $8.4M@24 months, 6kg payload, 20 min., 50km alt., 80 m. dia. (2) Case #2: $10.4M@24 months, 6kg payload, 20 min., 60km alt, 130m. dia. (3) Case #3: $13.6M@36 months, 30kg payload, 30 min., 90km alt., 200m. dia. The initial breakout cost for the parachute system is approximately $2M@24 months. This report identifies that although the challenges of the mega-meso-chute may be difficult, they can be surmounted and valuable results can be achieved.

Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Lianhong; Meyers, T. P.; Pallardy, Stephen G.

2006-01-01

The purpose of this paper is to examine the mechanism that controls the variation of surface energy partitioning between latent and sensible heat fluxes at a temperate deciduous forest site in central Missouri, USA. Taking advantage of multiple micrometeorological and ecophysiological measurements and a prolonged drought in the middle of the 2005 growing season at this site, we studied how soil moisture, atmospheric vapor pressure deficit (VPD), and net radiation affected surface energy partitioning. We stratified these factors to minimize potential confounding effects of correlation among them. We found that all three factors had direct effects on surface energy partitioning,more » but more important, all three factors also had crucial indirect effects. The direct effect of soil moisture was characterized by a rapid decrease in Bowen ratio with increasing soil moisture when the soil was dry and by insensitivity of Bowen ratio to variations in soil moisture when the soil was wet. However, the rate of decrease in Bowen ratio when the soil was dry and the level of soil moisture above which Bowen ratio became insensitive to changes in soil moisture depended on atmospheric conditions. The direct effect of increased net radiation was to increase Bowen ratio. The direct effect of VPD was very nonlinear: Increased VPD decreased Bowen ratio at low VPD but increased Bowen ratio at high VPD. The indirect effects were much more complicated. Reduced soil moisture weakened the influence of VPD but enhanced the influence of net adiation on surface energy partitioning. Soil moisture also controlled how net radiation influenced the relationship between surface energy partitioning and VPD and how VPD affected the relationship between surface energy partitioning and net radiation. Furthermore, both increased VPD and increased net radiation enhanced the sensitivity of Bowen ratio to changes in soil moisture and the effect of drought on surface energy partitioning. The direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning identified in this paper provide a target for testing atmospheric general circulation models in their representation of land-atmosphere coupling.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, G.; Abarbanel, H.; Carruthers, P.

If the current growth rate in the use of fossil fuels continues at 4.3% per year, then the CO/sub 2/ concentration in the atmosphere can be expected to double by about 2035 provided the current partition of CO/sub 2/ between the atmosphere, biosphere, and oceans is maintained as is the current mix of fuels. Slower rates of anticipated growth of energy use lead to a doubling of the carbon content of the atmosphere sometime in the period 2040 to 2060. This report addresses the questions of the sources of atmospheric CO/sub 2/; considers distribution of the present CO/sub 2/ amongmore » the atmospheric, oceanic, and biospheric reservoir; and assesses the impact on climate as reflected by the average ground temperature at each latitude of significant increases in atmospheric CO/sub 2/. An analytic model of the atmosphere was constructed (JASON Climate Model). Calculation with this zonally averaged model shows an increase of average surface temperature of 2.4/sup 0/ for a doubling of CO/sub 2/. The equatorial temperature increases by 0.7/sup 0/K, while the poles warm up by 10 to 12/sup 0/K. The warming of climate will not necessarily lead to improved living conditions everywhere. Changes in sea level, in agricultural productivity, and in water availability can be anticipated, but the dimensions of their economic, political, or social consequences can not.« less

Improved atmospheric 3D BSDF model in earthlike exoplanet using ray-tracing based method

NASA Astrophysics Data System (ADS)

Ryu, Dongok; Kim, Sug-Whan; Seong, Sehyun

2012-10-01

The studies on planetary radiative transfer computation have become important elements to disk-averaged spectral characterization of potential exoplanets. In this paper, we report an improved ray-tracing based atmospheric simulation model as a part of 3-D earth-like planet model with 3 principle sub-components i.e. land, sea and atmosphere. Any changes in ray paths and their characteristics such as radiative power and direction are computed as they experience reflection, refraction, transmission, absorption and scattering. Improved atmospheric BSDF algorithms uses Q.Liu's combined Rayleigh and aerosol Henrey-Greenstein scattering phase function. The input cloud-free atmosphere model consists of 48 layers with vertical absorption profiles and a scattering layer with their input characteristics using the GIOVANNI database. Total Solar Irradiance data are obtained from Solar Radiation and Climate Experiment (SORCE) mission. Using aerosol scattering computation, we first tested the atmospheric scattering effects with imaging simulation with HRIV, EPOXI. Then we examined the computational validity of atmospheric model with the measurements of global, direct and diffuse radiation taken from NREL(National Renewable Energy Laboratory)s pyranometers and pyrheliometers on a ground station for cases of single incident angle and for simultaneous multiple incident angles of the solar beam.

Exoplanetary Atmospheres-Chemistry, Formation Conditions, and Habitability.

PubMed

Madhusudhan, Nikku; Agúndez, Marcelino; Moses, Julianne I; Hu, Yongyun

2016-12-01

Characterizing the atmospheres of extrasolar planets is the new frontier in exoplanetary science. The last two decades of exoplanet discoveries have revealed that exoplanets are very common and extremely diverse in their orbital and bulk properties. We now enter a new era as we begin to investigate the chemical diversity of exoplanets, their atmospheric and interior processes, and their formation conditions. Recent developments in the field have led to unprecedented advancements in our understanding of atmospheric chemistry of exoplanets and the implications for their formation conditions. We review these developments in the present work. We review in detail the theory of atmospheric chemistry in all classes of exoplanets discovered to date, from highly irradiated gas giants, ice giants, and super-Earths, to directly imaged giant planets at large orbital separations. We then review the observational detections of chemical species in exoplanetary atmospheres of these various types using different methods, including transit spectroscopy, Doppler spectroscopy, and direct imaging. In addition to chemical detections, we discuss the advances in determining chemical abundances in these atmospheres and how such abundances are being used to constrain exoplanetary formation conditions and migration mechanisms. Finally, we review recent theoretical work on the atmospheres of habitable exoplanets, followed by a discussion of future outlook of the field.

Atmospheric effects on laser eye safety and damage to instrumentation

NASA Astrophysics Data System (ADS)

Zilberman, Arkadi; Kopeika, Natan S.

2017-10-01

Electro-optical sensors as well as unprotected human eyes are extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. Laser detector/eye hazard depends on the interaction between the laser beam and the media in which it traverses. The environmental conditions including terrain features, atmospheric particulate and water content, and turbulence, may alter the laser's effect on the detector/eye. It is possible to estimate the performance of an electro-optical system as long as the atmospheric propagation of the laser beam can be adequately modeled. More recent experiments and modeling of atmospheric optics phenomena such as inner scale effect, aperture averaging, atmospheric attenuation in NIR-SWIR, and Cn2 modeling justify an update of previous eye/detector safety modeling. In the present work, the influence of the atmospheric channel on laser safety for personnel and instrumentation is shown on the basis of theoretical and experimental data of laser irradiance statistics for different atmospheric conditions. A method for evaluating the probability of damage and hazard distances associated with the use of laser systems in a turbulent atmosphere operating in the visible and NIR-SWIR portions of the electromagnetic spectrum is presented. It can be used as a performance prediction model for directed energy engagement of ground-based or air-based systems.

Evaluation of atmospheric density models and preliminary functional specifications for the Langley Atmospheric Information Retrieval System (LAIRS)

NASA Technical Reports Server (NTRS)

Lee, T.; Boland, D. F., Jr.

1980-01-01

This document presents the results of an extensive survey and comparative evaluation of current atmosphere and wind models for inclusion in the Langley Atmospheric Information Retrieval System (LAIRS). It includes recommended models for use in LAIRS, estimated accuracies for the recommended models, and functional specifications for the development of LAIRS.

Overview of current research on atmospheric interactions with wildland fires

Treesearch

Warren E. Heilman

1996-01-01

Changes in the large-scale mean thermal structure of the atmosphere have the potential for affecting the dynamics of the atmosphere across the entire spectrum of scales that govern atmospheric processes. Inherent in these changes are interactions among the scales that could change, resulting in an alteration in the frequency of regional weather systems conducive to...

Wildland fire emissions, carbon, and climate: Plume rise, atmospheric transport, and chemistry processes

Treesearch

Warren Heilman; Yongqiang Liu; Shawn Urbanski; Vladimir Kovalev; Robert Mickler

2014-01-01

This paper provides an overview and summary of the current state of knowledge regarding critical atmospheric processes that affect the distribution and concentrations of greenhouse gases and aerosols emitted from wildland fires or produced through subsequent chemical reactions in the atmosphere. These critical atmospheric processes include the dynamics of plume rise,...

Comparison of diverse methods for the correction of atmospheric effects on LANDSAT and SKYLAB images. [radiometric correction in Brazil

NASA Technical Reports Server (NTRS)

Parada, N. D. J. (Principal Investigator); Camara, G.; Dias, L. A. V.; Mascarenhas, N. D. D.; Desouza, R. C. M.; Pereira, A. E. C.

1982-01-01

Earth's atmosphere reduces a sensors ability in currently discriminating targets. Using radiometric correction to reduce the atmospheric effects may improve considerably the performance of an automatic image interpreter. Several methods for radiometric correction from the open literature are compared leading to the development of an atmospheric correction system.

Mars Atmospheric Chemistry and Astrobiology Workshop Summary

NASA Astrophysics Data System (ADS)

Allen, M.; Wennberg, P.

2002-09-01

The Mars Atmospheric Chemistry and Astrobiology (MACA) Workshop was held on the California Institute of Technology campus December 17-18, 2001. The prime objective of the workshop was to consider whether extant life beneath the surface, if it exists, would be in contact with the atmosphere and introduce a detectable signature in the atmosphere. To answer this question, the workshop also explored how well we understood the abiotic chemistry of the current atmosphere and other drivers of atmospheric composition (volcanoes, surface-atmosphere interactions, escape). The conclusions from this workshop will be presented.

The applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research

NASA Technical Reports Server (NTRS)

Fegley, Bruce, Jr.

1990-01-01

A review of the applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research during the past four decades is presented with an emphasis on chemical equilibrium models and thermochemical kinetics. Several current problems in planetary atmospheres research such as the origin of the atmospheres of the terrestrial planets, atmosphere-surface interactions on Venus and Mars, deep mixing in the atmospheres of the gas giant planets, and the origin of the atmospheres of outer planet satellites all require laboratory data on the kinetics of thermochemical reactions for their solution.

Earth Global Reference Atmospheric Model (GRAM) Overview and Updates: DOLWG Meeting

NASA Technical Reports Server (NTRS)

White, Patrick

2017-01-01

What is Earth-GRAM (Global Reference Atmospheric Model): Provides monthly mean and standard deviation for any point in atmosphere - Monthly, Geographic, and Altitude Variation; Earth-GRAM is a C++ software package - Currently distributed as Earth-GRAM 2016; Atmospheric variables included: pressure, density, temperature, horizontal and vertical winds, speed of sound, and atmospheric constituents; Used by engineering community because of ability to create dispersions in atmosphere at a rapid runtime - Often embedded in trajectory simulation software; Not a forecast model; Does not readily capture localized atmospheric effects.

Detecting and Understanding Changing Arctic Carbon Emissions

NASA Astrophysics Data System (ADS)

Bruhwiler, L.

2017-12-01

Warming in the Arctic has proceeded faster than anyplace on Earth. Our current understanding of biogeochemistry suggests that we can expect feedbacks between climate and carbon in the Arctic. Changes in terrestrial fluxes of carbon can be expected as the Arctic warms, and the vast stores of organic carbon frozen in Arctic soils could be mobilized to the atmosphere, with possible significant impacts on global climate. Quantifying trends in Arctic carbon exchanges is important for policymaking because greater reductions in anthropogenic emissions may be required to meet climate goals. Observations of greenhouse gases in the Arctic and globally have been collected for several decades. Analysis of this data does not currently support significantly changed Arctic emissions of CH4, however it is difficult to detect changes in Arctic emissions because of transport from lower latitudes and large inter-annual variability. Unfortunately, current space-based remote sensing systems have limitations at Arctic latitudes. Modeling systems can help untangle the Arctic budget of greenhouse gases, but they are dependent on underlying prior fluxes, wetland distributions and global anthropogenic emissions. Also, atmospheric transport models may have significant biases and errors. For example, unrealistic near-surface stability can lead to underestimation of emissions in atmospheric inversions. We discuss our current understanding of the Arctic carbon budget from both top-down and bottom-up approaches. We show that current atmospheric inversions agree well on the CH4 budget. On the other hand, bottom-up models vary widely in their predictions of natural emissions, with some models predicting emissions too large to be accommodated by the budget implied by global observations. Large emissions from the shallow Arctic ocean are also inconsistent with atmospheric observations. We also discuss the sensitivity of the current atmospheric network to what is likely small, gradual increases in emissions over time by examining modeled and observed spatial and seasonal variability. An issue we will consider is whether well-mixed background atmospheric records are more likely to detect changing Arctic emissions compared to stronger, but more variable signal from local sources.

Middle Atmosphere Electrodynamics During a Thunderstorm

NASA Technical Reports Server (NTRS)

Croskey, Charles L.

1996-01-01

Rocket-based instrumentation investigations of middle atmospheric electrodynamics during thunderstorms were conducted in coordination with balloon-measurements at Wallops Island, Virginia. Middle atmosphere electrodynamics and energy coupling are of particular importance to associated electrical processes at lower and higher altitudes. Objectives of this research effort included: (1) investigation of thunderstorm effects on middle atmosphere electrical structure, including spatial and temporal dependence; (2) characterization of electric field transients and the associated energy deposited at various altitudes; (3) evaluation of the vertical Maxwell current density over a thunderstorm to study the coupling of energy to higher altitudes; and (4) investigation of the coupling of energy to the ionosphere and the current supplied to the 'global circuit.'

Monsoon Variability in the Arabian Sea from Enhanced and Standard Horizontal Resolution Coupled Climate Models.

NASA Astrophysics Data System (ADS)

McClean, J.; Veneziani, C.; Maltrud, M. E.; Taylor, M.; Bader, D. C.; Branstetter, M. L.; Evans, K. J.; Mahajan, S.

2016-02-01

The circulation of the upper ocean in the Arabian Sea switches direction seasonally due to the change in direction of the prevailing winds associated with the Indian Monsoon. Predictability of the monsoon circulation, however, is uncertain due to incomplete understanding of the physical processes operating on the monsoon and other time scales, particularly interannual and intraseasonal. We use the Community Earth System Model (CESM) with enhanced horizontal resolution in each of its components relative to standard coupled climate model resolution, to better understand these time scale interactions. A standard resolution CESM counterpart is used to assess how horizontal resolution impacts the depiction of these processes. In the enhanced resolution case, 0.25° Community Atmosphere Model 5 (CAM5) is coupled to, among other components, the tripolar nominal 0.1° Parallel Ocean Program 2 (POP2). The fine resolution CESM simulation was run for 85 years; constant 1850 preindustrial forcing was used throughout the run, allowing us to isolate internal variability of the coupled system. Model parameters were adjusted ("tuned") to produce an acceptably small top of the atmosphere radiation imbalance. The reversal of the Somali Current (SC), the western boundary current off northeast Africa, has typically been associated with that of the monsoon. The SC reverses from southwestward in boreal winter to northeastward in summer; coastal upwelling is induced by the summer monsoonal winds. Recently it has been shown from new observations that the SC starts to reverse prior to the monsoon switch. Westward propagating Rossby waves have been implicated as responsible for the early SC reversal. We will discuss the sequencing of remote and local forcing on the timing of the spring inter-monsoonal switch in the direction of the SC and the appearance of the Great Whirl off the Oman Coast. Particularly, we consider how the Indian Ocean Dipole (IOD) acts to modify the seasonal strength and variability of the western boundary current system including upwelling. We look for a connection between interannual upwelling variability and that of rainfall off the west coast of India. As well, we examine changes due to the IOD in the upper ocean temperature and salinity structure along the Rossby wave propagation route in the Arabian Sea.

Environmental impact of biogas: A short review of current knowledge.

PubMed

Paolini, Valerio; Petracchini, Francesco; Segreto, Marco; Tomassetti, Laura; Naja, Nour; Cecinato, Angelo

2018-04-13

The social acceptance of biogas is often hampered by environmental and health concerns. In this study, the current knowledge about the impact of biogas technology is presented and discussed. The survey reports the emission rate estimates of the main greenhouse gases (GHG), namely CO 2 , CH 4 and N 2 O, according to several case studies conducted over the world. Direct emissions of gaseous pollutants are then discussed, with a focus on nitrogen oxides (NO x ); evidences of the importance of suitable biomass and digestate storages are also reported. The current knowledge on the environmental impact induced by final use of digestate is critically discussed, considering both soil fertility and nitrogen release into atmosphere and groundwater; several case studies are reported, showing the importance of NH 3 emissions with regards to secondary aerosol formation. The biogas upgrading to biomethane is also included in the study: with this regard, the methane slip in the off-gas can significantly reduce the environmental benefits.

The K Dwarf Advantage for Biosignatures

NASA Astrophysics Data System (ADS)

Arney, Giada; Domagal-Goldman, Shawn David; Meadows, Victoria

2018-01-01

Biosignature detection is typically studied in the context of an atmosphere in chemical disequilibrium. Oxygen (O2) and methane (CH4) are generally considered the “canonical” biosignature disequilibrium pair. However, the modern CH4 concentration poses a major detection challenge to future direct imaging telescopes, and it has been difficult for Earth to accumulate spectrally detectable quantities of O2 and CH4 over its history (Olson et al 2016, Reinhard et al 2017). Even the lower atmospheric levels of O2 typical of the Earth’s Proterozoic eon (0.01-1% of the modern O2 amount) may have resulted in a reduced photochemical lifetime of CH4 due to decreased UV shielding of CH4 (Claire et al 2006, Goldblatt et al 2006). However, while the above is true for an Earthlike planet orbiting a sunlike star, the situation changes for other stars. For instance, Segura et al (2005) found longer photochemical lifetimes for CH4 in the atmospheres of Earthlike planets orbiting M dwarfs. M dwarfs, however, present several barriers to planetary habitability including desiccation during the stellar super-luminous pre-main sequence phase (Lugar and Barnes 2015) and tidal locking. K dwarfs, which comprise about 12% of all main sequence stars, avoid these M dwarf hazards, and will be important targets for future exoplanet direct imaging missions. Using a photochemical model, we find CH4 and O2 are simultaneously detectable in the atmospheres of K dwarf planets with various O2 concentrations ranging between Proterozoic levels and modern O2 amounts. For instance, for a planet with an Earth-like CH4 surface flux (1 x 1011 molecules/cm2/s) and a Proterozoic-like O2 level (1% of modern), the planet generates a CH4 surface mixing ratio of 1x10-5 for a planet orbiting the sun, and 1.5x10-4 – an order of magnitude more CH4 – for a planet orbiting a K6V star. This is enough to produce detectable CH4 and O2 for the planet orbiting the K6V star. We discuss the implications of this “K dwarf advantage” for biosignature searches in the context of potential future direct imaging exoplanet missions currently under study such as HabEx and LUVOIR.

Looking inside volcanoes with the Imaging Atmospheric Cherenkov Telescopes

NASA Astrophysics Data System (ADS)

Del Santo, M.; Catalano, O.; Cusumano, G.; La Parola, V.; La Rosa, G.; Maccarone, M. C.; Mineo, T.; Sottile, G.; Carbone, D.; Zuccarello, L.; Pareschi, G.; Vercellone, S.

2017-12-01

Cherenkov light is emitted when charged particles travel through a dielectric medium with velocity higher than the speed of light in the medium. The ground-based Imaging Atmospheric Cherenkov Telescopes (IACT), dedicated to the very-high energy γ-ray Astrophysics, are based on the detection of the Cherenkov light produced by relativistic charged particles in a shower induced by TeV photons interacting with the Earth atmosphere. Usually, an IACT consists of a large segmented mirror which reflects the Cherenkov light onto an array of sensors, placed at the focal plane, equipped by fast electronics. Cherenkov light from muons is imaged by an IACT as a ring, when muon hits the mirror, or as an arc when the impact point is outside the mirror. The Cherenkov ring pattern contains information necessary to assess both direction and energy of the incident muon. Taking advantage of the muon detection capability of IACTs, we present a new application of the Cherenkov technique that can be used to perform the muon radiography of volcanoes. The quantitative understanding of the inner structure of a volcano is a key-point to monitor the stages of the volcano activity, to forecast the next eruptive style and, eventually, to mitigate volcanic hazards. Muon radiography shares the same principle as X-ray radiography: muons are attenuated by higher density regions inside the target so that, by measuring the differential attenuation of the muon flux along different directions, it is possible to determine the density distribution of the interior of a volcano. To date, muon imaging of volcanic structures has been mainly achieved with detectors made up of scintillator planes. The advantage of using Cherenkov telescopes is that they are negligibly affected by background noise and allow a consistently improved spatial resolution when compared to the majority of the current detectors.

Convective and Stratiform Precipitation Processes and their Relationship to Latent Heating

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Lang, Steve; Zeng, Xiping; Shige, Shoichi; Takayabu, Yukari

2009-01-01

The global hydrological cycle is central to the Earth's climate system, with rainfall and the physics of its formation acting as the key links in the cycle. Two-thirds of global rainfall occurs in the Tropics. Associated with this rainfall is a vast amount of heat, which is known as latent heat. It arises mainly due to the phase change of water vapor condensing into liquid droplets; three-fourths of the total heat energy available to the Earth's atmosphere comes from tropical rainfall. In addition, fresh water provided by tropical rainfall and its variability exerts a large impact upon the structure and motions of the upper ocean layer. An improved convective -stratiform heating (CSH) algorithm has been developed to obtain the 3D structure of cloud heating over the Tropics based on two sources of information: 1) rainfall information, namely its amount and the fraction due to light rain intensity, observed directly from the Precipitation Radar (PR) on board the TRMM satellite and 2) synthetic cloud physics information obtained from cloud-resolving model (CRM) simulations of cloud systems. The cloud simulations provide details on cloud processes, specifically latent heating, eddy heat flux convergence and radiative heating/cooling, that. are not directly observable by satellite. The new CSH algorithm-derived heating has a noticeably different heating structure over both ocean and land regions compared to the previous CSH algorithm. One of the major differences between new and old algorithms is that the level of maximum cloud heating occurs 1 to 1.5 km lower in the atmosphere in the new algorithm. This can effect the structure of the implied air currents associated with the general circulation of the atmosphere in the Tropics. The new CSH algorithm will be used provide retrieved heating data to other heating algorithms to supplement their performance.

Developing Atmospheric Retrieval Methods for Direct Imaging Spectroscopy of Gas Giants in Reflected Light I: Methane Abundances and Basic Cloud Properties

NASA Technical Reports Server (NTRS)

Lupu, R. E.; Marley, M. S.; Lewis, N.; Line, M.; Traub, W.; Zahnle, K.

2016-01-01

Reflected light spectroscopy and photometry of cool, directly imaged extrasolar giant planets are expected to be performed in the next decade by space-based telescopes equipped with optical wavelength coronagraphs and integral field spectrographs, such as the Wide-Field Infrared Survey Telescope (WFIRST). We are developing a new atmospheric retrieval methodology to help assess the science return and inform the instrument design for such future missions, and ultimately interpret the resulting observations. Our retrieval technique employs an albedo model coupled with both a Markov chain Monte Carlo Ensemble Sampler (emcee) and a multimodal nested sampling algorithm (MultiNest) to map the posterior distribution. This combination makes the global evidence calculation more robust for any given model, and highlights possible discrepancies in the likelihood maps. Here we apply this methodology to simulated spectra of cool giant planets. As a proof-of-concept, our current atmospheric model contains 1 or 2 cloud layers, methane as a major absorber, and a H2-He background gas. This 6-to-9 parameter model is appropriate for Jupiter-like planets and can be easily expanded in the future. In addition to deriving the marginal likelihood distribution and confidence intervals for the model parameters, we perform model selection to determine the significance of methane and cloud detection as a function of expected signal-to-noise, in the presence of spectral noise correlations. After internal validation, the method is applied to realistic reflected-light spectra of Jupiter, Saturn, and HD 99492 c, a likely observing target. We find that the presence or absence of clouds and methane can be determined with high accuracy, while parameters uncertainties are model-dependent.

Enviro-HIRLAM online integrated meteorology-chemistry modelling system: strategy, methodology, developments and applications (v7.2)

NASA Astrophysics Data System (ADS)

Baklanov, Alexander; Smith Korsholm, Ulrik; Nuterman, Roman; Mahura, Alexander; Pagh Nielsen, Kristian; Hansen Sass, Bent; Rasmussen, Alix; Zakey, Ashraf; Kaas, Eigil; Kurganskiy, Alexander; Sørensen, Brian; González-Aparicio, Iratxe

2017-08-01

The Environment - High Resolution Limited Area Model (Enviro-HIRLAM) is developed as a fully online integrated numerical weather prediction (NWP) and atmospheric chemical transport (ACT) model for research and forecasting of joint meteorological, chemical and biological weather. The integrated modelling system is developed by the Danish Meteorological Institute (DMI) in collaboration with several European universities. It is the baseline system in the HIRLAM Chemical Branch and used in several countries and different applications. The development was initiated at DMI more than 15 years ago. The model is based on the HIRLAM NWP model with online integrated pollutant transport and dispersion, chemistry, aerosol dynamics, deposition and atmospheric composition feedbacks. To make the model suitable for chemical weather forecasting in urban areas, the meteorological part was improved by implementation of urban parameterisations. The dynamical core was improved by implementing a locally mass-conserving semi-Lagrangian numerical advection scheme, which improves forecast accuracy and model performance. The current version (7.2), in comparison with previous versions, has a more advanced and cost-efficient chemistry, aerosol multi-compound approach, aerosol feedbacks (direct and semi-direct) on radiation and (first and second indirect effects) on cloud microphysics. Since 2004, the Enviro-HIRLAM has been used for different studies, including operational pollen forecasting for Denmark since 2009 and operational forecasting atmospheric composition with downscaling for China since 2017. Following the main research and development strategy, further model developments will be extended towards the new NWP platform - HARMONIE. Different aspects of online coupling methodology, research strategy and possible applications of the modelling system, and fit-for-purpose model configurations for the meteorological and air quality communities are discussed.

MARLI: MARs LIdar for global climate measurements from orbit

NASA Astrophysics Data System (ADS)

Allan, G. R.; Riris, H.; Sun, X.; Yu, A. W.; Abshire, J. B.

2017-12-01

NASA-GSFC is developing a pulsed multifunction lidar instrument to remotely measure winds in the Martian atmosphere from orbit. The key capabilities of this multifunctional atmospheric pulsed lidar will include continuous measurement of the aerosol backscatter profiles, the cross polarized (ice) backscatter profiles, the Doppler (wind profiles), and the range to the scattering surface from orbit. Our approach for MARLI is to use a direct detection lidar with efficient lasers, a large area low-mass telescope, a simple and rugged Doppler discriminator and with photon-sensitive detectors. The induced Doppler shifts on laser backscattered from aerosols in the Martian atmosphere will be detected using a time-resolved change in transmission through a solid etalon from two, slightly off-axis backscattered beams and the edge technique. In this presentation we report on the current progress of the core measurement of wind. We have demonstrated in the lab Doppler measurements down to 5m/s using a spinning target a pulsed lidar and edge technique. The laser is a seeded, pulsed-YAG in a MOPA configuration, operating at 1064nm producing pulses of 20ns and at a few mJ at 4KHz. Center frequency drift is less than 10MHz per minute. The Doppler discriminator is a solid etalon of 60 mm diameter and 40 mm thick with a peak transmission of over 65% and a bandpass of 100MHz FWHM. The detector is a cooled MCT array. We will also report on the deployment of the breadboard instrument to the GGAO to directly measure surface winds using the 48" telescope. The results from our field trials, the laser, detector and instrument will be more fully described in the presentation.

Effect of spanwise variations in gust intensity on the lift due to atmospheric turbulence

NASA Technical Reports Server (NTRS)

Diederich, Franklin W; Drischler, Joseph A

1957-01-01

The effect of spanwise variations in gust intensity on the power spectrum directly due to atmospheric turbulence is calculated for several analytic approximations to the correlation function or power spectra of atmospheric turbulence, for several spanwise weighing functions (span loadings), and for various angles of sweepback.

Dirty Snow, Atmospheric Warming, and Climate Feedbacks from Boreal Black Carbon Emissions

NASA Astrophysics Data System (ADS)

Flanner, M. G.; Zender, C. S.; Randerson, J. T.; Jin, Y.

2005-12-01

Black carbon (BC) emitted from boreal fires darkens snow and sea-ice surfaces, increases solar absorption in the atmosphere, and decreases the incident flux at the surface. Although global surface forcing of darkened snow/ice is small relative to atmospheric forcing, the former directly triggers ice-albedo feedback, whereas the latter directly alters the atmospheric lapse rate. This highlights the importance of examining climate feedback strength as well as instantaneous forcings. We used a coupled land-atmosphere GCM (NCAR CAM3) to compare the relative forcings and climate feedbacks of BC emitted from a suite of boreal forest fires over the last decade, accounting for both enhanced snow/ice and atmospheric absorption by BC. The net change in absorbed energy at the surface was about three times greater than the instantaneous surface forcing when BC interactively heated the snow. Timing and location of fires determined the magnitude of darkened snow/ice feedback potential. We also assessed climate feedback strength from BC emitted globally during extreme high and low fire years, including the 1998 fire season.

Atmospheric ions, boreal forests and impacts on climate

NASA Astrophysics Data System (ADS)

Manninen, H. E.; Nieminen, T.; Franchin, A.; Järvinen, E.; Kontkanen, J.; Hirsikko, A.; Hõrrak, U.; Mirme, A.; Tammet, H.; Kerminen, V.-M.; Petäjä, T.; Kulmala, M.

2012-04-01

Aerosol particles play an important role in the Earth's atmosphere and in the climate system: They scatter and absorb solar radiation, facilitate chemical processes, and serve as seeds for cloud formation. The aerosol particles have direct cooling and warming effects on climate (IPCC, 2007). Secondary new particle formation (NPF) is a globally important source of aerosol particles (Kulmala and Kerminen, 2008). Currently, the mechanisms of particle formation and the vapors participating in this process are, however, not truly understood. Several formation and growth mechanisms have been proposed for the very first steps of the process: homogeneous, heterogeneous, ion-induced and kinetic nucleation and activation type cluster growth. Small ions are part of the atmospheric aerosol spectrum, and in atmospheric sciences study of ion-aerosol interactions is essential. Small ions are small molecular clusters carrying a net electric charge. They are produced by ionisation of molecules in the air. Typically the small ion concentrations vary in the range of 100-2000 cm-3 in both polarities (Hirsikko et al., 2011). Ion-induced NPF is limited by the ion production rate, which typically is around 10 ion pairs cm-3s-1 in the boundary layer over the ground. The ion production rate has strong spatial and temporal dependence. The ionisation mechanisms change with altitude: radon and gamma radiation from the ground and galactic cosmic rays dominate close to the Earth's surface, while higher in the free troposphere cosmic rays become the main driving factor. In order to fully explain atmospheric NPF and subsequent growth, we need to measure directly the very initial steps of the formation processes. Air ion spectrometers measure the mobility distributions of charged aerosol particles in the mobility diameter range of 0.8-42 nm (Mirme et al., 2007; Tammet et al., 2011). Neutral cluster and air ion spectrometers measure additionally the mobility distribution of neutral particles larger than 2 nm in diameter by charging the aerosol sample with unipolar corona chargers (Manninen et al., 2009). According to earlier studies, the atmospheric nucleation and cluster activation take place at the mobility diameter range of 1.5-2 nm. Therefore, the ion spectrometers allow direct measurements at exactly the size where atmospheric nucleation takes place. The results indicate that the ion-induced nucleation contributes ~1-30% to the NPF events in most atmospheric conditions (Manninen et al., 2010). In other words, neutral particle formation seems to dominate over ion-mediated mechanisms, at least in the boreal forest conditions. Acknowledgements. This research was supported by the Academy of Finland Center of Excellence program (project number 1118615). Hirsikko, A. et al.: Atmospheric ions and nucleation: a review of observations, Atmos. Chem. Phys., 11, 767-798, 2011. IPCC, Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK and New York, NY, USA, 996 pp, 2007. Kulmala, M., and Kerminen, V.-M.: On the growth of atmospheric nanoparticles, Atmos. Res., 90, 132-150, 2008. Manninen, H.E. et al.: Long-term field measurements of charged and neutral clusters using Neutral cluster and Air Ion Spectrometer (NAIS). Boreal Env. Res. 14, 591-605, 2009. Manninen, H.E. et al., EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events, Atmos. Chem. Phys., 10, 7907-7927, 2010. Mirme, A. et al.: A Wide-range multi-channel Air Ion Spectrometer, Boreal Environ. Res., 12, 247-264, 2007. Tammet, H.: Symmetric inclined grid mobility analyzer for the measurement of charged clusters and fine nanoparticles in atmospheric air. Aerosol Science and Technology, 45, 468 - 479, 2011.

The Atmospheric Dynamics of Venus

NASA Astrophysics Data System (ADS)

Sánchez-Lavega, Agustín; Lebonnois, Sebastien; Imamura, Takeshi; Read, Peter; Luz, David

2017-11-01

We review our current knowledge of the atmospheric dynamics of Venus prior to the Akatsuki mission, in the altitude range from the surface to approximately the cloud tops located at about 100 km altitude. The three-dimensional structure of the wind field in this region has been determined with a variety of techniques over a broad range of spatial and temporal scales (from the mesoscale to planetary, from days to years, in daytime and nighttime), spanning a period of about 50 years (from the 1960s to the present). The global panorama is that the mean atmospheric motions are essentially zonal, dominated by the so-called super-rotation (an atmospheric rotation that is 60 to 80 times faster than that of the planetary body). The zonal winds blow westward (in the same direction as the planet rotation) with a nearly constant speed of ˜ 100 m s^{-1} at the cloud tops (65-70 km altitude) from latitude 50°N to 50°S, then decreasing their speeds monotonically from these latitudes toward the poles. Vertically, the zonal winds decrease with decreasing altitude towards velocities ˜ 1-3 m s^{-1} in a layer of thickness ˜ 10 km close to the surface. Meridional motions with peak speeds of ˜ 15 m s^{-1} occur within the upper cloud at 65 km altitude and are related to a Hadley cell circulation and to the solar thermal tide. Vertical motions with speeds ˜1-3 m s^{-1} occur in the statically unstable layer between altitudes of ˜ 50 - 55 km. All these motions are permanent with speed variations of the order of ˜10%. Various types of wave, from mesoscale gravity waves to Rossby-Kelvin planetary scale waves, have been detected at and above cloud heights, and are considered to be candidates as agents for carrying momentum that drives the super-rotation, although numerical models do not fully reproduce all the observed features. Momentum transport by atmospheric waves and the solar tide is thought to be an indispensable component of the general circulation of the Venus atmosphere. Another conspicuous feature of the atmospheric circulation is the presence of polar vortices. These are present in both hemispheres and are regions of warmer and lower clouds, seen prominently at infrared wavelengths, showing a highly variable morphology and motions. The vortices spin with a period of 2-3 days. The South polar vortex rotates around a geographical point which is itself displaced from the true pole of rotation by ˜ 3 degrees. The polar vortex is surrounded and constrained by the cold collar, an infrared-dark region of lower temperatures. We still lack detailed models of the mechanisms underlying the dynamics of these features and how they couple (or not) to the super-rotation. The nature of the super-rotation relates to the angular momentum stored in the atmosphere and how it is transported between the tropics and higher latitudes, and between the deep atmosphere and upper levels. The role of eddy processes is crucial, but likely involves the complex interaction of a variety of different types of eddy, either forced directly by radiative heating and mechanical interactions with the surface or through various forms of instability. Numerical models have achieved some significant recent success in capturing some aspects of the observed super-rotation, consistent with the scenario discussed by Gierasch (J. Atmos. Sci. 32:1038-1044, 1975) and Rossow and Williams (J. Atmos. Sci. 36:377-389, 1979), but many uncertainties remain, especially in the deep atmosphere. The theoretical framework developed to explain the circulation in Venus's atmosphere is reviewed, as well as the numerical models that have been built to elucidate the super-rotation mechanism. These tools are used to analyze the respective roles of the different waves in the processes driving the observed motions. Their limitations and suggested directions for improvements are discussed.

Earth-atmosphere system and surface reflectivities in arid regions from Landsat MSS data

NASA Technical Reports Server (NTRS)

Otterman, J.; Fraser, R. S.

1976-01-01

Previously developed programs for computing atmospheric transmission and scattering of the solar radiation are used to compute the ratios of the earth-atmosphere system (space) directional reflectivities in the nadir direction to the surface Lambertian reflectivity, for the four bands of the Landsat multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa, and Central America from the spectral radiance levels measured by the Landsat MSS. From these space reflectivities, surface reflectivities are computed applying the pertinent graphs. These surface reflectivities are used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory and in situ measurements.

A comparison of GLAS SAT and NMC high resolution NOSAT forecasts from 19 and 11 February 1976

NASA Technical Reports Server (NTRS)

Atlas, R.

1979-01-01

A subjective comparison of the Goddard Laboratory for Atmospheric Sciences (GLAS) and the National Meteorological Center (NMC) high resolution model forecasts is presented. Two cases where NMC's operational model in 1976 had serious difficulties in forecasting for the United States were examined. For each of the cases, the GLAS model forecasts from initial conditions which included satellite sounding data were compared directly to the NMC higher resolution model forecasts, from initial conditions which excluded the satellite data. The comparison showed that the GLAS satellite forecasts significantly improved upon the current NMC operational model's predictions in both cases.

Photographer : JPL Range : 6.5 million kilometers (4 million miles) Six violet images of Jupiter

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : 6.5 million kilometers (4 million miles) Six violet images of Jupiter makes the mosaic photo, showing the Great Red Spot as a swirling vortex type motion. This motion is also seen in several nearby white clouds. These bright white clouds and the Red Spot are rotating in a counter clockwise direction, except the peculiar filimentary cloud to the right of the Red Spot is going clockwise. The top of the picture shows the turbulence from the equatorial jet and more northerly atmospheric currents. The smallest clouds shown are only 70 miles (120 km) across.

Biogenic Aerosols – Effects on Climate and Clouds. Cloud Optical Depth (COD) Sensor Three-Waveband Spectrally-Agile Technique (TWST) Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niple, E. R.; Scott, H. E.

2016-04-01

This report describes the data collected by the Three-Waveband Spectrally-agile Technique (TWST) sensor deployed at Hyytiälä, Finland from 16 July to 31 August 2014 as a guest on the Biogenic Aerosols Effects on Climate and Clouds (BAECC) campaign. These data are currently available from the Atmospheric Radiation Measurement (ARM) Data Archive website and consists of Cloud Optical Depth (COD) measurements for the clouds directly overhead approximately every second (with some dropouts described below) during the daylight periods. A good range of cloud conditions were observed from clear sky to heavy rainfall.

Why is the VLT Very Efficient?

NASA Astrophysics Data System (ADS)

Comerón, F.

2009-09-01

The operations model of the ESO Very Large Telescope (VLT) heavily relies on a full-scale implementation of Service Mode observing. In this contribution we review the main features of ESO's approach to Service Mode at the VLT, we outline the advantages offered by this mode, and the challenges faced when implementing it given the wide diversity of instrumentation and instrument modes currently available at the VLT and the VLT Interferometer (VLTI). We give special emphasis to the part of this challenge directly derived from the evolution of the atmospheric conditions, which drive the short-term scheduling of the different scientific programmes competing for the available time.

Data Assimilation with the Extended Cmam: Nudging to Re-Analyses of the Lower Atmosphere

NASA Astrophysics Data System (ADS)

Fomichev, V. I.; Beagley, S. R.; Shepherd, M. G.; Semeniuk, K.; Mclandress, C. W.; Scinocca, J.; McConnell, J. C.

2012-12-01

The extended CMAM is currently being run in a forecast mode allowing the use of the model to simulate specific events. The current analysis period covers 1990-2010. The model is forced using ERA-Interim re-analyses via a nudging technique for the troposphere/stratosphere in combination with the GCM evolution in the lower atmosphere. Thus a transient forced model state is created in the lower atmosphere. The upper atmosphere is allowed to evolve in response to the observed conditions occurring in the lower atmosphere and in response to other transient forcing's such as SSTs, solar flux, and CO2 and CFC boundary changes. This methodology allows specific events and observations to be more successfully compared with the model. The model results compared to TOMS and ACE observations show a good agreement.

Operational Prototype Development of a Global Aircraft Radiation Exposure Nowcast

NASA Astrophysics Data System (ADS)

Mertens, Christopher; Kress, Brian; Wiltberger, Michael; Tobiska, W. Kent; Bouwer, Dave

Galactic cosmic rays (GCR) and solar energetic particles (SEP) are the primary sources of human exposure to high linear energy transfer (LET) radiation in the atmosphere. High-LET radiation is effective at directly breaking DNA strands in biological tissue, or producing chemically active radicals in tissue that alter the cell function, both of which can lead to cancer or other adverse health effects. A prototype operational nowcast model of air-crew radiation exposure is currently under development and funded by NASA. The model predicts air-crew radiation exposure levels from both GCR and SEP that may accompany solar storms. The new air-crew radiation exposure model is called the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. NAIRAS will provide global, data-driven, real-time exposure predictions of biologically harmful radiation at aviation altitudes. Observations are utilized from the ground (neutron monitors), from the atmosphere (the NCEP Global Forecast System), and from space (NASA/ACE and NOAA/GOES). Atmospheric observations characterize the overhead mass shielding and the ground-and space-based observations provide boundary conditions on the incident GCR and SEP particle flux distributions for transport and dosimetry calculations. Radiation exposure rates are calculated using the NASA physics-based HZETRN (High Charge (Z) and Energy TRaNsport) code. An overview of the NAIRAS model is given: the concept, design, prototype implementation status, data access, and example results. Issues encountered thus far and known and/or anticipated hurdles to research to operations transition are also discussed.

Dependence of Photochemical Escape of Oxygen at Mars on Solar Radiation and Solar Wind Interaction

NASA Astrophysics Data System (ADS)

Cravens, T.; Rahmati, A.; Lillis, R. J.; Fox, J. L.; Bougher, S. W.; Jakosky, B. M.

2016-12-01

The evolution of the atmosphere of Mars and the loss of volatiles over the life of the solar system is a key topic in planetary science. An important loss process in the ionosphere is photochemical escape. In particular, dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Several theoretical models have been constructed over the years to study hot oxygen and its escape from Mars. These model have a number of uncertainties, particularly for the elastic cross sections of O collisions with target neutral species. Recently, the Mars Atmosphere and Volatile Evolution Mission (MAVEN) mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., the solar wind). The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to: (1) study the role that solar flux and solar wind variations have on escape and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. Not surprisingly, we find, in agreement with more elaborate numerical models, that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The role for atmospheric loss that ion transport plays in the topside ionosphere and how the solar wind interaction drives this will also be discussed.

SOA formation from photooxidation of naphthalene and methylnaphthalenes with m-xylene and surrogate mixtures

NASA Astrophysics Data System (ADS)

Chen, Chia-Li; Li, Lijie; Tang, Ping; Cocker, David R.

2018-05-01

SOA formation is not well predicted in current models in urban area. The interaction among multiple anthropogenic volatile organic compounds is essential for the SOA formation in the complex urban atmosphere. Secondary organic aerosol (SOA) from the photooxidation of naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene as well as individual polycyclic aromatic hydrocarbons (PAHs) mixed with m-xylene or an atmospheric surrogate mixture was explored in the UCR CE-CERT environmental chamber under urban relevant low NOx and extremely low NOx (H2O2) conditions. Addition of m-xylene suppressed SOA formation from the individual PAH precursor. A similar suppression effect on SOA formation was observed during the surrogate mixture photooxidation suggesting the importance of gas-phase chemical reactivity to SOA formation. The SOA growth rate for different PAH-m-xylene mixtures was strongly correlated with initial [HO2]/[RO2] ratio but negatively correlated with initial m-xylene/NO ratio. Decreasing SOA formation was observed for increasing m-xylene/PAHs ratios and increasing initial m-xylene/NO ratio. The SOA chemical composition characteristics such as f44 versus f43, H/C ratio, O/C ratio, and the oxidation state of the carbon OSbarc were consistent with a continuously aging with the SOA exhibiting characteristics of both individual precursors. SOA formation from PAHs was also suppressed within an atmospheric surrogate mixture compared to the SOA formed from individual PAHs, indicating that atmospheric reactivity directly influences SOA formation from PAHs.

A super-Earth transiting a nearby low-mass star.

PubMed

Charbonneau, David; Berta, Zachory K; Irwin, Jonathan; Burke, Christopher J; Nutzman, Philip; Buchhave, Lars A; Lovis, Christophe; Bonfils, Xavier; Latham, David W; Udry, Stéphane; Murray-Clay, Ruth A; Holman, Matthew J; Falco, Emilio E; Winn, Joshua N; Queloz, Didier; Pepe, Francesco; Mayor, Michel; Delfosse, Xavier; Forveille, Thierry

2009-12-17

A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earth's mass (M[symbol:see text]), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b (refs 8, 9), but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55M[symbol:see text]), and a radius 2.68 times Earth's radius (R[symbol:see text]), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.

Algorithm for Atmospheric Corrections of Aircraft and Satellite Imagery

NASA Technical Reports Server (NTRS)

Fraser, Robert S.; Kaufman, Yoram J.; Ferrare, Richard A.; Mattoo, Shana

1989-01-01

A simple and fast atmospheric correction algorithm is described which is used to correct radiances of scattered sunlight measured by aircraft and/or satellite above a uniform surface. The atmospheric effect, the basic equations, a description of the computational procedure, and a sensitivity study are discussed. The program is designed to take the measured radiances, view and illumination directions, and the aerosol and gaseous absorption optical thickness to compute the radiance just above the surface, the irradiance on the surface, and surface reflectance. Alternatively, the program will compute the upward radiance at a specific altitude for a given surface reflectance, view and illumination directions, and aerosol and gaseous absorption optical thickness. The algorithm can be applied for any view and illumination directions and any wavelength in the range 0.48 micron to 2.2 micron. The relation between the measured radiance and surface reflectance, which is expressed as a function of atmospheric properties and measurement geometry, is computed using a radiative transfer routine. The results of the computations are presented in a table which forms the basis of the correction algorithm. The algorithm can be used for atmospheric corrections in the presence of a rural aerosol. The sensitivity of the derived surface reflectance to uncertainties in the model and input data is discussed.

Algorithm for atmospheric corrections of aircraft and satellite imagery

NASA Technical Reports Server (NTRS)

Fraser, R. S.; Ferrare, R. A.; Kaufman, Y. J.; Markham, B. L.; Mattoo, S.

1992-01-01

A simple and fast atmospheric correction algorithm is described which is used to correct radiances of scattered sunlight measured by aircraft and/or satellite above a uniform surface. The atmospheric effect, the basic equations, a description of the computational procedure, and a sensitivity study are discussed. The program is designed to take the measured radiances, view and illumination directions, and the aerosol and gaseous absorption optical thickness to compute the radiance just above the surface, the irradiance on the surface, and surface reflectance. Alternatively, the program will compute the upward radiance at a specific altitude for a given surface reflectance, view and illumination directions, and aerosol and gaseous absorption optical thickness. The algorithm can be applied for any view and illumination directions and any wavelength in the range 0.48 micron to 2.2 microns. The relation between the measured radiance and surface reflectance, which is expressed as a function of atmospheric properties and measurement geometry, is computed using a radiative transfer routine. The results of the computations are presented in a table which forms the basis of the correction algorithm. The algorithm can be used for atmospheric corrections in the presence of a rural aerosol. The sensitivity of the derived surface reflectance to uncertainties in the model and input data is discussed.

Degree and Direction of Polarization of Multiple Scattered Light. 2: Earth's Atmosphere with Aerosols.

PubMed

Plass, G N; Kattawar, G W

1972-12-01

The degree of polarization as well as the direction of the polarization are calculated by a Monte Carlo method for the reflected and transmitted photons from the earth's atmosphere. The solar photons are followed through multiple collisions with the aerosols and the Rayleigh scattering centers in the atmosphere. The aerosol number density as well as the ratio of aerosol to Rayleigh scattering vary with height. The aerosol index of refraction is assumed to be 1.55. The proportion of aerosol to Rayleigh scattering is appropriately chosen at each wavelength (lambda = 0.4 micro and 0.7 micro); ozone absorption is included where appropriate. Three different aerosol number densities are used to study the effects of aerosol variations. Results are given for a solar zenith angle of 81.37 degrees and various surface albedos. The radiance and polarization of the reflected and transmitted photons is particularly sensitive to the amount of aerosols in the atmosphere at certain angles of observation. The direction of pola ization shows little dependence on the surface albedo.

Investigations on physics of planetary atmospheres and small bodies of the Solar system, extrasolar planets and disk structures around the stars

NASA Astrophysics Data System (ADS)

Vidmachenko, A. P.; Delets, O. S.; Dlugach, J. M.; Zakhozhay, O. V.; Kostogryz, N. M.; Krushevska, V. M.; Kuznyetsova, Y. G.; Morozhenko, O. V.; Nevodovskyi, P. V.; Ovsak, O. S.; Rozenbush, O. E.; Romanyuk, Ya. O.; Shavlovskiy, V. I.; Yanovitskij, E. G.

2015-12-01

The history and main becoming stages of Planetary system physics Department of the Main astronomical observatory of National academy of Sciences of Ukraine are considered. Fundamental subjects of department researches and science achievements of employees are presented. Fields of theoretical and experimental researches are Solar system planets and their satellites; vertical structures of planet atmospheres; radiative transfer in planet atmospheres; exoplanet systems of Milky Way; stars having disc structures; astronomical engineering. Employees of the department carry out spectral, photometrical and polarimetrical observations of Solar system planets, exoplanet systems and stars with disc structures. 1. From the history of department 2. The main directions of department research 3. Scientific instrumentation 4. Telescopes and observation stations 5. Theoretical studies 6. The results of observations of planets and small Solar system bodies and their interpretation 7. The study of exoplanets around the stars of our galaxy 8. Spectral energy distribution of fragmenting protostellar disks 9. Cooperation with the National Technical University of Ukraine (KPI) and National University of Ukraine "Lviv Polytechnic" to study the impact of stratospheric aerosol changes on weather and climate of the Earth 10. International relations. Scientific and organizational work. Scientific conferences, congresses, symposia 11. The main achievements of the department 12. Current researches 13. Anniversaries and awards

Comparison of Global Martian Plasma Models in the Context of MAVEN Observations

NASA Astrophysics Data System (ADS)

Egan, Hilary; Ma, Yingjuan; Dong, Chuanfei; Modolo, Ronan; Jarvinen, Riku; Bougher, Stephen; Halekas, Jasper; Brain, David; Mcfadden, James; Connerney, John; Mitchell, David; Jakosky, Bruce

2018-05-01

Global models of the interaction of the solar wind with the Martian upper atmosphere have proved to be valuable tools for investigating both the escape to space of the Martian atmosphere and the physical processes controlling this complex interaction. The many models currently in use employ different physical assumptions, but it can be difficult to directly compare the effectiveness of the models since they are rarely run for the same input conditions. Here we present the results of a model comparison activity, where five global models (single-fluid MHD, multifluid MHD, multifluid electron pressure MHD, and two hybrid models) were run for identical conditions corresponding to a single orbit of observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We find that low-altitude ion densities are very similar across all models and are comparable to MAVEN ion density measurements from periapsis. Plasma boundaries appear generally symmetric in all models and vary only slightly in extent. Despite these similarities there are clear morphological differences in ion behavior in other regions such as the tail and southern hemisphere. These differences are observable in ion escape loss maps and are necessary to understand in order to accurately use models in aiding our understanding of the Martian plasma environment.

Procedure for generating global atmospheric engine emissions data from future supersonic transport aircraft. The 1990 high speed civil transport studies

NASA Technical Reports Server (NTRS)

Sohn, R. A.; Stroup, J. W.

1990-01-01

The input for global atmospheric chemistry models was generated for baseline High Speed Civil Transport (HSCT) configurations at Mach 1.6, 2.2, and 3.2. The input is supplied in the form of number of molecules of specific exhaust constituents injected into the atmosphere per year by latitude and by altitude (for 2-D codes). Seven exhaust constituents are currently supplied: NO, NO2, CO, CO2, H2O, SO2, and THC (Trace Hydrocarbons). An eighth input is also supplied, NO(x), the sum of NO and NO2. The number of molecules of a given constituent emitted per year is a function of the total fuel burned by a supersonic fleet and the emission index (EI) of the aircraft engine for the constituent in question. The EIs for an engine are supplied directly by the engine manufacturers. The annual fuel burn of a supersonic fleet is calculated from aircraft performance and economic criteria, both of which are strongly dependent on basic design parameters such as speed and range. The altitude and latitude distribution of the emission is determined based on 10 Intern. Air Transport Assoc. (IATA) regions chosen to define the worldwide route structure for future HSCT operations and the mission flight profiles.

Sterilization by negative and positive DC plasma with a micro discharge gap at atmospheric pressure

NASA Astrophysics Data System (ADS)

Li, Hua; Jiang, Lin-Xiu; Jiang, Yong-Rong; Zhu, Jian-Min; Chen, Zhen-Cheng

2017-11-01

A new needle-to-droplet electrode structure with a micro discharge gap (2 mm) was designed to achieve direct current (DC) discharge plasma in ambient air with the aim of using the plasma to sterilize liquids. Without using noble gases or an external air flow, we succeeded in generating both a negative and positive DC plasma at atmospheric pressure. The plasma was driven by a 0 to -20,000 V, 100 W DC power supply. A stainless steel needle with a tip diameter of ˜ 50μm and a 200-μL droplet of bacteria-containing liquid served as the electrodes. At atmospheric pressure and room temperature (23∘C), utilizing the negative DC plasma, the discharge time lasted 10 s; the results showed that the higher the discharge voltage, the more efficient the sterilization effect. Conversely, when we applied a voltage of -5.5 kV, we found that the sterilization effect was more efficient for longer discharge times. Our findings demonstrate that Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) can be killed in about 30 s. Our experiments show that our sterilization method required less time and was more efficient for positive than for negative DC plasma under the same conditions.

Experimental Investigation of Pulsed Nanosecond Streamer Discharges for CO2 Reforming

NASA Astrophysics Data System (ADS)

Pachuilo, Michael; Levko, Dima; Raja, Laxminarayan; Varghese, Philip

2016-09-01

Rapid global industrialization has led to an increase in atmospheric greenhouse gases, specifically carbon dioxide levels. Plasmas present a great potential for efficient reforming of greenhouse gases. There are several plasma discharges which have been reported for reforming process: dielectric barrier discharges (DBD), microwave discharges, and glide-arcs. Microwave discharges have CO2 conversion energy efficiency of up to 40% at atmospheric conditions, while glide-arcs have 43% and DBD 2-10%. In our study, we analyze a single nanosecond pulsed cathode directed streamer discharge in CO2 at atmospheric pressure and temperature. We have conducted time resolved imaging with spectral bandpass filters of a streamer discharge with an applied negative polarity pulse. The image sequences have been correlated to the applied voltage and current pulses. From the spectral filters we can determine where spatially and temporally excited species are formed. In this talk we report on spectroscopic studies of the discharge and estimate plasma properties such as temperature and density of excited species and electrons. Furthermore, we report on the effects of pulse polarity as well as anodic streamer discharges on the CO2 conversion efficiency. Finally, we will focus on the effects of vibrational excitation on carbon dioxide reforming efficiency for streamer discharges. Our experimental results will be compared with an accompanying plasma computational model studies.

Occurrence and persistence of future atmospheric stagnation events

NASA Astrophysics Data System (ADS)

Horton, Daniel E.; Skinner, Christopher B.; Singh, Deepti; Diffenbaugh, Noah S.

2014-08-01

Poor air quality causes an estimated 2.6-4.4 million premature deaths per year. Hazardous conditions form when meteorological components allow the accumulation of pollutants in the near-surface atmosphere. Global-warming-driven changes to atmospheric circulation and the hydrological cycle are expected to alter the meteorological components that control pollutant build-up and dispersal, but the magnitude, direction, geographic footprint and public health impact of this alteration remain unclear. We used an air stagnation index and an ensemble of bias-corrected climate model simulations to quantify the response of stagnation occurrence and persistence to global warming. Our analysis projects increases in stagnation occurrence that cover 55% of the current global population, with areas of increase affecting ten times more people than areas of decrease. By the late twenty-first century, robust increases of up to 40 days per year are projected throughout the majority of the tropics and subtropics, as well as within isolated mid-latitude regions. Potential impacts over India, Mexico and the western US are particularly acute owing to the intersection of large populations and increases in the persistence of stagnation events, including those of extreme duration. These results indicate that anthropogenic climate change is likely to alter the level of pollutant management required to meet future air quality targets.

Correspondence between sound propagation in discrete and continuous random media with application to forest acoustics.

PubMed

Ostashev, Vladimir E; Wilson, D Keith; Muhlestein, Michael B; Attenborough, Keith

2018-02-01

Although sound propagation in a forest is important in several applications, there are currently no rigorous yet computationally tractable prediction methods. Due to the complexity of sound scattering in a forest, it is natural to formulate the problem stochastically. In this paper, it is demonstrated that the equations for the statistical moments of the sound field propagating in a forest have the same form as those for sound propagation in a turbulent atmosphere if the scattering properties of the two media are expressed in terms of the differential scattering and total cross sections. Using the existing theories for sound propagation in a turbulent atmosphere, this analogy enables the derivation of several results for predicting forest acoustics. In particular, the second-moment parabolic equation is formulated for the spatial correlation function of the sound field propagating above an impedance ground in a forest with micrometeorology. Effective numerical techniques for solving this equation have been developed in atmospheric acoustics. In another example, formulas are obtained that describe the effect of a forest on the interference between the direct and ground-reflected waves. The formulated correspondence between wave propagation in discrete and continuous random media can also be used in other fields of physics.

The Reference Forward Model (RFM)

NASA Astrophysics Data System (ADS)

Dudhia, Anu

2017-01-01

The Reference Forward Model (RFM) is a general purpose line-by-line radiative transfer model, currently supported by the UK National Centre for Earth Observation. This paper outlines the algorithms used by the RFM, focusing on standard calculations of terrestrial atmospheric infrared spectra followed by a brief summary of some additional capabilities and extensions to microwave wavelengths and extraterrestrial atmospheres. At its most basic level - the 'line-by-line' component - it calculates molecular absorption cross-sections by applying the Voigt lineshape to all transitions up to ±25 cm-1 from line-centre. Alternatively, absorptions can be directly interpolated from various forms of tabulated data. These cross-sections are then used to construct infrared radiance or transmittance spectra for ray paths through homogeneous cells, plane-parallel or circular atmospheres. At a higher level, the RFM can apply instrumental convolutions to simulate measurements from Fourier transform spectrometers. It can also calculate Jacobian spectra and so act as a stand-alone forward model within a retrieval scheme. The RFM is designed for robustness, flexibility and ease-of-use (particularly by the non-expert), and no claims are made for superior accuracy, or indeed novelty, compared to other line-by-line codes. Its main limitations at present are a lack of scattering and simplified modelling of surface reflectance and line-mixing.

Ancient low–molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw

USGS Publications Warehouse

Drake, Travis W.; Wickland, Kimberly P.; Spencer, Robert G. M.; McKnight, Diane M.; Striegl, Robert G.

2015-01-01

Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high–temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low–molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters.

Ancient low-molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw.

PubMed

Drake, Travis W; Wickland, Kimberly P; Spencer, Robert G M; McKnight, Diane M; Striegl, Robert G

2015-11-10

Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high-temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low-molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters.

Ancient low–molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw

PubMed Central

Drake, Travis W.; Wickland, Kimberly P.; Spencer, Robert G. M.; McKnight, Diane M.; Striegl, Robert G.

2015-01-01

Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high–temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low–molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters. PMID:26504243