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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Utilizing Earth Observations of Soil Freeze/Thaw Data and Atmospheric Concentrations to Estimate Cold Season Methane Emissions in the Northern High Latitudes

The northern wetland methane emission estimates have large uncertainties. Inversion models are a qualified method to estimate the methane fluxes and emissions in northern latitudes but when atmospheric observations are sparse, the models are only as good as their a priori estimates. Thus, improving a priori estimates is a competent way to reduce uncertainties and enhance emission estimates in the sparsely sampled regions. Here, we use a novel way to integrate remote sensing soil freeze/thaw (F/T) status from SMOS satellite to better capture the seasonality of methane emissions in the northern high latitude. The SMOS F/T data provide daily information of soil freezing state in the northern latitudes, and in this study, the data is used to define the cold season in the high latitudes and, thus, improve our knowledge of the seasonal cycle of biospheric methane fluxes. The SMOS F/T data is implemented to LPX-Bern DYPTOP model estimates and the modified fluxes are used as a biospheric a priori in the inversion model CarbonTracker Europe-CH 4 . The implementation of the SMOS F/T soil state is shown to be beneficial in improving the inversion model’s cold season biospheric flux estimates. Our results show that cold season biospheric CH4 emissions in northern high latitudes are approximately 0.60 Tg lower than previously estimated, which corresponds to 17% reduction in the cold season biospheric emissions. This reduction is partly compensated by increased anthropogenic emissions in the same area (0.23 Tg), and the results also indicates that the anthropogenic emissions could have even larger contribution in cold season than estimated here.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Computational Fluid Dynamics Modeling of Solar Thermal Dry Reforming of Methane in a Parabolic Trough

Computational fluid dynamics simulations of solar-thermal dry reforming of methane using a parabolic trough configuration were performed. Parametric simulations of different combinations of gas flow rate, receiver tube emissivity, and geometric concentration ratio were conducted to determine configurations that could achieve the required catalyst temperatures of at least 700 °C to achieve high conversion of CH4 and CO2 to H2 and CO. Results showed that the concentration ratio of the parabolic trough collector had to be increased from ~70 to ~120 and the receiver-tube emissivity had to be reduced to ~0.2 to achieve bulk average catalyst temperatures of greater than 700 °C. Lower gas flow rates also reduced enthalpic heat losses and increased catalyst temperatures.

Ho, Clifford↗
DOE OSTI2020

NGEE Arctic Soil Micro-warming Experiment Temperature Profiles, Council Road Mile Marker 71, Seward Peninsula, Alaska, 2017-2019

The reported soil temperature profile measurements (24 locations - 2 probes with 5 and 6 thermistors, respectively - Fig. 1 and Fig. 2) were initiated as part of a soil micro-warming experiment at the Council Road Mile Marker 71 Site (CN_MM71) in September 2017. From 2017 through August 2019, these were measurements of ambient pre-treatment plot conditions. This tussock tundra site (with underlying permafrost) experiences annual frost heaving that causes a vertical movement of the ground surface, hence causing some of the upper most temperature thermistors to be at surface level or above ground and recorded therefore air temperatures near the surface and not below ground soil temperature (see section on Quality Assurance). After August 2019, these measurements ended in preparation for transitioning to the experimental warming of individual plots. The reported temperature data are nominally 3-hour averages of measurements made at varying frequencies (3-hour maximum) with frequencies that depended upon power (solar) availability to operate the sensors (see section in documentation on Methods). The number of values and the standard deviation for each 3-hour average (where appropriate) are also provided. These measurements are located near the NGEE-Arctic CO2 and CH4 eddy covariance tower at the Council Road Site (US-NGC: NGEE Arctic Council, https://ameriflux.lbl.gov/sites/siteinfo/US-NGC#overview) and auxiliary data at https://doi.org/10.5440/1526749. This dataset contains four *.csv files and one *.pdf file. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1971

Filament-wound, fiberglass cryogenic tank supports

The design, fabrication, and testing of filament-wound, fiberglass cryogenic tank supports for a LH2 tank, a LF2/FLOX tank and a CH4 tank. These supports consist of filament-wound fiberglass tubes with titanium end fittings. These units were satisfactorily tested at cryogenic temperatures, thereby offering a design that can be reliably and economically produced in large or small quantities. The basic design concept is applicable to any situation where strong, lightweight axial load members are desired.

Carter, J. S.↗
NASA NTRS1972

Technology Development of a Biowaste Resistojet, Volume 2

The thruster development effort of the biowaste resistojet program is reported. Under this program, several variations of the concentric tube resistojet were built and tested. Because of the corrosive nature of the biowaste gases available for propellants, thruster effort was concentrated on the use of noble metals (platinum and its alloys) for the critical center tube heating element. This tube must operate at high temperatures. Initially the biowaste gases were projected to be CO2, CH4, H2O or H2 with only very small amounts of O2 or N2. However, during 1971, results from experimental life support tests indicated that the oxygen content would probably be in the range from 0.5 to 1.0%. To achieve the desired high specific impulses, metal temperatures as high as 1700 K (3060 R) were considered desirable goals. The first thruster, designated Mark 1, employed the alloy platinum-rhodium for the center tube. Although this material was oxidation resistant and had high strength relative to pure platinum, experimental materials tests showed that this alloy suffered from carbonyl reactions when tested on pure CO2. These reactions resulted in a depletion of rhodium and significantly weakened the tubes. The next series of thrusters were designated Mark 2 and employed platinum-iridium for the center tubes.

Phillips, D. G.↗
NASA NTRS1971

Absorbing ice model of interstellar grains.

Extinction curves have been calculated for Mie scattering by grains with a refractive index m equals to n - ik, where n was between 1.3 and 2.0 and k varied from 0 to 0.5. A good fit for the observed interstellar extinction in the wavelength region of 0.1 to 2.0 microns was obtained for particles with a radius of 0.1 micron and m equal to 1.3 - 0.2i. Inclusion of the changes in the refractive index in the vacuum ultraviolet region due to the strong absorptions of methane, ammonia and water does not appreciably alter these results. Theoretical extinction curves for the composite medium of H2O, NH3, CH4, and graphite show a general agreement with the observed interstellar reddening curve over the whole spectral range, in addition to producing kinks in the far-ultraviolet region.

Swamy, K. S. K.↗
NASA NTRS1972

Photochemistry and lifetimes of interstellar molecules.

Quantitative discussion of the photochemistry and lifetime against photodecomposition of five interstellar molecules: H2CO, NH3, H2O, CH4, and CO. For the first four molecules, primary photochemical decomposition processes yielding atomic and molecular hydrogen are considered in addition to photoionization. The quantum yield for decomposition of these molecules is unity. For CO, only decomposition to ground-state carbon and oxygen atoms occur, but the quantum yield is not known and may be considerably less than unity. The radiation field in obscuring clouds is estimated, using an interstellar extinction curve for the Perseus region.

Stief, L. J.↗
NASA NTRS1972

Foreign-gas broadening of nitrous oxide absorption lines.

We have measured the foreign-gas broadening coefficients for collisional broadening of lines in the nu-3 fundamental of N2O by He, Ne, Ar, Kr, Xe, H2, D2, and CH4. These coefficients, which give the ratio of the line-broadening ability of these gases to the line-broadening ability of N2, can be used with recent measurements and calculations of N2 broadening to obtain optical collision cross sections.

Tubbs, L. D.↗
NASA NTRS1972

The composition of the Martian atmosphere - Minor constituents.

The Mariner 6 and 7 infrared spectrometers provided data which, in principle, determine upper limits on the possible atmospheric abundance of every gaseous substance that was undetected but which has recognized absorptions in the accessible spectral region, 1.9 to 14.4 microns. Through supporting laboratory determinations of curves of growth under pressure-broadening conditions appropriate to Mars, upper limits can be specified (expressed first in cm-atm, STP, for a vertical column and then in parts per million) for NO2, NH3, C3O2, SO2, OCS, NO, O3, CH4, N2O, HCL, HBr, and H2S. In addition, considerations of band contours, moments of inertia, and experimental absorption coefficients make it possible to place useful upper limits on 27 additional substances that were not detected and for which curves of growth have not been measured.

Horn, D.↗
NASA NTRS1972

Total absorption cross sections of several gases of aeronomic interest at 584 A.

Total photoabsorption cross sections have been measured at 584.3 A for N2, O2, Ar, CO2, CO, NO, N2O, NH3, CH4, H2, and H2S. A monochromator was used to isolate the He I 584 line produced in a helium resonance lamp, and thin aluminum filters were used as absorption cell windows, thereby eliminating possible errors associated with the use of undispersed radiation or windowless cells. Sources of error are examined, and limits of uncertainty are given. Previous relevant cross-sectional measurements and possible error sources are reviewed. Wall adsorption as a source of error in cross-sectional measurements has not previously been considered and is discussed briefly.

Starr, W. L.↗
NASA NTRS1972

Upper limits for an atmosphere on Io.

The May 14, 1971, occultation of beta Scorpii C by Io was successfully observed in ultraviolet light near Kingston, Jamaica. Within the limits established by time resolution and the signal-to-noise ratio, both the disappearance and reappearance were found to be instantaneous. Upper limits for the surface pressure for N2, CH4, and H2 atmospheres are 0.09, 0.13, and 44. microbar, respectively. The corresponding number densities are 6.2 x 10 to the 12th power, 9.4 x 10 to the 12th power, and 3.2 x 10 to the 15th power per cu cm. An isothermal atmosphere at a temperature of 100 K was assumed.

Smith, B. A.↗
NASA NTRS1972

Recent developments in the inversion by the method of relaxation

The relaxation method for inverse solution of the full radiative transfer equation is generalized to solve for all the atmospheric parameters that appear in the integrand as functions or functionals, without any a priori information about the expected solution. Illustrations are presented using the 7.5 micron CH4 band for determining temperature profiles in the Jovian atmosphere, and the 6.3 micron band for determining the water vapor mixing ratio in the earth's atmosphere.

Chahine, M. T.↗
NASA NTRS1972

Nature and Origin of Cometary Heads

In cometary spectra the three major constituents seem to be OH, H, and O. Their common precursor is likely to be water, whose rates of evaporation and dissociation have so far not led to a major discrepancy with the observations. This type of explanation, however, has not led to a positive identification of other parent molecules. With the known solar intensities, all the molecules that have been suggested, as NH3, CH4, etc, would lead to lifetimes one-to-two orders of magnitude larger than needed by the coma observations. An alternate hypothesis is that the precursors are not molecules, but icy particles stripped from the nucleus by the evaporating gases. By evaporating within an icy halo, the grains would liberate either parent molecules with very short lifetimes or some of the radicals themselves. Recent laboratory work suggests that the grains could be made of clathrate hydrates of gases or of radicals. The observations appear to indicate the presence of icy grains within the inner coma.

Delsemme, A. H.↗
NASA NTRS1973

Development of a breadboard model correlation interferometer for the carbon monoxide pollution experiment

The breadboard model of the correlation interferometer for the Carbon Monoxide Pollution Experiment has been designed, fabricated, and tested. Laboratory, long-path, and atmospheric tests which were performed show the technique to be a feasible method for obtaining a global carbon monoxide map and a vertical carbon monoxide profile and similar information is readily obtainable for methane as well. In addition, the technique is readily applicable to other trace gases by minor instrumental changes. As shown by the results and the conclusions, it has been determined that CO and CH4 data can be obtained with an accuracy of 10% using this technique on the spectral region around 2.3 microns.

Bortner, M. H.↗
NASA NTRS1973

Development of large diameter carbon monofilament

A process for preparing large diameter carbon-boron monofilament was developed. The process involves chemical vapor depositing a carbon-boron alloy monofilament from a BCl3, CH4, and H2 gas mixture onto a carbon substrate. Amorphous alloys were formed when gaseous mixtures containing greater than 20 percent methane (80 percent BCl3) were used. The longest uninterrupted lengths of carbon-boron monofilament were produced using a CH4/BCl3 gas ratio of 2.34. It was found that the properties of the carbon-boron alloy monofilament improved when the carbon substrate was precleaned in chlorine. The highest strength monofilament was attained when a CH4/BCl3 gas volume ratio of 0.44 was 28 million N/sq cm (40 million psi). While the highest strengths were attained in this run, the 0.44 gas ratio and other CH4/BCl3 ratios less than 2.34 would not yield long runs. Runs using these ratios were usually terminated because of a break in the monofilament within the reactor. It is felt better process control could probably be achieved by varying the amount of hydrogen; the BCl3/H2 ratio was kept constant in these studies.

Jacob, B.↗
NASA NTRS1973

A spectroscopic study of CW chemical lasers.

A subsonic transverse-flow chemical laser has been instrumented to permit measurements of vibration-rotation state populations and laser output spectra under flow conditions typical of present CW hydrogen halide laser operation. Measurements are presented for the F + HI, F + HBr, F + CH4, F + HCl, F + H2, Cl + HI, and Cl + HBr atom-exchange reaction systems. CW operation was found to be characterized by relatively modest departures from Maxwell-Boltzmann vibrational energy distributions at all stages of reaction in contrast to pulsed operation based on similar reactions.

Rosen, D. I.↗
NASA NTRS1973

Infrared spectra of the Galilean satellites of Jupiter.

Spectra of the four Galilean satellites from 1 to 4 microns were obtained with a Michelson interferometer. The spectra show that the albedo of Io is quite flat and shows no absorptions in the region observed. Europa and Ganymede have large amounts of water ice on their surface. Callisto shows some faint ice absorptions. Upper limits of 0.5 cm-atm (STP) corresponding to .00000006 atm partial surface pressure were set for CH4 and NH3 on all four satellites.

Fink, U.↗