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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

An assessment of OH airglow interference on the remote sensing of stratospheric HCl via limb sounding in the near-I.R.

Chemiluminescent emission from the formation of vibrationally excited OH at an altitude of approximately 85 km presents a barrier to earth-limb measurements of NIR emissions originating in the stratosphere. High-resolution measured spectra of OH airglow have not been reported, and thus it is difficult to assess its impact on moderately-high-resolution earth-limb spectroscopy capable of looking between strong OH lines. Low-resolution rocketborne spectrometer earth-limb measurements of OH airglow are mathematically inverted to recover vibrational-state populations that are used to simulate a higher resolution spectrum in the neighbourhood of 2843/cm. Implications for remote sensing HCl are presented.

Mergenthaler, J. L.↗
NASA NTRS1987

Airborne intercomparison of nitric oxide measurement techniques

Results from an airborne intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted during missions flown in the fall of 1983 and spring of 1984. Instruments intercompared included a laser-induced fluorescence (LIF) system and two chemiluminescence instruments (CL). NO mixing ratios from below 5 pptv (parts per trillion by volume) to greater than 100 pptv were reported, with the majority less than 20 pptv. Good correlation was observed between the measurements reported by the CL and LIF techniques. The general level of agreement observed for the ensemble of measurements obtained during the two missions provides the basis from which one can conclude that equally 'valid' measurements of background levels of NO can be expected from either CL or LIF instruments. At the same time the periods of disagreement that were observed between the CL and LIF instruments as well as between the two CL instruments highlight the difficulty of obtaining reliable measurements with NO mixing ratios in the 5-20 pptv range and emphasize the vigilance that should be maintained in future NO measurements.

Hoell, James M., Jr.↗
NASA NTRS1987

Comparison of in situ stratospheric ozone measurements obtained during the MAP/GLOBUS 1983 campaign

Data from five types of in situ ozone sensors flown aboard ballons during the MAP/GLOBUS 1983 campaign were found to agree to within 5 percent uncertainty throughout the middle atmosphere. A description of the individual techniques and the error budget is given in addition to explanations for the discrepancies found at higher and lower altitudes. In comparison to UV photometry values, results from two electrochemical techniques were found to be greater in the lower atmosphere and to be lower in the upper atmosphere. In general, olefin chemiluminescence results were within 8 percent of the UV photometry results. Ozone column contents measured by the indigo colorization technique for two altitude regions of about 6 km height were greater than measurements from other techniques by 52 and 17 percent, respectively.

Aimedieu, P.↗
NASA NTRS1987

Determination of O2(a1Delta g) and O2(b1Sigma + g) yields in the reaction O + ClO yields Cl + O2 - Implications for photochemistry in the atmosphere of Venus

A discharge flow apparatus with a chemiluminescence detector was used to investigate the reaction O + ClO yields Cl + O2(asterisk), where O2(asterisk) = O2(a1Delta g) or O2(b1Sigma + g). It is found that the observed O2(a1Delta g) airglow of Venus cannot be explained in the framework of standard photochemistry using the experimental results obtained here and those reported in the recent literature. The possibility of an alternative source of O atoms derived from SO2 photolysis in the Venus mesosphere is suggested.

Leu, Ming-Taun↗
NASA NTRS1988

Measurements of NO and total reactive odd-nitrogen, NOy, in the Antarctic stratosphere

Measurements of NO and total reactive N, NOy, were made as part of the Airborne Antarctic Ozone Experiment conducted in Punta Arenas, Chile during Aug. and Sept. 1987. The total reactive N reservoir includes the species NO, NO2, NO3, N2 O5, HNO3, and ClONO2. The instrument was located on board the NASA ER2 aircraft which conducted 12 flights over the Antarctic continent reaching altitudes of 18 km at 72 deg S latitude. The NOy technique utilized the conversion of component NOy species to NO on a gold catalyst and the subsequent detection of NO by the chemiluminescence reaction of NO with ozone. Since the inlet sample line is heated and the catalyst operates at 300 C, NOy incorporated in aerosols evaporates and is converted to NO. NO was measured on two separate flights by removing the catalyst from the sample inlet line.

Fahey, D. W.↗
NASA NTRS1989

Measurements of nitric oxide in the stratosphere at 44 N in autumn

Precision of the chemiluminescent instrument for balloon-borne NO measurement was improved by precise determinations of the flow rates of the sample air and the calibration NO in N2 gas. Based on the new calibration of these values, NO mixing ratio in the stratosphere was reanalyzed. The revision of the NO data does not at all alter the form of the diurnal variation. The average of the four NO profiles between 15 and 32 km obtained at 44 N in autumn is given.

Kondo, Y.↗
NASA NTRS1988

An intercomparison of results from ferrous sulphate and photolytic converter techniques for measurements of NO(x) made during the NASA GTE/CITE 1 aircraft program

Two techniques designed for measurements of NO(x (NO + NO2) were intercompared during aircraft flights made in the spring of 1984 in the middle free troposphere over the eastern Pacific Ocean and southwestern U.S. One NO chemiluminescence instrument was equipped with a ferrous sulphate converter, another with a photolytic converter. The ferrous sulphate-equipped instrument was apparently much less specific for NO2. It registered levels about three times larger than the photolytic converter and gave NO2/NO ratios that were much larger than photochemical calculations would indicate as reasonable. Additionally, the results imply that active NO(x) was only 10-20 percent of the total odd nitrogen in the middle free troposphere.

Ridley, B. A.↗
NASA NTRS1988

Intercomparison of NO column measurements during MAP/GLOBUS 1985

Simultaneous NO column measurements made in France in September, 1985, using several techniques, are compared with one another. The observed NO distributions vary significantly from day to day. It is shown that NO measurements using IR or UV absorption are self-consistent and show good agreement with predictions from a one-dimensional photochemical model. In situ chemiluminescent measurements produced NO columns which were systematically higher than those predicted.

Mckenzie, R. L.↗
NASA NTRS1989

Profiles of nitric oxide in the upper stratosphere

Results are presented from NO measurements obtained with a chemiluminescent NO detector and an in situ ozone instrument aboard high altitude balloons launched at Air sur L'Adour and Gap, France. NO profiles were obtained between 35 and 40 km in the late morning of September 17, 1987 and the early afternoon of June 18, 1988. The average NO concentration was 9 ppbv at 35 km, increasing with altitude to 11.5 ppbv at 40 km. The difference in the temperature profile significantly contributes to the observed change in the NO concentration.

Kondo, Y.↗
NASA NTRS1990

A mid-latitude balloon-borne observation of total odd nitrogen

A balloon-borne instrument to measure total odd nitrogen NO(y) has been developed. A converter which enables catalytic conversion of NO(y) into nitric oxide on a heated gold surface is combined with a chemiluminescence detector. The conversion efficiency for NO2 was measured to be close to 100 percent at pressures between 60 and 7 mb. The major source of errors in the balloon-borne measurements are the uncertainties in the estimates of the sample flow rate and the zero level of the instrument. The NO(y) concentration was measured at altitudes between 12 and 28 km with a precision of about 25 percent on a balloon experiment conducted at latitude 44 deg N in June 1989. The NO(y) concentration has been measured to be 1.5 + or - 0.4, 3 + or - 0.7, 10 + or - 3, and 14 + or - 4 ppbv at altitudes of 17, 20, 25, and 28 km, respectively.

Kondo, Y.↗
NASA NTRS1990

An intercomparison of airborne nitrogen dioxide instruments

Results on NO2 instruments are reported from the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instruments tested were (1) a two-photon LIF system using a laser for NO2-NO photolysis, (2) a chemiluminescence (CL) detector using FeSO4 for NO2-NO conversion, (3) a CL detector using an arc lamp for NO2-NO photolysis, and (4) a tunable-laser-diode multipath-absorption system. The procedures for the CITE 2 ground-based and flight tests are described in detail, and the results are presented in extensive graphs. Instrument (2) was eliminated because the FeSO4 converted atmospheric PAN to NO, resulting in spuriously high NO2 values. The remaining instruments gave readings in 30-40-percent agreement at NO2 mixing ratios of 100-200 parts per trillion by volume (pptv). At ratios below 50 pptv, the correlation among the measurements was very poor, with a tendency for system (4) to give higher values than (1) or (3).

Gregory, G. L.↗
NASA NTRS1990

An intercomparison of airborne nitric oxide measurements - A second opportunity

Results are reported from a comparison of three tropospheric NO measurement instruments during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The instruments tested were those used in CITE 1 (Hoell et al., 1987): a two-photon LIF system and two chemiluminescence systems. It is found that the mixing ratios obtained with the three systems agreed to within 15-20 parts per trillion volume (pptv) for sampling perods of 1-6 min at mixing ratios less than 20 pptv; the average difference between pairs of measurements was 5-7 pptv, which is considered to be the uncertainty in state-of-the-art ambient NO measurements.

Gregory, Gerald L.↗
NASA NTRS1990

Measurements of the nitric acid to NO(x) ratio in the troposphere

Nitric acid concentrations, measured by both teflon/nylon filter packs (FP) and the tungstic oxide denuder (DEN), are compared with the average NO(x) concentrations from LIF and chemiluminescent methods. The HNO3/NO(x) ratio based on FPs ranged from 0.8 to 10.4, with a mean of 3.4. The DEN nitric acid concentrations produced ratios ranging from less than 0.3 to 9.8, with a mean of 2.6. Average marine ratios were larger than those from continental regions, in part due to continental anthropogenic sources of NO(x).

Huebert, B. J.↗
NASA NTRS1990

Observed and model-calculated NO2/NO ratios in tropospheric air sampled during the NASA GTE/CITE-2 field study

Airborne measurements of NO2/NO ratios in the free troposphere, obtained using two-photon LIF (TP-LIF) and chemiluminescence (CL) detectors during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986, are analyzed and compared with the predictions of a photochemical model. The derivation of the model is outlined, with an emphasis on the role of peroxy radicals in the fast photochemical cycling of NO and NO2 and the production of O3; the CITE 2 instruments and flight protocols are described; and the results are presented in extensive tables and graphs and discussed in detail. It was found that on three CITE 2 flights the CL data were systematically greater than the TP-LIF data; when these data were removed, the averaged values of the two instruments agreed to within 1 percent. The NO2/NO ratios predicted by the model are shown to be consistent with the measurements, although usually 20-25 percent lower.

Chameides, W. L.↗
NASA NTRS1990

Diurnal variation of nitric oxide in the upper stratosphere

Two recent measurements of the temporal variation of nitric oxide at constant altitude near 40 km are reported. The observations were made at float altitude with a balloon-borne chemiluminescence detector together with in situ ozone measurements. The first measurement was made at 44 N on September 17, 1987, at an altitude of 40 km from before sunrise until 1000 LT. The second observation was made at the same latitude on June 18, 1988, at 39 km from 0800 to 1230 LT. At an altitude of 40 km, nitric oxide was observed to start increasing very rapidly at sunrise when the solar zenith angle reached about 95 deg. After the rapid initial buildup, the rate of NO increase stabilized for 3 hours at about 1.2 ppbv/hour. Near 1100 LT at 39 km in summer, the NO mixing ratio was observed to become nearly constant. These features of the diurnal variation of NO are in accord with the temporal variation expected from a time-dependent zero-dimensional photochemical model.

Kondo, Y.↗
NASA NTRS1991

Soil emissions of nitric oxide in a seasonally dry tropical forest of Mexico

Soil emissions of NO were measured at the Chamela Biological Station, Mexico, using soil covers and a field apparatus of NO detection based on CrO3 conversion of NO to NO2 and detection of NO2 by chemiluminescence with Luminol. Mean NO fluxes from forest soils ranged from 0.14 to 0.52 ng NO-N/sq cm/hr during the dry season and from 0.73 to 1.27 ng NO-N/sq cm/hr during the wet season. A fertilized floodplain pasture exhibited higher fluxes, but an unfertilized upland pasture, which represents the fastest growing land use in the region, had flux rates similar to the forest sites. Wetting experiments at the end of the dry season caused large pulses of NO flux, equaling 10 percent to 20 percent of the estimated annual NO emissions of 0.5-1.0 kg N/ha from the forest sites. Absence of a forest canopy during the dry season and the first wet season rain probably results in substantial NO(x) export from the forest system that may be important to regional atmospheric chemical processes. Wetting experiments during the wet season and a natural rain event had little or no stimulatory effect on NO flux rates.

Davidson, Eric A.↗
NASA NTRS1993

Sensitive, Selective Test For Hydrazines

Derivatives of hydrazines formed, then subjected to gas chromatography and detected via chemiluminescence. In method of detecting and quantifying hydrazine vapors, vapors reacted with dinitro compound to enhance sensitivity and selectivity. Hydrazine (HZ), monomethyl hydrazine, (MMH), and unsymmetrical dimethylhydrazine (UDMH) analyzed quantitatively and qualitatively, either alone or in mixtures. Vapors collected and reacted with 2,4-dinitrobenzaldehyde, (DNB), making it possible to concentrate hydrazine in derivative form, thereby increasing sensitivity to low initial concentrations. Increases selectivity because only those constituents of sample reacting with DNB concentrated for analysis.

Roundbehler, David↗
NASA NTRS1993

A detailed evaluation of the heating efficiency in the middle atmosphere

The role of airglow losses in reducing the efficiency of solar heating in the Hartley, Huggins, and Chappuis bands of ozone in the Herzberg, Ly alpha, Schumann-Runge continuum, and in Schumann-Runge bands of molecular oxygen is investigated together with the role of heating due to seven chemical reactions in the middle atmosphere. The results of calculations of bulk efficiencies demonstrate that airglow and chemiluminescent emission significantly reduce the amount of energy available for heat throughout the mesosphere and lower thermosphere.

Mlynczak, Martin G.↗