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  • 1
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    In situ measurements of the NO2/NO ratio for testing atmospheric photochemical models (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Simultaneous in situ measurements of NO2, NO, O3, ClO, pressure and temperature have been made for the first time, presenting a unique opportunity to test our current understanding of the photochemistry of the lower stratospere. Data were collected from several flights of the ER-2 aircraft at mid-latitudes in May 1993 during NASA's Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE). The daytime ratio of NO2/NO remains fairly constant at 19 km with a typical value of 0.68 and standard deviation of +/- 17. The ratio observations are compared with simple steady-state calculations based on laboratory-measured reaction rates and modeled NO2 photolysis rates. At each measurement point the daytime NO2/NO with its measurements uncertainty overlap the results of steady-state caculations and associated uncertainty. Possible sources of error are examined in both model and measurements. It is shown that more accurate laboratory determinations of the NO + 03 reaction rate and of the NO2 cross-sections in the 200-220 K temperature range characteristic of the lower stratosphere would allow for a more robust test of our knowledge of NO(X) phtochemistry by reducing significant sources if uncertainties in the interpretation of statospheric measurements.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2555-2558
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  • 2
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    Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses of up to 1 ppbv, which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less than 196 -/+ 4 kelvin. High ClO was always accompanied by loss of HCl mixing ratios equal to 1/2(ClO+ 2Cl2O2). These data indicate that the heterogeneous reaction HCl + ClONO2 - Cl2 + HNO3 on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO2, not HCl.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 261; 5125; p. 1130-1134.
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  • 3
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    The BLISS measurements of NO2 - Some new insights (1991)
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    Publication Date: 2011-08-24
    Description: The present study compares the diurnal variation of NO2 measured near 30 km by the BLISS in situ laser spectrometer with calculations from a photochemical model that includes a detailed description of multiple scattering. Even better agreement is found between the data and the model, both at sunset and during the day. The conclusions of an earlier study that the high-resolution in situ measurements of NO2 facilitated validation of the understanding of the diurnal chemistry of NO2 are confirmed.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 2261-226
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  • 4
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    Laboratory measurements of NO2 line parameters near 1600/cm for the interpretation of stratospheric spectra (1990)
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    Publication Date: 2011-08-19
    Description: Tunable diode laser laboratory measurements of infrared spectral parameters of selected NO2 lines near 1600/cm have been made to assess the contribution of uncertainties in these parameters to stratospheric measurements of NO2 made using the Balloon-Borne Laser In-Situ Sensor (BLISS) tunable diode laser spectrometer. Relative line intensities are measured to accuracies of better than 2 percent, with a root-sum-squared uncertainty in the absolute linestrengths of 4.5 percent. Air-broadening coefficients have been determined from measurements at total pressures in the range 20-100 Torr, at temperatures of 293 K and 214 K. These results are also discussed in the light of the discrepancies between infrared instruments flown in the 1982 and 1983 Balloon Intercomparison Campaigns.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2157-216
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  • 5
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    Theoretical interpretation of N2O5 measurements (1991)
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    Publication Date: 2011-08-19
    Description: Recent measurements by Webster et al. (1990) have confirmed quantitatively the chemistry controlling the nighttime decay of NO2. Simple equations describing the nighttime behavior of NO2 and N2O5 are presented here. With measurements of the nighttime ozone and NO2 concentrations, these equations can be used to predict the amount of N2O5 produced at any time during the night. In this way, the N2O5 nighttime emission measurement of Roscoe (1982), Kunde et al. (1988) and sunrise measurements of the ATMOS experiment are all used to test theory. The measurements are found to be both self consistent and confirm the present understanding of nighttime NO2 conversion to N2O5. The variation of N2O5 by a factor of two between measurements is found to be consistent with theory.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 1213-121
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  • 6
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    In situ stratospheric measurements of HNO3 and HCl near 30 km using the balloon-borne laser in situ sensor tunable diode laser spectrometer (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In situ stratospheric measurements of the concentrations of the reservoir species HNO3 and HCl made during two flights of the high-resolution (0.0005/cm) balloon-borne laser in situ sensor instrument from Palestine, Texas, are reported. A measured HNO3 volume mixing ratio of 4.3 parts per billion by volume (ppbv) at 31 km altitude is about 1 ppbv larger than previously reported measurements at 32 deg N. An HCl mixing ratio of 1.6 ppbv at 29 km is in agreement with values obtained from earlier remote sensing techniques within the experimental uncertainties. Upper limits at 31 km of 0.4 ppbv for H2O2 and 0.2 ppbv for HOCl are also derived from analyses of spectra recorded near 1252/cm.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 16343-16
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  • 7
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    An examination of the total hydrogen budget of the lower stratosphere (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We analyze the hydrogen budget of the lower stratosphere using simultaneous in situ measurements of northern hemispheric water vapor (H2O) and methane (CH4) obtained during the spring Stratospheric Photochemistry, Aerosols, and Dynamics Expedition (SPADE), as well as previously published in situ H2 data. Based on this data, we conclude that approximately two H2O molecules are produced for each CH4 molecule destroyed. This implies that H2 production from CH4 oxidation is balanced by H2 oxidation. The uncertainty in this analysis is greatly reduced by the use of multiple data sets. Additionally, we infer that, on an annual and global average, H2O enters the stratosphere with a mixing ratio of 4.2 +/- 0.5 ppmv, and that the quasi-conserved quantity 2 x CH4 + H2O has a value of 7.6 +/- 0.6 ppmv in these northern hemishere air parcels (where xi denotes the mixing ratio of the constituent xi).
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2563-2566
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  • 8
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    A case study of the mountain lee wave event of January 6, 1992 (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A mountain wave event, observed at the southern tip of Greenland on January 6, 1992, was corroborated by three experiments: the Meteorological Measurement System (MMS), the Microwave Temperature Profiler (MTP), and the Reactive Nitrogen Instrument (NO/NO(y)). Gravity wave signatures with classical phase relationship between wind and temperature were observed on both the outbound and inbound legs at different altitudes. The waves showed both vertically propagating and evanescent properties. Characteristics of the dominant wave mode are: wavelength about = 35 km; vertical displacement about = 0.8 km, and peak-to-peak vertical wind about = 6/ms. With the prevailing wind at about = 37/ms, the stratospheric temperature was reduced by 6K to 195.5 K within 8 minutes. The implication and potential impact of mountain lee waves on the formation of polar stratospheric clouds (PSC's) are discussed.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 22; p. 2551-2554
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  • 9
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    Hydrochloric acid and the chlorine budget of the lower statosphere (1994)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Concentrations of HCl measurements in the lower stratosphere in 1993 by the ALIAS instrument on the ER-2 aircraft reveal that only 40% of inorganic chlorine (Cl(y), inferred from in situ measurements of organic chlorinated sources gases) is present as HCl, significantly lower than model predictions. Although the sum of measured HCl, ClO and ClONO2, the latter inferred from measurements of ClO and NO2 equals Cl(y) to within the incertainty of measurement, it is systematically less than Cl(y) by 30-50%. This discrepancy suggests that concentrations of ClONO2 may exceed those of HC; near 20 km altitude, consistent with a slower photolysis rate for ClONO2 than calculated using recommended cross sections. Comparison of profiles of HCl measured during 1992 and 1193 at mid-latitudes by balloon (BLISS and MARKIV), space shuttle (ATMOS), and satellite (HALOE) instruments with the aircraft data reveal an apparent pressure dependence to the HCl to Cl(y) ratio, consistent with a factor of 3-10 reduction in the photolysis rate for ClONO2 at ER-2 altitudes. However, the diurnal variation of ClO is well-simulated by models using the recommended photolysis rate, and simulations measurements of ClONO2 and HCl at mid-latitudes by ATMOS and MARKIV report HCl (HCL+ ClONO2) ratios greater than or equal to 50%. Premliminary measurements by ALIAS in the southern hemisphere report HCl/Cl(y) values of about 75%.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2575-2578
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