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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
    Details
    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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    In situ measurements of the ClO/HCl ratio: Heterogeneous processing on sulfate aerosols and polar stratospheric clouds (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90 deg N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv, remarkably constant ClO/HCl values of about 15% characterize the lower stratosphere. The observed values are significantly higher than those derived from a 2-D model using either gas phase photochemistry alone (2%), or including heterogeneous sulfate chemistry (5-10%). During the Arctic early spring, after conversion of HCl into reactive chlorine has taken place, the vortex edge is poorly defined by ClO levels. Loss of HCl and its slow recovery following low-temperature polar heterogeneous chemistry distinguishes HCl as a new and unique dynamical tracer of polar stratospheric clouds (PSC)-processed air.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 22; p. 2523-2526
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  • 3
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    Aircraft laser infrared absorption spectrometer (ALIAS) for polar ozone studies (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The ALIAS instrument is a very high resolution (0.0003/cm) scanning, tunable diode laser spectrometer designed to make direct, simultaneous measurements of NO2, HNO3, HCl, CH4, and either O3 or N2O (including vertical profiles of CH4 and N2O) in the polar stratosphere at sub-part-per-billion level sensitivities over integration times from 3 to 30 s. Unique features include a sample inlet/throttle system designed to achieve near-isokinetic sampling, in PSC events, an in-flight wavelength reference cell rack, mechanical fringe-spoilers, a four-laser/four-detector dewar with 24-hr hold-time operating at a fixed temperature without electrical regulation, and in-flight fast correlation routines for spectral drift compensation prior to spectral addition. Instrument design and test flight results are discussed in the light of ALIAS's role in the Winter 1991 Arctic aircraft stratospheric ozone campaigns out of Fairbanks, Alaska, and Bangor, Maine.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 187-194.
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  • 4
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    Intercomparison of haloe and ER-2 aircraft H2O and CH4 observations collected during the second Airborne Arctic Stratospheric Experiment (AASE-II) (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: HALOE observations of H2O and CH4 are compared with in situ techniques aboard the ER-2 aircraft during the northern winter of 1991/92, in particular for the dates 911208, 920108, 920217, 920222, and 920320 when the spatial coincidences are close, within +/- 1 deg latitude and +/- 12 deg longitude. The results reveal the limitations of comparing high resolution in situ aircraft data with a remote sounding limb scanner. Of the five comparison dates, three had HALOE/ER-2 coincidences which occurred near the edge of the Arctic vortex; the vertical variability in the HALOE results and the horizontal variability in the ER-2 observations on these days show that the vortex edge is not a region where exact agreement can be expected except by chance. On a 4th comparison date, there was substantial overlap away from the vortex edge, although for some species the aircraft data show considerable variability near the coincidence point. On the 5th comparison date, the ER-2 had no overlap in altitude with the lowest HALOE observations; however, a short linear interpolation over about 1 km altitude results in smooth composite profiles. Generally speaking the agreement between HALOE and the ER-2 at overlap altitudes is about 12 percent in the case of water vapor, which shows low horizontal and vertical variability. The agreement for methane, with limited data having altitude overlap, is better than 6 percent.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 12; p. 1243-1246.
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  • 5
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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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  • 6
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    MOD: An Instrument for the 2005 Mars Explorer Program HEDS Payload (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Mars Organic Detector (MOD) was recently selected for the definition phase of the HEDS '05 (originally scheduled for '03) lander instrument package for fundamental biology and in situ resource utilization. MOD is designed to detect organic compounds in rock and soil samples directly on the surface of Mars in order to assess the biological potential of the planet. In addition, a MOD Tunable Diode Laser Spectrometer (TDLS) will provide information on desorption and decomposition temperatures, as well as the release rates and quantities of water and carbon dioxide that can be liberated from regolith samples, thereby providing the parameters needed for the design of systems for the future large-scale in situ extraction of valuable consumable resources. A MOD TDLS will also measure the atmospheric water and carbon dioxide content, as well as the atmospheric carbon dioxide isotopic composition, in order to determine whether there is an isotopic offset between atmospheric and surface carbon.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Concepts and Approaches for Mars Exploration; Part 1; 9-10; LPI-Contrib-1062
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  • 7
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    In Situ Measurements of the ClO/HCl Ratio: Heterogeneous Processing on Sulfate Aerosols and Polar Stratospheric Clouds (1993)
    In:  CASI
    Details
    Publication Date: 2005-06-09
    Description: Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90 deg N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv, remarkably constant ClO/HCl values of about 15% characterize the lower stratosphere. The observed values are significantly higher than those derived from a 2-D model using either gas phase photochemistry alone (2%), or including heterogeneous sulfate chemistry (5-10%). During the Arctic early spring, after conversion of HCl into reactive chlorine has taken place, the vortex edge is poorly defined by ClO levels. Loss of HCl and its slow recovery following low-temperature polar heterogeneous chemistry distinguishes HCl as a new and unique dynamical tracer of PSC-processed air.
    Keywords: Environment Pollution
    Type: Airborne Arctic Stratospheric Expedition 2 Air Parcel Trajectories (ISSN 0094-8534); Volume 20; No. 22; 2523-2526; NASA-TM-112699
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  • 8
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    A Case Study of the Mountain Lee Wave Event of January 6, 1992 (1993)
    In:  CASI
    Details
    Publication Date: 2005-06-09
    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 approximately equals 35 km, vertical displacement approximately equals 0.8 km, and peak-to-peak vertical wind approximately equals 6 ms-1. With the prevailing wind at approximately equals 37 m/s, the stratospheric temperature was reduced by 6 K 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: Meteorology and Climatology
    Type: Airborne Arctic Stratospheric Expedition 2 Air Parcel Trajectories (ISSN 0094-8534); Volume 20; No. 22; 2551-2554; NASA-TM-112699
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  • 9
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    The BLISS measurements of NO2 - Some new insights (1991)
    In:  Other Sources
    Details
    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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  • 10
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    Laboratory measurements of NO2 line parameters near 1600/cm for the interpretation of stratospheric spectra (1990)
    In:  Other Sources
    Details
    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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