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  • 1
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    Validation of CLAES ClONO 2 measurements
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 9603-9620
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 9603-9620
    Abstract: The cryogenic limb array etalon spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite has made extensive measurements of thermal infrared radiation from the Earth's limb from which vertical concentration profiles of several stratospheric gases and multiwavelength aerosol absorption coefficients have been retrieved for the period from January 9, 1992, to May 5, 1993. This work examines stratospheric ClONO 2 concentrations from the current calibration and retrieval software which are designated version 7 data. These data provide the first near‐global view of this stratospheric species. This work evaluates data quality through (1) an analysis of estimated uncertainties and biases in the remote sensing process, (2) comparison with calculations using a two‐dimensional chemical model, (3) comparison with correlative data, and (4) an examination of various known limitations. The precision of CLAES ClONO 2 volume mixing ratio retrievals are within 15% in the range (10 〈 P 〈 50 mbar). The upper limit on estimated systematic error is 28% in the range (10 〈 P 〈 100 mbar) based on studies of error sources in midlatitude retrievals. The global distribution of ClONO 2 computed with the Lawrence Livermore National Laboratory two‐dimensional stratospheric chemistry model and the CLAES measurements agree qualitatively. However, above the profile peak the calculated concentration frequently exceeds the measurement. CLAES and ATMOS measurements show relatively good midlatitude agreement, suggesting that the major source of discrepancy is in the model. A possible explanation in terms of a missing reaction ClO + OH → HCl + O 2 is suggested. Also, the ClONO 2 diurnal cycle constructed from more than 30 days of CLAES data agrees well with the model. The CLAES ClONO 2 data diifer from correlative data acquired on flights of the shuttle‐based ATMOS and balloon‐borne instruments by less than 25% on the average in the 10 〈 P 〈 50 mbar range. At altitudes above 10 mbar the CLAES measurement is biased low with respect to correlative measurements. This discrepancy at high altitudes is consistent with the analysis showing a large increase of systematic errors above 10 mbar. Heavy tropical volcanic aerosol from the Mount Pinatubo eruption in June 1991 apparently interfered with ClONO 2 retrievals in the period before July 1992, causing anomalous peaks in the 20 〈 P 〈 30 mbar region accompanied by very small concentrations below the peak (P 〉 30 mbar). A similar effect associated with thick polar stratospheric clouds is identified. Overall, this validation study indicates that the majority of these data are of good quality and should be very useful in quantitative and qualitative chemical studies of the stratosphere.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD00449
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 2
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    Calibration of the Total Carbon Column Observing Network using aircraft profile data
    Copernicus GmbH ; 2010
    In:  Atmospheric Measurement Techniques Vol. 3, No. 5 ( 2010-10-06), p. 1351-1362
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 3, No. 5 ( 2010-10-06), p. 1351-1362
    Abstract: Abstract. The Total Carbon Column Observing Network (TCCON) produces precise measurements of the column average dry-air mole fractions of CO2, CO, CH4, N2O and H2O at a variety of sites worldwide. These observations rely on spectroscopic parameters that are not known with sufficient accuracy to compute total columns that can be used in combination with in situ measurements. The TCCON must therefore be calibrated to World Meteorological Organization (WMO) in situ trace gas measurement scales. We present a calibration of TCCON data using WMO-scale instrumentation aboard aircraft that measured profiles over four TCCON stations during 2008 and 2009. These calibrations are compared with similar observations made in 2004 and 2006. The results indicate that a single, global calibration factor for each gas accurately captures the TCCON total column data within error.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-3-1351-2010
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2010
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  • 3
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    Validation of ACE-FTS v2.2 measurements of HCl, HF, CCl〈sub〉3〈/sub〉F and CCl〈sub〉2〈/sub〉F〈sub〉2〈/sub〉 using space-, balloon- and ground-based instrument observations
    Copernicus GmbH ; 2008
    In:  Atmospheric Chemistry and Physics Vol. 8, No. 20 ( 2008-10-27), p. 6199-6221
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 8, No. 20 ( 2008-10-27), p. 6199-6221
    Abstract: Abstract. Hydrogen chloride (HCl) and hydrogen fluoride (HF) are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made halogenated source gases, in particular CFC-11 (CCl3F) and CFC-12 (CCl2F2), during the second half of the 20th century. It is important to continue monitoring the evolution of these source gases and reservoirs, in support of the Montreal Protocol and also indirectly of the Kyoto Protocol. The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is a space-based instrument that has been performing regular solar occultation measurements of over 30 atmospheric gases since early 2004. In this validation paper, the HCl, HF, CFC-11 and CFC-12 version 2.2 profile data products retrieved from ACE-FTS measurements are evaluated. Volume mixing ratio profiles have been compared to observations made from space by MLS and HALOE, and from stratospheric balloons by SPIRALE, FIRS-2 and Mark-IV. Partial columns derived from the ACE-FTS data were also compared to column measurements from ground-based Fourier transform instruments operated at 12 sites. ACE-FTS data recorded from March 2004 to August 2007 have been used for the comparisons. These data are representative of a variety of atmospheric and chemical situations, with sounded air masses extending from the winter vortex to summer sub-tropical conditions. Typically, the ACE-FTS products are available in the 10–50 km altitude range for HCl and HF, and in the 7–20 and 7–25 km ranges for CFC-11 and -12, respectively. For both reservoirs, comparison results indicate an agreement generally better than 5–10% above 20 km altitude, when accounting for the known offset affecting HALOE measurements of HCl and HF. Larger positive differences are however found for comparisons with single profiles from FIRS-2 and SPIRALE. For CFCs, the few coincident measurements available suggest that the differences probably remain within ±20%.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-8-6199-2008
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2008
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  • 4
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    Validation of nitric oxide and nitrogen dioxide measurements made by the Halogen Occultation Experiment for UARS platform
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 10241-10266
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 10241-10266
    Abstract: The Halogen Occultation Experiment (HALOE) experiment on Upper Atmosphere Research Satellite (UARS) performs solar occultation (sunrise and sunset) measurements to infer the composition and structure of the stratosphere and mesosphere. Two of the HALOE channels, centered at 5.26 μm and 6.25 μm, are designed to infer concentrations of nitric oxide and nitrogen dioxide respectively. The NO measurements extend from the lower stratosphere up to 130 km, while the NO 2 results typically range from the lower stratosphere to 50 km and higher near the winter terminator. Comparison with results from various instruments are presented, including satellite‐, balloon‐, and ground‐based measurements. Both NO and NO 2 can show large percentage errors in the presence of heavy aerosol concentrations, confined to below 25 km and before 1993. The NO 2 measurements show mean differences with correlative measurements of about 10 to 15% over the middle stratosphere. The NO 2 precision is about 7.5 × 10 −13 atm, degrading to 2 × 10 −12 atm in the lower stratosphere. The NO differences are similar in the middle stratosphere but sometimes show a low bias (as much as 35%) between 30 and 60 km with some correlative measurements. NO precision when expressed in units of density is nearly constant at 1 × 10 −12 atmospheres, or approximately 0.1 ppbv at 10.0 mb or 1.0 ppbv at 1.0 mb, and so forth when expressed in mixing ratio. Above 65 km, agreement in the mean with Atmospheric Trace Molecule Spectroscopy (ATMOS) NO results is very good, typically ±15%. Model comparisons are also presented, showing good agreement with both expected morphology and diurnal behavior for both NO 2 and NO.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD02143
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 5
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    Comparison of CLAES preliminary N 2 O 5 data with correlative data and a model
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 9657-9677
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 9657-9677
    Abstract: The cryogenic limb etalon array spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite (UARS) has made near‐global measurements of N 2 O 5 . Data for 388 days have been processed to version 7 (V7) for the period from January 9, 1992, to April 25, 1993. Results from UARS instruments, including CLAES and the improved stratospheric and mesospheric sounder (ISAMS) provide the first near‐global N 2 O 5 measurements. Retrieval below 3.16 mbar is adversely affected by aerosols and above 1.47 mbar by lack of signal and possible instrument effects, so data usage is recommended for just the three “UARS pressure surfaces” 3.16, 2.15, and 1.47 mbar. A comparison of the diurnal data variation with the model suggests there are offsets in the data that are to first order diurnally independent. These offsets are tabulated to facilitate subtraction, which is recommended for most data applications. Candidate mechanisms for the offsets are discussed. Comparisons of CLAES data with the offsets subtracted, with profiles obtained by the shuttle‐deployed Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment and concurrent ISAMS profiles, and with a profile obtained by the balloon‐borne NASA Jet Propulsion Laboratory (JPL) MARK IV instrument, show poorest agreement in equatorial regions at 3.15 mbar where CLAES values are larger by about 30 to 40%. At higher altitudes and latitudes the comparison improves and tends toward consistency with systematic error estimates that are based on instrument and retrieval process characterization and range from 14% at 3.16 mbar to 21% at 1.47 mbar. A similar estimate of random CLAES error ranges from 7% at 3.16 mbar to 26% at 1.47 mbar. By comparison, the average values of the error estimates generated by the production processing algorithm at 3.16 and 1.47 mbar are 8 and 36%, respectively, and the average values derived from the observed data variability are 19 and 24%. Confidence is enhanced by the good global scale agreement and correlation of CLAES and ISAMS during an N 2 O 5 enhancement event in early–mid‐January 1992 polar winter, in which values 〉 5.5 parts per billion at 3.16 mbar by volume are observed. A description of artifacts that may occur at 3.16 mbar and much less frequently at 2.15 mbar, during this and other enhancement conditions, and the demonstrated approach to eliminate these in future versions, is given in the text.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD03767
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 6
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    Subsidence, mixing, and denitrification of Arctic polar vortex air measured during POLARIS
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Atmospheres Vol. 104, No. D21 ( 1999-11-20), p. 26611-26623
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 104, No. D21 ( 1999-11-20), p. 26611-26623
    Abstract: We determine the degree of denitrification that occurred during the 1996–1997 Arctic winter using a technique that is based on balloon and aircraft borne measurements of NO y , N 2 O, and CH 4 . The NO y /N 2 O relation can undergo significant change due to isentropic mixing of subsided vortex air masses with extravortex air due to the high nonlinearity of the relation. These transport related reductions in NO y can be difficult to distinguish from the effects of denitrification caused by sedimentation of condensed HNO 3 . In this study, high‐altitude balloon measurements are used to define the properties of air masses that later descend in the polar vortex to altitudes sampled by the ER‐2 aircraft (i.e., ∼20 km) and mix isentropically with extravortex air. Observed correlations of CH 4 and N 2 O are used to quantify the degree of subsidence and mixing for individual air masses. On the basis of these results the expected mixing ratio of NO y resulting from subsidence and mixing, defined here as NO y **, is calculated and compared with the measured mixing ratio of NO y . Values of NO y and NO y ** agree well during most parts of the flights. A slight deficit of NO y versus NO y ** is found only for a limited region during the ER‐2 flight on April 26, 1997. This deficit is interpreted as indication for weak denitrification (∼2–3 ppbv) in that air mass. The small degree of denitrification is consistent with the general synoptic‐scale temperature history of the sampled air masses, which did not encounter temperatures below the frostpoint and had relatively brief encounters with temperatures below the nitric acid trihydrate equilibrium temperature. Much larger degrees of denitrification would have been inferred if mixing effects had been ignored, which is the traditional approach to diagnose denitrification. Our analysis emphasizes the importance of using other correlations of conserved species to be able to accurately interpret changes in the NO y /N 2 O relation with respect to denitrification.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD900463
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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  • 7
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    Comparison of MkIV balloon and ER‐2 aircraft measurements of atmospheric trace gases
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Atmospheres Vol. 104, No. D21 ( 1999-11-20), p. 26779-26790
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 104, No. D21 ( 1999-11-20), p. 26779-26790
    Abstract: On May 8, 1997, vertical profiles of over 30 different gases were measured remotely in solar occultation by the Jet Propulsion Laboratory MkIV Interferometer during a balloon flight launched from Fairbanks, Alaska. These gases included H 2 O, N 2 O, CH 4 , CO, NO x , NO y , HCl, ClNO 3 , CCl 2 F 2 , CCl 3 F, CCl 4 , CHClF 2 , CClF 2 CCl 2 F, SF 6 , CH 3 Cl, and C 2 H 6 , all of which were also measured in situ by instruments on board the NASA ER‐2 aircraft, which was making flights from Fairbanks during this same early May time period as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) experiment. A comparison of the gas volume mixing ratios in the upper troposphere and lower stratosphere reveals agreement better than 5% for most gases. The three significant exceptions to this are SF 6 and CCl 4 for which the remote measurements exceed the in situ observations by 15–20% at all altitudes, and H 2 O for which the remote measurements are up to 30% smaller than the in situ observations near the hygropause.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD900379
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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  • 8
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    The budget and partitioning of stratospheric chlorine during the 1997 Arctic summer
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Atmospheres Vol. 104, No. D21 ( 1999-11-20), p. 26653-26665
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 104, No. D21 ( 1999-11-20), p. 26653-26665
    Abstract: Volume mixing ratio profiles of HCl, HOCl, ClNO 3 , CH 3 Cl, CFC‐12, CFC‐11, CCl 4 , HCFC‐22, and CFC‐113 were measured simultaneously from 9 to 38 km by the Jet Propulsion Laboratory MkIV Fourier Transform Infrared solar absorption spectrometer during two balloon flights from Fairbanks, Alaska (64.8°N), on May 8 and July 8, 1997. The altitude variation of total organic chlorine (CCl y ), total inorganic chlorine (Cl y ), and the nearly constant value (3.7±0.2 ppbv) of their sum (Cl TOT ) demonstrates that the stratospheric chlorine species available to react with O 3 are supplied by the decomposition of organic chlorinated compounds whose abundances are well quantified. Measured profiles of HCl and ClNO 3 agree well with profiles found by photochemical model (differences 〈 10% for altitudes below 35 km) constrained by various other constituents measured by MkIV. The production of HCl by ClO + OH plays a relatively small role in the partitioning of HCl and ClNO 3 for the sampled air masses. However, better agreement with the measured profiles of HCl and ClNO 3 is obtained when this source of HCl is included in the model. Both the measured and calculated [ClNO 3 ]/[HCl] ratios exhibit the expected near linear variation with [O 3 ] 2 /[CH 4 ] over a broad range of altitudes. MkIV measurements of HCl, ClNO 3 , and CCl y agree well with ER‐2 in situ observations of these quantities for directly comparable air masses. These results demonstrate good understanding of the budget of stratospheric chlorine and that the partitioning of inorganic chlorine is accurately described by photochemical models that employ JPL97 reaction rates and production of HCl from ClO + OH for the environmental conditions encountered: relatively warm temperatures, long periods of solar illumination, and relatively low aerosol surface areas.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD900245
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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  • 9
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    Comparison of correlative data with HNO 3 version 7 from the CLAES instrument deployed on the NASA Upper Atmosphere Research Satellite
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 9621-9656
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 9621-9656
    Abstract: The cryogenic limb array etalon spectrometer (CLAES) aboard UARS made near‐global measurements of HNO 3 and 388 days from January 9, 1992, to April 25, 1993, have been processed to data version 7 (V7). Results from UARS instruments, including CLAES, the improved stratospheric and mesospheric sounder, and the microwave limb sounder, provide the first near‐global documentation of the evolution of denitrification in the Antarctic 1992 winter and spring vortex. We provide a description of the CLAES HNO 3 V7 quality that includes comparisons with correlative measurements to assess overall quality, accuracy, and precision. Correlative profiles of volume mixing ratio (vmr) included those obtained by the space shuttle deployed ATMOS in two missions, March–April 1992 and April 1993, data from a variety of balloon‐borne instruments at midlatitude (11 profiles), and in high‐latitude northern winter (six profiles), and LIMS data. In general, the CLAES V7 HNO 3 maximum values of vmr were of the order of 6–15% less than correlative for CLAES values ≤8 parts per billion by volume (ppbv). However, when CLAES peak vmr values were 10 to 13 ppbv, then CLAES values exceeded correlative by 0–7%. The comparisons were within the combined instrumental error estimates, or observed measurement variability, for the large majority of comparisons. As discussed, the retrieval of future versions will utilize updated spectral parameters and will also correct for a small uncompensated drift in radiometric calibration that occurred in the latter part of the mission. This is expected to improve the comparisons in the ≤8 ppbv range, perhaps at the expense of those in the ≥8 ppbv range. The data obtained January 9 to April 15, 1992, in comparison with data obtained January 9 to April 15, 1993, reveal strikingly evident 1‐year period deseasonalized trends on a global basis. These trends agree quantitatively with available correlative data suitable for trend analysis. These include ATMOS in the southern midlatitudes and published long‐term time series of HNO 3 column obtained at 45°S and 20°N. These trends reveal a large decrease in the southern hemisphere and small increases in the northern hemisphere, such that the global average is toward a decrease. The global average decrease we attribute to the diminishing influence of heterogeneous conversion of N 2 O 5 to HNO 3 as the Pinatubo aerosol settles out during this time period, and the HNO 3 recovers toward pre‐Pinatubo conditions. We establish plausibility that the small increases in the north are due to hemispherically asymmetric QBO‐like effects that are strong in the northern hemisphere and weak in the southern hemisphere and are phased to produce an increase in HNO 3 over the 1‐year time period of just the right magnitude to more than offset decrease due to settling out of the Pinatubo aerosol. Based on this study, our range of confidence in the CLAES HNO 3 V7 product is from 70 to 3 mbar, in comparison with correlative data, and the precision on this range is of the order of 0.3–1.0 ppbv. This precision was derived from data repeatability and agrees within a factor of 2 or better with estimates based on instrument characterization and with error estimates embedded within the V7 data.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD03759
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 10
    Online Resource
    Online Resource
    A comparison of Arctic HNO 3 profiles measured by the Improved Limb Atmospheric Spectrometer and balloon‐borne sensors
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Atmospheres Vol. 105, No. D5 ( 2000-03-16), p. 6761-6771
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 105, No. D5 ( 2000-03-16), p. 6761-6771
    Abstract: The Improved Limb Atmospheric Spectrometer (ILAS), a solar occultation infrared satellite sensor, was launched in August 1996. The ILAS validation balloon campaigns were carried out from Kiruna, Sweden (68°N, 21°E), in February and March 1997 and Fairbanks, Alaska (65°N, 148°W), in April and May 1997. During these campaigns, measurements of nitric acid (HNO 3 ) were made using infrared emission spectrometers (Cold Atmospheric Emission Spectral Radiometer, Michelson Interferometer for Passive Atmospheric Sounding‐Balloon‐Borne version 2, and farinfrared spectrometer) and infrared solar occultation spectrometers (Limb Profile Monitor of the Atmosphere and Mark IV interferometer). An in situ experiment (Chemiluminescence Detector) measured total reactive nitrogen (NO y ,), from which HNO 3 mixing ratios in the lower stratosphere were calculated. In addition, an in situ NO y , measurement was also made at 12 km altitude from the Deutsche Luft‐und Raumfahrt Falcon aircraft in January 1997. The ILAS version 3.10 HNO 3 mixing ratios obtained at the nearest location and averaged ILAS mixing ratios obtained within certain criteria were compared with the balloon data. The precision of the ILAS measurements was estimated from the random differences to be 0.8 parts per billion by volume (ppbv), corresponding to about 35% at 15 km and 10–15% at 20–35 km. While the absolute accuracy estimated from the systematic differences was as good as 0.5 ppbv (5%) at 20 km, the ILAS HNO 3 mixing ratios were systematically lower than the balloon values by 1 ppbv (15–20%) at 25–30 km. The error in the altitude registration in the ILAS retrieval algorithm is a possible cause for the negative bias at higher altitudes.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD901057
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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