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  • 1
    Online Resource
    Online Resource
    Development of the Antarctic ozone hole
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D15 ( 1996-09-20), p. 20909-20924
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D15 ( 1996-09-20), p. 20909-20924
    Abstract: A Lagrangian chemical model is used to simulate the formation of the Antarctic “ozone hole”: the decrease in high‐latitude southern hemisphere ozone between mid‐August and mid‐September of each year. The model benchmark simulation of HNO 3 , ClONO 2 , ClO, and ozone for September 17, 1992, is in good agreement with UARS observations. Simulations of the ozone column over the years 1979–1994 show quantitative agreement with the secular decline in Antarctic ozone and change in the area of the ozone hole as observed by the total ozone mapping spectrometer (TOMS). The model calculates that the Antarctic ozone loss and ozone hole area both increased linearly with time after the early 1970s until the early 1990s. After the early 1990s the growth of the area of the ozone hole slows as a result of the slowing of the growth rate of total inorganic chlorine. A hypothetical doubling of the 1992 atmospheric chlorine amount would expand the ozone hole to the very edge of the polar vortex.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD01707
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Validation studies using multiwavelength Cryogenic Limb Array Etalon Spectrometer (CLAES) observations of stratospheric aerosol
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 9757-9773
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 9757-9773
    Abstract: Validation studies of multiwavelength Cryogenic Limb Array Etalon Spectrometer (CLAES) observations of stratospheric aerosol are discussed. An error analysis of the CLAES aerosol extinction data is presented. Aerosol extinction precision values are estimated at latitudes and times at which consecutive Upper Atmosphere Research Satellite (UARS) orbits overlap. Comparisons of CLAES aerosol data with theoretical Mie calculations, based upon in situ particle size measurements at Laramie, Wyoming, are presented. CLAES aerosol data are also compared to scaled aerosol extinction measured by the Stratospheric Aerosol and Gas Experiment (SAGE II) and Atmospheric Trace Molecule Spectroscopy (ATMOS) experiments. Observed and calculated extinction spectra, from CLAES, Improved Stratospheric and Mesospheric Sounder (ISAMS), and Halogen Occultation Experiment (HALOE) data, are compared. CLAES extinction data have precisions between 10 and 25%, instrumental biases near 30%, and accuracies between 33 and 43%.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD03225
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
    detail.hit.zdb_id: 161666-3
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  • 3
    Online Resource
    Online Resource
    Stratospheric trace constituents simulated by a three‐dimensional general circulation model: Comparison with UARS data
    American Geophysical Union (AGU) ; 1995
    In:  Journal of Geophysical Research: Atmospheres Vol. 100, No. D7 ( 1995-07-20), p. 13951-13966
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 100, No. D7 ( 1995-07-20), p. 13951-13966
    Abstract: Constituent distributions are presented from the NASA Langley three‐dimensional general circulation model, incorporating a comprehensive chemistry scheme. A 7‐year, gas phase model simulation was performed to investigate long‐term model stability. In addition, a 1‐year simulation was made using parameterized polar heterogeneous processes and reactions occurring on sulfate aerosols. The results of these simulations are compared with species climatologies and with satellite data sets in order to characterize and evaluate model performance and identify aspects of the chemical scheme requiring improvement. The agreement between the modeled seasonal variation of total ozone and the measurement climatologies is satisfactory but with some differences with respect to the depth and persistence of the southern springtime ozone depletion. Comparisons of the model simulation with observations made from UARS were performed. There is good accord between the microwave limb sounder observations of ozone and the model. Areas of agreement and disagreement are revealed between the model and the cryogenic array etalon spectrometer measurements of HNO 3 and ClONO 2 , suggesting the need for a more detailed representation of sulfate aerosol processes in the model. The comparison between the modeled and the measured partitioning of odd chlorine species is improved in the upper stratosphere by the inclusion of an additional pathway to HCl from the reaction of ClO + OH.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD01278
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1995
    detail.hit.zdb_id: 161666-3
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  • 4
    Online Resource
    Online Resource
    Distribution of Antarctic polar stratospheric clouds as seen by the CLAES experiment
    American Geophysical Union (AGU) ; 1997
    In:  Journal of Geophysical Research: Atmospheres Vol. 102, No. D15 ( 1997-08-20), p. 19161-19170
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 102, No. D15 ( 1997-08-20), p. 19161-19170
    Abstract: The distribution and optical characteristics of Antarctic polar stratospheric clouds (PSCs) during the winter of 1992 as seen from the cryogenic limb array etalon spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite (UARS) are presented. The CLAES measurements are the first extensive stratospheric aerosol observations through much of the Antarctic polar night. An analysis of the vertical and areal distribution using the aerosol absorption coefficient measured at 780 cm −1 is presented, including a polar map showing the frequency of PSC occurrence during the two CLAES Antarctic viewing periods June 11 to July 10 and August 16 to September 18. The PSC seasonal evolution from CLAES is compared with a climatology based on the Stratospheric Aerosol Measurements II (SAM II) system. The frequency of PSC occurrence in the CLAES data sampled at latitudes similar to those observed with SAM II shows general agreement with the climatology. Some obvious differences between details of the PSC evolution seen by CLAES and the climatology are investigated with 1992 SAM II aerosol extinction data and shown to be due to intra‐annual variations specific to 1992, which appear in both data sets.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/97JD01077
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1997
    detail.hit.zdb_id: 161666-3
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  • 5
    Online Resource
    Online Resource
    Tilt Tunable Ultra Narrow-Band Filters for High Resolution Infrared Photometry
    Optica Publishing Group ; 1975
    In:  Applied Optics Vol. 14, No. 3 ( 1975-03-01), p. 765-
    Details
    In: Applied Optics, Optica Publishing Group, Vol. 14, No. 3 ( 1975-03-01), p. 765-
    Type of Medium: Online Resource
    ISSN: 0003-6935 , 1539-4522
    URL: Article
    DOI: 10.1364/AO.14.000765
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 1975
    detail.hit.zdb_id: 207387-0
    detail.hit.zdb_id: 1474462-4
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  • 6
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    Online Resource
    Stratospheric temperature measurements by two collocated NDSC lidars during UARS validation campaign
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 10287-10297
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 10287-10297
    Abstract: The NASA Goddard Space Flight Center (GSFC) mobile lidar system was deployed at the Observatoire de Haute Provence (OHP), during an Upper Atmosphere Research Satellite (UARS)/Network for Detection of Stratospheric Change (NDSC) correlative measurement campaign (July–August 1992). The objective of this campaign was twofold: to intercompare two independent lidars and to provide ground‐based UARS correlative ozone and temperature validation measurements. This paper, for the first time, presents a coincident temperature intercomparison between two independently operating temperature lidar systems of similar capabilities. Systems and retrieval algorithms have been described and discussed in terms of error sources. The comparison of the two analyses have shown very similar results up to the upper mesosphere. The statistical mean differences of 0.5 K in the stratosphere and about 2 K in the mesosphere suggests insignificant bias throughout except below 35 km, where one of the data sets is contaminated by the volcanic aerosols from the eruption of Mount Pinatubo. Profiles of the root‐mean‐square (RMS) of the differences are in good agreement with random error estimates, except around 35–40 km where RMS is larger. These measurements can be used as the ground reference for UARS temperature validation. However, the spatial‐temporal coincidence between satellite and lidar needs to be carefully considered for meaningful validation.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD00516
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
    detail.hit.zdb_id: 161666-3
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  • 7
    Online Resource
    Online Resource
    Accuracy and precision of cryogenic limb array etalon spectrometer (CLAES) temperature retrievals
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Atmospheres Vol. 101, No. D6 ( 1996-04-30), p. 9583-9601
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D6 ( 1996-04-30), p. 9583-9601
    Abstract: The Cryogenic Limb Array Etalon Spectrometer (CLAES) measured emission from the 792 cm −1 Q branch of CO 2 , from which temperature distributions in the stratosphere and low mesosphere were derived. Here we briefly review the measurement technique, concentrating on aspects that affect the temperature determination. Comparison of many pairs of retrievals at the same location (near 32°N or 32°S) measured on sequential orbits (time separation of 96 min) shows a precision ranging from approximately 0.8 K at 68 mbar to about 3.5 K at 0.2 mbar, which agrees with simulations incorporating random noise and short‐period spacecraft motions. Comparisons of globally analyzed CLAES data with National Meteorological Center (NMC) and U.K. Meteorological Office (UKMO) analyses show general agreement, with CLAES tending to be cooler by about 2 K, except in the tropics and high‐latitude winter conditions. This is supported by comparisons with individual radiosondes and several lidars that indicate that the agreement is within 2 K throughout the profile (except for a narrow layer around 3 mbar). An error analysis also indicates that systematic errors should be roughly 2 K, independent of altitude. The systematic differences at low latitudes appear to be due to tropical waves, which have vertical wavelengths too short to be seen by the TIROS Operational Vertical Sounder (TOVS) instruments. There are no correlative rocketsondes or lidars to help resolve the reasons for the high‐latitude differences. Comparisons with other Upper Atmosphere Research Satellite (UARS) data should shed additional light on this question.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD00052
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
    detail.hit.zdb_id: 161666-3
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  • 8
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    Online Resource
    Assimilation of photochemically active species and a case analysis of UARS data
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Atmospheres Vol. 104, No. D15 ( 1999-08-20), p. 18715-18737
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 104, No. D15 ( 1999-08-20), p. 18715-18737
    Abstract: We present a short overview of applications of estimation theory in atmospheric chemistry and discuss some common methods of gridding and mapping of irregular satellite observations of chemical constituents. It is shown that these methods are unable to produce truly synoptic maps of short‐lived photochemically active species due to insufficient temporal and spatial density of satellite observations. The only way to overcome this limitation is to supplement observations with prior independent information given, for instance, by atmospheric numerical models and/or climatologies. Objective approaches to combining such prior information with observations are commonly referred to as data assimilation. Mathematical basis of data assimilation known as optimal estimation equations is presented following Lorenc [1986]. Two particular techniques of data assimilation, the variational method and the extended Kalman filter, are briefly described, and their applications to time‐dependent numerical photochemical models are discussed. We investigate validity of the linear approximation which is utilized in both methods, present time evolution of the linearization and covariance matrices, and discuss some of their properties. On the basis of ideas of Fisher and Lary [1995] we then employ a trajectory model and a photochemical box model for assimilation and mapping of the Upper Atmosphere Research Satellite (UARS) measurements of chemical species. The assimilation is performed using the variational technique and the extended Kalman filter, and results of both methods are presented and discussed.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD900225
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
    detail.hit.zdb_id: 161666-3
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  • 9
    Online Resource
    Online Resource
    Interhemispheric differences in springtime production of HCl and ClONO 2 in the polar vortices
    American Geophysical Union (AGU) ; 1995
    In:  Journal of Geophysical Research: Atmospheres Vol. 100, No. D7 ( 1995-07-20), p. 13967-13978
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 100, No. D7 ( 1995-07-20), p. 13967-13978
    Abstract: UARS observations of O 3 and ClO (Microwave Limb Sounder), ClONO 2 and HNO 3 (Cryogenic Array Etalon Spectrometer), NO, NO 2 , and HCl (Halogen Occultation Experiment), and model calculations are used to produce an exposition of the different processes through which the reservoir gases ClONO 2 and HCl are reformed at the end of the polar winter. Comparison of the observations within the polar vortices shows that HCl increases more rapidly in the Antarctic vortex in spring than in the Arctic vortex. Model analysis shows that this occurs because the O 3 concentrations in the southern vortex fall well below those in the northern vortex. The Cl/ClO fraction calculated for the southern hemisphere is therefore up to 30 times higher, leading to rapid HCl formation by Cl + CH 4 . The concentrations of NO observed by HALOE are substantially lower for the northern hemisphere than for the southern hemisphere, even for similar values of the concentration of HNO 3 and the production of NO X from HNO 3 through photolysis and reaction with OH. This is consistent with the dependence of the NO/NO X ratio on the O 3 concentration, i.e., the daytime production rate of NO 2 via NO + O 3 is reduced, leading to higher NO in the southern hemisphere. This higher concentration of NO also contributes to the rapid HCl increase as Cl production from ClO + NO is enhanced.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JD00698
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1995
    detail.hit.zdb_id: 161666-3
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  • 10
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    Online Resource
    Temporal evolution of chlorine monoxide in the middle stratosphere
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Atmospheres Vol. 105, No. D4 ( 2000-02-27), p. 4459-4469
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 105, No. D4 ( 2000-02-27), p. 4459-4469
    Abstract: The temporal evolution of stratospheric chlorine monoxide (ClO) at northern midlatitudes is studied over different scales: diurnal and seasonal variations. Data sets include temperature profiles, and ClO, HCl, ClONO 2 , NO 2 , O 3 , H 2 O, and CH 4 mixing ratios as measured from 10 to 0.46 hPa (i.e., from ∼30 to ∼55 km) by the Microwave Limb Sounder (MLS), by the Halogen Occultation Experiment, and by the Cryogenic Limb Array Etalon Spectrometer instruments aboard the UARS satellite from at most September 1991 to June 1997 within the band 40°–50°N. The time evolution of these species is interpreted by comparison with results from a “zero‐dimensional” (0‐D) purely photochemical model and from the SLIMCAT three‐dimensional (3‐D) chemical transport model over the Plateau de Bure station (45°N, 10°E) from September 1991 to March 1998. A maximum confidence value for the yield in the reaction ClO + OH → HCl + O 2 is deduced from the analysis to be in the range 0.05–0.10±0.03, which is consistent with recent laboratory data, suggesting a value of ∼0.05–0.06±0.02. Comparisons between the ClO diurnal variations measured by MLS and calculated by the 0‐D model agree to within 10% around the maximum of ClO (∼40 km) and within 5% elsewhere. The ClO diurnal variation is induced by variations in the partitioning with HOCl and ClONO 2 below 50 km and by variations in the partitioning within the ClO x (=Cl+ClO) family above. The agreement between measured and modeled seasonal variations of ClO implies an evolution above 30 km essentially dictated by the variation in the partitioning with HCl, together with the partitioning within the ClO x family above 40 km. The differences between measured and modeled ClO seasonal variations above 50 km are attributed to uncertainties in the relative rates of the sources of HCl (reactions of Cl with CH 4 and HO 2 ).
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JD900995
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
    detail.hit.zdb_id: 161666-3
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