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  • 1
    Online Resource
    Online Resource
    PMCs and the water frost point in the Arctic summer mesosphere
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 23 ( 2001-12), p. 4449-4452
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 23 ( 2001-12), p. 4449-4452
    Abstract: In August, 1997 the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) obtained vertical profiles of OH number density and polar mesospheric cloud (PMC) brightness by scanning the limb up to 71° N while the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) obtained co‐located vertical profiles of temperature. MAHRSI OH densities are converted to water vapor using a one‐dimensional model that assumes photochemical equilibrium. By combining water vapor profiles with CRISTA temperatures we map the frost point both vertically and horizontally in the Arctic summer mesosphere. Our data show that supersaturation can exist between 80‐87 km suggesting that growth of ice particles is limited to these altitudes. Additionally, we find that not only is supersaturation an insufficient condition for a PMC but also that PMCs can exist in apparently unsaturated air.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2001GL013598
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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  • 2
    Online Resource
    Online Resource
    The 2.5 THz heterodyne spectrometer THOMAS: Measurement of OH in the middle atmosphere and comparison with photochemical model results
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Atmospheres Vol. 105, No. D17 ( 2000-09-16), p. 22211-22223
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 105, No. D17 ( 2000-09-16), p. 22211-22223
    Abstract: The interpretation of recent odd hydrogen measurements in the stratosphere from balloons and in the mesosphere from space indicates a serious lack of understanding in atmospheric HO x chemistry. In order to resolve these persisting problems, coincident measurements of HO x molecules and/or measurements that cover both altitude regions are desirable. In this work, the airborne 2.5THz heterodyne spectrometer Terahertz OH Measurement Airborne Sounder (THOMAS) is introduced. Since the first THOMAS measurements in 1994/1995, the spectrometer was significantly improved by modification or replacement of individual components. The THOMAS instrumental setup and properties are presented together with a retrieval algorithm for atmospheric parameters based on a Phillips‐Tikhonov regularization scheme. Furthermore, the results of a complete error assessment are given. In August 1997, during the second CRISTA/MAHRSI campaign (Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere / Middle Atmosphere High Resolution Spectrograph Investigation), OH observations were performed by THOMAS covering altitudes between about 30 and 90 km over a full diurnal cycle. Hydroxyl column densities derived from THOMAS measurements are presented and compared to photochemical model results. The model calculations using the standard HO x chemistry systematically show higher values by about 15% for the 40–90 km and 50–90 km OH columns. Moreover, a recently proposed change of an HO x chemistry reaction rate is included into the comparison which, for the same altitude intervals, yields OH column densities that are about 10% lower than the THOMAS measurements. A detailed comparison of the THOMAS and MAHRSI measurements is presented in a seperate publication [ Englert et al. , 2000].
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2000JD900305
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 2969341-X
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    detail.hit.zdb_id: 3094268-8
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    detail.hit.zdb_id: 2016804-4
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    SSG: 16,13
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  • 3
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    Online Resource
    Satellite observations of upper stratospheric and mesospheric OH: The HO x dilemma
    American Geophysical Union (AGU) ; 2000
    In:  Geophysical Research Letters Vol. 27, No. 17 ( 2000-09), p. 2613-2616
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 27, No. 17 ( 2000-09), p. 2613-2616
    Abstract: We report the first observations of the vertical distribution of hydroxyl (OH) from the upper stratosphere to the mesopause. The Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) made these measurements in August 1997. The data confirm the results from the earlier November 1994 MAHRSI mission that were confined to altitudes above 50 km, namely that mesospheric OH densities are 25 to 35% lower than predicted by standard photochemical theory. However, the new observations show that below 50 km the OH density increases rapidly and at 43 km altitude it is larger than that expected from standard theory. This represents a serious dilemma for our understanding of odd‐hydrogen chemistry because the same key reactions are thought to dominate OH/HO 2 partitioning in both regions. We show that neither standard photochemical theory nor any previously proposed changes are adequate to explain the OH observations in both the upper stratosphere and mesosphere.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2000GL011698
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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  • 4
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    Educational and Social Competencies at 8 Years in Children With Threshold Retinopathy of Prematurity in the CRYO-ROP Multicenter Study
    American Academy of Pediatrics (AAP) ; 2004
    In:  Pediatrics Vol. 113, No. 4 ( 2004-04-01), p. 790-799
    Details
    In: Pediatrics, American Academy of Pediatrics (AAP), Vol. 113, No. 4 ( 2004-04-01), p. 790-799
    Abstract: Objective. To describe the educational status and special education services at 8 years among children who had threshold retinopathy of prematurity (ROP). Methods. A prospective study was conducted of a cohort of children who had birth weight of & lt;1251 g and threshold ROP in the Cryotherapy for Retinopathy of Prematurity multicenter study. At age 5.5 years, visual status, functional skills, and social information were obtained. At 8 years, special education classes, developmental disabilities, rehabilitation therapies, and academic and social competencies were determined by questionnaire. Visual status was considered favorable/unfavorable on the basis of the better eye. Results. Of 255 survivors, 216 (85%) were evaluated at both 5.5 and 8 years. Major impairments were significantly more prevalent in children with unfavorable versus favorable visual status: cerebral palsy (39% vs 16%), developmental disability (57% vs 22%), autism (9% vs 1%), and epilepsy (23% vs 3%). Special education services (63% vs 27%), below-grade-level academic performance (84% vs 48%), and school-based rehabilitation services were significantly less common in children with favorable visual status. Favorable visual status, favorable functional ratings at 5.5 years, markers of higher socioeconomic status, and nonblack race were associated with significantly lower rates of both special education placement and below-grade-level academic performance at age 8. On multivariate logistic regression, only favorable visual status and functional status remained significant predictors for decreasing special education placement. Conclusion. Threshold ROP is associated with high rates of developmental, educational, and social challenges in middle childhood; preserved vision was associated with a clear advantage, with more than half of the children with favorable visual status performing at grade level.
    Type of Medium: Online Resource
    ISSN: 0031-4005 , 1098-4275
    URL: Article
    DOI: 10.1542/peds.113.4.790
    Language: English
    Publisher: American Academy of Pediatrics (AAP)
    Publication Date: 2004
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  • 5
    Online Resource
    Online Resource
    Discovery of a water vapor layer in the Arctic summer mesosphere: Implications for polar mesospheric clouds
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 18 ( 2001-09-15), p. 3601-3604
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 18 ( 2001-09-15), p. 3601-3604
    Abstract: We report the discovery of a layer of enhanced water vapor in the Arctic summer mesosphere that was made utilizing two new techniques for remotely determining water vapor abundances. The first utilizes Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) OH measurements as a proxy for water vapor. The second is a reanalysis of Halogen Occultation Experiment (HALOE) water vapor data with a technique to simultaneously determine polar mesospheric cloud (PMC) ice particle extinction along with the water vapor abundance. These results reveal a narrow layer of enhanced water vapor centered between 82–84 km altitude and coincident with PMCs, that exhibits water vapor mixing ratios of 10–15 ppmv. This indicates that a higher degree of supersaturation is present in the PMC region, and that PMCs are thus more efficient at sequestering total water (both ice particles and vapor) within the layer, than previously believed.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2001GL013217
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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  • 6
    Online Resource
    Online Resource
    First confirmation that water ice is the primary component of polar mesospheric clouds
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 6 ( 2001-03-15), p. 971-974
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 6 ( 2001-03-15), p. 971-974
    Abstract: Polar mesospheric clouds (PMCs) have been measured in the infrared for the first time by the Halogen Occultation Experiment (HALOE). PMC extinctions retrieved from measurements at eight wavelengths show remarkable agreement with model spectra based on ice particle extinction. The infrared spectrum of ice has a unique signature, and the HALOE‐model agreement thus provides the first physical confirmation that water ice is the primary component of PMCs. PMC particle effective radii were estimated from the HALOE extinctions based on a first order fit of model extinctions.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2000GL012104
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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  • 7
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    Online Resource
    A reactive species model for chlorine decay and THM formation under rechlorination conditions
    Elsevier BV ; 2003
    In:  Water Research Vol. 37, No. 11 ( 2003-6), p. 2654-2666
    Details
    In: Water Research, Elsevier BV, Vol. 37, No. 11 ( 2003-6), p. 2654-2666
    Type of Medium: Online Resource
    ISSN: 0043-1354
    URL: Article
    DOI: 10.1016/S0043-1354(03)00067-8
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2003
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    SSG: 14
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  • 8
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    Online Resource
    Atmospheric biomarkers of subsurface life on Mars : ATMOSPHERIC BIOMARKERS ON MARS
    American Geophysical Union (AGU) ; 2002
    In:  Geophysical Research Letters Vol. 29, No. 24 ( 2002-12), p. 24-1-24-4
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 29, No. 24 ( 2002-12), p. 24-1-24-4
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2002GL015377
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2002
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    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 9
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    Io's ultraviolet aurora: Remote sensing of Io's interaction
    American Geophysical Union (AGU) ; 2000
    In:  Geophysical Research Letters Vol. 27, No. 18 ( 2000-09-15), p. 2893-2896
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 27, No. 18 ( 2000-09-15), p. 2893-2896
    Abstract: With the recent observations of Io's very striking equatorial aurora by Roesler et al. [1999], it is now possible to remotely sense Io's local interaction with the Io plasma torus. Here we present an explanation for the formation of Io's aurora which implies that Io's electron flow is strongly rotated and shielded around Io. The Hall effect close to Io breaks the interaction symmetry to produce a brighter anti‐Jovian radiation spot, and it also results in rotated Alfvén wings. Observations of Io's aurora also impose new constraints on Io's atmosphere. We find, among other things, an atomic oxygen to sulfur dioxide ratio of ∼20%.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2000GL003824
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 10
    Online Resource
    Online Resource
    Water vapor enhancement in the polar summer mesosphere and its relationship to polar mesospheric clouds
    American Geophysical Union (AGU) ; 2003
    In:  Geophysical Research Letters Vol. 30, No. 20 ( 2003-10)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 30, No. 20 ( 2003-10)
    Abstract: Polar mesospheric water vapor exhibits a strong seasonal cycle, with summer mixing ratios dramatically higher than in winter. It is generally accepted that vertical transport from ∼50 km altitude towards the mesopause is one driver behind this change, however, upwelling alone cannot explain observed H 2 O changes. H 2 O near 83 km increases from 1 ppmv in winter to over 8 ppmv in summer, and upwelling accounts for roughly half of this increase. It has been suggested that evaporation of polar mesospheric clouds (PMCs) should produce a layer of enhanced water vapor. This idea was explored using particle measurements from the Halogen Occultation Experiment (HALOE) to derive the equivalent gas phase H 2 O contained in PMCs. Comparing these estimates to HALOE water vapor measurements suggests that PMC evaporation is a large component in H 2 O enhancement near 83 km during summer.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2003GL018089
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2003
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    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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