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  • 1
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    Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-01-09
    Description: The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wennberg -- Hanisco -- Jaegle -- Jacob -- Hintsa -- Lanzendorf -- Anderson -- Gao -- Keim -- Donnelly -- Negro -- Fahey -- McKeen -- Salawitch -- Webster -- May -- Herman -- Proffitt -- Margitan -- Atlas -- Schauffler -- Flocke -- McElroy -- Bui -- New York, N.Y. -- Science. 1998 Jan 2;279(5347):49-53.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉P. O. Wennberg, T. F. Hanisco, E. J. Hintsa, E. J. Lanzendorf, J. G. Anderson, Department of Chemistry and Chemical Biology and Department of Earth and Planetary Sciences, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA. L. Ja.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9417019" target="_blank"〉PubMed〈/a〉
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Free Radicals Within the Antarctic Vortex: The Role of CFCs in Antarctic Ozone Loss (1991)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1991-01-04
    Description: How strong is the case linking global release of chlorofluorocarbons to episodic disappearance of ozone from the Antarctic stratosphere each austral spring? Three lines of evidence defining a link are (i) observed containment in the vortex of ClO concentrations two orders of magnitude greater than normal levels; (ii) in situ observations obtained during ten high-altitude aircraft flights into the vortex as the ozone hole was forming that show a decrease in ozone concentrations as ClO concentrations increased; and (iii) a comparison between observed ozone loss rates and those predicted with the use of absolute concentrations of ClO and BrO, the rate-limiting radicals in an array of proposed catalytic cycles. Recent advances in our understanding of the kinetics, photochemistry, and structural details of key intermediates in these catalytic cycles as well as an improved absolute calibration for ClO and BrO concentrations at the temperatures and pressures encountered in the lower antarctic stratosphere have been essential for defining the link.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, J G -- Toohey, D W -- Brune, W H -- New York, N.Y. -- Science. 1991 Jan 4;251(4989):39-46.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17778601" target="_blank"〉PubMed〈/a〉
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  • 3
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    The potential for ozone depletion in the arctic polar stratosphere (1991)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1991-05-31
    Description: The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. Most of the available chlorine (HCl and ClONO(2)) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl(2)O(2) throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO(3), and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15% at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8% losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50% over the next two decades, ozone losses recognizable as an ozone hole may well appear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brune, W H -- Anderson, J G -- Toohey, D W -- Fahey, D W -- Kawa, S R -- Jones, R L -- McKenna, D S -- Poole, L R -- New York, N.Y. -- Science. 1991 May 31;252(5010):1260-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17842951" target="_blank"〉PubMed〈/a〉
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  • 4
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    UV dosage levels in summer: increased risk of ozone loss from convectively injected water vapor (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-07-28
    Description: The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic system extraordinarily sensitive to convective injection into the mid-latitude lower stratosphere in summer. Were the intensity and frequency of convective injection to increase as a result of climate forcing by the continued addition of CO(2) and CH(4) to the atmosphere, increased risk of ozone loss and associated increases in ultraviolet dosage would follow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, James G -- Wilmouth, David M -- Smith, Jessica B -- Sayres, David S -- New York, N.Y. -- Science. 2012 Aug 17;337(6096):835-9. doi: 10.1126/science.1222978. Epub 2012 Jul 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA. anderson@huarp.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22837384" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Carbon Dioxide/chemistry ; Catalysis ; Chlorine Compounds/chemistry ; *Convection ; Methane/chemistry ; Ozone/*chemistry ; Radiation Dosage ; *Seasons ; *Steam ; *Ultraviolet Rays
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  • 5
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    Evidence for deep magma injection beneath Lake Tahoe, Nevada-California (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-08-07
    Description: A deep earthquake swarm in late 2003 at Lake Tahoe, California (Richter magnitude 〈 2.2; depth of 29 to 33 kilometers), was coeval with a transient displacement of 6 millimeters horizontally outward from the swarm and 8 millimeters upward measured at global positioning system station Slide Mountain (SLID) 18 kilometers to the northeast. During the first 23 days of the swarm, hypocentral depths migrated at a rate of 2.4 millimeters per second up-dip along a 40-square-kilometer structure striking north 30 degrees west and dipping 50 degrees to the northeast. SLID's transient velocity of 20 millimeters per year implies a lower bound of 200 nanostrains per year (parts per billion per year) on local strain rates, an order of magnitude greater than the 1996 to 2003 regional rate. The geodetic displacement is too large to be explained by the elastic strain from the cumulative seismic moment of the sequence, suggesting an aseismic forcing mechanism. Aspects of the swarm and SLID displacements are consistent with lower-crustal magma injection under Lake Tahoe.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, Kenneth D -- von Seggern, David -- Blewitt, Geoffrey -- Preston, Leiph -- Anderson, John G -- Wernicke, Brian P -- Davis, James L -- New York, N.Y. -- Science. 2004 Aug 27;305(5688):1277-80. Epub 2004 Aug 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Nevada Seismological Laboratory, University of Nevada, Reno, NV 89557, USA. ken@seismo.unr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15297623" target="_blank"〉PubMed〈/a〉
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  • 6
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    The seasonal evolution of reactive chlorine in the northern hemisphere stratosphere (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-08-27
    Description: In situ measurements of chlorine monoxide (ClO) at mid- and high northern latitudes are reported for the period October 1991 to February 1992. As early as mid-December and throughout the winter, significant enhancements of this ozone-destroying radical were observed within the polar vortex shortly after temperatures dropped below 195 k. Decreases in ClO observed in February were consistent with the rapid formation of chlorine nitrate (ClONO(2)) by recombination of ClO with nitrogen dioxide (NO(2)) released photochemically from nitric acid (HNO(3)). Outside the vortex, ClO abundances were higher than in previous years as a result of NOx suppression by heterogeneous reactions on sulfate aerosols enhanced by the eruption of Mount Pinatubo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Toohey, D W -- Avallone, L M -- Lait, L R -- Newman, P A -- Schoeberl, M R -- Fahey, D W -- Woodbridge, E L -- Anderson, J G -- New York, N.Y. -- Science. 1993 Aug 27;261(5125):1134-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17790345" target="_blank"〉PubMed〈/a〉
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  • 7
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    Chemical loss of ozone in the arctic polar vortex in the winter of 1991-1992 (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-08-27
    Description: In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expedition II (AASE II) in the winter of 1991-1992. The analysis indicates removal of 15 to 20 percent of ambient ozone because of elevated concentrations of chlorine monoxide and bromine monoxide. Observations during AASE II define rates of removal of chlorine monoxide attributable to reaction with nitrogen dioxide (produced by photolysis of nitric acid) and to production of hydrochloric acid. Ozone loss ceased in March as concentrations of chlorine monoxide declined. Ozone losses could approach 50 percent if regeneration of nitrogen dioxide were inhibited by irreversible removal of nitrogen oxides (denitrification), as presently observed in the Antarctic, or without denitrification if inorganic chlorine concentrations were to double.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Salawitch, R J -- Wofsy, S C -- Gottlieb, E W -- Lait, L R -- Newman, P A -- Schoeberl, M R -- Loewenstein, M -- Podolske, J R -- Strahan, S E -- Proffitt, M H -- Webster, C R -- May, R D -- Fahey, D W -- Baumgardner, D -- Dye, J E -- Wilson, J C -- Kelly, K K -- Elkins, J W -- Chan, K R -- Anderson, J G -- New York, N.Y. -- Science. 1993 Aug 27;261(5125):1146-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17790349" target="_blank"〉PubMed〈/a〉
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  • 8
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    Removal of Stratospheric O3 by Radicals: In Situ Measurements of OH, HO2, NO, NO2, ClO, and BrO (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-10-21
    Description: Simultaneous in situ measurements of the concentrations of OH, HO(2), ClO, BrO, NO, and NO(2) demonstrate the predominance of odd-hydrogen and halogen free-radical catalysis in determining the rate of removal of ozone in the lower stratosphere during May 1993. A single catalytic cycle, in which the rate-limiting step is the reaction of HO(2) with ozone, accounted for nearly one-half of the total O(3) removal in this region of the atmosphere. Halogen-radical chemistry was responsible for approximately one-third of the photochemical removal of O(3); reactions involving BrO account for one-half of this loss. Catalytic destruction by NO(2), which for two decades was considered to be the predominant loss process, accounted for less than 20 percent of the O(3) removal. The measurements demonstrate quantitatively the coupling that exists between the radical families. The concentrations of HO(2) and ClO are inversely correlated with those of NO and NO(2). The direct determination of the relative importance of the catalytic loss processes, combined with a demonstration of the reactions linking the hydrogen, halogen, and nitrogen radical concentrations, shows that in the air sampled the rate of O(3) removal was inversely correlated with total NOx, loading.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wennberg, P O -- Cohen, R C -- Stimpfle, R M -- Koplow, J P -- Anderson, J G -- Salawitch, R J -- Fahey, D W -- Woodbridge, E L -- Keim, E R -- Gao, R S -- Webster, C R -- May, R D -- Toohey, D W -- Avallone, L M -- Proffitt, M H -- Loewenstein, M -- Podolske, J R -- Chan, K R -- Wofsy, S C -- New York, N.Y. -- Science. 1994 Oct 21;266(5184):398-404.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17816682" target="_blank"〉PubMed〈/a〉
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  • 9
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    Chlorine chemistry on polar stratospheric cloud particles in the arctic winter (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-08-27
    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 part per billion by volume (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 HCI mixing ratios equal to (1/2)(ClO + 2Cl(2)O(2)). These data indicate that the heterogeneous reaction HCl + ClONO(2) --〉 Cl(2) + HNO(3) on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO(2), not HCl.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Webster, C R -- May, R D -- Toohey, D W -- Avallone, L M -- Anderson, J G -- Newman, P -- Lait, L -- Schoeberl, M R -- Elkins, J W -- Chan, K R -- New York, N.Y. -- Science. 1993 Aug 27;261(5125):1130-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17790344" target="_blank"〉PubMed〈/a〉
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  • 10
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    Free radicals in the stratosphere: a new observational technique (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-06-14
    Description: A new approach to in situ observations of trace reactive species in the stratosphere is described. A balloon-borne system, floating 40 kilometers above the earth's surface, successfully lowered and then retracted a cluster of instruments a distance of 12 kilometers on a filament of Kevlar. This instrument cluster is capable of detecting gas-phase free radicals at the part-per-trillion level. The suspended instrument array has excellent stability and has been used to measure atomic oxygen concentrations in the stratosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, J G -- Hazen, N L -- McLaren, B E -- Rowe, S P -- Schiller, C M -- Schwab, M J -- Solomon, L -- Thompson, E E -- Weinstock, E M -- New York, N.Y. -- Science. 1985 Jun 14;228(4705):1309-11.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17799118" target="_blank"〉PubMed〈/a〉
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