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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Multimodel Estimates of Atmospheric Lifetimes of Long-lived Ozone-Depleting Substances: Present and Future

We have diagnosed the lifetimes of long-lived source gases emitted at the surface and removed in the stratosphere using six three-dimensional chemistry-climate models and a two-dimensional model. The models all used the same standard photochemical data. We investigate the effect of different definitions of lifetimes, including running the models with both mixing ratio (MBC) and flux (FBC) boundary conditions. Within the same model, the lifetimes diagnosed by different methods agree very well. Using FBCs versus MBCs leads to a different tracer burden as the implied lifetime contained in the MBC value does not necessarily match a model's own calculated lifetime. In general, there are much larger differences in the lifetimes calculated by different models, the main causes of which are variations in the modeled rates of ascent and horizontal mixing in the tropical midlower stratosphere. The model runs have been used to compute instantaneous and steady state lifetimes. For chlorofluorocarbons (CFCs) their atmospheric distribution was far from steady state in their growth phase through to the 1980s, and the diagnosed instantaneous lifetime is accordingly much longer. Following the cessation of emissions, the resulting decay of CFCs is much closer to steady state. For 2100 conditions the model circulation speeds generally increase, but a thicker ozone layer due to recovery and climate change reduces photolysis rates. These effects compensate so the net impact on modeled lifetimes is small. For future assessments of stratospheric ozone, use of FBCs would allow a consistent balance between rate of CFC removal and model circulation rate

CFC↗
DOE OSTI2023

Midlatitude Ozone Depletion and Air Quality Impacts from Industrial Halogen Emissions in the Great Salt Lake Basin

We report aircraft observations of extreme levels of HCl and the dihalogens Cl 2 , Br 2 , and BrCl in an industrial plume near the Great Salt Lake, Utah. Complete depletion of O 3 was observed concurrently with halogen enhancements as a direct result of photochemically produced halogen radicals. Observed fluxes for Cl 2 , HCl, and NO x agreed with facility-reported emissions inventories. Bromine emissions are not required to be reported in the inventory, but are estimated as 173 Mg year –1 Br 2 and 949 Mg year –1 BrCl, representing a major uncounted oxidant source. A zero-dimensional photochemical box model reproduced the observed O 3 depletions and demonstrated that bromine radical cycling was principally responsible for the rapid O 3 depletion. Inclusion of observed halogen emissions in both the box model and a 3D chemical model showed significant increases in oxidants and particulate matter (PM 2.5 ) in the populated regions of the Great Salt Lake Basin, where winter PM 2.5 is among the most severe air quality issues in the U.S. The model shows regional PM 2.5 increases of 10%–25% attributable to this single industrial halogen source, demonstrating the impact of underreported industrial bromine emissions on oxidation sources and air quality within a major urban area of the western U.S.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

A feasibility study of methods for stopping the depletion of ozone over Antarctica

Ways of stopping the ozone depletion in the ozone hole over Antarctica were studied. The basic objectives were: (1) to define and understand the phenomenon of the ozone hole; (2) to determine possible methods of stopping the ozone depletion; (3) to identify unknowns about the hole and possible solutions. Two basic ways of attacking the problem were identified. First is replenishment of ozone as it is being depleted. Second is elimination of ozone destroying agents from the atmosphere. The second method is a more permanent form of the solution. Elimination and replenishment methods are discussed in detail.

Source record↗
NASA NTRS1976

Effect of odd hydrogen on ozone depletion by chlorine reactions

The present paper discusses how the shape of the ozone layer changes under the influence of injected ClX for several choices of two key HOx reaction rates. The two HOx reactions are: OH + HO2 yields H2O + O2 and O + HO2 yields OH + O2. Results of calculations are presented which show that the two reaction rates determine the stratospheric concentrations of OH and HO2, and that these concentrations regulate the amount by which the stratospheric ozone column can be reduced due to injections of odd chlorine. It is concluded that the amount of ozone reduction by a given mixing ratio of ClX will remain very uncertain until the significance of several possible feedback effects involving HOx in a chlorine-polluted atmosphere are determined and measurements of the reaction rates and HOx concentrations are made at the relevant temperatures.

Donahue, T. M.↗
NASA NTRS1999

Ozone Depletion, UVB and Atmospheric Chemistry

The primary constituents of the Earth's atmosphere are molecular nitrogen and molecular oxygen. Ozone is created when ultraviolet light from the sun photodissociates molecular oxygen into two oxygen atoms. The oxygen atoms undergo many collisions but eventually combine with a molecular oxygen to form ozone (O3). The ozone molecules absorb ultraviolet solar radiation, primarily in the wavelength region between 200 and 300 nanometers, resulting in the dissociation of ozone back into atomic oxygen and molecular oxygen. The oxygen atom reattaches to an O2 molecule, reforming ozone which can then absorb another ultraviolet photon. This sequence goes back and forth between atomic oxygen and ozone, each time absorbing a uv photon, until the oxygen atom collides with and ozone molecule to reform two oxygen molecules.

Stolarski, Richard S.↗
NASA NTRS1999

Ozone Depletion, UVB and Atmospheric Chemistry

The primary constituents of the Earth's atmosphere are molecular nitrogen and molecular oxygen. Ozone is created when ultraviolet light from the sun photodissociates molecular oxygen into two oxygen atoms. The oxygen atoms undergo many collisions but eventually combine with a molecular oxygen to form ozone (O3). The ozone molecules absorb ultraviolet solar radiation, primarily in the wavelength region between 200 and 300 nanometers, resulting in the dissociation of ozone back into atomic oxygen and molecular oxygen. The oxygen atom reattaches to an O2 molecule, reforming ozone which can then absorb another ultraviolet photon. This sequence goes back and forth between atomic oxygen and ozone, each time absorbing a uv photon, until the oxygen atom collides with and ozone molecule to reform two oxygen molecules.

Stolarski, Richard S.↗
NASA NTRS1992

Ozone depletion in the upper stratosphere estimated from satellite and Space Shuttle data

Shuttle Solar Backscatter Ultraviolet (SSBUV) spectrometer observations of ozone concentrations in the upper stratosphere made in October 1989 are combined here with measurements made in October 1980 by the similar SBUV instruments on NASA's Nimbus-7 satellite. It is shown that the ozone concentration near 45 km has decreased during this period by about 7 +/- 2 percent. The trend is consistent with predictions of a 2D photochemical model.

Hilsenrath, Ernest↗
NASA NTRS2005

A Model of the Effect of Ozone Depletion on Lower-Stratospheric Structure

We have run two twenty-year integrations of a global circulation model using 1978-1980 and 1998-2000 monthly mean ozone climatologies. The ozone climatology is used solely in the radiation scheme of the model. Several key differences between the model runs will be presented. The temperature and potential vorticity (PV) structure of the lower stratosphere, particularly in the Southern Hemisphere, is significantly changed using the 1998-2000 ozone climatology. In the Southern Hemisphere summer, the lapse rate and PV-defined polar tropopauses are both at altitudes on the order of several hundred meters greater than the 1978-1980 climatological run. The 380 K potential temperature surf= is likewise at a greater altitude. The mass of the extratropical lowermost stratosphere (between the tropopause and 380 K surface) remains unchanged. The altitude differences are not observed in the Northern Hemisphere. The different ozone fields do not produce a significant change in the annual extratropical stratosphere-troposphere exchange of mass although slight variations in the spatial distribution of the exchange exist. We are also investigating a delay in the breakup of the Southern Hemisphere polar vortex due to the differing ozone climatologies.

Olsen, Mark A.↗
NASA NTRS1994

Subsidence of aircraft engine exhaust in the stratosphere: Implications for calculated ozone depletions

The deposition altitude of nitrogen oxides and other exhaust species emitted by stratospheric aircraft is a crucial parameter in determining the impact of these emissions on stratospheric ozone. We have utilized a model for the wake of a High-Speed Civil Transport (HSCT) to estimate the enhancements in water and reductions in ozone in these wakes as a function of time. Radiative calculations indicate differential cooling rates as large as -5K/day at the beginning of the far-wake regime, mostly due to the enhanced water abundance. These cooling rates would imply a net sinking of the wakes of about 1.2 km after three days in the limit of no mixing. Calculated mid-latitude column ozone reductions due to emissions from a Mach 2.4 HSCT would then change from about -1% to -06%. However, more realistic calculations adopting moderate mixing for the wake reduce the net sinking to less than 0.2 km, making the impact of radiative subsidence negligible.

Rodriguez, J. M.↗
NASA NTRS1992

More rapid polar ozone depletion through the reaction of HOCl with HCl on polar stratospheric clouds

The direct reaction of HOCl with HCl is shown here to play a critical part in polar ozone loss. Observations of high levels of OClO and ClO in the springtime Antarctic stratosphere confirm that most of the available chlorine is in the form of ClO(x). But current photochemical models have difficulty converting HCl to ClO(x) rapidly enough in early spring to account fully for the observations. Here, a chemical model is used to show that the direct reaction of HOCl with HCl provides the missing mechanism. As alternative sources of nitrogen-containing oxidants have been converted in the late autumn to inactive HNO3 by known reactions on the sulfate layer aerosols, the reaction of HOCl with HCl on polar stratospheric clouds becomes the most important pathway for releasing that stratospheric chlorine which goes into polar night as HCl.

Prather, Michael J.↗
NASA NTRS1991

The potential for ozone depletion in the Arctic polar stratosphere

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 (CHl and ClONO2) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl2O2 thoroughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO3, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15 percent at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8 percent losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50 percent over the next two decades, ozone losses recognizable as an ozone hole may well appear.

Brune, W. H.↗
NASA NTRS1992

A contribution toward understanding the biospherical significance of Antarctic ozone depletion

The paper presents and compares measurements of biologically active UV radiation made by the NSF scanning spectroradiometer (UV-monitor) at Palmer Station, Antarctica, during the Austral springs of 1988, 1989, and 1990. Column ozone abundance above Palmer Station is computed from these measurements using a multiple wavelength algorithm. Two contrasting action spectra are employed to estimate the biologically relevant dose from the spectral measurements: a standard weighting function for damage to DNA, and a new action spectrum representing the potential for photosynthesis inhibition in Antarctic phytoplankton. The former weights only UV-B wavelengths (280-320 nm) and gives the most weight to wavelengths shorter than 300 nm, while the latter includes large contributions out to 355 nm. Ozone abundances and dose-weighted irradiances provided by the NSF UV-monitor are used to derive the radiation amplification factors for both DNA- and phytoplankton-effective irradiance.

Lubin, Dan↗
NASA NTRS1990

Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex

An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator.

Yung, Yuk L.↗
NASA NTRS1990

Analysis of the eight-year trend in ozone depletion from empirical models of solar backscattered ultraviolet instrument degradation

Arguments are presented showing that the basic empirical model of the solar backscatter UV (SBUV) instrument degradation used by Cebula et al. (1988) in their analysis of the SBUV data is likely to lead to an incorrect estimate of the ozone trend. A correction factor is given as a function of time and altitude that brings the SBUV data into approximate agreement with the SAGE, SME, and Dobson network ozone trends. It is suggested that the currently archived SBUV ozone data should be used with caution for periods of analysis exceeding 1 yr, since it is likely that the yearly decreases contained in the archived data are too large.

Herman, J. R.↗
NASA NTRS1994

Contributions of a Tunable Diode Laser Instrument (ATLAS) to the Stratospheric Ozone Depletion Question

The Airborne Tunable Laser Absorption Spectrometer - ATLAS - was designed and built at the NASA Ames Research Center and operates on the NASA ER-2 high altitude research aircraft. ATLAS has taken part in a number of important polar and mid-latitude research campaigns, since 1987, focused on various aspects of stratospheric ozone chemistry and dynamics. The chief measurement carried out by the ATLAS second harmonic diode laser spectrometer is of the important atmospheric tracer N2O. Using N2O as an inert tracer we have been able to gain significant new information on polar vortex dynamics and on the correlations of several important long-lived tracers in the stratosphere. The correlation of N2O with NOy (total reactive nitrogen) has been shown to be linear for a great variety of unperturbed stratospheric conditions, and the breakdown of this correlation has been used to detect denitrification by PSCs in the polar vortex, especially in the Antarctic spring. Denitrification is an important step in the process of ozone hole formation in the austral spring. Correlations of N2O with CFCs and CH4 have led to improved estimates of atmospheric lifetimes of these important molecules. Finally the correlation of N2O with CO2, the latter now being measured with great precision by a new instrument on the ER-2, has led to a significant new tool for studying horizontal and vertical mixing in the lower stratosphere, a tool which is very useful in assessing the potential effects of high speed civil transport aircraft in the lower stratosphere. A new, light-weight version of ATLAS is currently being built for unmanned high altitude aircraft, specifically the new Perseus vehicle. We will give a brief description of this effort.

Loewenstein, Max↗
NASA NTRS2008

The GEOS Chemistry Climate Model: Implications of Climate Feedbacks on Ozone Depletion and Recovery

The Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) has been developed by combining the atmospheric chemistry and transport modules developed over the years at Goddard and the GEOS general circulation model, also developed at Goddard. The first version of the model was used in the CCMVal intercomparison exercises that contributed to the 2006 WMO/UNEP Ozone Assessment. The second version incorporates the updated version of the GCM (GEOS 5) and will be used for the next round of CCMVal evaluations and the 2010 Ozone Assessment. The third version, now under development, incorporates the combined stratosphere and troposphere chemistry package developed under the Global Modeling Initiative (GMI). We will show comparison to past observations that indicate that we represent the ozone trends over the past 30 years. We will also show the basic temperature, composition, and dynamical structure of the simulations. We will further show projections into the future. We will show results from an ensemble of transient and time-slice simulations, including simulations with fixed 1960 chlorine, simulations with a best guess scenario (Al), and simulations with extremely high chlorine loadings. We will discuss planned extensions of the model to include emission-based boundary conditions for both anthropogenic and biogenic compounds.

Stolarski, Richard S.↗
NASA NTRS1989

Ozone depletion, greenhouse gases, and climate change

This symposium was organized to study the unusual convergence of a number of observations, both short and long term that defy an integrated explanation. Of particular importance are surface temperature observations and observations of upper atmospheric temperatures, which have declined significantly in parts of the stratosphere. There has also been a dramatic decline in ozone concentration over Antarctica that was not predicted. Significant changes in precipitation that seem to be latitude dependent have occurred. There has been a threefold increase in methane in the last 100 years; this is a problem because a source does not appear to exist for methane of the right isotopic composition to explain the increase. These and other meteorological global climate changes are examined in detail.

Mooney, Harold A.↗