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  • 1
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    Physical processes in polar stratospheric ice clouds (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The formulation and evolution of polar stratospheric ice clouds are simulated using a one-dimensional model of cloud microphysics. It is found that the optical thickness and particle size of ice clouds depend on the cooling rate of the air in which the cloud formed. It is necessary that there be an energy barrier to ice nucleation upon the preexisting aerosols in order to account for the cooling rate dependence of the cloud properties.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 11359-11
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  • 2
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    Stratospheric aerosol modification by supersonic transport and space shuttle operations - Climate implications (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The potential effects on stratospheric aerosols of supersonic transport emissions of sulfur dioxide gas and submicron soot granules, and space shuttle rocket emissions of aluminum oxide particulates are estimated. An interactive particle-gas model of the stratospheric aerosol layer is used to calculate changes due to exhaust emissions, and an accurate radiation transport model is employed to compute the effect of aerosol changes on the earth's average surface temperature. It is concluded that the release of large numbers of small particles (soot or aluminum oxide) into the stratosphere should not lead to a corresponding significant increase in the concentration of large, optically active aerosols, but that the increase in large particles is severely limited by the total mass of sulfate available to make large particles in situ, and by the rapid loss of small seed particles via coagulation. We find that a fleet of several hundred advanced supersonic aircraft operating daily at 20 km, or the launch of one space shuttle rocket per week, could produce roughly a 20% increase in the large-particle concentration of the stratosphere. We find, in addition, that aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology; 19; Jan. 198
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  • 3
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    A one-dimensional model describing aerosol formation and evolution in the stratosphere. I - Physical processes and mathematical analogs. II - Sensitivity studies and comparison with observations (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A new time-dependent one-dimensional model of the stratospheric sulfate aerosol layer is developed. The model treats atmospheric photochemistry and aerosol physics in detail and includes the interaction between gases and particles explicitly. It is shown that the numerical algorithms used in the model are quite precise. Sensitivity studies and comparison with observations are made. The simulated aerosol physics generates a particle layer with most of the observed properties. The sensitivity of the calculated properties to changes in a large number of aeronomic aerosol parameters is discussed in some detail. The sensitivity analysis reveals areas where the aerosol model is most uncertain. New observations are suggested that might help resolve important questions about the origin of the stratospheric aerosol layer.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences; 36; Apr. 197
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  • 4
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    Stratospheric aerosol modification by supersonic transport operations with climate implications (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The potential effects on stratospheric aerosois of supersonic transport emissions of sulfur dioxide gas and submicron size soot granules are estimated. An interactive particle-gas model of the stratospheric aerosol is used to compute particle changes due to exhaust emissions, and an accurate radiation transport model is used to compute the attendant surface temperature changes. It is shown that a fleet of several hundred supersonic aircraft, operating daily at 20 km, could produce about a 20% increase in the concentration of large particles in the stratosphere. Aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-RP-1058 , A-7938
    Format: application/pdf
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  • 5
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    Stratospheric aerosols - Observation and theory (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Important chemical and physical roles of aerosols are discussed, and properties of stratospheric aerosols as revealed by experimental data are described. In situ measurements obtained by mechanical collection and scattered-light detection yield the overall size distribution of the aerosols, and analyses of preserved aerosol precursor gases by wet chemical, cryogenic and spectroscopic techniques indicate the photochemical sources of particle mass. Aerosol chemical reactions including those of gaseous precursors, those in aqueous solution, and those on particle surfaces are discussed, in addition to aerosol microphysical processes such as nucleation, condensation/evaporation, coagulation and sedimentation. Models of aerosols incorporating such chemical and physical processes are presented, and simulations are shown to agree with measurements. Estimates are presented for the potential aerosol changes due to emission of particles and gases by aerospace operations and industrial consumption of fossil fuels, and it is demonstrated that although the climatic effects of existing levels of stratospheric aerosol pollution are negligible, potential increases in those levels might pose a future threat.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Reviews of Geophysics and Space Physics; 20; May 1982
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  • 6
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    The NASA-Ames Research Center stratospheric aerosol model. 2. Sensitivity studies and comparison with observatories (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Sensitivity tests were performed on a one-dimensional, physical-chemical model of the unperturbed stratospheric aerosols, and model calculations were compared with observations. The tests and comparisons suggest that coagulation controls the particle number mixing ratio, although the number of condensation nuclei at the tropopause and the diffusion coefficient at high altitudes are also important. The sulfur gas source strength and the aerosol residence time are much more important than the supply of condensation nuclei in establishing mass and large particle concentrations. The particle size is also controlled mainly by gas supply and residence time. In situ observations of the aerosols and laboratory measurements of aerosols, parameters that can provide further information about the physics and chemistry of the stratosphere and the aerosols found there are provided.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-TP-1363 , A-7551
    Format: application/pdf
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  • 7
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    An assessment of the effect of supersonic aircraft operations on the stratospheric ozone content (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An assessment of the potential effect on stratospheric ozone of an advanced supersonic transport operations is presented. This assessment, which was undertaken because of NASA's desire for an up-to-date evaluation to guide programs for the development of supersonic technology and improved aircraft engine designs, uses the most recent chemical reaction rate data. From the results of the present assessment it would appear that realistic fleet sizes should not cause concern with regard to the depletion of the total ozone overburden. For example, the NOx emission of one type designed to cruise at 20 km altitude will cause the ozone overburden to increase by 0.03% to 0.12%, depending upon which vertical transport is used. These ozone changes can be compared with the predictions of a 1.74% ozone decrease (for 100 Large SST's flying at 20 km) made in 1974 by the FAA's Climatic Impact Assessment Program.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-RP-1026 , A-7399
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  • 8
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    The NASA Ames Research Center one- and two-dimensional stratospheric models. Part 1: The one-dimensional model (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A one-dimensional model of stratospheric trace constituents is described in detail. Specifically, the numerical solution of the species continuity equations, including a technique for treating the stiff differential equations representing the chemical kinetic terms, and an appropriate method for simulating the diurnal variations of the species concentrations, are discussed. A specialized treatment of atmospheric photodissociation rates is outlined in the text. The choice of a vertical eddy diffusivity profile and its success in predicting the vertical tracer distributions (carbon 14, methane, and nitrous oxide) are also discussed.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-TP-1002 , A-6983
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  • 9
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    A study of Type I polar stratospheric cloud formation (1994)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Mechanisms for the formation of Type I (nitric acid-based) polar stratospheric clouds (PSCs) are discussed. If the pre-existing sulfate aerosols are liquid prior to PSC formation, then nitric acid particles (Type Ib) form by HNO3 dissolution in aqueous H2SO4 solution droplets. This process does not require a nucleation step for the formation of HNO3 aerosols, so most pre-existing aerosols grow to become relatively small HNO3-containing particles. At significantly lower temperatures, the resulting supercooled solutions (Type Ib) may freeze to form HNO3 ice particles (Type Ia). If the pre-existing sulfate aerosols are initially solid before PSC formation, then HNO3 vapor can be deposited directly on the frozen sulfate particles. However, because an energy barrier to the condensation exists a nucleation mechanism is involved. Here, we suggest a unique nucleation mechanism that involves formation of HNO3/H20 solutions on the sulfate ice particles. These nucleation processes may be highly selective, resulting in the formation of relatively small number of large particles.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 15; p. 1619-1622
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  • 10
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    The NASA-AMES Research Center Stratospheric Aerosol Model. 1. Physical Processes and Computational Analogs (1979)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: A time-dependent one-dimensional model of the stratospheric sulfate aerosol layer is presented. In constructing the model, a wide range of basic physical and chemical processes are incorporated in order to avoid predetermining or biasing the model predictions. The simulation, which extends from the surface to an altitude of 58 km, includes the troposphere as a source of gases and condensation nuclei and as a sink for aerosol droplets. The size distribution of aerosol particles is resolved into 25 categories with particle radii increasing geometrically from 0.01 to 2.56 microns such that particle volume doubles between categories.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-TP-1362 , A-7532
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