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  • 1
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    Vertical transport by convective clouds: Comparisons of three modeling approaches (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A preliminary comparison of the GEOS-1 (Goddard Earth Observing System) data assimilation system convective cloud mass fluxes with fluxes from a cloud-resolving model (the Goddard Cumulus Ensemble Model, GCE) is reported. A squall line case study (10-11 June 1985 Oklahoma PRESTORM episode) is the basis of the comparison. Regional (central U. S.) monthly total convective mass flux for June 1985 from GEOS-1 compares favorably with estimates from a statistical/dynamical approach using GCE simulations and satellite-derived cloud observations. The GEOS-1 convective mass fluxes produce reasonable estimates of monthly-averaged regional convective venting of CO from the boundary layer at least in an urban-influenced continental region, suggesting that they can be used in tracer transport simulations.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 9; p. 1089-1092
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  • 2
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    Tracer transport for realistic aircraft emission scenarios calculated using a three-dimensional model (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A three-dimensional transport model, which uses winds from a stratospheric data assimilation system, is used to study the transport of supersonic aircraft exhaust in the lower stratosphere. A passive tracer is continuously injected into the transport model. The tracer source distribution is based on realistic scenarios for the daily emission rate of reactive nitrogen species for all forecasted flight routes. Winds are from northern hemisphere winter/spring months for 1979 and 1989; there are minimal differences between the tracer integrations for the 2 years. During the integration, peak tracer mixing ratios in the flight corridors are compared with the zonal mean and found to be greater by a factor of 2 or less. This implies that the zonal mean assumption used in two dimensional models is reasonable during winter and spring. There is a preference for pollutant buildup in the heavily traveled North Pacific and North Atlantic flight corridors. Pollutant concentration in the corridors depends on the position of the Aleutian anticyclone and the northern hemisphere polar vortex edge.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D3; p. 5203-5214
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  • 3
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    A comparison of winds from the STRATAN data assimilation system to balanced wind estimates (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Winds derived from a stratospheric and tropospheric data assimilation system (STRATAN) are compared with balance winds derived from National Meteorological Center/Climate Analysis Center (NMC/CAC) heights. At middle latitudes in the lower stratosphere, the results show that STRATAN winds are comparable to the balance winds. In addition STRATAN winds provide useful horizontal divergence analyses, and hence, vertical velocity fields. More generally, the STRATAN winds are useful in a more extended domain than the balanced winds. In particular, they are useful in the Tropics and the upper stratosphere where the balanced winds fail. The assimilation also captures the quasi-biennial oscillation, but does not do a good job of representing tropical waves.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 51; 15; p. 2309-2315
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  • 4
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    Implications of three-dimensional tracer studies for two-dimensional assessments of the impact of supersonic aircraft on stratospheric ozone (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A 2D model which uses residual circulation and diffusion and a 3D model which uses winds from a stratospheric data assimilation system are used to estimate transport and dispersion of supersonic aircraft exhaust in the lower stratosphere. The seasonal behavior of the exhaust fields in the two models are is similar, but there is a significant difference in the placement of stratosphere/troposphere exchange in the two models. In the 2D model, exhaust transport to the troposphere occurs mostly at high latitudes, while in the 3D model it occurs at middle latitudes and is clearly associated with synoptic scale events. This may be particularly important to assessment calculations, as the pollutant source is mostly in middle latitudes. The 3D model is also used to examine the transport and dispersion of exhaust in three typical flight corridors: North Atlantic, North Pacific, and tropical. There are no systematic differences that suggest that one corridor is inherently more or less polluting than another.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; D5; p. 8949-8963.
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  • 5
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    Episodic total ozone minima and associated effects on heterogeneous chemistry and lower stratospheric transport (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Three-dimensional model simulations are used to describe the January 31, 1989 ozone minihole over Stavanger, Norway. This minihole is typical of many transient events in the lower stratosphere that arise because of cyclonic-scale disturbances in the troposphere. Although the ozone reduction is a short-lived reversible dynamical event, through heterogeneous chemical processes there can be a significant transfer of chlorine from reservoir molecules to active radicals. This chemically perturbed air is defined as processed air, and it is found that a single event can produce enough processed air to reduce the HCl in the entire polar vortex. Chemical processing on clouds associated with transient events is shown to be a major source of processed air in the polar vortex in December before background temperatures are cold enough for more uniform heterogeneous conversion.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; D8, M
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  • 6
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    The minor stratospheric warming of January 1989 - Results from STRATAN, a stratospheric-tropospheric data assimilation system (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Using a stratospheric-tropospheric data assimilation system, referred to as STRATAN, a minor sudden stratospheric warming that occurred in January 1989 is investigated. The event had a maximum influence on the stratospheric circulation near 2 hPa. The zonal mean circulation reversed briefly in the polar region as the temperature increased 34 K in 3 days. The cause of the warming is shown to be the rapid development and subsequent movement of a warm anomaly, which initially developed in the midlatitudes. The development of the warm anomaly is caused by adiabatic descent, and the dissipation by radiative cooling. A brief comparison with the NMC analysis and temperature sounding data is also presented.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 120; 221-229
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  • 7
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    Application of a monotonic upstream-biased transport scheme to three-dimensional constituent transport calculations (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The application of van Leer's scheme, a monotonic, upstream-biased differencing scheme, to three-dimensional constituent transport calculations is shown. The major disadvantage of the scheme is shown to be a self-limiting diffusion. A major advantage of the scheme is shown to be its ability to maintain constituent correlations. The scheme is adapted for a spherical coordinate system with a hybrid sigma-pressure coordinate in the vertical. Special consideration is given to cross-polar flow. The vertical wind calculation is shown to be extremely sensitive to the method of calculating the divergence. This sensitivity implies that a vertical wind formulation consistent with the transport scheme is essential for accurate transport calculations. The computational savings of the time-splitting method used to solve this equation are shown. Finally, the capabilities of this scheme are illustrated by an ozone transport and chemistry model simulation.
    Keywords: GEOPHYSICS
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 2456-246
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  • 8
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    Three-dimensional simulations of wintertime ozone variability in the lower stratosphere (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The evolution of ozone has been calculated for the winters of 1979 and 1989 using winds derived from the stratospheric data assimilation system STRATAN. The ozone fields calculated using this technique are found to compare well with satellite-measured fields for simulations of 2-3 months. This paper presents comparisons of model fields with both satellite and sonde measurements to verify that stratospheric transport processes are properly represented by this modeling technique. Attention is focused on the Northern Hemisphere middle and high latitudes at the 10-hPa level and below, where transport processes are most important to the ozone distribution. First-order quantities and derived budgets from both the model and satellite data are presented. By sampling the model with a limb-viewing satellite and then Kalman filtering the 'observations' of the model, it is shown that transient subplanetary-scale features that are essential to the ozone budget are missed by the satellite system.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 5055-507
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  • 9
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    Effect of solar proton events on the middle atmosphere during the past two solar cycles as computed using a two-dimensional model (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper investigates the effects of solar proton events (SPEs) on the middle atmosphere during the past two solar cycles (1963-1984), by examining changes in the production of odd nitrogen, NO(y), and ozone and using a proton energy degradation scheme to derive ion pair production rates. These calculations show that NO(y) is not substantially changed over a solar cycle by SPEs; significant SPEs last only 1-5 days, tend to occur near solar maximum, and are typically months to years apart, preventing a build up of SPE-produced NO(y). Fractional ozone changes are even smaller than the fractional NO(y) changes and are significant only for the August 1972 SPE. Ozone, like NO(y), returns to its ambient levels on time scales of several months to a year.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7417-742
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  • 10
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    Spatial and temporal variability of the extent of chemically processed stratospheric air (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Simulations of the spatial and temporal variability of the extent of chemically processed air in the Arctic stratosphere have been carried out using a three-dimensional chemistry-transport model for the winters of 1979 and 1989. Chemically processed air is identified in the model as that in which the amounts of hydrogen chloride (HCl) calculated with parameterized loss for conditions appropriate to polar stratospheric cloud (PSC) formation are substantially smaller than those calculated in a model with gas phase chemistry only. It is seen that chemically processed air may be identified over much of the Arctic lower stratosphere from early January to late February, with HCl depletions being larger in 1989 than in 1979. Near the latitude of the Arctic circle, there is important spatial and temporal variability in the extent of chemically processed air. There is some evidence for transport to midlatitudes of processed air during these winters, but the HCl reductions are much smaller and more sporadic than those near the pole. At 62 and 42N, processed air is calculated to occur preferentially over the longitude regions from 60-120E and 270-330E.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 29-32
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