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  • 1
    Electronic Resource
    Electronic Resource
    A critical analysis of the concept of planetary wave breaking (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 733-755 
    Details
    ISSN: 1420-9136
    Keywords: wave breaking ; stratospheric transport ; planetary waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The concept of planetary wave breaking (McIntyre andPalmer, 1983; 1984) is critically reviewed. It is concluded that the wave breaking signature is not unique to any particular dynamic event in the stratosphere. Therefore, the classification of stratospheric transport events, such as ‘wave breaking’, groups fundamentally different events together. Better qualification of the wave breaking signature and a more solid theoretical basis of planetary wave breaking must be presented if the concept is to be of significant utility in describing stratospheric tracer transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878405
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Vertical transport by convective clouds: Comparisons of three modeling approaches (1995)
    In:  Other Sources
    Details
    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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  • 3
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    A comparison of winds from the STRATAN data assimilation system to balanced wind estimates (1994)
    In:  Other Sources
    Details
    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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    The minor stratospheric warming of January 1989 - Results from STRATAN, a stratospheric-tropospheric data assimilation system (1992)
    In:  Other Sources
    Details
    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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  • 5
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    Tracer evolution in winds generated by a global spectral mechanistic model (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The lower boundary of a spectral mechanistic model is prescribed with 100 hPa geopotentials, and its performance during a November 1989 through March 1990 integration is compared with National Meteorological Center observations. Although the stratopause temperatures quickly become biased near the pole in both hemispheres, the model develops a residual mean circulation which shows significant descent over the winter pole and ascent in the tropics and over the summer pole at pressures less than 10 hPa. The daily correspondence of observed to modeled features in the upper stratosphere and mesosphere degrades after one month. However, the long-term variability qualitatively follows the observations. The results of off-line transport experiments are also described. A passive tracer is instantaneously injected into the flow over the poles and evolves in a manner which is consistent with the residual mean circulation. It demonstrates a significant cross-equatorial flux in the mesosphere near solstice, and air which originates in the southern hemisphere polar mesosphere can be found descending deep into the nothern polar stratosphere at the end of the integration. Nitrous oxide is also transported, and its ability to act as a dynamical tracer is evaluated by comparison to the evolution of the passive tracer.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D3; p. 5399-5420
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  • 6
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    Evaluation of Transport in the Lower Tropical Stratosphere in a Global Chemistry and Transport Model (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Off-line models of the evolution of stratospheric constituents use meteorological information from a general circulation model (GCM) or from a data assimilation system (DAS). Here we focus on transport in the tropics and between the tropics and middle latitudes. Constituent fields from two simulations are compared with each other and with observations. One simulation uses winds from a GCM and the second uses winds from a DAS that has the same GCM at its core. Comparisons of results from the two simulations with observations from satellite, aircraft, and sondes are used to judge the realism of the tropical transport. Faithful comparisons between simulated fields and observations for O3, CH4, and the age-of-air are found for the simulation using the GCM fields. The same comparisons for the simulation using DAS fields show rapid upward tropical transport and excessive mixing between the tropics and middle latitudes. The unrealistic transport found in the DAS fields may be due to the failure of the GCM used in the assimilation system to represent the quasi-biennial oscillation. The assimilation system accounts for differences between the observations and the GCM by requiring implicit forcing to produce consistency between the GCM and observations. These comparisons suggest that the physical consistency of the GCM fields is more important to transport characteristics in the lower tropical stratosphere than the elimination bias with respect to meteorological observations that is accomplished by the DAS. The comparisons presented here show that GCM fields are more appropriate for long-term calculations to assess the impact of changes in stratospheric composition because the balance between photochemical and transport terms is likely to be represented correctly.
    Keywords: Geophysics
    Format: application/pdf
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  • 7
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    Constituent Data Assimilation: Challenges and Limitations (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The assimilation of observations of atmospheric constituents naturally divides into two major pieces. The first is the assimilation of trace gases whose variability is related to atmospheric motions. The second is the assimilation of trace gases which are sharply influenced by chemical exchange between different constituents. In order to advance beyond the initial successes of explorative investigation of assimilation techniques, tremendous challenges must be met to improve the geophysical integrity of assimilated data products. A subject of special interest is ozone near the tropopause. At the tropopause the information from both the observations and the model simulation becomes most uncertain. However a number of important geophysical parameters, e.g. stratosphere-troposphere exchange and tropospheric ozone, require the assimilation to have high accuracy at the tropopause. This talk will review the current status of the quality of assimilated data products near the tropopause, what must be done to improve the assimilation near the tropopause, and the intrinsic limitations that will require additional sources of information in order for the field to advance.
    Keywords: Geophysics
    Type: 2001 Fall AGU Meeting; Dec 10, 2001 - Dec 14, 2001; San Francisco, CA; United States
    Format: text
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  • 8
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    The Evolution of Stratospheric Data Assimilation Systems (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The use of model-assimilated meteorological observations for stratospheric research has become routine since the late 1980's. The first stratospheric assimilation systems were straightforward extensions of systems developed for tropospheric weather forecasting. During the 1990's systems were developed that more directly addressed the specifics of stratospheric applications. These developments include better treatment of the satellite observations and improved models that better represent the residual circulation in the assimilated data sets. This talk will review the evolution of stratospheric data assimilation and its application, especially to problems of tracer transport. The new data assimilation currently under validation at NASA will be described in some detail, and results from the validation exercise will be presented. This data assimilation system sits at the foundation of a proposed stratospheric reanalysis that covers the era of the Upper Atmosphere Research Satellite (UARS).
    Keywords: Geophysics
    Type: 8th International Association of Meteorology and Atmospheric Sciences Symposium; Jul 10, 2001 - Jul 18, 2001; Innsbruck; Austria
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  • 9
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    Three Dimensional Model Simulation of Constituent Transport in the Lowermost Stratosphere (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The composition, transport and photochemistry of the lowermost stratosphere, i.e., that part of the atmosphere which is above the tropopause, poleward of the tropics, and at potential temperature lower than the potential temperature of the tropical tropopause (about 380K) are of practical interest for understanding global ozone behavior. Because this region is a transition between transport regimes characterized by different scales of dynamics, it is especially difficult to model realistically. Through comparisons of observations of ozone, carbon dioxide and water vapor with results from a chemistry and transport model using winds from a global meteorological assimilation system, we have established that the model provides a good representation of several important aspects of constituent behavior. These include the constituent gradients near the tropopause as well as the annual cycle of constituents and the altitude dependence of the annual cycle from the tropopause into the middle stratosphere. This talk draws together these results to form a unified picture of transport into the lowermost extratropical stratosphere. In particular, the importance of convective transport to the distribution of both short-lived, and long-lived constituents in the lowermost stratosphere will be evaluated.
    Keywords: Geophysics
    Type: Jan 09, 2000 - Jan 14, 2000; Long Beach, CA; United States
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  • 10
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    Thermodynamic balance of three-dimensional stratospheric winds derived from a data assimilation procedure (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The NASA/Goddard three-dimensional chemistry and transport model is driven by winds from a stratospheric data assimilation system. Synoptic- and planetary-scale patterns, apparent in satellite observations of trace constituents, are successfully reproduced for seasonal integrations. As model integrations proceed, however, the quality of simulations decreases, and systematic differences between calculation and measurement appear. The differences are explained by examining the zonal-mean residual circulation. The vertical velocity w-bar (sup star) is calculated two ways: (1) from the diabatic heating rates and temperature tendency and (2) from the Eulerian vertical velocity and the horizontal eddy heat flux convergence. The results from these calculations differ substantially. Periodic insertion of observational data during the assimilation process continually shocks the general circulation model and produces these differences, which leads to an overestimate of the mean vertical heat and cconstituent transport. Such differences are expected to be general to all data assimilation products. This interpretation is corroborated by two-dimensional (2D) model calculations. When w-bar(sup star) is calculated from (2), the 2D ozone evolution is unrealistic and qualitatively similar to the 3D model simulation. The 2D ozone evolution is reasonable when w-bar (sup star) from (1).
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 50; 17; p. 2987-2993
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