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  • 1
    Online Resource
    Online Resource
    Role of Gravity Waves in a Vortex-Split Sudden Stratospheric Warming in January 2009
    American Meteorological Society ; 2020
    In:  Journal of the Atmospheric Sciences Vol. 77, No. 10 ( 2020-10-01), p. 3321-3342
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 77, No. 10 ( 2020-10-01), p. 3321-3342
    Abstract: The role of gravity waves (GWs) in a sudden stratospheric warming (SSW) event that occurred in January 2009 (SSW09) is investigated using the MERRA-2 dataset. Nearly 2 weeks prior to the central date (lag = 0), at which the zonal-mean zonal wind at 10 hPa and 60°N first becomes negative, westward GW drag (GWD) is significantly enhanced in the lower mesosphere and stratosphere. At 5 days before lag = 0, planetary waves (PWs) of zonal wavenumber 2 (ZWN-2) in the stratosphere are enhanced, while PWs of ZWN-1 are weakened, which are evident from the amplitudes of the PWs and their Eliassen–Palm flux divergence (EPD). To examine the relationship between PWs and GWs, a nonconservative GWD (NCGWD) source term of the linearized quasigeostrophic potential vorticity equation is considered. A ZWN-2 pattern of the NCGWD forcing is developed around z = 55–60 km with a secondary peak around z = 40 km just before the PWs of ZWN-2 in the stratosphere began to enhance. A significant positive correlation between the NCGWD forcing in the upper stratosphere and lower mesosphere (USLM; 0.3–0.1 hPa in the present data) and the PWs of ZWN-2 in the stratosphere (5–1 hPa) exists. This result demonstrates that the amplification of the PWs of ZWN-2 in the stratosphere before the onset of SSW09 is likely related to the generation of PWs by GWD in the USLM, which is revealed by the enhanced downward-propagating PWs of ZWN-2 into the stratosphere from above.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    URL: Article
    DOI: 10.1175/JAS-D-20-0039.1
    DOI: 10.1175/JAS-D-20-0039.s1
    RVK:
    UA 4800
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Test of a convectively forced gravity wave drag parameterization in a general circulation model
    Springer Science and Business Media LLC ; 2010
    In:  Asia-Pacific Journal of Atmospheric Sciences Vol. 46, No. 1 ( 2010-2), p. 1-10
    Details
    In: Asia-Pacific Journal of Atmospheric Sciences, Springer Science and Business Media LLC, Vol. 46, No. 1 ( 2010-2), p. 1-10
    Type of Medium: Online Resource
    ISSN: 1976-7633 , 1976-7951
    URL: Article
    DOI: 10.1007/s13143-010-0001-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2010
    detail.hit.zdb_id: 2545937-5
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  • 3
    Online Resource
    Online Resource
    Propagation of gravity waves and its effects on pseudomomentum flux in a sudden stratospheric warming event
    Copernicus GmbH ; 2020
    In:  Atmospheric Chemistry and Physics Vol. 20, No. 12 ( 2020-07-01), p. 7617-7644
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 12 ( 2020-07-01), p. 7617-7644
    Abstract: Abstract. Effects of realistic propagation of gravity waves (GWs) on distribution of GW pseudomomentum fluxes are explored using a global ray-tracing model for the 2009 sudden stratospheric warming (SSW) event. Four-dimensional (4D; x–z and t) and two-dimensional (2D; z and t) results are compared for various parameterized pseudomomentum fluxes. In ray-tracing equations, refraction due to horizontal wind shear and curvature effects are found important and comparable to one another in magnitude. In the 4D, westward pseudomomentum fluxes are enhanced in the upper troposphere and northern stratosphere due to refraction and curvature effects around fluctuating jet flows. In the northern polar upper mesosphere and lower thermosphere, eastward pseudomomentum fluxes are increased in the 4D. GWs are found to propagate more to the upper atmosphere in the 4D, since horizontal propagation and change in wave numbers due to refraction and curvature effects can make it more possible that GWs elude critical level filtering and saturation in the lower atmosphere. GW focusing effects occur around jet cores, and ray-tube effects appear where the polar stratospheric jets vary substantially in space and time. Enhancement of the structure of zonal wave number 2 in pseudomomentum fluxes in the middle stratosphere begins from the early stage of the SSW evolution. An increase in pseudomomentum fluxes in the upper atmosphere is present even after the onset in the 4D. Significantly enhanced pseudomomentum fluxes, when the polar vortex is disturbed, are related to GWs with small intrinsic group velocity (wave capture), and they would change nonlocally nearby large-scale vortex structures without substantially changing local mean flows.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-20-7617-2020
    DOI: 10.5194/acp-20-7617-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 4
    Online Resource
    Online Resource
    Momentum Flux Spectrum of Convectively Forced Gravity Waves: Can Diabatic Forcing Be a Proxy for Convective Forcing?
    American Meteorological Society ; 2005
    In:  Journal of the Atmospheric Sciences Vol. 62, No. 11 ( 2005-11-01), p. 4113-4120
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 62, No. 11 ( 2005-11-01), p. 4113-4120
    Abstract: The momentum flux of convectively forced internal gravity waves is calculated using explicitly resolved model-simulated gravity wave data. The momentum flux in a control simulation with nonlinearity and cloud microphysical processes is compared with that in quasi-linear dry simulations with either diabatic forcing or nonlinear forcing. It is found that the momentum flux induced by either of these two sources is significantly different from each other and also from the momentum flux in the control simulation. This is because the spectral distribution and magnitude of each wave source are significantly different and the cancellation of the momentum flux by cross-correlation terms between the two sources cannot be included in the momentum flux by a single source. This suggests that a parameterization of convectively forced gravity waves must take into account nonlinear forcing as well as diabatic forcing in order to qualitatively and quantitatively represent the reference-level momentum flux spectrum.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/JAS3610.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2005
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    A Lagrangian Spectral Parameterization of Gravity Wave Drag Induced by Cumulus Convection
    American Meteorological Society ; 2008
    In:  Journal of the Atmospheric Sciences Vol. 65, No. 4 ( 2008-04-01), p. 1204-1224
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 65, No. 4 ( 2008-04-01), p. 1204-1224
    Abstract: A Lagrangian spectral parameterization of gravity wave drag (GWD) induced by cumulus convection (GWDC) is developed based on ray theory and several assumptions and implemented into the NCAR Whole Atmosphere Community Climate Model. The Lagrangian parameterization calculates explicitly gravity wave (GW) propagation that has been treated too simply in existing column-based parameterizations. For comparison with column-based parameterization, a hydrostatic and Boussinesq version of the Lagrangian parameterization is used in the present study. One-day convective GW-packet trajectories demonstrate that the Lagrangian parameterization calculates reasonably the GW-packet propagation, and GW packets propagate upward along curved paths determined by Doppler shifting and the variation of stability. The GW trajectories show that the horizontal extent of GW propagation can be as large as 20° as GWs approach critical levels. Comparison with column-based parameterization through one-month simulations indicates that the magnitude of GWDC is much increased due mainly to the vertical convergence of GW packets in the lower stratosphere and equatorial troposphere with the Lagrangian parameterization. However, this increase in GWDC is found to be essentially dependent on the horizontal propagation characteristics of GWs. In climate simulations, it is found that the easterly flow in the equatorial stratosphere and mesospheric subtropical jet are improved through the Lagrangian parameterization. With the Lagrangian parameterization, interannual variability is significantly enhanced in the equatorial lower stratosphere and exhibits a structure related to the onset of the westerly phase of the stratospheric quasi-biennial oscillations. Finally, limitations of the current Lagrangian parameterization and required improvements are noted.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/2007JAS2369.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2008
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Momentum Flux Spectrum of Convectively Forced Internal Gravity Waves and Its Application to Gravity Wave Drag Parameterization. Part I: Theory
    American Meteorological Society ; 2005
    In:  Journal of the Atmospheric Sciences Vol. 62, No. 1 ( 2005-01-01), p. 107-124
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 62, No. 1 ( 2005-01-01), p. 107-124
    Abstract: The phase-speed spectrum of momentum flux by convectively forced internal gravity waves is analytically formulated in two- and three-dimensional frameworks. For this, a three-layer atmosphere that has a constant vertical wind shear in the lowest layer, a uniform wind above, and piecewise constant buoyancy frequency in a forcing region and above is considered. The wave momentum flux at cloud top is determined by the spectral combination of a wave-filtering and resonance factor and diabatic forcing. The wave-filtering and resonance factor that is determined by the basic-state wind and stability and the vertical configuration of forcing restricts the effectiveness of the forcing, and thus only a part of the forcing spectrum can be used for generating gravity waves that propagate above cumulus clouds. The spectral distribution of the wave momentum flux is largely determined by the wave-filtering and resonance factor, but the magnitude of the momentum flux varies significantly according to spatial and time scales and moving speed of the forcing. The wave momentum flux formulation in the two-dimensional framework is extended to the three-dimensional framework. The three-dimensional momentum flux formulation is similar to the two-dimensional one except that the wave propagation in various horizontal directions and the three-dimensionality of forcing are allowed. The wave momentum flux spectrum formulated in this study is validated using mesoscale numerical model results and can reproduce the overall spectral structure and magnitude of the wave momentum flux spectra induced by numerically simulated mesoscale convective systems reasonably well.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/JAS-3363.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2005
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Impact of a Convectively Forced Gravity Wave Drag Parameterization in NCAR CCM3
    American Meteorological Society ; 2004
    In:  Journal of Climate Vol. 17, No. 18 ( 2004-09), p. 3530-3547
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 17, No. 18 ( 2004-09), p. 3530-3547
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/1520-0442(2004)017〈3530:IOACFG〉2.0.CO;2
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2004
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 8
    Online Resource
    Online Resource
    Effects of Nonlinearity on Convectively Forced Internal Gravity Waves: Application to a Gravity Wave Drag Parameterization
    American Meteorological Society ; 2008
    In:  Journal of the Atmospheric Sciences Vol. 65, No. 2 ( 2008-02-01), p. 557-575
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 65, No. 2 ( 2008-02-01), p. 557-575
    Abstract: In the present study, the authors propose a way to include a nonlinear forcing effect on the momentum flux spectrum of convectively forced internal gravity waves using a nondimensional numerical model (NDM) in a two-dimensional framework. In NDM, the nonlinear forcing is represented by nonlinear advection terms multiplied by the nonlinearity factor (NF) of the thermally induced internal gravity waves for a given specified diabatic forcing. It was found that the magnitudes of the waves and resultant momentum flux above the specified forcing decrease with increasing NF due to cancellation between the two forcing mechanisms. Using the momentum flux spectrum obtained by the NDM simulations with various NFs, a scale factor for the momentum flux, normalized by the momentum flux induced by diabatic forcing alone, is formulated as a function of NF. Inclusion of the nonlinear forcing effect into current convective gravity wave drag (GWD) parameterizations, which consider diabatic forcing alone by multiplying the cloud-top momentum flux spectrum by the scale factor, is proposed. An updated convective GWD parameterization using the scale factor is implemented into the NCAR Whole Atmosphere Community Climate Model (WACCM). The 10-yr simulation results, compared with those by the original convective GWD parameterization considering diabatic forcing alone, showed that the magnitude of the zonal-mean cloud-top momentum flux is reduced for wide range of phase speed spectrum by about 10%, except in the middle latitude storm-track regions where the cloud-top momentum flux is amplified. The zonal drag forcing is determined largely by the wave propagation condition under the reduced magnitude of the cloud-top momentum flux, and its magnitude decreases in many regions, but there are several areas of increasing drag forcing, especially in the tropical upper mesosphere and lower thermosphere.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/2007JAS2255.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2008
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Characteristics of gravity waves generated in the jet-front system in a baroclinic instability simulation
    Copernicus GmbH ; 2016
    In:  Atmospheric Chemistry and Physics Vol. 16, No. 8 ( 2016-04-19), p. 4799-4815
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 16, No. 8 ( 2016-04-19), p. 4799-4815
    Abstract: Abstract. An idealized baroclinic instability case is simulated using a  ∼  10 km resolution global model to investigate the characteristics of gravity waves generated in the baroclinic life cycle. Three groups of gravity waves appear around the high-latitude surface trough at the mature stage of the baroclinic wave. They have horizontal and vertical wavelengths of 40–400 and 2.9–9.8 km, respectively, in the upper troposphere. The two-dimensional phase-velocity spectrum of the waves is arc shaped with a peak at 17 m s−1 eastward. These waves have difficulty in propagating upward through the tropospheric westerly jet. At the breaking stage of the baroclinic wave, a midlatitude surface low is isolated from the higher-latitude trough, and two groups of quasi-stationary gravity waves appear near the surface low. These waves have horizontal and vertical wavelengths of 60–400 and 4.9–14 km, respectively, and are able to propagate vertically for long distances. The simulated gravity waves seem to be generated by surface fronts, given that the structures and speeds of wave phases are coherent with those of the fronts.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-16-4799-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 10
    Online Resource
    Online Resource
    Generation Mechanisms of Convectively Forced Internal Gravity Waves and Their Propagation to the Stratosphere
    American Meteorological Society ; 2003
    In:  Journal of the Atmospheric Sciences Vol. 60, No. 16 ( 2003-08), p. 1960-1980
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 60, No. 16 ( 2003-08), p. 1960-1980
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/1520-0469(2003)060〈1960:GMOCFI〉2.0.CO;2
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2003
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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