A General Circulation Model Study of the Impact of a Stratospheric Sudden Warming Event on Tropical Convection

Kodera, Kunihiko; Mukougawa, Hitoshi; Kuroda, Yoji

doi:10.2151/sola.2011-050

Cited by 15 publications

(20 citation statements)

References 21 publications

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“…Our previous numerical experiment also shows that, when local cooling occurs near the tropopause, upwelling enhances, accompanying a warming in the lower TTL and the upper troposphere (see Fig. 4 of Kodera et al, 2011a). A global nonhydrostatic model study (Eguchi et al, 2015) also confirmed the relationship suggested in the present result.…”

Section: Summary and Discussionsupporting

confidence: 89%

“…A possible impact of stratospheric meridional circulation on cumulus heating has been suggested by Thuburn and Craig (2000) in a simplified general circulation model experiment. Stratospheric upwelling effects on tropical convection is also confirmed by a more realistic general circulation model forecast study (Kodera et al, 2011a). These models make use of cumulus parameterization to account for the effect of convection into large-scale circulation.…”

Section: Introductionmentioning

confidence: 60%

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The role of convective overshooting clouds in tropical stratosphere–troposphere dynamical coupling

et al. 2015

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Abstract. This paper investigates the role of deep convection and overshooting convective clouds in stratospheretroposphere dynamical coupling in the tropics during two large major stratospheric sudden warming events in January 2009 and January 2010. During both events, convective activity and precipitation increased in the equatorial Southern Hemisphere as a result of a strengthening of the BrewerDobson circulation induced by enhanced stratospheric planetary wave activity. Correlation coefficients between variables related to the convective activity and the vertical velocity were calculated to identify the processes connecting stratospheric variability to the troposphere. Convective overshooting clouds showed a direct relationship to lower stratospheric upwelling at around 70-50 hPa. As the tropospheric circulation change lags behind that of the stratosphere, outgoing longwave radiation shows almost no simultaneous correlation with the stratospheric upwelling. This result suggests that the stratospheric circulation change first penetrates into the troposphere through the modulation of deep convective activity.

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Section: Summary and Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 60%

The role of convective overshooting clouds in tropical stratosphere–troposphere dynamical coupling

et al. 2015

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“…12d). Previous model studies (Thuburn and Craig, 2000;Kodera et al, 2011) showed that changes in stratospheric meridional circulation affect tropical convective activity through changes in static stability in the tropical tropopause region (Eguchi et al, 2015). In the present experiments also, suppression of equatorial ascending motion occurs in the troposphere in connection with the reduction of stratospheric mean meridional circulation change, as can be seen in the residual circulation differences in Fig.…”

Section: Stratosphere-troposphere Dynamical Coupling Processessupporting

confidence: 80%

How can we understand the global distribution of the solar cycle signal on the Earth's surface?

Kodera

Thiéblemont²,

Yukimoto

et al. 2016

Atmos. Chem. Phys.

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Abstract. To understand solar cycle signals on the Earth's surface and identify the physical mechanisms responsible, surface temperature variations from observations as well as climate model data are analysed to characterize their spatial structure. The solar signal in the annual mean surface temperature is characterized by (i) mid-latitude warming and (ii) no overall tropical warming. The mid-latitude warming during solar maxima in both hemispheres is associated with a downward penetration of zonal mean zonal wind anomalies from the upper stratosphere during late winter. During the Northern Hemisphere winter this is manifested by a modulation of the polar-night jet, whereas in the Southern Hemisphere, the upper stratospheric subtropical jet plays the major role. Warming signals are particularly apparent over the Eurasian continent and ocean frontal zones, including a previously reported lagged response over the North Atlantic. In the tropics, local warming occurs over the Indian and central Pacific oceans during high solar activity. However, this warming is counterbalanced by cooling over the cold tongue sectors in the southeastern Pacific and the South Atlantic, and results in a very weak zonally averaged tropical mean signal. The cooling in the ocean basins is associated with stronger cross-equatorial winds resulting from a northward shift of the ascending branch of the Hadley circulation during solar maxima. To understand the complex processes involved in the solar signal transfer, results of an idealized middle atmosphere-ocean coupled model experiment on the impact of stratospheric zonal wind changes are compared with solar signals in observations. Model integration of 100 years of strong or weak stratospheric westerly jet condition in winter may exaggerate long-term ocean feedback. However, the role of ocean in the solar influence on the Earth's surface can be better seen. Although the momentum forcing differs from that of solar radiative forcing, the model results suggest that stratospheric changes can influence the troposphere, not only in the extratropics but also in the tropics through (i) a downward migration of wave-zonal mean flow interactions and (ii) changes in the stratospheric mean meridional circulation. These experiments support earlier evidence of an indirect solar influence from the stratosphere.

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“…As a pilot study, simulation data from a global nonhydrostatic model (NICAM), where moist convection is explicitly represented, were analysed. The impact of the SSWs has been confirmed in a previous ensemble mean forecast study of a conventional GCM by implementing a perturbation in the extratropical initial field to produce or to suppress the SSW (Kodera et al, 2011). Note, however, that the cumulus convection is parameterized in this GCM, so that we further need to verify whether similar results are obtained by using a global cloud resolving model.…”

Section: Summary and Discussionsupporting

confidence: 61%

“…Thuburn and Craig (2000) used momentum forcing in a simplified global general circulation model (GCM) to show that a change in the stratospheric meridional circulation modified cumulus heating in the TTL as well as the tropopause height. Kodera et al (2011) constructed a more realistic forecast experiment by incorporating an atmospheric blocking-type circulation anomaly in the North Atlantic in the initial conditions to amplify planetary waves and produce strong BD circulation later in the stratosphere. The results showed similar effects in the tropics to those seen in observational studies; that is, the tropical convective activity was enhanced zonally, especially in the Southern Hemisphere (SH), and cooling at the tropopause region associated with the SSW event was capable of modulating tropical convective activity.…”

Section: Introductionmentioning

confidence: 99%

A global non-hydrostatic model study of a downward coupling through the tropical tropopause layer during a stratospheric sudden warming

2015

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Abstract. The dynamical coupling process between the stratosphere and troposphere in the tropical tropopause layer (TTL) during a stratospheric sudden warming (SSW) in boreal winter was investigated using simulation data from a global non-hydrostatic model (NICAM) that does not use cumulus parameterization. The model reproduced well the observed tropical tropospheric changes during the SSW, including the enhancement of convective activity following the amplification of planetary waves. Deep convective activity was enhanced in the latitude zone 20-10 • S, in particular over the southwest Pacific and southwest Indian Ocean. Although the upwelling in the TTL was correlated with that in the stratosphere, the temperature tendency in the TTL changed little due to a compensation by diabatic heating originating from cloud formation. This result suggests that the stratospheric meridional circulation affects cloud formation in the TTL.

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A General Circulation Model Study of the Impact of a Stratospheric Sudden Warming Event on Tropical Convection

Cited by 15 publications

References 21 publications

The role of convective overshooting clouds in tropical stratosphere–troposphere dynamical coupling

The role of convective overshooting clouds in tropical stratosphere–troposphere dynamical coupling

How can we understand the global distribution of the solar cycle signal on the Earth's surface?

A global non-hydrostatic model study of a downward coupling through the tropical tropopause layer during a stratospheric sudden warming

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