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| Titel |
Contributions of equatorial planetary and gravity waves to the QBO evolution in a GCM with a parameterization of convective gravity waves |
| VerfasserIn |
Young-Ha Kim, Hye-Yeong Chun |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099416
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| Publikation (Nr.) |
 EGU/EGU2014-15192.pdf |
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| Zusammenfassung |
| The equatorial planetary waves and gravity waves (GWs) in the stratosphere and
their contributions to the QBO evolution are investigated in a 54-year (1953–2006)
AMIP-type simulation using a climate configuration of the Unified Model (HadGEM2).
In order to take into account the internal GWs forced by cumulus convection, a
convective GW parameterization is implemented in the HadGEM2 in addition to the
existing GW parameterizations. The parameterized convective GWs account for
about 40% of the total parameterized-GW momentum flux at 100 hPa in the low- to
mid-latitudes. In the simulation, the equatorial QBO is reproduced with realistic
periods (19–31 months) and amplitude (~19.8 m s-1). The asymmetries between
the QBO phases in the period, amplitude and descent rate of the shear zone are
also captured, which is similar to observed. The simulated wind and temperature
variables are spectrally decomposed, and the (model-resolved) equatorial waves
are classified into Kelvin waves, Rossby waves, mixed Rossby-gravity waves, and
inertia-GWs using the spectra. The Eliassen–Palm flux of each wave at the tropical
tropopause and the stratosphere is calculated, and the propagation and attenuation of
the resolved waves are investigated as well as those of the parameterized GWs.
Among the resolved waves, only the Kelvin waves and the inertia-GWs propagate
vertically into the equatorial stratosphere with substantial amplitudes. The Kelvin
waves attenuate significantly in the lowermost stratosphere and contribute to the
easterly-to-westerly transition of the QBO phase by 3–4 m s-1 month-1. The contribution of
the inertia-GWs is much smaller (~1 m s-1 month-1) as their magnitude is smaller
than that of the Kelvin waves. The parameterized GWs contribute predominantly
(15–20 m s-1 month-1) to the simulated QBO in both phases. Finally, the equatorial
planetary waves in the reanalysis and their difference from the simulation are discussed. |
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