Stratospheric Variability at a glance – Analysis of the intra decadal timescale and the QBO
Autor: | Duy Cai, Phoebe Graf, Martin Dameris, Patrick Jöckel, Hella Garny, Felix Bunzel |
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Rok vydání: | 2016 |
Předmět: |
Oscillation
05 social sciences High variability 0507 social and economic geography Power spectral analysis Spectral density Atmospheric sciences 050701 cultural studies Spectral line 0506 political science Airy wave theory Climatology 050602 political science & public administration Environmental science Model configuration Stratosphere Physics::Atmospheric and Oceanic Physics |
Popis: | In this study the stratospheric variability is analysed from decadal to seasonal timescales. Relevant processes for the decadal timescale are identified by means of power spectral analysis. The inspection of the ERA-Interim reanalysis data set shows considerably high variability at the 12 and 6 months period. But also in the extra tropical region at intra-annual to seasonal timescales clear peaks in the power spectrum arise. In addition to that, the quasi-biennial oscillation (QBO) obviously contributes to the stratospheric variability at decadal timescales. Regarding the power spectrum of EMAC 2.52 model simulations, only a model configuration with a vertical resolution smaller than 1 km in the stratosphere is capable to capture the relevant features of the spectrum. In particular, the model with a coarser distribution of vertical levels cannot reproduce the QBO signal. The analysis of the corresponding wave spectra reveals that, if the vertical resolution is insufficient, primarily the Mixed-Rossby-Gravity waves cannot be adequately reproduced. Estimates made by linear wave theory show that for reanalysis data the Mixed-Rossby-Gravity waves with equivalent depths between 50 m to 250 m are relevant for the QBO. In order to resolve these relevant waves, model simulations need to consider a vertical resolution of at least 1 km. |
Databáze: | OpenAIRE |
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