Budget study of the internal variability in ensemble simulations of the Canadian Regional Climate Model at the seasonal scale

Nikiema, Oumarou et Laprise, René (2011). « Budget study of the internal variability in ensemble simulations of the Canadian Regional Climate Model at the seasonal scale ». Journal of Geophysical Research: Atmospheres, 116(D16112).

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Previous investigations with nested regional climate models have revealed that simulations are sensitive to the initial conditions (IC). This results in internal variability (IV) in ensembles of simulations initialized with small differences in IC. In a previous study, a quantitative budget calculation has documented the physical processes responsible for the rapid growth of IV in simulations with the Canadian Regional Climate Model (CRCM). By using an ensemble of 20 simulations performed for the 1993 summer season, we extend the previous study to further our understanding about the physical processes responsible for the maintenance and fluctuations of IV in a seasonal simulation with CRCM. We have identified and quantified various terms in the prognostic budget equations of IV for the potential temperature and the absolute vorticity. For these studied variables, the covariance of fluctuations acting on the gradient of the ensemble mean of variables generally contributes to increasing the IV, indicating that the transport of heat and vorticity is down the gradient of ensemble mean potential temperature and absolute vorticity. The horizontal transport of IV by ensemble mean flow acts as a sink term, the IV transport out of the study domain contributing to reduce the IV. On average in the troposphere and at the seasonal scale, results confirm that there is no trend in IV although it greatly fluctuates in time. Our results also show that IV is a natural phenomenon arising from the chaotic nature of the atmosphere. In a time-averaged sense, the IV budget reduces to a balance between generation and destruction terms.

Type: Article de revue scientifique
Mots-clés ou Sujets: Internal variability, North American climate, ensemble of simulations, regional climate models
Unité d'appartenance: Centres institutionnels > Centre pour l'étude et la simulation du climat à l'échelle régionale (ESCER)
Faculté des sciences > Département des sciences de la Terre et de l'atmosphère
Déposé par: René Laprise
Date de dépôt: 01 avr. 2016 18:47
Dernière modification: 19 avr. 2016 18:18
Adresse URL : http://archipel.uqam.ca/id/eprint/8071


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