気候システムセミナー

日時：金曜日 13:30-15:00
場所：東京大学柏キャンパス 総合研究棟270室
（＊変更の場合もありますので、詳細は下記の予定をご確認ください）

今後の予定

• (1) 14:00-15:30 岡島秀樹（東京大学 大気海洋研究所）
  TBD
  (2) 15:30-17:00 山崎邦子（東京大学 大気海洋研究所）
  Obtaining diverse behaviors in a climate model without the use of flux adjustments
• Place: General Research Bldg. 2F room 270.
• Time: 14:00-17:00 on May 25, 2012.
Abstract:
(1)TBD
(2)Efforts have been made in past research to attain a wide range of atmosphere and ocean model behaviors by varying the parameters in model physics in perturbed physics ensembles (PPE). No PPE experiment, however, has been successful, to our knowledge, in obtaining a large spread of ocean model behavior compared to that exhibited in the ensemble of structurally different models (multi model ensemble), e.g. the CMIP3 ensemble. In this work we randomly vary model parameters of a coupled GCM within plausible ranges elicited from model developers in a space-filling latin-hypercube design containing 10,000 parameter combinations. The ensemble is run over the distributed computing platform of climateprediction.net under fixed pre-industrial forcing without flux adjustment. Furthermore, we resample a second, 20,000 member ensemble of perturbations conditioned on the diagnosed fluxes from the first ensemble to not drift significantly away from a realistic initial base state, a key step since we are not using flux adjustment. The conditioned ensemble is also run under the same fixed pre-industrial forcing as the first. The members of the conditioned ensemble attain the distribution of radiative fluxes very similar to those predicted. The radiatively balanced models within the conditioned ensemble show reasonably realistic regional control base climates in the atmosphere with deviations from observational data similar to those found in the CMIP3 ensemble, although there is a global mean bias. The range of predicted equilibrium climate sensitivities of the conditioned ensemble is substantially smaller than that obtained with flux adjustment (Stainforth et al. 2005), but still larger than the range in the CMIP3 ensemble (Solomon et al. 2007). The Atlantic Meridional Overturning Circulation (AMOC) exhibits a spread in strength as wide as that found in the CMIP3 ensemble. The conditioned ensemble is thus expected to have a wide range of change in the AMOC strength when it is run under enhanced CO2 conditions (Gregory et al. 2005). We conclude that flux adjustment is not a pre-requisite for obtaining a broad spread of behavior in a perturbed physics ensemble.

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