[A-AS05] 大規模な水蒸気場と組織化した雲システム

[AAS05-12] Dependence of the reproducibility of the MJO convection on differences in the surface flux conditions in NICAM

*末松 環¹、小玉 知央²、八代 尚³、柳瀬 友朗⁴、三浦 裕亮⁵、宮川 知己¹、佐藤 正樹¹ (1.東京大学大気海洋研究所、2.海洋研究開発機構、3.国立環境研究所、4.京都大学大学院理学研究科、5.東京大学大学院理学系研究科)

キーワード：非静力学正２０面体格子大気モデル、雲解像モデル、マッデン・ジュリアン振動

Simulation of the Madden-Julian Oscillation has been notoriously difficult in atmospheric models. Although it has been over a decade since the first realistic simulation of the Madden-Julian Oscillation has succeeded using the non-icosahedral atmospheric model (NICAM; Miura et al. 2007), reproducibility of the MJO remains highly sensitive to parameters that are often difficult to fix from observation or theory, and require empirical tuning based on model behaviors. Moreover, model settings fine-tuned for MJO simulations are not necessarily compatible with longer simulations due to biases in the long-term mean. Therefore, the selection of parameters that adequately simulate the MJO without undermining the long-term mean remains a challenging problem.
To address this problem, we conducted parameter sweep experiments on NICAM on parameters that regulate the surface latent heat fluxes, which in turn influence the development of convection. From the parameter sweep experiments, we selected parameter sets that best simulate the MJO case from December to January 2019, and investigated how the changes in the parameters influenced the month-long mean states. We found that while the best performing parameter sets for MJO simulation displayed overly high surface latent heat flux over the equatorial Pacific, it also mitigated the double ITCZ bias in the month-mean precipitation patterns.