Vertical structure and physical processes of the Madden‐Julian oscillation: Exploring key model physics in climate simulations
Vertical structure and physical processes of the Madden‐Julian oscillation: Exploring key model physics in climate simulations
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DOI：
10.1002/2014jd022375
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发表时间：
2015-05
期刊：
影响因子：
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通讯作者：
Xianan Jiang;D. Waliser;P. Xavier;J. Petch;N. Klingaman;S. Woolnough;B. Guan;G. Bellon;T. Crueg
中科院分区：
文献类型：
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作者：
Xianan Jiang;D. Waliser;P. Xavier;J. Petch;N. Klingaman;S. Woolnough;B. Guan;G. Bellon;T. Crueg
为了减少在大气环流模式（GCMs）中表达Madden - Julian振荡（MJO）的不足，协调了一个关于MJO垂直结构和物理过程的全球模式评价项目。本文报告了该项目的气候模拟部分的结果。结果表明，在这些最新一代gcm中，MJO仍然是一个巨大的挑战。在所有参与模式中，只有大约四分之一的模式能很好地模拟MJO的系统向东传播。较好的MJO模式较好地模拟了观测到的垂直向西倾斜随MJO高度的变化，而较差的MJO模式则不能。在这些较差的MJO模式中，对流层低层对流以东的阻尼开尔文波响应可能是MJO预处理过程缺失的原因。进行了几个面向过程的诊断，以区分现实MJO模拟的关键过程。虽然在一个模式中，印度太平洋的大尺度降雨分区和低层平均纬向风与MJO技能没有密切联系，但两个指标，包括高降雨和低降雨事件之间的低层相对湿度差和季节平均总湿度稳定性，与MJO表现出统计上显著的相关性。进一步表明，云辐射反馈的增加往往与季节内变率幅度的减小有关，这与先前提出的MJO辐射不稳定性理论不相容。本研究的结果证实，纳入海气相互作用可以显著改善MJO的模拟。
Aimed at reducing deficiencies in representing the Madden‐Julian oscillation (MJO) in general circulation models (GCMs), a global model evaluation project on vertical structure and physical processes of the MJO was coordinated. In this paper, results from the climate simulation component of this project are reported. It is shown that the MJO remains a great challenge in these latest generation GCMs. The systematic eastward propagation of the MJO is only well simulated in about one fourth of the total participating models. The observed vertical westward tilt with altitude of the MJO is well simulated in good MJO models but not in the poor ones. Damped Kelvin wave responses to the east of convection in the lower troposphere could be responsible for the missing MJO preconditioning process in these poor MJO models. Several process‐oriented diagnostics were conducted to discriminate key processes for realistic MJO simulations. While large‐scale rainfall partition and low‐level mean zonal winds over the Indo‐Pacific in a model are not found to be closely associated with its MJO skill, two metrics, including the low‐level relative humidity difference between high‐ and low‐rain events and seasonal mean gross moist stability, exhibit statistically significant correlations with the MJO performance. It is further indicated that increased cloud‐radiative feedback tends to be associated with reduced amplitude of intraseasonal variability, which is incompatible with the radiative instability theory previously proposed for the MJO. Results in this study confirm that inclusion of air‐sea interaction can lead to significant improvement in simulating the MJO.