Cloud Radiative Feedbacks and El Niño–Southern Oscillation
Cloud Radiative Feedbacks and El Niño–Southern Oscillation
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DOI：
10.1175/jcli-d-18-0842.1
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发表时间：
2019-07
影响因子：
4.9
通讯作者：
E. Middlemas;A. Clement;B. Medeiros;B. Kirtman
中科院分区：
文献类型：
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作者：
E. Middlemas;A. Clement;B. Medeiros;B. Kirtman
云辐射反馈通过社区地球系统模型 1.2 版 (CESM1.2) 中的“云锁定”被禁用，导致厄尔尼诺南方涛动 (ENSO) 周期从 2-7 年转变为十年时间尺度。我们假设云辐射反馈可能通过三种方式影响周期性：1）通过海面温度异常（SSTA）的负短波云反馈调节局部热通量进入赤道太平洋地下；2）抑制副热带东南太平洋海温异常的持续性，从而使南太平洋经向模态影响 ENSO 事件的持续时间；或 3）控制离赤道西风的经向宽度，从而影响 ENSO 事件的周期性。 ENSO 通过引发更长的罗斯比波。 CESM1.2 中的云锁定结果与另一项研究的结果形成对比，该研究发现，由于异常沃克环流缺乏正长波反馈，不同全球气候模型中的云锁定导致所有时间尺度的 ENSO 震级下降。 CESM1.2包含对异常沃克环流的正长波反馈，但其对地表的影响与海洋动力学脱钩，或者反馈仅在年际时间尺度上活跃。另外还考虑了 ENSO 中云辐射反馈在其他全球气候模型中的作用。特别是，结果表明，无法通过多模型诊断分析来预测云辐射反馈在 ENSO 中的作用。相反，必须直接更改它们。
Cloud radiative feedbacks are disabled via “cloud-locking” in the Community Earth System Model, version 1.2 (CESM1.2), to result in a shift in El Niño–Southern Oscillation (ENSO) periodicity from 2–7 years to decadal time scales. We hypothesize that cloud radiative feedbacks may impact the periodicity in three ways: by 1) modulating heat flux locally into the equatorial Pacific subsurface through negative shortwave cloud feedback on sea surface temperature anomalies (SSTA), 2) damping the persistence of subtropical southeast Pacific SSTA such that the South Pacific meridional mode impacts the duration of ENSO events, or 3) controlling the meridional width of off-equatorial westerly winds, which impacts the periodicity of ENSO by initiating longer Rossby waves. The result of cloud-locking in CESM1.2 contrasts that of another study, which found that cloud-locking in a different global climate model led to decreased ENSO magnitude across all time scales due to a lack of positive longwave feedback on the anomalous Walker circulation. CESM1.2 contains this positive longwave feedback on the anomalous Walker circulation, but either its influence on the surface is decoupled from ocean dynamics or the feedback is only active on interannual time scales. The roles of cloud radiative feedbacks in ENSO in other global climate models are additionally considered. In particular, it is shown that one cannot predict the role of cloud radiative feedbacks in ENSO through a multimodel diagnostic analysis. Instead, they must be directly altered.