Diurnal Circulation Adjustment and Organized Deep Convection
Diurnal Circulation Adjustment and Organized Deep Convection
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DOI：
10.1175/jcli-d-17-0693.1
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发表时间：
2018-04
影响因子：
4.9
通讯作者：
J. Ruppert;C. Hohenegger
中科院分区：
文献类型：
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作者：
J. Ruppert;C. Hohenegger
这项研究研究了热带有组织的深度结构的昼夜周期，并通过考虑重力波相中的循环中的反馈。在有组织的连接的典型空间尺度上强迫昼夜的植物（≤500km）。进行平衡（RCE）以进一步探索这些模拟。对流。 “动态的多云 - 切割差分辐射”机制放大器大约30％，并将夜间降水峰延迟约5小时。 - 主要的机制控制着昼夜的放大器。云顶冷却（即，失去速率机制）在夜间导致底部较重的循环，对流区域的局部局部（即差异）高度短波变暖可在白天循环循环因此，循环的产生是从夜间的底部沉重到白天最高的，以定性的一致方式，观察到的Hadley Cell的昼夜脉动由ITCZ驱动。
This study investigates the diurnal cycle of tropical organized deep convection and the feedback in large-scale circulation. By considering gravity wave phase speeds, we find that the circulation adjustment into weak temperature gradient (WTG) balance occurs rapidly (<6 h) relative to diurnal diabatic forcing on the spatial scales typical of organized convection (≤500 km). Convection-permitting numerical simulations of self-aggregation in diurnal radiative–convective equilibrium (RCE) are conducted to explore this further. These simulations depict a pronounced diurnal cycle of circulation linked to organized convection, which indeed maintains WTG balance to first order. A set of sensitivity experiments is conducted to assess what governs the diurnal cycle of organized convection. We find that the “direct radiation–convection interaction” (or lapse-rate) mechanism is of primary importance for diurnal precipitation range, while the “dynamic cloudy–clear differential radiation” mechanism amplifies the range by approximately 30%, and delays the nocturnal precipitation peak by around 5 h. The differential radiation mechanism therefore explains the tendency for tropical heavy rainfall to peak in the early morning, while the lapse-rate mechanism primarily governs diurnal amplitude. The diurnal evolution of circulation can be understood as follows. While nocturnal deep convection invigorated by cloud-top cooling (i.e., the lapse-rate mechanism) leads to strong bottom-heavy circulation at nighttime, the localized (i.e., differential) top-heavy shortwave warming in the convective region invigorates circulation at upper levels in daytime. A diurnal evolution of the circulation therefore arises, from bottom heavy at nighttime to top heavy in daytime, in a qualitatively consistent manner with the observed diurnal pulsing of the Hadley cell driven by the ITCZ.