On the Role of Wind–Evaporation–SST Feedbacks in the Subseasonal Variability of the East Pacific ITCZ
On the Role of Wind–Evaporation–SST Feedbacks in the Subseasonal Variability of the East Pacific ITCZ
复制标题
风—蒸发—海温反馈在东太平洋 ITCZ 次季节变化中的作用
DOI：
10.1175/jcli-d-22-0849.1
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发表时间：
2024
影响因子：
4.9
通讯作者：
Karnauskas, Kristopher B.
中科院分区：
文献类型：
--
作者：
Ganguly, Indrani;Gonzalez, Alex O.;Karnauskas, Kristopher B.
热带辐合带（ITCZ）是赤道附近近地表辐合和降水的纬向拉长带。在北半球春季，东太平洋 ITCZ 在日常时间尺度上沿纬度迁移到次季节时间尺度，气候模型在一年中的这个时候表现出最大的 ITCZ 偏差。在这项工作中，我们研究了与 2 月至 4 月期间 ITCZ 仅位于赤道以北（nITCZ 事件）与 ITCZ 位于赤道两侧或赤道以南（dsITCZ 事件）相比，连续几天与东太平洋 ITCZ 纬度位置变化相关的海气相互作用。 nITCZ和dsITCZ事件期间海面温度（SST）异常和表面潜热通量（SLHF）异常的分布遵循经典的风-蒸发-SST（WES）正反馈机制。然而，另一种机制，即考虑海温异常对垂直分层和动量混合的影响，会引起 WES 负反馈。我们的结果表明，在表层，在事件发生前的几周内，总体上会出现正向 WES 反馈，随后在 ITCZ 事件后出现负向 WES 反馈，另一种机制涉及空气-海洋湿度差异，限制其间发生的蒸发。此外，反馈分量的空间结构几乎是北春季东太平洋上空这些相反的 ITCZ 事件的镜像。最后，我们发现了解每天到每周不同的 ITCZ 事件（nITCZ 和 dsITCZ）期间的海气相互作用有助于查明不同半球 ITCZ 的基本过程有何不同。
The intertropical convergence zone (ITCZ) is a zonally elongated band of near-surface convergence and precipitation near the equator. During boreal spring, the eastern Pacific ITCZ migrates latitudinally on daily to subseasonal time scales, and climate models exhibit the greatest ITCZ biases during this time of the year. In this work, we investigate the air–sea interactions associated with the variability in the eastern Pacific ITCZ’s latitudinal location for consecutive days when the ITCZ is only located north of the equator (nITCZ events) compared to when the ITCZ is on both sides of the equator or south of the equator (dsITCZ events) during February–April. The distribution of sea surface temperature (SST) anomalies and surface latent heat flux (SLHF) anomalies during the nITCZ and dsITCZ events follow the classic wind–evaporation–SST (WES) positive feedback mechanism. However, an alternative mechanism, embracing the effect of SST anomalies on vertical stratification and momentum mixing, gives rise to a negative WES feedback. Our results show that in the surface layer, there is a general progression of positive WES feedbacks happening in the weeks leading to the events followed by negative WES feedbacks occurring after the ITCZ events, with an alternate mechanism involving air–sea humidity differences limiting evaporation occurring in between. Additionally, the spatial structures of the components of the feedbacks are nearly mirror images for these opposite ITCZ events over the east Pacific during boreal spring. In closing, we find that understanding the air–sea interactions during daily to weekly varying ITCZ events (nITCZ and dsITCZ) helps to pinpoint how fundamental processes differ for ITCZs in different hemispheres.