The Influence of Intraseasonal Oscillations on Humid Heat in the Persian Gulf and South Asia
The Influence of Intraseasonal Oscillations on Humid Heat in the Persian Gulf and South Asia
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DOI：
10.1175/jcli-d-21-0488.1
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发表时间：
2022-07-01
影响因子：
4.9
通讯作者：
Sobel, Adam
中科院分区：
文献类型：
--
作者：
Ivanovich, Catherine;Anderson, Weston;Sobel, Adam
人类通过以汗水为基础的蒸发冷却来对抗热应激的基本能力受到环境空气温度和湿度的调节，这使得湿热成为影响人类健康的关键因素。在这项研究中，我们将两个焦点区域的极端湿热的发生与两种相关的季节内气候变率模式联系起来：Madden-Julian振荡(MJO)和北方夏季季节内振荡(BSISO)。在波斯湾和南亚的5-6月和7-8月季节，在某些振荡阶段，湿球温度达到288摄氏度的可能性几乎是其他阶段的两倍。研究发现，湿度的变化在不同程度上是所有三个地区湿球温度异常高的重要因素，受到明显的局部环流异常的影响。在波斯湾，与季节内振荡的对流传播中心相关的气候风的减弱使得潮湿空气的异常陆上平流。南亚西北部地区异常高的湿球温度与正的比湿度异常密切相关，这些异常与振荡的对流活动阶段有关。在印度东南海岸，高湿球温度与季节内振荡的对流不活跃阶段有关，这表明它们可能是由于季风休息期间地表日照增加和蒸发冷却减少所致。我们的结果有助于为极端湿热影响极大的地区的亚季节预测奠定基础。
Humans' essential ability to combat heat stress through sweat-based evaporative cooling is modulated by ambient air temperature and humidity, making humid heat a critical factor for human health. In this study, we relate the occurrence of extreme humid heat in two focus regions to two related modes of intraseasonal climate variability: the Madden-Julian oscillation (MJO) and the boreal summer intraseasonal oscillation (BSISO). In the Persian Gulf and South Asia during the May-June and July-August seasons, wet-bulb temperatures of 288C are found to be almost twice as likely during certain oscillation phases than in others. Variations in moisture are found, to varying degrees, to be an important ingredient in anomalously high wet-bulb temperatures in all three areas studied, influenced by distinct local circulation anomalies. In the Persian Gulf, weakening of climatological winds associated with the intraseasonal oscillation's propagating center of convection allows for anomalous onshore advection of humid air. Anomalously high wet-bulb temperatures in the northwestern region of South Asia are closely aligned with positive specific humidity anomalies associated with the convectively active phase of the oscillation. On the southeastern coast of India, high wet-bulb temperatures are associated with convectively inactive phases of the intraseasonal oscillation, suggesting that they may be driven by increased surface insolation and reduced evaporative cooling during monsoon breaks. Our results aid in building a foundation for subseasonal predictions of extreme humid heat in regions where it is highly impactful.