Radiative Effects of Clouds and Water Vapor on an Axisymmetric Monsoon
Radiative Effects of Clouds and Water Vapor on an Axisymmetric Monsoon
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DOI：
10.1175/jcli-d-19-0974.1
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发表时间：
2020-10
影响因子：
4.9
通讯作者：
M. Byrne;L. Zanna
中科院分区：
文献类型：
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作者：
M. Byrne;L. Zanna
季风是夏季环流，塑造热带和亚热带的气候和社会。这里使用水上行星模拟研究控制轴对称季风的辐射效应及其对气候变化的响应。利用辐射锁定技术分解了云、水汽和二氧化碳对轴对称季风的影响。云和水蒸气的季节变化强烈调节轴对称季风，使净降水量减少约一半。季节性长波云和水汽效应对轴对称季风的变暖和湿润被强烈的短波云效应抵消。短波云效应还将轴对称季风的爆发加快了大约两周，而长波云和水汽效应则延迟了爆发。概念模型将季风爆发的时间与表面冷却的效率联系起来。在气候变化模拟中，二氧化碳强迫和水蒸气反馈对轴对称季风有类似的影响，使地表变暖并湿润该地区。相比之下，云对地表温度的影响可以忽略不计，但却主导着季风环流响应。介绍了理解云辐射效应如何影响季风环流对气候变化的响应的新视角。辐射锁定模拟和分析促进了对辐射过程如何影响轴对称季风的理解，并建立了解释观测、最先进模型和不同气候状态下季风-辐射耦合的框架。
Monsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling an axisymmetric monsoon and its response to climate change are investigated using aquaplanet simulations. The influences of clouds, water vapor, and CO2 on the axisymmetric monsoon are decomposed using the radiation-locking technique. Seasonal variations in clouds and water vapor strongly modulate the axisymmetric monsoon, reducing net precipitation by approximately half. Warming and moistening of the axisymmetric monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect also expedites onset of the axisymmetric monsoon by approximately two weeks, whereas longwave cloud and water vapor effects delay onset. A conceptual model relates the timing of monsoon onset to the efficiency of surface cooling. In climate change simulations CO2 forcing and the water vapor feedback have similar influences on the axisymmetric monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the monsoon circulation response. A new perspective for understanding how cloud radiative effects shape the monsoon circulation response to climate change is introduced. The radiation-locking simulations and analyses advance understanding of how radiative processes influence an axisymmetric monsoon, and establish a framework for interpreting monsoon–radiation coupling in observations, in state-of-the-art models, and in different climate states.