Abstract. Reliable attribution of Asian summer monsoon variations to aerosol forcing is critical to reducing uncertainties in future projections of regional water availability, which is of utmost importance for risk management and adaptation planning in this densely populated region. Yet, simulating the monsoon remains a challenge for climate models that suffer from long-standing biases, undermining their reliability in attributing anthropogenically forced changes. We analyze a suite of climate model experiments to identify a link between model biases and monsoon responses to Asian aerosols and associated physical mechanisms, including the role of large-scale circulation changes. The aerosol impact on monsoon precipitation and circulation is strongly influenced by a model's ability to simulate the spatio-temporal variability in the climatological monsoon winds, clouds, and precipitation across Asia, which modulates the magnitude and efficacy of aerosol–cloud–precipitation interactions, an important component of the total aerosol response. There is a strong interplay between South Asia and East Asia monsoon precipitation biases and their relative predominance in driving the overall monsoon response. We found a striking contrast between the early- and late-summer aerosol-driven changes ascribable to opposite signs and seasonal evolution of the biases in the two regions. A realistic simulation of the evolution of the large-scale atmospheric circulation is crucial to realize the full extent of the aerosol impact over Asia. These findings provide important implications for better understanding and constraining the diversity and inconsistencies of model responses to aerosol changes over Asia in historical simulations and future projections.

中文翻译：

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亚洲气溶胶对受区域降水偏差强烈调节的夏季风的影响


摘要。将亚洲夏季风变化可靠地归因于气溶胶强迫对于减少未来区域水资源供应预测的不确定性至关重要，这对于这个人口稠密地区的风险管理和适应规划至关重要。然而，模拟季风对于气候模型来说仍然是一个挑战，这些模型长期存在偏差，削弱了其归因于人为强迫变化的可靠性。我们分析了一系列气候模型实验，以确定模型偏差和季风对亚洲气溶胶的反应之间的联系以及相关的物理机制，包括大规模环流变化的作用。气溶胶对季风降水和环流的影响很大程度上受到模型模拟亚洲气候季风、云和降水时空变化的能力的影响，该模型调节气溶胶-云-降水相互作用的强度和效力，总气溶胶响应的重要组成部分。南亚和东亚季风降水偏差及其在驱动整体季风响应方面的相对优势之间存在很强的相互作用。我们发现夏初和夏末气溶胶驱动的变化之间存在显着对比，这归因于两个地区偏差的相反迹象和季节演变。对大规模大气环流演变的真实模拟对于全面了解亚洲气溶胶的影响至关重要。这些发现为更好地理解和限制历史模拟和未来预测中亚洲气溶胶变化模型响应的多样性和不一致提供了重要意义。