Future changes in atmospheric rivers over East Asia under stratospheric aerosol intervention
Future changes in atmospheric rivers over East Asia under stratospheric aerosol intervention
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DOI：
10.5194/acp-23-1687-2023
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发表时间：
2023-01
影响因子：
6.3
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中科院分区：
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摘要。大气河流与历史上东亚极端降水事件密切相关。在以前的研究中已经广泛讨论了在全球变暖下这种天气系统的预估增加，而平流层气溶胶的作用，特别是平流层气溶胶干预（SAI）的实施，在这种变化中的作用仍然未知。基于英国地球系统模式（UKESM1）的综合模拟，我们研究了一系列气候强迫下ARs及其相关的平均和极端降水频率的变化，包括高（SSP5-8.5）和中（SSP2-4.5）水平的温室气体排放情景、SAI地球工程（g6硫）的部署和太阳变暗（G6solar）。结果表明，在气候变暖的情况下，东亚大部分地区的AR频率和AR相关降水显著增加，其中中国南方的变化最为明显。比较G6solar和共享社会经济路径（SSP）两种情景，g6硫模拟表明SAI在一定程度上有效改善了亚热带地区AR活动的增加；然而，它可能导致中高纬度地区，特别是中国东北地区的ar和相关降水更加明显的增加。这种响应与副热带西风急流的进一步减弱有关，而副热带西风急流有利于中高纬AR活动。这是由于与整个热带地区气溶胶降温有关的对流层中高层的热膨胀经向梯度减小所驱动的，尽管SAI有效地改善了气候变暖下热膨胀的普遍增加。SAI对人口稠密地区的这种副作用意味着在考虑用地球工程方法减轻气候变化下的水文风险时必须谨慎。
Abstract. Atmospheric rivers (ARs) are closely associated with historical extreme precipitation events over East Asia. The projected increase in such weather systems under global warming has been extensively discussed in previous studies, while the role of stratospheric aerosol, particularly for the implementation of stratospheric aerosol intervention (SAI), in such a change remains unknown. Based on an ensemble of the UK Earth System Model (UKESM1) simulations, here we investigate changes in the frequency of ARs and their associated mean and extreme precipitation under a range of climate forcing, including greenhouse gas emission scenarios of high (SSP5–8.5) and medium (SSP2–4.5) levels, the deployment of SAI geoengineering (G6sulfur), and solar dimming (G6solar). The result indicates a significant increase in AR frequency and AR-related precipitation over most of East Asia in a warmer climate, and the most pronounced changes are observed in southern China. Comparing G6solar and both the Shared Socioeconomic Pathway (SSP) scenarios, the G6sulfur simulations indicate that SAI is effective at partly ameliorating the increases in AR activity over the subtropical region; however, it may result in more pronounced increases in ARs and associated precipitation over the upper-midlatitude regions, particularly northeastern China. Such a response is associated with the further weakening of the subtropical westerly jet stream under SAI that favours the upper-midlatitude AR activity. This is driven by the decreased meridional gradient of thermal expansion in the mid–high troposphere associated with aerosol cooling across the tropical region, though SAI effectively ameliorates the widespread increase in thermal expansion under climate warming. Such a side effect of SAI over the populated region implies that caution must be taken when considering geoengineering approaches to mitigating hydrological risk under climate change.