This study investigates the response of Indian summer monsoon (ISM) precipitation to CO₂ removal, with a specific focus on regional and subseasonal variations. Following CO₂ removal, monsoon circulation weakens throughout the summer owing to the reduced large-scale meridional temperature gradient around India. Weakened monsoon circulation decreases the local-scale thermodynamic stability within India, following monsoon-onset periods. While the frequency of synoptic-scale ISM low-pressure systems (LPSs) decreases overall, the lower thermodynamic stability causes the LPSs to form and resultantly shift west and south from their typical paths, last longer and move more quickly zonally during August and September. Changes in these rain-producing processes induce distinct regional (Western Ghats, south-central-east India, and Tamil Nadu) and subseasonal precipitation responses. Also, extreme precipitation exhibits similar patterns, but is more strongly affected by changes in LPS. Our results suggest that reliable future projections of regional hydroclimate change require a more accurate understanding of multi-scale precipitation processes.

本研究调查了印度夏季季风 （ISM） 降水对 CO₂ 去除的响应，特别关注区域和次季节变化。去除 CO₂ 后，由于印度周围大尺度经向温度梯度的减少，整个夏季的季风环流减弱。季风开始期后，季风环流减弱降低了印度境内局部尺度的热力学稳定性。虽然天气尺度的 ISM 低压系统 （LPS） 的频率总体上有所下降，但较低的热力学稳定性导致 LPS 形成并因此在 8 月和 9 月期间从其典型路径向西和向南移动，持续时间更长，纬向移动更快。这些降雨过程的变化会引起不同的区域性（西高止山脉、印度中南部和泰米尔纳德邦）和次季节性降水响应。此外，极端降水表现出类似的模式，但受 LPS 变化的影响更大。我们的结果表明，对区域水文气候变化的可靠未来预测需要更准确地理解多尺度降水过程。