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Isolating Fast and Slow Response of the Regional Climate over Asian Monsoon Region to Anthropogenic Aerosols using Variable Resolution-CESM

Regional climate is expected to respond differently to diverse drivers of anthropogenic climate change, and the representation of the response is model and resolution dependent. We use a recently developed version of the Community Earth System Model (version 1.2) with variable resolution (VR-CESM) to examine the impact of anthropogenic aerosols on regional climate over Asian Monsoon region. In the model, we implement a refined grid with a horizontal resolution of 0.25 degree (~28 km) over Asian Monsoon region and a resolution of 1 degree globally. The rapid and slow response to anthropogenic aerosols is disentangled by prescribing sea surface temperature (SST) and aerosol emissions at mid-20th century (1950) and present (2000) levels respectively. We examine the roles of the fast and slow response in shaping the regional climate response to increasing emissions of anthropogenic aerosols, focusing on changes in radiation, precipitation, and the strength of the Indian Summer Monsoon. We also assess the fast and slow adjustments of water extremes and emphasize the sub-regional diversity of the adjustments. This study highlights the importance of SST feedbacks, associated with increasing anthropogenic aerosols, in driving changes in both regional climatology and extreme events and demonstrates the utility of VR-CESM in capturing these changes in regional climate.