Impact of secondary organic aerosol on climate over East Asia for 1980–2020

 Secondary organic aerosol (SOA) is produced through photochemical reactions between volatile organic compounds and oxidants in the atmosphere. SOA may have a strong climatic effect because it contains not only colorless carbon, which merely scatters light, but also colored carbon, which can absorb light. However, the climatic effect of SOA is still unclear because the coupled climate−atmospheric chemistry model has limitations in SOA simulation owing to the chemical complexity and high computing power consumption. Therefore, it is necessary to examine the long-term climate effects of SOA through a sophisticated SOA scheme. In this study, we investigate the effect of SOA on climate in East Asia using a long-term simulation by coupling the SOA scheme in the climate−atmospheric chemistry model. We developed an SOA module for the climate model that minimizes chemical processes and computing power consumption through parameterization using empirical parameters. The simulated SOA suitably captured the observed SOA, indicating that the SOA scheme is successfully coupled in the climate−atmospheric chemistry model. We conducted a control and two sensitivity simulations with four ensemble simulations for 1980–2020 to investigate the effect of whole radiative and only absorptive forcing of SOA on climate in East Asia. Climate change in the control simulation for 1980–2020 is much closer to reanalysis data than sensitivity simulation, implying a large contribution of SOA on East Asian climate in recent decades. Sensitivity simulation suggests that the light absorption of SOA affects the East Asian climate, causing an increase in temperature at the surface and a decrease in atmospheric stability. Considering that the simulated SOA concentration shows a noticeable increasing trend in East Asia over recent decades, our results imply that SOA has had a significant impact on long-term climate change over East Asia. Therefore, SOA simulation should be included in climate simulations in East Asia.