The East Asian climate is profoundly influenced by complex interactions between the atmosphere, ocean, and land. A research team led by Prof. DAN Li at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, has developed the Regional Integrated Earth Model System version 4.0 (RIEMS4.0), providing new mechanistic insights into how regional air-sea coupling shapes the East Asian summer climate.

Their findings were recently published in Journal of Geophysical Research: Atmospheres.

The team conducted a comparative analysis of RIEMS4.0 (air-sea coupled), its standalone atmospheric component (WRF), and a CMIP6 multi-model ensemble for the period 1991–2014. Results showed that the coupled RIEMS4.0 outperforms uncoupled simulations in reproducing the spatial pattern of summer daily mean and maximum surface air temperatures across East Asia.

"A key improvement is the substantial reduction of the persistent warm bias in WRF over eastern China by approximately 0.7°C in root mean square error," said Dr. LI Kai, first author of the study.

The model developed a more realistic representation of key physical processes. By explicitly coupling the ocean and atmosphere, RIEMS4.0 better simulated the exchange of surface sensible and latent heat fluxes, which modulated the energy supply to the atmosphere. Furthermore, it improved the simulation of cloud-radiative processes and the land-sea thermal contrast.

This research established regional air-sea coupling as an essential, active driver—not just a passive boundary condition—for achieving accurate historical climate simulations in regional models.