[H-CG26] Adaptation to climate change and its social implementation

[HCG26-P02] Impact of Aerosol and greenhouse gas forcing on late summer precipitation over the East Asian transitional climate zone with Relative humidity as a contributing factor in CMIP6 Model Simulation

*Paul Ayodele Adigun¹, koji Dairaku¹ (1.University of Tsukuba)

Keywords:transition zone , interdecadal variability, late-summer, rear edges, front edge

Using historical simulations from the Coupled Model inter-comparison Project Phase 6 (CMIP6), the contributions of greenhouse gasses, anthropogenic aerosols, and natural forcing to the reported declining trend in late summer precipitation over East Asia's transitional climatic zone (TCZ) was evaluated. Late summer precipitation across the TCZ has decreased significantly between the period of 1951 and 2013, as agreed upon by the five gridded precipitation datasets utilized in this study. Relative humidity (RH) may affect the perceived relationship between aerosols and precipitation. The relationship between aerosols and precipitation in the TCZ was equally delineated, using RH as a possible contributing factor. Our result shows that CESM2, ACCESS-ESM1-5, GFDL-ESM4, and HadGEM2-GC31 out of the 13 estimated models capture the amplitude of the observed trend. in addition our findings suggest anthropogenic aerosols may have weakened the circulation of the East Asian monsoon, leading to the drying trend over the TCZ. Furthermore, the empirical orthogonal function (EOF) was used to quantify the observed trend, which includes significant inter-decadal variability. The dominating EOF of observed precipitation accounts for roughly 30.3%, while the second EOF accounts for 13.5% of the total variance, with somewhat higher magnitude in the front edge and lower magnitude in the rear edges. The links between the multi-model ensemble (MME) leading mode and precipitation variability are reproduced. However, persistent bias still exists when compared to observation in simulating late-summer precipitation variability. This research is designed to provide the backdrop and scientific justification for conducting vulnerability and risk assessments across the East Asia transition zone owing to uncertainty in coupled models.