The Inter-Model Uncertainty of Projected Precipitation Change in Northern China: The Modulating Role of North Atlantic Sea Surface Temperature

Precipitation changes in northern China are projected to increase in the Coupled Model Inter-comparison Project Phase 6 (CMIP6) multi-model ensemble. However, these projections are accompanied by notable inter-model uncertainty, and the sources of this uncertainty remain largely unexplored. By analyzing 30 CMIP6 models, this research explores the source of inter-model uncertainty in projected precipitation change and reveals the fundamental mechanism driving uncertainty spread. Following the empirical orthogonal function of inter-model projected precipitation change, the leading mode displays a seesaw spatial pattern between northwest and north China. This phenomenon predominantly stems from the inter-model divergence of projected sea surface temperature (SST) warming in the North Atlantic. Further scrutinizing the ocean mixed layer heat budget, we discover that the combined effect of surface sensible heat flux, net surface shortwave radiation flux, and ocean heat transport convergence influences heat flux and SST change of North Atlantic. The multi-model projections indicate that localized increases in solar radiation and heat convergence warm sea surface, raising SST and initiating convective motion. This convective motion subsequently transforms the 200 hPa teleconnection wave train, leading to an anti-phase pattern over northern China. This wave pattern modulates total cloud cover percentage, influences surface upward latent heat flux, and adjusts the top of atmosphere outgoing longwave radiation, collectively resulting in the seesaw pattern. Our study underscores the pivotal role of inter-model disparities in North Atlantic SST warming projection, which is a primary driver of precipitation uncertainty in northern China. These insights offer an essential foundation for refining and diminishing inter-model uncertainty. The Coupled Model Inter-comparison Project Phase 6 multi-model ensemble projects significant precipitation uncertainty due to differences in couplers and components of the global system model. This study identifies the discrepancies in projected North Atlantic sea surface temperature (SST) warming as the primary source of inter-model uncertainty for projected precipitation changes in northern China. The projected SST warming amplifies heat transfer from the ocean surface to the atmosphere, intensifying upward air motion. This process alters the teleconnection wave trains at 200 hPa, propagating downstream to form an anti-phase pattern in northern China. These upper atmospheric shifts regulate upward and subsiding motions, influence total cloud cover percentage, modify the top of atmosphere outgoing longwave radiation, and impact surface upward latent heat flux. Together, these atmospheric dynamics forge a seesaw spatial precipitation pattern in northern China. The combined effect of surface sensible heat flux, net surface shortwave radiation flux, and ocean heat transport convergence influence heat flux and SST change in the North Atlantic. Our findings elucidate the complex spread process of inter-model uncertainty in precipitation projection, setting the stage for more precise projection in northern China. The leading precipitation pattern exhibits a seesaw in northern China due to inter-model differences in North Atlantic sea surface temperature (SST) warming The model with a higher SST warming tends to induce a strong teleconnection wave train, resulting in a more pronounced seesaw pattern Surface sensible heat flux, net surface shortwave radiation flux, and ocean heat transport convergence influence heat flux and SST change