Association of the cloud radiative effect with the changes in the northern edge of Hadley circulation between the CMIP5 and CMIP6 models in boreal summer

In this study, the relationship between the cloud radiative effect and the northern boundary of the Hadley circulation (HC) in summer is analyzed using the reanalysis data and the simulation data from the coupled model intercomparison project (CMIP) phases 5 and 6. The results indicate that the accuracy of the simulated HC’s northern extent has improved in CMIP6 compared to CMIP5. Further investigation reveals that the shortwave cloud radiative effect (SWCRE) is a crucial factor that influences the HC’s northern extent simulation. The changes in SWCRE mainly attributed to low-cloud types in the Northern Hemisphere, particularly over the subtropical and extratropical North Pacific. The direct radiation is the primary contributor to the difference in SWCRE that further causes the difference in simulated HC’s northern extent between CMIP5 and CMIP6. Dynamic diagnosis identifies the convective transport of dry static energy as a key factor associated with the differences in the simulated HC’s northern limit. The convective transport exhibits a strong relationship with the projected changes in the HC’s northern boundary from low-emission to high-emission scenarios. The findings of this study provide compelling evidence for improving our understanding of the further changes in the Hadley circulation.