Projection of the East Asian westerly jet under six global warming targets

This study investigates the projected changes in the East Asian westerly jet(EAJ)under six global warming targets(1.5℃,2.0℃,2.5℃,3.0℃,3.5℃,and 4.0℃)relative to the present climate,using the outputs of CMIP5 models.The results show that the westerly tends to weaken slightly under the 1.5℃warming target.Under the 2.0℃target,it is projected to intensify south of the EAJ’s axis(approximately 40°N)and decay north of the axis.This change becomes increasingly evident under the 2.5℃and higher warming targets,which suggests that the EAJ’s axis will move farther and farther southward,but its intensity will change little with increasing global warming.Further analyses suggest that the change in the EAJ is closely related to the inhomogeneous rising rate of air temperature in the mid–upper troposphere.The relatively slow-rising air temperature in the mid–upper troposphere over the EAJ’s entrance and exit regions will lead to a negative(positive)meridional temperature gradient to the south(north),and will then accelerate(decelerate)the westerly on the EAJ’s south/north side.

Projected changes in the western North Pacific subtropical high under six global warming targets

The summer western North Pacific subtropical high(WNPSH) has large influences on the East Asian summer climate. Many studies have focused on the projected changes in the WNPSH, but little is known about the changes under different global warming targets, such as 1.5℃ and 2.0℃. This study investigates the changes in the WNPSH under six global warming targets(1.5℃, 2.0℃, 2.5℃,3.0℃, 3.5℃, and 4.0℃) in both the mid-and lower troposphere, using the outputs of CMIP5 model in historical simulations and under Representative Concentration Pathway 8.5. The projected changes in the WNPSH, which is measured by multiple variables, show that it changes little under the 1.5℃ target in the mid-troposphere, but weakens and retreats approximately 2.5° in longitude under the 2.0℃ target. It tends to linearly weaken with warming greater than 2.5℃ and shifts eastward by approximately 6.0° in longitude by the 4.0℃ target. Meanwhile, the WNPSH intensifies and extends westward under the 1.5℃ target in the lower troposphere, but changes little with warming rising from 1.5℃ to 2.0℃. It is projected to extend westward by approximately2.0° in longitude by the 4.0℃ target.