Abstract
This study concentrated on representations of summer North Africa and West Pacific subtropical highs (NASH, WPSH) in CMIP6 simulations and investigated the possible external forcing contributing to the simulation results. The results show an acceptable performance in the simulation of the two subtropical highs. Models performing well in capturing the spatial pattern of the WPSH also tend to perform well for the NASH, inferring that the two subtropical highs are likely to be forced by the same dynamic processes of the northern hemispheric subtropical high belt. By reconstructing indices such as intensity, area and boundaries, it is highlighted that there is a strong correlation between the variability in WPSH and NASH indices and a similar periodicity reflecting potential teleconnections between the two subtropical highs. Further investigation indicates a positive SST anomaly linking ENSO with the subtropical highs. It is revealed that a better ENSO simulation contributes to an improved simulation of the two subtropical highs. It also shows that the simulation of NASH depends on the simulation of WPSH so that good ENSO simulation models can perfectly reproduce the role of the WPSH in driving NASH by examining Rossby wave activities in the extratropics.