Relationship between the Hadley Circulation and Mid-latitude SST in CMIP5 Simulations

The relationship between the width of the Hadley circulation and mid-latitude sea surface temperature (SST) among different CMIP5 models is the focus of this study. It is found that for both climatology and trends the width of the Northern Hemisphere (NH) Hadley circulation is closely related to the mid-latitude SSTs. We first examine the climatological width of the NH Hadley circulation. Models with higher mid-latitude SSTs have wider Hadley cells. For the trends, models with stronger SST warming in mid-latitudes generate greater poleward expansion of the Hadley cell. We also find that the baroclinic instability play an important role in determining the climatological width and the trend of the Hadley circulation. Our results suggest that the performances of simulating SST patterns and their trend in model have important influences on the climatological width and trends of the Hadley circulation.