The Asymmetric Response of the Spring and Autumn Atmospheric Circulation over East Asia to a Warming Climate

Abstract

Climate models project stronger summer monsoons and weaker winter monsoons in a warmer future over East Asia. This is because the large-scale land–sea temperature contrast and resulting pressure differences will be larger during the boreal summer but smaller during the boreal winter. However, how the atmospheric circulation evolves during the transition between the seasons remains poorly understood. In this paper, we analyze the modelling results from the historical and shared socioeconomic pathways (SSP) 5–8.5 future scenario experiments generated as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). We show that the timing of the sign-reversal of the land–sea sea-level pressure difference moves significantly later through the boreal autumn during the late 21st century, but that there is little difference in the sign-reversal during spring. This asymmetric seasonal response is associated with a greater land–sea difference in surface temperature increase and pressure drop in autumn than in spring. In addition, models with a greater global annual mean surface temperature change show a later autumn transition, whereas no such relationship is evident for the spring transition.