Remote influence of the Atlantic multidecadal oscillation on the autumn surface air temperature in Southwest China

Southwest China (SWC) is one of the major grain-producing areas in China, and the surface air temperature (SAT) during autumn has a significant influence on grain production and planting. It is therefore important to understand temporal changes in the SAT over SWC (SWC-SAT). Our analysis of observational and reanalysis datasets shows that the autumn SWC-SAT exhibits significant multidecadal variability. There is also a significantly strong positive correlation between the autumn SWC-SAT and the Atlantic Multidecadal Oscillation (AMO) time series (correlation coefficient = 0.85). These results suggest that the AMO is a remote driver of multidecadal variability in the autumn SWC-SAT. Further analyses show that the North Atlantic sea surface temperature anomalies (SSTA) associated with the AMO modulate the multidecadal variability of the autumn SWC-SAT through triggering the Africa-Asia multidecadal teleconnection pattern (AAMT). Specifically, the AAMT corresponds to geopotential height anomalies over the SWC, which adjust the local thickness of the air column and thereby induce multidecadal variability of autumn SWC-SAT. This potential mechanism, derived from observational and reanalysis datasets, was verified using a linear barotropic model and the Community Atmosphere Model Version 4. Combining observations and numerical modeling simulations, our results indicate that the North Atlantic SSTA may act as a key pacemaker for the multidecadal SAT variability over the SWC.