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A recent hypothesis holds that changes to the East Asian summer rainfall are characterized by changes in the timing and duration of its intraseasonal stages, controlled by the meridional position of the westerlies relative to the Tibetan Plateau. This hypothesis is examined in the context of the leading mode of East Asian summer (July–August) rainfall. One phase of this “tripole” mode—characterized by less rainfall over central eastern China and increased rainfall over northeastern and southeastern China—is tied to an earlier termination of Meiyu that results in a significantly shorter Meiyu and longer Midsummer stage. This phase also exhibits an earlier northward transition of the westerlies to the north of the Plateau, essentially mirroring the changes to precipitation seasonality. The reverse does not hold true for the opposite phase. Our results show direct observational evidence for the meridional position of the westerlies to control East Asian summer monsoon seasonality. Leading mode of July‐August East Asian rainfall variability caused by changes in timing of Meiyu termination and duration of Meiyu/MidsummerChanges to timing and duration associated with variation in the meridional migration of westerlies relative to the Tibetan PlateauResults show direct observational evidence for meridional position of westerlies to control East Asian summer monsoon seasonality

The relationship between Atlantic meridional overturning circulation (AMOC) variability and high‐latitude North Atlantic buoyancy changes is complicated by the latter both driving, and responding to, AMOC changes. A maximum covariance analysis applied to a 1,201‐year preindustrial control simulation reveals two leading modes that separate these two distinct roles of North Atlantic temperature and salinity as related to AMOC variability. A linear combination of the two modes accounts for most of the variation of a widely used AMOC index. The same analysis applied to another control simulation known to possess two distinct regimes of AMOC variability—oscillatory and red‐noise—suggests that the North Atlantic buoyancy‐forced AMOC variability is present in both regimes but is weaker in the latter, and moreover there is pronounced multidecadal/centennial AMOC behavior in the latter regime that is unrelated to North Atlantic buoyancy forcing. Atlantic meridional overturning circulation (AMOC) variations cause significant changes to the global climate. High‐latitude North Atlantic temperature and salinity variations modify the AMOC through changing the buoyancy of the upper ocean. However, this identification is complicated by the reverse relationship, that North Atlantic temperature and salinity changes with AMOC. When we apply maximum covariance analysis—a spatiotemporal analysis designed to find coupled patterns between two climate fields—to a preindustrial control simulation of a fully coupled climate model, it extracts the two coupling relationships. Moreover, the combination of these two behaviors is sufficient to characterize the AMOC variations. When we apply the same analysis method to another control simulation exhibiting two regimes of AMOC variability—oscillatory and red‐noise—it reveals that the red‐noise regime has a marked reduction to the AMOC variability resulting from North Atlantic buoyancy forcing, and a corresponding increase in multidecadal/centennial AMOC variations of undetermined origin. Maximum covariance analysis reveals two modes that separate cause‐and‐effect between Atlantic meridional overturning circulation (AMOC) and North Atlantic temperature/salinity in a control simulationThe two modes effectively span the temporal behavior of AMOC variability as represented by the AMOC maximum streamfunction indexAnalysis of simulation with oscillatory and red‐noise AMOC regimes indicate that North Atlantic‐forced AMOC is suppressed in latter regime Maximum covariance analysis reveals two modes that separate cause‐and‐effect between Atlantic meridional overturning circulation (AMOC) and North Atlantic temperature/salinity in a control simulation The two modes effectively span the temporal behavior of AMOC variability as represented by the AMOC maximum streamfunction index Analysis of simulation with oscillatory and red‐noise AMOC regimes indicate that North Atlantic‐forced AMOC is suppressed in latter regime