The effect of regional warming on the East Asian summer monsoon

East Asian summer monsoon (EASM) precipitation has changed significantly due to regional warming. In this study, effect of regional warming on the EASM summer precipitation is investigated during 1979–2018 with a particular emphasis on the frontogenesis. The frontogenetic function shows that change in circulation and temperature distribution associated with regional warming is fairly consistent with precipitation change. Specifically, changes in temperature gradient and deformation, both in terms of its magnitude and direction with respect to thermal gradient, result in cross-frontal circulation change with respect to its position and magnitude; this, in turn, is closely linked with EASM precipitation change. Due to warming, frontal circulation has weakened except in the mature stage, when the front is over the Kuroshio Current. From a slightly southward shifted position, the northward migration of the front is more precipitous than in the past reaching its northern-most latitude earlier by ~ 2 weeks. On the other hand, the southward migration has become slightly sluggish. In association with the frontogenesis, large-scale precipitation is more strongly affected north of ~ 30° N. South of ~ 25° N, precipitation change is due largely to convective precipitation.