Revisiting the East Asian summer monsoon structure: a combined effect of condensational heating and synoptic eddy activities

Abstract

The East Asian summer monsoon (EASM) is a unique regional monsoon in the subtropics involving not only tropical but midlatitude processes. Most of the previous studies identi ed the role of condensational heating which is largely relevant to the tropical moisture transport in determining the dynamical structure of EASM. However, how midlatitude synoptic eddy activities can affect the EASM structure has not been well recognized. With dynamical diagnoses, this study revisits the EASM structure by emphasizing the roles of feedbacks of condensational heating versus synoptic eddy activities. As EASM is characterized by a grand low-level low with strong humid southerly ows extending from the tropics to the northeastern Asia, its vertical structure is found to have a distinct meridional difference bounded at around 35.5 o N. In the southern domain, EASM features a meridional overturning cell and a baroclinic structure with an upper-level high versus a lower-level low in geopotential height, which are primarily controlled by substantial condensational heating due to abundant monsoon precipitation. However, in the northern domain, EASM exhibits an equivalent barotropic structure with an upper-level low versus a lower-level low. Such a unique structure results from a combined effect of feedbacks of condensational heating and synoptic eddy activities, in which the upper-level low is dominated by the synoptic eddy dynamical feedback while the lower-level low is induced by the both feedbacks. The role of the midlatitude transient eddy activities in shaping the EASM structure proposed in this study provides a new perspective for understanding the formation and variation of EASM.. Zhu Q, He J, and Wang P, 1986: A study of circulation differences between East-Asian and Indian summer monsoons with their interaction. Adv Atmos Sci, 3,[466][467][468][469][470][471][472][473][474][475][476][477]

Summer Extreme Rainfall Over the Middle and Lower Reaches of Yangtze River: Role of Synoptic Patterns in Historical Changes and Future Projections

“…Specifically, SP‐Cluster 1 (SP‐Cluster 3) is characterized by a strong ridge (trough) near Lake Baikal (48–58°N, 103–113°E), while SP‐Clusters 2 (SP‐Cluster 4) is associated with a strong ridge (trough) near Northeast China (42–53°N, 125–137°E). This is consistent with recent studies suggesting that the East Asia summer rainfall is closely related to mid‐ and high‐latitude disturbances, in addition to anomalies over the subtropical and tropical western North Pacific (Chen et al., 2023; Hu, Deng, Zhou, Cui, & Dong, 2019; X. Li & Lu, 2017; J. Li, Zwiers, et al., 2021; X. Li et al., 2023; Z. Xu, Huang, et al., 2023). Therefore, each typical SP has three critical locations at subtropical, extratropical and mid‐latitude regions (Figures 2a–2d).…”