How can anomalous western North Pacific Subtropical High intensify in late summer?

• Published in: Geophysical research letters 2013-05, Vol.40 (10), p.2349-2354
• Main Authors: Xiang, Baoqiang, Wang, Bin, Yu, Weidong, Xu, Shibin
• Format: Article
• Language: English
• Subjects: Amplification; Atmospheric precipitations; Control systems; Control theory; Convection; East Asian monsoon; El Nino; El Nino-Southern Oscillation event; Evaporation; Feedback; Indian Ocean; Indian Ocean warming; Loads (forces); local air-sea interaction; Marine; Mean precipitation; Meteorology; Monsoon trough; Monsoons; Ocean temperature; Ocean-atmosphere interaction; Precipitation; Sea surface; seasonal march of mean state; Southern Oscillation; Storms; Summer; Summer monsoon; Surface temperature; Tropical climate; western North Pacific subtropical high; Wind
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/grl.50431

The western North Pacific (WNP) Subtropical High (WNPSH) is a controlling system for East Asian Summer monsoon and tropical storm activities, whereas what maintains the anomalous summertime WNPSH has been a long‐standing riddle. Here we demonstrate that the local convection‐wind‐evaporation‐SST (CWES) feedback relying on both mean flows and mean precipitation is key in maintaining the WNPSH, while the remote forcing from the development of the El Niño/Southern Oscillation is secondary. Strikingly, the majority of strong WNPSH cases exhibit anomalous intensification in late summer (August), which is dominantly determined by the seasonal march of the mean state. That is, enhanced mean precipitation associated with strong WNP monsoon trough in late summer makes atmospheric response much more sensitive to local SST forcing than early summer. Key PointsSeasonal march of mean state is key in intensifying the WNPSH in late summerLocal air‐sea feedback is strong enough in maintaining the WNPSH in late summerThe air‐sea interaction in the Indian Ocean is important for WNPSH