A New Upper-Level Circulation Index for the East Asian Summer Monsoon Variability

作者：Zhao, Guijie; Huang, Gang^*; Wu, Renguang; Tao, Weichen; Gong, Hainan; Qu, Xia; Hu, Kaiming

来源：Journal of Climate, 2015, 28(24): 9977-9996.

DOI：10.1175/JCLI-D-15-0272.1

• WESTERN NORTH PACIFIC
• INTERDECADAL VARIATIONS
• INTERANNUAL VARIATIONS
• CMIP5 MODELS
• EL-NINO
• WINTER MONSOON
• BOREAL SUMMER
• PART I
• CHINA
• CLIMATE

The East Asian summer monsoon (EASM) and its variability involve circulation systems in both the tropics and midlatitudes as well as in both the lower and upper troposphere. Considering this fact, a new EASM index (NEWI) is proposed based on 200-hPa zonal wind, which takes into account wind anomalies in the southern (about 5 degrees N), middle (about 20 degrees N), and northern areas (about 35 degrees N) of East Asia. The NEWI can capture the interannual EASM-related climate anomalies and the interdecadal variability well. Compared to previous indices, the NEWI shows a better performance in describing precipitation and air temperature variations over East Asia. It can also show distinct climate anomalous features in early and late summer. The NEWI is tightly associated with the East Asian-Pacific or the Pacific-Japan teleconnection, suggesting a possible role of internal dynamics in the EASM variability. Meanwhile, the NEWI is significantly linked to El Nino-Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies. Furthermore, the NEWI is highly predictable in the ENSEMBLES models, indicating its advantage for operational prediction of the EASM. The physical mechanism of the EASM variability as represented by the NEWI is also explicit. Both warm advection anomalies of temperature by anomalous westerly winds and the advection of anomalous positive relative vorticity by northerly basic winds cause anomalous ascending motion over the mei-yu-changma-baiu rainfall area, and vice versa over the South China Sea area. Hence, this NEWI would be a good choice to study, monitor, and predict the EASM.

• 出版日期2015-12
• 单位中国科学院大学; 中国科学院大气物理研究所