Authors:
XUE Fenga and ZHAO Jun-Jiea,b
a International Center for Climate and Environment Sciences (ICCES), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing,China;
b Meteorological Training Center of Shanxi Province, Taiyuan, China
Abstract:
Based on the composite result of six major La Ni？a events during 1979–2012, the authors reveal the intraseasonal variation of the East Asian summer monsoon (EASM) and summer rainfall in East Asia in La Ni？a years. Due to a higher SST over the western Pacific warm pool in the proceeding winter and spring, warm pool convection in summer is enhanced, leading to a cyclonic anomaly in the subtropical western Pacific. As a result, the western Pacific subtropical high is located more northeastward, and the seasonal march in East Asia is thus accelerated. This anomalous pattern tends to change with the seasonal march, with a maximum anomaly in July. Besides, there is less Mei-yu rainfall in the Yangtze River basin, with an earlier start and termination. The rainfall distribution in East Asia during La Ni？a years is characterized by a zonal pattern of less rainfall in eastern China and more rainfall over the oceanic region of the western Pacific. By comparison, a meridional pattern is found during El Ni？o years, with less rainfall in the tropics and more rainfall in the subtropics and midlatitudes. Therefore, the influence of La Ni？a on the EASM cannot be simply attributed to an antisymmetric influence of El Ni？o.
Key words:
La Ni？a; East Asian summer monsoon; intraseasonal variation; western Pacific subtropical high
Citation:
Feng XUE & Jun-Jie ZHAO (2017) Intraseasonal variation of the East Asian summer monsoon in La Ni？a years, Atmospheric and Oceanic Science Letters, 10:2, 156-161, DOI: 10.1080/16742834.2016.1254008