Coherent Modes of Global SST and Summer Rainfall over China: An Assessment of the Regional Impacts of the 1997–98 El Niño

Abstract

In this paper, the authors have identified three coherent modes of summertime rainfall variability over China and global sea surface temperature (SST) for the period of 1955–98 by Singular Value Decomposition. Based on these modes, the impacts of the 1997–98 El Niño on major drought and flood occurrences over China have been assessed. The first mode can be identified with the growing phase of El Niño superimposed on a warming trend since the mid-1950s. This mode strongly influences rainfall over northern China. The second mode comprises a quasi-biennial (QB) variability manifested in alternate wet and dry years over the Yangtze River Valley (YRV) of central China. The third mode is dominated by a quasi-decadal oscillation in eastern China between the Yangtze River and the Yellow River, with an opposite tendency in southern China. Using a mode-by-mode reconstruction, the contributions of these leading modes to the 1997 and 1998 observed rainfall anomalies are evaluated. It is found that the severe... Abstract In this paper, the authors have identified three coherent modes of summertime rainfall variability over China and global sea surface temperature (SST) for the period of 1955–98 by Singular Value Decomposition. Based on these modes, the impacts of the 1997–98 El Niño on major drought and flood occurrences over China have been assessed. The first mode can be identified with the growing phase of El Niño superimposed on a warming trend since the mid-1950s. This mode strongly influences rainfall over northern China. The second mode comprises a quasi-biennial (QB) variability manifested in alternate wet and dry years over the Yangtze River Valley (YRV) of central China. The third mode is dominated by a quasi-decadal oscillation in eastern China between the Yangtze River and the Yellow River, with an opposite tendency in southern China. Using a mode-by-mode reconstruction, the contributions of these leading modes to the 1997 and 1998 observed rainfall anomalies are evaluated. It is found that the severe...