Asymmetric relationships between El Ni?o/La Ni?a and floods/droughts in the following summer over Chongqing, China

摘要

This study presents a detailed analysis of the asymmetric relationships between the warm/cold phase of the El Ni?o–Southern Oscillation and the typical flood/drought years in summer over Chongqing. Furthermore, its underpinning mechanisms are also explored. The results show that: (1) El Ni?o and La Ni?a have an asymmetric influence on summer precipitation in the following year over Chongqing. Generally, the composite atmospheric circulation anomalies for El Ni?o years are consistent with the composite results for typical flood years in summer over Chongqing, which indicates a tight link between typical flood years in summer over Chongqing and El Ni?o events. However, the relationship between typical drought years in summer over Chongqing and La Ni?a events is not significant. (2) From winter to the following summer, the extent of positive SST anomalies in the equatorial eastern Pacific associated with typical flood years in summer over Chongqing shrinks, whereas in the tropical Indian Ocean, the extent slightly expands. This trend indicates that the impact of El Ni?o on typical flood years in summer over Chongqing is maintained through the ‘relay effect’ of SSTs in the tropical Indian Ocean, which is the result of a lagged response of positive SST anomalies in the tropical Indian Ocean to El Ni?o events in winter.