A super El Niño event occurred in 2015/2016.The sea surface temperature (SST) anomaly in the Niño3 area in the winter of 2015/2016 was over 2.5℃.This strong El Niño was an Eastern Pacific type event and had strong impacts on global climate conditions.In the present paper,by employing NCEP/NCAR reanalysis,Hadley SST and CMAP precipitation data,we examine the impacts of this El Niño event on the Australian summer monsoon circulation and precipitation anomalies from the peak phase to the decaying phase of the 2015/2016 strong El Niño event.We also examine the mechanism behind these impacts.Affected by this El Niño event,the precipitation in most areas of Australia significantly decreased,and in some areas even reduced by 60% to 80%.Two mechanisms can explain the influence of this El Niño event on Australian rainfall.The first is horizontal circulation anomaly-related.A Gill-type response of the atmosphere to the SST anomalies in the tropical region occurred,inducing horizontal circulation anomalies and hence weakening the Australian summer monsoon.Specifically,negative SST anomalies in the equatorial western Pacific during both the peak and decaying phases of the 2015/2016 strong El Niño event led to negative heat source anomalies locally,resulting in two anomalous anticyclonic circulations that were respectively situated on the northern and southern sides of the equator.The anomalous anticyclonic circulation in the region south of the Maritime Continent(MC) region weakened the Australian summer monsoon,suppressing the upward movement locally and hence reducing the rainfall over Australia.The second mechanism is vertical circulation-related.During the super El Niño event of 2015/2016,anomalous vertical circulation existed,with its upward motion branch in the equatorial eastern and central Pacific and downward branch in Australia.This anomalous vertical circulation directly bridged the gap between the central equatorial Pacific and Australia,facilitating the reduction in precipitation over Australia.During the peak phase of this El Niño event,anomalous Walker circulation was observed,with upward motion in the central equatorial Pacific due to the positive anomalies of SST,but downward motion in the MC regions.Meanwhile,another vertical circulation system was well defined in a slanted vertical plane from Australia northeastwards to the central equatorial Pacific.This was,of course,related to the weakened Australian summer monsoon.As a result,this northeast-southwest cell of vertical circulation played an important role in maintaining negative anomalies of rainfall over Australia.Moreover,the anomalous upward motion was observed in the southern part of China,which associated in a compensative manner with the downward motion in the MC regions and Australia.These anomalous vertical motions formed an anomalous vertical circulation system that meridionally connected Australia and southern China.This vertical circulation suggests a possible indirect effect of a weakened East Asian winter monsoon anomaly,as induced by this super El Niño event,on the Australian summer monsoon.All the results presented in this study will be beneficial for a better understanding of the underlying mechanisms of Australian monsoon variations in association with super ENSO events,as well as for uncovering clues to predicting Australian summer rainfall.