The Relationship Between ENSO And IOD And Its Influence On Jianghuai Meiyu

Based on the 1950—2017 data of NOAA monthly Ni?o3,Ni?o4 and Ni?o3.4 index,Kaplan Extended SST V2 monthly SST anomaly and JAMSTEC monthly SST DMI,the 1979 — 2017 data of stations' daily rainfall provided by China Meteorological Data Network,ERA-Interim daily height field,wind field and land pressure field reanalysis data.By using wavelet analysis,correlation analysis,EOF analysis and synthetic analysis to reseach different types of ENSO and the relationship between the IOD,under different circumstances of the cold and warm ENSO events and different types of warm events occurs alone or occurs with IOD to analyze the different effect on Jianghuai Meiyu precipitation.The results showed that(1)There were 20 El Ni?o events,14 La Nina events and 30 IOD events from 1950 to 2017,eight of the El Ni?o events occurred were EP-type El Ni?o events and 11 were CP-type El Ni?o events.The ENSO events mainly oscillate on the 5a time scale,followed by the 16 a time scale,and the IOD events fluctuate significantly on the time scale of 1-4a.(2)The EP type has an abnormal warming of the SST in the eastern Pacific Ocean,and there is significant warming in the Ni?o3 and Ni?o1+2 areas;while the CP type has an abnormal warming of the SST in the Central Pacific region,and there is significant warming in the Ni?o4 and Ni?o3.4 regions.(3)When an El Ni?o event occurs,it sometimes happens with the IOD event,there is a certain correlation between them.The correlation coefficient between EP index and DMI is 0.55,and the correlation coefficient between CP index and DMI is 0.39.(4)When the EP El Ni?o occurs alone,the precipitation in the Changjiang basin and most of its north is significantly less.When the CP El Ni?o occurs alone,the precipitation in the central part of the Jianghuai region increases significantly.When the EP El Ni?o occurs with IOD,the precipitation in the entire Jianghuai region is significantly higher than usual.When the CP El Ni?o occurs with IOD,the precipitation in the Changjiang basin and the eastern part of the Jianghuai region is relatively low,so it can be inferred that IOD event can enhance the influence to EP El Nino on the precipitation leading to heavy precipitation in the Jianghuai region,and weaken the influence to CP El Nino thus reducing the precipitation in the Jianghuai region.In addition,take 2016 as an example,has detailed analysis of Jianghuai Meiyu.