Statistical Characteristics Of The South Indian Ocean Dipole Mode And Its Impact On Precipitation In Chin

This paper explores the characteristics of the Southern Indian Ocean sea surface temperature anomalies(SSTA)during the winter of 1979-2020 using Extended Reconstructed SST V5(ERSST V5)sea surface temperature data provided by the National Oceanic and Atmospheric Administration(NOAA),NCEP/NCAR reanalysis 1 data provided by the National Center for Environmental Prediction and the National Center for Atmospheric Research and other observational data.The spatial and temporal characteristics and evolution mechanism of the Southern Indian Ocean Dipole(SIOD)are studied using the Empirical Orthogonal Function,wavelet analysis,correlation analysis,and composite analysis.And its impact on winter and spring precipitation in China through the Indian Ocean Intertropical Convergence Zone(ITCZ),an intermediate variable,is analyzed.In addition,the independent and synergistic effects of pure SIOD events,SIOD and El Ni?o-Southern Oscillation(ENSO)events on summer precipitation in China,and their influential mechanisms are explored respectively.The results indicate that:(1)The first mode of EOF analysis of SSTA in the South Indian Ocean displays an southwest-northeast inverse phase distribution,namely SIOD mode,with an interpretation variance of 25.1%.This phenomenon has obvious seasonal phase-locking with the anomaly pattern peaking in winter.Using wavelet analysis,it is found that the SIOD changes periodically mainly on the 6-7a timescale over the period studied in this paper.Through synthetic analysis we know that the formation of the SIOD is mainly due to the synergistic contribution by multiple elements such as latent heat flux,sea level pressure,shortwave radiation flux and mixed layer depth.(2)After interpolating the precipitation data,the Indian Ocean ITCZ(35°-75°E)position is obtained through integration calculation.The SIOD has a substantial impact on the Indian Ocean ITCZ location throughout the winter and the ensuing spring.SIOD has an impact on the precipitation in the middle and lower reaches of the Yangtze River through the Indian Ocean ITCZ position variability.(3)Based on the correlation analysis,it is found that there was a strong inverse correlation between SIOD and ENSO.By calculating SWPI,NEPI and SIODI,it is proved that both of them have a certain impact on summer precipitation in China.In SIOD and ENSO cooccurrence years,there is a direct correlation between precipitation in eastern China and water vapor in the Pacific,and the occurrence of CP La Ni?a(EP El Ni?o)has an increasing(decreasing)effect on the summer precipitation in the middle and lower reaches of the Yangtze River following the SIOD events.Using mathematical methods,this paper discusses the effects of SIOD on precipitation in winter as well as the following spring and summer in China,which will,to a certain extent,help to improve the prediction of precipitation in the middle and lower reaches of the Yangtze River,reduce the economic losses caused by meteorological disasters,and promote the development of the national economy.