Indian Ocean Tropical Cyclone Genesis Influenced By The Indian Ocean Dipole Mode

Based on the north Indian ocean tropical cyclone data from Joint Typhoon Warning Center(JTWC),and the monthly reanalysis data provided by National Centers for Environmental Prediction(NCEP)and the National Center for Atmospheric Research(NCAR),also using monthly Sea Surface Temperature from the US National Oceanic and Atmospheric Administration(NOAA)?Discussed the effects of the Indian Ocean Dipole(IOD)on the formation of indian ocean tropical cyclone.Obtaining the following main conclusion:(1)The first modal of the Indian Ocean tropical cyclone genesis empirical orthogonal function spatial distribution is reverse between the east of Indian Ocean and the west of Indian Ocean.Which is dominated by the interannual variation of 3-6 years.(2)IOD has a significant modulation effect on the formation of tropical cyclones in the Indian Ocean.There is a significant correlation between IOD and the first modal of the spatial variation of the tropical cyclone generation in the Indian Ocean.In the IOD negative phase,the frequency of tropical cyclone generation in the eastern Indian Ocean increased,and the frequency of tropical cyclone generation in the western Indian Ocean decreased.The IOD positive phase showed the opposite pattern.And the modal modulation effect of IOD on the formation of the tropical cyclone in the Indian Ocean is independent of the ENSO signal.(3)The indian ocean dipole mainly modulates the genesis formation of tropical cyclones by influencing the atmospheric circulation above indian ocean.When indian ocean dipole at the positive(nagtive)phase,the sea surface temperature is warmer(cooler)than average sea surface temperature in the west of indian ocean,vertical wind shear is much weaker(stronger)than average vertical wind shear,relative humidity is less(more),vertical velocity is stronger(weaker),all of those made the number of tropical cyclone is more(less).The number of tropical cyclone in the southeast of indian ocean is opposite with other area of indian ocean.Particularly,Relative humidity terms and vertical velocity terms may be the main factors that IOD affect the reverse pattern of east-west tropical cyclone generation.