Impact Of ENSO And North Atlantic SST Anomalies On The Spring Atlantic Storm Track

Based on NOAA monthly sea surface temperature data(ERSST.v5)and NCEP/NCAR global reanalysis data,the relationship between the springtime Atlantic storm track(AST)and sea surface temperature anomaly(SSTA)over the tropical eastern Pacific Ocean and North Atlantic is investigated.The main conclusions are as follows.(1)There is a significant interannual relationship between El Ni?o-Southern Oscillation(ENSO)and the meridional position of AST in spring,and this interannual relationship is modulated by the Atlantic Multidecadal Oscillation(AMO).Both the results of the reanalysis data and model simulations show that the meridional displacement of the AST is significantly correlated with ENSO during negative AMO phase,while no significant relationship is found during positive AMO phase.This may be due to the difference of 500-hPa geopotential height anomalies induced by ENSO in different AMO phases.AMO may affect the westerly jet,the local eddy growth rate(EGR)and baroclinic energy conversion by adjusting the 500 hPa wave train associated with ENSO,which further leads to the meridional displacement of AST.(2)The intensity of springtime AST is affected by the North Atlantic SSTA associated with ENSO.During an El Ni?o(La Ni?a)event,the SST over the tropical and northwestern region of the North Atlantic has an anomaly warming(cooling),while the SST over the midwestern regions has an anomaly cooling(warming).On the interannual timescale,El Ni?o(La Ni?a)-related SSTA over three regions lead to a weakened(strengthened)springtime AST by influencing westerly jets,net heat flux,EGR,and baroclinic energy conversions.On the interdecadal timescale,El Ni?o(La Ni?a)-related SSTA over midwestern regions causes anomalies in westerly jets,EGR,and baroclinic energy conversions,weakening(strengthening)the intensity of springtime AST;while net heat flux anomalies suppresses the changes of AST.(3)In addition to ENSO-related SSTA,the North Atlantic own SSTA is also closely related to the intensity of springtime AST.There is a relatively stable anti-correlation between SSTA from East Newfoundland to the Mid-Atlantic ridge and AST intensity in spring.The relationship between SSTA over the mid-western of the Sargasso Sea and the intensity of AST is significantly correlated after 1994.While the relationship between SSTA over the tropical eastern of the North Atlantic and the intensity of AST in spring is modulated by AMO.During negative AMO phase,the warming(cooling)of SSTA over the tropical eastern of the North Atlantic results in the overall intensity of AST weakening(strengthening).While during thepositive AMO phase,the warming(cooling)SSTA over the same regions causes the weakened(strengthened)storm track activities in the eastern and western regions of the climatological AST.