ENSO Influence on Subsequent Early‐Summer North American Atmospheric Circulation: Role of Land‐Atmosphere Interaction

Abstract Air‐sea interaction is widely recognized as a key pathway through which El Niño‐Southern Oscillation (ENSO) events exert delayed impacts. This study highlights an additional role of land‐atmosphere interactions in modulating North American atmospheric circulation during ENSO‐post early summer. Using reanalysis data and numerical simulations, we identify an ocean‐land‐atmosphere relay mechanism. El Niño‐induced persistent upstream sea surface temperature anomalies enhance moisture transport into North America, which triggers a dipole pattern of land temperature anomalies—cooling in the midlatitudes and warming at higher latitudes—through surface turbulent latent heat flux and shortwave radiation. These land surface anomalies feedback on the atmosphere via modifications in sensible heat flux and longwave radiation, weakening low‐level meridional air temperature gradient and atmospheric baroclinicity. The resulting negative transient eddy vorticity forcing induces an equivalent barotropic geopotential high anomaly and weakens the westerly jet around 50°N. These findings underscore the essential role of land‐atmosphere coupling in extending ENSO's summer influence.