Understanding the Impacts of Tropical Sea Surface Temperature Biases on ENSO Driven North American Precipitation

The El Niño-Southern Oscillation (ENSO) has a well-documented impact on precipitation patterns in North America. However, the remote impact of tropical sea surface temperature (SST) biases on ENSO and its teleconnection patterns remains a lingering problem in climate models. This study aims to distinguish the relative impacts of the tropical Pacific, Atlantic and Indian Ocean SST biases on ENSO-induced precipitation in North America through a series of nudging experiments in the historical climate of the Community Earth System Model (CESM). Simulations in which SST biases are removed in the target regions are carried out to assess the impact of errors on ENSO and their contribution to precipitation statistics over North America. Both the cold tongue and remote tropical Atlantic biases have notable impacts on ENSO dynamics, altering key ocean-atmosphere feedback mechanisms and, consequently, their impact on ENSO-induced precipitation over North America. The Indian Ocean exerts a smaller yet noteworthy influence. This study serves as an important step in better characterizing the impact of SST biases on tropical trans basin and ENSO teleconnections.