ENSO Diversity and the Simulation of Its Teleconnections to Winter Precipitation Extremes Over the US in High Resolution Earth System Models

Accounting for the diversity in El Nino Southern Oscillation (ENSO)'s spatial pattern, with the novel ENSO longitudinal index (ELI), we evaluate the simulation of its teleconnections to US winter precipitation extremes by seven global high-resolution (HR) Earth System Models (ESM). Six (four) HR ESMs simulate the observed increase in precipitation extremes over Southwest US (Southeast US) during ELI-defined El Nino events better than their low-resolution counterparts, which are low-biased. The stronger ENSO-dependence over the Southwest US and Southeast US in those models is associated with an improved simulation of moisture flux into the regions and/or storm track activity there. HR ESMs, however, generally overestimate the increase in precipitation extremes over the Pacific-Northwest during La Nina events. Model bias there is associated with bias in moisture transport into the region during La Nina events, which is amplified by the enhanced vertical mass fluxes in HR.

Automated summary

Using the novel ENSO longitudinal index (ELI) to account for the diversity in El Nino Southern Oscillation (ENSO)'s spatial pattern, we assess the teleconnections of ENSO to US winter precipitation extremes simulated by seven global high-resolution Earth System Models (ESM). The high-resolution models generally outperform the low-resolution models in simulating the observed increase in precipitation extremes over Southwest US and Southeast US during El Nino events defined by ELI. The stronger ENSO-dependence in these models is attributed to improved simulation of moisture flux and storm track activity in the regions. However, the high-resolution models tend to overestimate the increase in precipitation extremes over the Pacific-Northwest during La Nina events, which is associated with bias in moisture transport and enhanced vertical mass fluxes in these models.