The simulation of ENSO teleconnections in a resolved scales hierarchy of earth system models.

Abstract

Extracting regional precipitation predictability on sub-seasonal to seasonal timescales from low frequency variability phenomena, like El Nino Southern Oscillation (ENSO), remains a challenge. The coupling of sea surface temperature anomalies and deep convective activity associated with Tropical Pacific variability including during ENSO events contributes significantly to the diabatic heating of the tropical troposphere. The resulting Rossby waves that emanate from the tropical atmosphere then regulate remote tele-connections. Sub-grid scale deep convection parametrizations, however, are one of the largest sources of error in the current generation of earth system models and thus also lead to erroneous simulations of ENSO teleconnections. Here, we evaluate the simulation of ENSO teleconnections to US winter precipitation extremes in a hierarchy of earth system models spanning spatial resolutions from 100 km to 25 km as they explicitly resolve finer scales. We also evaluate US Department of Energy’s Energy Exascale Earth System Model’s Multi-scale Modeling Framework (E3SM-MMF) model configuration that embeds a cloud resolving model in each model grid point to explicitly resolve deep convection. We find that models credibly simulate the observed ENSO teleconnections to US winter precipitation mean and extremes over Southeast and Southwest US. High resolution models and the MMF model are generally found to improve upon their low-resolution counterparts. The enhancements are largely due to the improved simulation of ENSO-dependent storm track activity and moisture fluxes into the regions.