B06. Resolution Sensitivity of the simulation of teleconnections to extremes

Title

Model resolution sensitivity of the simulation of NAO and ENSO teleconnections to precipitation extremes

Authors

Salil Mahajan (ORNL)

Abstract

We evaluate the impact of model resolution on the simulation of teleconnections of low frequency climate modes of variability on precipitation extremes in E3SMv1 and v0. We quantify the linear dependence of precipitation extremes over US and Europe on North Atlantic Oscillation (NAO) and ENSO using Generalized Extreme Value (GEV) theory in ensembles of coupled (and uncoupled) production E3SM nominal 1-degree and 0.25-degree resolution simulations. In general, the high-res model improves the simulation of these teleconnections both in magnitude and spatial pattern. For example, as compared to the low-resolution model the high-res model simulates a stronger impact of NAO on daily precipitation extremes over the western slopes of mountain ranges South-western Norway, North-western UK and the Western Balkan states, but underperforms the low-res model over South-western Iberian peninsula. And, the high-res model better simulates the ENSO-dependence of precipitation extremes over Southeastern US, but underperforms the low-res model over Western US.  These improvements are largely due to an improved simulation of vertical moisture flux from the boundary layer and enhanced stable condensation in the high-res model. However, that effect is offset by the poor simulation of the teleconnections to extra-tropical cyclone activity and moisture availability in the high-res model.