Presenter: Sam Stevenson and Xingying Huang

Title: A First Look at the E3SMv1 Large Ensemble

Abstract:

Projections of future climate change are crucial for a wide variety of applications, making an understanding of the associated uncertainties essential. This is often complicated by the large extent of internally generated climate variability, which can be comparable to the forced climate change signal on decadal to multidecadal timescales. For this reason, single-model initial condition large ensembles (SMILEs) have been performed with multiple climate/Earth system models. These ensembles are configured in a variety of different ways, and the relative effects of different ensemble initialization schemes are as yet not well understood. Here we present a new large ensemble with the Energy Exascale Earth System Model version 1 (E3SM1), a 20 member ensemble which uses a novel ‘macro’ initialization method designed to maximize the independence of the initial coupled atmosphere/ocean state of each ensemble member. E3SM1 represents the structure of Pacific climate variability well compared with observations, although the global surface temperature trend is flatter than observed due to the model's high sensitivity to aerosol forcing. A comparison of the variability in ensemble spread between E3SM1 and other large ensembles indicates that the macro initialization strategy provides a much larger sampling of internal variability during the first few decades of simulation time; interestingly, the exact choice of macro initial conditions appears not to contribute substantially to ensemble spread. This has implications both for the construction of future SMILEs and for the potential for initial conditions to affect the evolution of climate variability on multidecadal timescales.

Date

06 May 2021

Time

PT: 8:30 am
ET: 11:30 am

Call Info

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Attendees

Presentation

Time	Title	Presenter	Presentation	Recording	Notes
30 min	E3SMallhands_stevenson_15april2021.pdf	Sam Stevenson	PDF of Presentation	MP4 Movie (on the E3SM YouTube Channel)

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