Subseasonal Bias and Skill in FV3 Simulations Using Two Different Physics Suites

As NOAA continues its transition to the Finite-Volume Cubed-Sphere (FV3) dynamical core for atmospheric modeling, much of the focus has been on short- to medium-range prediction (i.e., lead times out to 2 weeks). In addition, however, FV3 is in the process of being implemented for NOAA’s subseasonal-to-seasonal prediction needs, which will incorporate coupling to ocean (MOM6) and sea-ice (CICE5) models. In the present work, two sets of FV3 simulations in an uncoupled mode integrating out to subseasonal time scales (35 days) are presented: one set uses a suite of atmospheric physics parameterizations developed at NOAA’s Environmental Modeling Center (the “EMC suite”), whereas the other set uses a part of a physics suite (parameterizations for convection, planetary boundary-layer, land-surface, and cloud microphysics processes) developed initially for short-range prediction at NOAA/ESRL/Global Systems Division (the “GSD suite”). The two suites are compared against each other in terms of subseasonal (weeks 3-4) systematic errors, and of predictive skill for phenomena including but not limited to the Madden-Julian Oscillation. Preliminary results indicate that each suite has its relative strengths and weaknesses, i.e., neither physics suite exhibits unilaterally better performance in terms of bias and predictive skill at subseasonal time scales at this point. The lessons learned from this study – which is run without coupling to ocean and sea-ice models – will be incorporated to guide development of physics suites that are robust in their performance for multiple time scales (“minutes to months”), that are carried out in both uncoupled (atmosphere only) and coupled (atmosphere-ocean-ice) frameworks.