Effects of model resolution, physics, and coupling on Southern Hemisphere storm tracks in CESM1.3 — Australian Meteorological and Oceanographic Society
  1. Schedule
  2. Afternoon Tea + Poster Session 2
  3. Effects of model resolution, physics, and coupling on Southern Hemisphere storm tracks in CESM1.3

Effects of model resolution, physics, and coupling on Southern Hemisphere storm tracks in CESM1.3 (#2020)

Gerald A Meehl 1 , Dongxia Yang 2 , Julie M Arblaster 1 2 , Susan C Bates 1 , Nan Rosenbloom 1 2 , Richard Neale 1 , Julio Bacmeister 1 , Peter H Lauritzen 1 , Frank Bryan 1 , Justin Small 1 , John Truesdale 1 , Cecile Hannay 1 , Christine Shields 1 , Warren G Strand 1 , John Dennis 1 , Gokhan Danabasoglu 1
  1. National Center for Atmospheric Research, NCAR, Boulder, Colorado , USA
  2. Monash University, Melbourne, VIC, Australia

It is generally assumed that new model generations with higher resolutions will produce a better simulation of Southern Hemisphere midlatitude storm tracks. But what are the roles of model dynamics and sea-air interaction? Here we studied historical simulations with variants of the Community Earth System Model version 1 (CESM1) that evolved from CESM1.1 to CESM1.3, which involve different atmospheric model resolutions with different cloud physics formulations, coupled to different ocean model resolutions. It is found that increasing the resolution from 1˚ to 0.25˚ in the atmosphere (same physics) coupled to the 1˚-ocean intensifies the strength of the storm tracks closer to observations.  The 0.25˚-atmosphere with the older CESM1.1 physics coupled to the 0.1˚-ocean has a degraded storm track compared to the 0.25˚-atmosphere with CESM1.3 physics coupled to the 1˚-ocean, due to fewer low clouds, warmer Southern Ocean SSTs, and a weaker meridional temperature gradient. Therefore, deficient physics in the atmospheric model can negate the gains attained by higher resolution in atmosphere and ocean.

#amos2020